Jump to content
Main menu Navigation ●Main page ●Contents ●Current events ●Random article ●About Wikipedia ●Contact us ●Donate Contribute ●Help ●Learn to edit ●Community portal ●Recent changes ●Upload file
●Create account ●Log in ●Create account ● Log in Pages for logged out editors learn more ●Contributions ●Talk
View source for Module:Citation/CS1/Identifiers

●Module ●Talk ●Read ●View source ●View history Tools Actions ●Read ●View source ●View history General ●What links here ●Related changes ●Upload file ●Special pages ●Page information ●Get shortened URL ●Download QR code ●Wikidata item ← Module:Citation/CS1/Identifiers You do not have permission to edit this page, for the following reasons:
This page is transcluded in a cascade-protected page, so only administrators can edit it.
Why is the page protected?

Cascading protection is used to prevent vandalism to particularly visible pages, such as the Main Page and a few very highly used templates.
This page is transcluded in the following page, which is protected with the "cascading" option:
Wikipedia:Cascade-protected items/content
What can I do?

Discuss this page with others.
For move-protected pages, see requested moves.
Request that the page's protection level be reduced.
Find out more about how to get started editing Wikipedia.
If you have noticed an error or have a suggestion for a simple, non-controversial change, you can submit an edit request by clicking the button below and following the instructions. An administrator may then make the change on your behalf. Please check the talk page first in case the issue is already being discussed.
Submit an edit request
If you wrote any text, please save it temporarily to your device until you can edit this page.
You can view and copy the source of this page:
--[[--------------------------< F O R W A R D   D E C L A R A T I O N S >--------------------------------------
]]

local has_accept_as_written, is_set, in_array, set_message, select_one,   -- functions in Module:Citation/CS1/Utilities
  substitute, make_wikilink;

local z;                  -- table of tables defined in Module:Citation/CS1/Utilities

local cfg;                  -- table of configuration tables that are defined in Module:Citation/CS1/Configuration


--[[--------------------------< P A G E   S C O P E   V A R I A B L E S >--------------------------------------

declare variables here that have page-wide scope that are not brought in from other modules; that are created here and used here

]]

local auto_link_urls = {};              -- holds identifier URLs for those identifiers that can auto-link |title=


--============================<< H E L P E R   F U N C T I O N S >>============================================

--[[--------------------------< W I K I D A T A _ A R T I C L E _ N A M E _ G E T >----------------------------

as an aid to internationalizing identifier-label wikilinks, gets identifier article names from Wikidata.

returns :<lang code>:<article title> when <q> has an <article title> for <lang code>; nil else

for identifiers that do not have q, returns nil

for wikis that do not have mw.wikibase installed, returns nil

]]

local function wikidata_article_name_get (<span class="ltr">q</span>)
 if not is_set (<span class="ltr">q</span>) or (q and not mw.wikibase) then       -- when no q number or when a q number but mw.wikibase not installed on this wiki
  return nil;                -- abandon
 end

 local wd_article;
 local this_wiki_code = cfg.this_wiki_code;         -- Wikipedia subdomain; 'en' for en.wikipedia.org

 wd_article = mw.wikibase.getSitelink (q, this_wiki_code .. 'wiki');   -- fetch article title from WD; nil when no title available at this wiki

 if wd_article then
  wd_article = table.concat ({':', this_wiki_code, ':', wd_article});  -- interwiki-style link without brackets if taken from WD; leading colon required
 end

 return wd_article;               -- article title from WD; nil else
end


--[[--------------------------< L I N K _ L A B E L _ M A K E >------------------------------------------------

common function to create identifier link label from handler table or from Wikidata

returns the first available of
 1. redirect from local wiki's handler table (if enabled)
 2. Wikidata (if there is a Wikidata entry for this identifier in the local wiki's language)
 3. label specified in the local wiki's handler table
 
]]

local function link_label_make (handler)
 local wd_article;
 
 if not (cfg.use_identifier_redirects and is_set (handler.redirect)) then -- redirect has priority so if enabled and available don't fetch from Wikidata because expensive
  wd_article = wikidata_article_name_get (handler.q);      -- if Wikidata has an article title for this wiki, get it;
 end
 
 return (cfg.use_identifier_redirects and is_set (handler.redirect) and handler.redirect) or wd_article or handler.link;
end


--[[--------------------------< E X T E R N A L _ L I N K _ I D >----------------------------------------------

Formats a wiki-style external link

]]

local function external_link_id (options)
 local url_string = options.id;
 local ext_link;
 local this_wiki_code = cfg.this_wiki_code;         -- Wikipedia subdomain; 'en' for en.wikipedia.org
 local wd_article;               -- article title from Wikidata
 
 if options.encode == true or options.encode == nil then
  url_string = mw.uri.encode (url_string, 'PATH');
 end

 if options.auto_link and is_set (options.access) then
  auto_link_urls[options.auto_link] = table.concat ({options.prefix, url_string, options.suffix});
 end

 ext_link = mw.ustring.format ('[%s%s%s %s]', options.prefix, url_string, options.suffix or "", mw.text.nowiki (options.id));
 if is_set (options.access) then
  ext_link = substitute (cfg.presentation['ext-link-access-signal'], {cfg.presentation[options.access].class, cfg.presentation[options.access].title, ext_link}); -- add the free-to-read / paywall lock
 end

 return table.concat ({
  make_wikilink (link_label_make (options), options.label),    -- redirect, Wikidata link, or locally specified link (in that order)
  options.separator or '&nbsp;',
  ext_link
  });
end


--[[--------------------------< I N T E R N A L _ L I N K _ I D >----------------------------------------------

Formats a wiki-style internal link

TODO: Does not currently need to support options.access, options.encode, auto-linking and COinS (as in external_link_id),
but may be needed in the future for :m:Interwiki_map custom-prefixes like :arxiv:, :bibcode:, :DOI:, :hdl:, :ISSN:,
:JSTOR:, :Openlibrary:, :PMID:, :RFC:.

]]

local function internal_link_id (options)
 local id = mw.ustring.gsub (options.id, '%d', cfg.date_names.local_digits); -- translate 'local' digits to Western 0-9

 return table.concat (
  {
  make_wikilink (link_label_make (options), options.label),    -- wiki-link the identifier label
  options.separator or '&nbsp;',           -- add the separator
  make_wikilink (
   table.concat (
    {
    options.prefix,
    id,                -- translated to Western digits
    options.suffix or ''
    }),
   substitute (cfg.presentation['bdi'], {'', mw.text.nowiki (options.id)}) -- bdi tags to prevent Latin script identifiers from being reversed at RTL language wikis
   );                 -- nowiki because MediaWiki still has magic links for ISBN and the like; TODO: is it really required?
  });
end


--[[--------------------------< I S _ E M B A R G O E D >------------------------------------------------------

Determines if a PMC identifier's online version is embargoed. Compares the date in |pmc-embargo-date= against
today's date.  If embargo date is in the future, returns the content of |pmc-embargo-date=; otherwise, returns
an empty string because the embargo has expired or because |pmc-embargo-date= was not set in this cite.

]]

local function is_embargoed (embargo)
 if is_set (embargo) then
  local lang = mw.getContentLanguage();
  local good1, embargo_date, todays_date;
  good1, embargo_date = pcall (lang.formatDate, lang, 'U', embargo);
  todays_date = lang:formatDate ('U');
 
  if good1 then               -- if embargo date is a good date
   if tonumber (embargo_date) >= tonumber (todays_date) then   -- is embargo date is in the future?
    return embargo;             -- still embargoed
   else
    set_message ('maint_pmc_embargo');        -- embargo has expired; add main cat
    return '';              -- unset because embargo has expired
   end
  end
 end
 return '';                 -- |pmc-embargo-date= not set return empty string
end


--[=[-------------------------< I S _ V A L I D _ R X I V _ D A T E >------------------------------------------

for biorxiv, returns true if:
 2019-12-11T00:00Z <= biorxiv_date < today + 2 days
for medrxiv, returns true if:
 2020-01-01T00:00Z <= medrxiv_date < today + 2 days
 
The dated form of biorxiv identifier has a start date of 2019-12-11.  The Unix timestamp for that date is {{#time:U|2019-12-11}} = 1576022400
The medrxiv identifier has a start date of 2020-01-01.  The Unix timestamp for that date is {{#time:U|2020-01-01}} = 1577836800

<rxiv_date> is the date provided in those |biorxiv= parameter values that are dated and in |medrxiv= parameter values at time 00:00:00 UTC
<today> is the current date at time 00:00:00 UTC plus 48 hours
 if today's date is 2023-01-01T00:00:00 then
  adding 24 hours gives 2023-01-02T00:00:00 – one second more than today
  adding 24 hours gives 2023-01-03T00:00:00 – one second more than tomorrow

inputs:
 <y>, <m>, <d> – year, month, day parts of the date from the birxiv or medrxiv identifier
 <select> 'b' for biorxiv, 'm' for medrxiv; defaults to 'b'

]=]

local function is_valid_rxiv_date (y, m, d, select)
 if 0 == tonumber (<span class="ltr">m</span>) and 12 < tonumber (<span class="ltr">m</span>) then        -- <m> must be a number 1–12
  return false;
 end
 if 0 == tonumber (<span class="ltr">d</span>) and 31 < tonumber (<span class="ltr">d</span>) then        -- <d> must be a number 1–31; TODO: account for month length and leap yer?
  return false;
 end
 
 local rxiv_date = table.concat ({y, m, d}, '-');       -- make ymd date string
 local good1, good2;
 local rxiv_ts, tomorrow_ts;             -- to hold Unix timestamps representing the dates
 local lang_object = mw.getContentLanguage();

 good1, rxiv_ts = pcall (lang_object.formatDate, lang_object, 'U', rxiv_date);  -- convert rxiv_date value to Unix timestamp 
 good2, tomorrow_ts = pcall (lang_object.formatDate, lang_object, 'U', 'today + 2 days' ); -- today midnight + 2 days is one second more than all day tomorrow
 
 if good1 and good2 then              -- lang.formatDate() returns a timestamp in the local script which tonumber() may not understand
  rxiv_ts = tonumber (rxiv_ts) or lang_object:parseFormattedNumber (rxiv_ts); -- convert to numbers for the comparison;
  tomorrow_ts = tonumber (tomorrow_ts) or lang_object:parseFormattedNumber (tomorrow_ts);
 else
  return false;               -- one or both failed to convert to Unix timestamp
 end

 local limit_ts = ((select and ('m' == select)) and 1577836800) or 1576022400; -- choose the appropriate limit timesatmp

 return ((limit_ts <= rxiv_ts) and (rxiv_ts < tomorrow_ts))     -- limit_ts <= rxiv_date < tomorrow's date
end


--[[--------------------------< IS _ V A L I D _ I S X N >-----------------------------------------------------

ISBN-10 and ISSN validator code calculates checksum across all ISBN/ISSN digits including the check digit.
ISBN-13 is checked in isbn().

If the number is valid the result will be 0. Before calling this function, ISBN/ISSN must be checked for length
and stripped of dashes, spaces and other non-ISxN characters.

]]

local function is_valid_isxn (isxn_str, len)
 local temp = 0;
 isxn_str = { isxn_str:byte(1, len) };          -- make a table of byte values '0' → 0x30 .. '9' → 0x39, 'X' → 0x58
 len = len + 1;                -- adjust to be a loop counter
 for i, v in ipairs (isxn_str) do           -- loop through all of the bytes and calculate the checksum
  if v == string.byte ("X" ) then           -- if checkdigit is X (compares the byte value of 'X' which is 0x58)
   temp = temp + 10 * (len - i);          -- it represents 10 decimal
  else
   temp = temp + tonumber (string.char (<span class="ltr">v</span>) )*(len-i);
  end
 end
 return temp % 11 == 0;              -- returns true if calculation result is zero
end


--[[--------------------------< IS _ V A L I D _ I S X N _ 1 3 >-----------------------------------------------

ISBN-13 and ISMN validator code calculates checksum across all 13 ISBN/ISMN digits including the check digit.
If the number is valid, the result will be 0. Before calling this function, ISBN-13/ISMN must be checked for length
and stripped of dashes, spaces and other non-ISxN-13 characters.

]]

local function is_valid_isxn_13 (isxn_str)
 local temp=0;
 
 isxn_str = { isxn_str:byte(1, 13) };          -- make a table of byte values '0' → 0x30 .. '9' → 0x39
 for i, v in ipairs (isxn_str) do
  temp = temp + (3 - 2*(i % 2)) * tonumber (string.char (<span class="ltr">v</span>) );   -- multiply odd index digits by 1, even index digits by 3 and sum; includes check digit
 end
 return temp % 10 == 0;              -- sum modulo 10 is zero when ISBN-13/ISMN is correct
end


--[[--------------------------< N O R M A L I Z E _ L C C N >--------------------------------------------------

LCCN normalization (https://www.loc.gov/marc/lccn-namespace.html#normalization)
1. Remove all blanks.
2. If there is a forward slash (/) in the string, remove it, and remove all characters to the right of the forward slash.
3. If there is a hyphen in the string:
 a. Remove it.
 b. Inspect the substring following (to the right of) the (removed) hyphen. Then (and assuming that steps 1 and 2 have been carried out):
  1. All these characters should be digits, and there should be six or less. (not done in this function)
  2. If the length of the substring is less than 6, left-fill the substring with zeroes until the length is six.

Returns a normalized LCCN for lccn() to validate.  There is no error checking (step 3.b.1) performed in this function.

]]

local function normalize_lccn (lccn)
 lccn = lccn:gsub ("%s", "");            -- 1. strip whitespace

 if nil ~= string.find (lccn, '/') then
  lccn = lccn:match ("(.-)/");           -- 2. remove forward slash and all character to the right of it
 end

 local prefix
 local suffix
 prefix, suffix = lccn:match ("(.+)%-(.+)");         -- 3.a remove hyphen by splitting the string into prefix and suffix

 if nil ~= suffix then              -- if there was a hyphen
  suffix = string.rep("0", 6-string.len (suffix)) .. suffix;    -- 3.b.2 left fill the suffix with 0s if suffix length less than 6
  lccn = prefix..suffix;             -- reassemble the LCCN
 end
 
 return lccn;
 end


--============================<< I D E N T I F I E R   F U N C T I O N S >>====================================

--[[--------------------------< A R X I V >--------------------------------------------------------------------

See: https://arxiv.org/help/arxiv_identifier

format and error check arXiv identifier.  There are three valid forms of the identifier:
the first form, valid only between date codes 9107 and 0703, is:
 arXiv:<archive>.<class>/<date code><number><version>
where:
 <archive> is a string of alpha characters - may be hyphenated; no other punctuation
 <class> is a string of alpha characters - may be hyphenated; no other punctuation; not the same as |class= parameter which is not supported in this form
 <date code> is four digits in the form YYMM where YY is the last two digits of the four-digit year and MM is the month number January = 01
  first digit of YY for this form can only 9 and 0
 <number> is a three-digit number
 <version> is a 1 or more digit number preceded with a lowercase v; no spaces (undocumented)
 
the second form, valid from April 2007 through December 2014 is:
 arXiv:<date code>.<number><version>
where:
 <date code> is four digits in the form YYMM where YY is the last two digits of the four-digit year and MM is the month number January = 01
 <number> is a four-digit number
 <version> is a 1 or more digit number preceded with a lowercase v; no spaces

the third form, valid from January 2015 is:
 arXiv:<date code>.<number><version>
where:
 <date code> and <version> are as defined for 0704-1412
 <number> is a five-digit number

]]

local function arxiv (options)
 local id = options.id;
 local class = options.Class;            -- TODO: lowercase?
 local handler = options.handler;
 local year, month, version;
 local err_msg = false;              -- assume no error message
 local text;                 -- output text
 
 if id:match("^%a[%a%.%-]+/[<span class="ltr">90</span>]%d[<span class="ltr">01</span>]%d%d%d%d$") or id:match("^%a[%a%.%-]+/[<span class="ltr">90</span>]%d[<span class="ltr">01</span>]%d%d%d%dv%d+$") then -- test for the 9107-0703 format with or without version
  year, month = id:match("^%a[%a%.%-]+/([<span class="ltr">90</span>]%d)([<span class="ltr">01</span>]%d)%d%d%d[v%d]*$");
  year = tonumber (year);
  month = tonumber (month);
  if ((not (90 < year or 8 > year)) or (1 > month or 12 < month)) or  -- if invalid year or invalid month
   ((91 == year and 7 > month) or (7 == year and 3 < month)) then  -- if years ok, are starting and ending months ok?
    err_msg = true;             -- flag for error message
  end

 elseif id:match("^%d%d[<span class="ltr">01</span>]%d%.%d%d%d%d$") or id:match("^%d%d[<span class="ltr">01</span>]%d%.%d%d%d%dv%d+$") then -- test for the 0704-1412 with or without version
  year, month = id:match("^(%d%d)([<span class="ltr">01</span>]%d)%.%d%d%d%d[v%d]*$");
  year = tonumber (year);
  month = tonumber (month);
  if ((7 > year) or (14 < year) or (1 > month or 12 < month)) or   -- is year invalid or is month invalid? (doesn't test for future years)
   ((7 == year) and (4 > month)) then         -- when year is 07, is month invalid (before April)?
    err_msg = true;             -- flag for error message
  end

 elseif id:match("^%d%d[<span class="ltr">01</span>]%d%.%d%d%d%d%d$") or id:match("^%d%d[<span class="ltr">01</span>]%d%.%d%d%d%d%dv%d+$") then -- test for the 1501- format with or without version
  year, month = id:match("^(%d%d)([<span class="ltr">01</span>]%d)%.%d%d%d%d%d[v%d]*$");
  year = tonumber (year);
  month = tonumber (month);
  if ((15 > year) or (1 > month or 12 < month)) then      -- is year invalid or is month invalid? (doesn't test for future years)
   err_msg = true;              -- flag for error message
  end

 else
  err_msg = true;               -- not a recognized format; flag for error message
 end

 if err_msg then
  options.coins_list_t['ARXIV'] = nil;         -- when error, unset so not included in COinS
 end
 
 local err_msg_t = {};
 if err_msg then
  set_message ('err_bad_arxiv');
 end

 text = external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
   prefix = handler.prefix, id = id, separator = handler.separator, encode = handler.encode, access = handler.access});

 if is_set (class) then
  if id:match ('^%d+') then
   text = table.concat ({text, ' [[https://arxiv.org/archive/', class, ' ', class, ']]'}); -- external link within square brackets, not wikilink
  else
   set_message ('err_class_ignored');
  end
 end

 return text;
end


--[[--------------------------< B I B C O D E >--------------------------------------------------------------------

Validates (sort of) and formats a bibcode ID.

Format for bibcodes is specified here: https://adsabs.harvard.edu/abs_doc/help_pages/data.html#bibcodes

But, this: 2015arXiv151206696F is apparently valid so apparently, the only things that really matter are length, 19 characters
and first four digits must be a year.  This function makes these tests:
 length must be 19 characters
 characters in position
  1–4 must be digits and must represent a year in the range of 1000 – next year
  5 must be a letter
  6–8 must be letter, digit, ampersand, or dot (ampersand cannot directly precede a dot; &. )
  9–18 must be letter, digit, or dot
  19 must be a letter or dot

]]

local function bibcode (options)
 local id = options.id;
 local access = options.access;
 local handler = options.handler;
 local ignore_invalid = options.accept;
 local err_type;
 local err_msg = '';
 local year;

 local text = external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
  prefix = handler.prefix, id = id, separator = handler.separator, encode = handler.encode,
  access = access});
 
 if 19 ~= id:len() then
  err_type = cfg.err_msg_supl.length;
 else
  year = id:match ("^(%d%d%d%d)[%a][%w&%.][%w&%.][%w&%.][%w.]+[%a%.]$");
  if not year then              -- if nil then no pattern match
   err_type = cfg.err_msg_supl.value;         -- so value error
  else
   local next_year = tonumber (os.date ('%Y')) + 1;     -- get the current year as a number and add one for next year
   year = tonumber (year);            -- convert year portion of bibcode to a number
   if (1000 > year) or (year > next_year) then
    err_type = cfg.err_msg_supl.year;        -- year out of bounds
   end
   if id:find('&%.') then
    err_type = cfg.err_msg_supl.journal;       -- journal abbreviation must not have '&.' (if it does it's missing a letter)
   end
   if id:match ('.........%.tmp%.') then        -- temporary bibcodes when positions 10–14 are '.tmp.'
    set_message ('maint_bibcode');
   end
  end
 end

 if is_set (err_type) and not ignore_invalid then       -- if there was an error detected and accept-as-written markup not used
  set_message ('err_bad_bibcode', {err_type});
  options.coins_list_t['BIBCODE'] = nil;         -- when error, unset so not included in COinS
 end

 return text;
end


--[[--------------------------< B I O R X I V >-----------------------------------------------------------------

Format bioRxiv ID and do simple error checking.  Before 2019-12-11, biorXiv IDs were 10.1101/ followed by exactly
6 digits.  After 2019-12-11, biorXiv IDs retained the six-digit identifier but prefixed that with a yyyy.mm.dd. 
date and suffixed with an optional version identifier.

The bioRxiv ID is the string of characters:
 https://doi.org/10.1101/078733 -> 10.1101/078733
or a date followed by a six-digit number followed by an optional version indicator 'v' and one or more digits:
 https://www.biorxiv.org/content/10.1101/2019.12.11.123456v2 -> 10.1101/2019.12.11.123456v2
 
see https://www.biorxiv.org/about-biorxiv

]]

local function biorxiv (options)
 local id = options.id;
 local handler = options.handler;
 local err_msg = true;              -- flag; assume that there will be an error
 
 local patterns = {
  '^10%.1101/%d%d%d%d%d%d$',            -- simple 6-digit identifier (before 2019-12-11)
  '^10%.1101/(20%d%d)%.(%d%d)%.(%d%d)%.%d%d%d%d%d%dv%d+$',    -- y.m.d. date + 6-digit identifier + version (after 2019-12-11)
  '^10%.1101/(20%d%d)%.(%d%d)%.(%d%d)%.%d%d%d%d%d%d$',     -- y.m.d. date + 6-digit identifier (after 2019-12-11)
  }
 
 for _, pattern in ipairs (patterns) do          -- spin through the patterns looking for a match
  if id:match (pattern) then
   local y, m, d = id:match (pattern);         -- found a match, attempt to get year, month and date from the identifier

   if m then               -- m is nil when id is the six-digit form
    if not is_valid_rxiv_date (y, m, d, 'b') then     -- validate the encoded date; 'b' for biorxiv limit
     break;              -- date fail; break out early so we don't unset the error message
    end
   end
   err_msg = nil;              -- we found a match so unset the error message
   break;                -- and done
  end
 end                   -- err_cat remains set here when no match

 if err_msg then
  options.coins_list_t['BIORXIV'] = nil;         -- when error, unset so not included in COinS
  set_message ('err_bad_biorxiv');          -- and set the error message
 end
 
 return external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
   prefix = handler.prefix, id = id, separator = handler.separator,
   encode = handler.encode, access = handler.access});
end


--[[--------------------------< C I T E S E E R X >------------------------------------------------------------

CiteSeerX use their own notion of "doi" (not to be confused with the identifiers resolved via doi.org).

The description of the structure of this identifier can be found at Help_talk:Citation_Style_1/Archive_26#CiteSeerX_id_structure

]]

local function citeseerx (options)
 local id = options.id;
 local handler = options.handler;
 local matched;

 local text = external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
  prefix = handler.prefix, id = id, separator = handler.separator, encode = handler.encode,
  access = handler.access});
 
 matched = id:match ("^10%.1%.1%.[1-9]%d?%d?%d?%.[1-9]%d?%d?%d?$");
 if not matched then
  set_message ('err_bad_citeseerx' );
  options.coins_list_t['CITESEERX'] = nil;        -- when error, unset so not included in COinS
 end

 return text;
end


--[[--------------------------< D O I >------------------------------------------------------------------------

Formats a DOI and checks for DOI errors.

DOI names contain two parts: prefix and suffix separated by a forward slash.
 Prefix: directory indicator '10.' followed by a registrant code
 Suffix: character string of any length chosen by the registrant

This function checks a DOI name for: prefix/suffix.  If the DOI name contains spaces or endashes, or, if it ends
with a period or a comma, this function will emit a bad_doi error message.

DOI names are case-insensitive and can incorporate any printable Unicode characters so the test for spaces, endash,
and terminal punctuation may not be technically correct but it appears, that in practice these characters are rarely
if ever used in DOI names.

https://www.doi.org/doi_handbook/2_Numbering.html    -- 2.2 Syntax of a DOI name
https://www.doi.org/doi_handbook/2_Numbering.html#2.2.2   -- 2.2.2 DOI prefix

]]

local function doi (options)
 local id = options.id;
 local inactive = options.DoiBroken
 local access = options.access;
 local ignore_invalid = options.accept;
 local handler = options.handler;
 local err_flag;

 local text;
 if is_set (inactive) then
  local inactive_year = inactive:match("%d%d%d%d");      -- try to get the year portion from the inactive date
  local inactive_month, good;

  if is_set (inactive_year) then
   if 4 < inactive:len() then           -- inactive date has more than just a year (could be anything)
    local lang_obj = mw.getContentLanguage();      -- get a language object for this wiki
    good, inactive_month = pcall (lang_obj.formatDate, lang_obj, 'F', inactive); -- try to get the month name from the inactive date
    if not good then
     inactive_month = nil;          -- something went wrong so make sure this is unset
    end
   end
  end                  -- otherwise, |doi-broken-date= has something but it isn't a date
  
  if is_set (inactive_year) and is_set (inactive_month) then
   set_message ('maint_doi_inactive_dated', {inactive_year, inactive_month, ' '});
  elseif is_set (inactive_year) then
   set_message ('maint_doi_inactive_dated', {inactive_year, '', ''});
  else
   set_message ('maint_doi_inactive');
  end
  inactive = " (" .. cfg.messages['inactive'] .. ' ' .. inactive .. ')';
 end

 local registrant = mw.ustring.match (id, '^10%.([^/]+)/[^%s–]-[^%.,]$'); -- registrant set when DOI has the proper basic form

 local registrant_err_patterns = {           -- these patterns are for code ranges that are not supported 
  '^[^1-3]%d%d%d%d%.%d+$',            -- 5 digits with subcode (0xxxx, 40000+); accepts: 10000–39999
  '^[^1-6]%d%d%d%d$',              -- 5 digits without subcode (0xxxx, 60000+); accepts: 10000–69999
  '^[^1-9]%d%d%d%.%d+$',            -- 4 digits with subcode (0xxx); accepts: 1000–9999
  '^[^1-9]%d%d%d$',              -- 4 digits without subcode (0xxx); accepts: 1000–9999
  '^%d%d%d%d%d%d+',              -- 6 or more digits
  '^%d%d?%d?$',               -- less than 4 digits without subcode (3 digits with subcode is legitimate)
  '^%d%d?%.[%d%.]+',              -- 1 or 2 digits with subcode
  '^5555$',                -- test registrant will never resolve
  '[^%d%.]',                -- any character that isn't a digit or a dot
  }

 if not ignore_invalid then
  if registrant then              -- when DOI has proper form
   for i, pattern in ipairs (registrant_err_patterns) do    -- spin through error patterns
    if registrant:match (pattern) then        -- to validate registrant codes
     err_flag = set_message ('err_bad_doi');      -- when found, mark this DOI as bad
     break;              -- and done
    end
   end
  else
   err_flag = set_message ('err_bad_doi');        -- invalid directory or malformed
  end
 else
  set_message ('maint_doi_ignore');
 end

 if err_flag then
  options.coins_list_t['DOI'] = nil;          -- when error, unset so not included in COinS
 else
  if not access and cfg.known_free_doi_registrants_t[registrant] then  -- |doi-access=free not set and <registrant> is known to be free
   set_message ('maint_doi_unflagged_free');       -- set a maint cat
  end
 end
 
 text = external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
  prefix = handler.prefix, id = id, separator = handler.separator, encode = handler.encode, access = access,
  auto_link = not (err_flag or is_set (inactive) or ignore_invalid) and 'doi' or nil -- do not auto-link when |doi-broken-date= has a value or when there is a DOI error or (to play it safe, after all, auto-linking is not essential) when invalid DOIs are ignored
  }) .. (inactive or '');

 return text;
end


--[[--------------------------< H D L >------------------------------------------------------------------------

Formats an HDL with minor error checking.

HDL names contain two parts: prefix and suffix separated by a forward slash.
 Prefix: character string using any character in the UCS-2 character set except '/'
 Suffix: character string of any length using any character in the UCS-2 character set chosen by the registrant

This function checks a HDL name for: prefix/suffix.  If the HDL name contains spaces, endashes, or, if it ends
with a period or a comma, this function will emit a bad_hdl error message.

HDL names are case-insensitive and can incorporate any printable Unicode characters so the test for endashes and
terminal punctuation may not be technically correct but it appears, that in practice these characters are rarely
if ever used in HDLs.

Query string parameters are named here: https://www.handle.net/proxy_servlet.html.  query strings are not displayed
but since '?' is an allowed character in an HDL, '?' followed by one of the query parameters is the only way we
have to detect the query string so that it isn't URL-encoded with the rest of the identifier.

]]

local function hdl (options)
 local id = options.id;
 local access = options.access;
 local handler = options.handler;
 local query_params = {              -- list of known query parameters from https://www.handle.net/proxy_servlet.html
  'noredirect',
  'ignore_aliases',
  'auth',
  'cert',
  'index',
  'type',
  'urlappend',
  'locatt',
  'action',
  }
 
 local hdl, suffix, param = id:match ('(.-)(%?(%a+).+)$');     -- look for query string
 local found;

 if hdl then                 -- when there are query strings, this is the handle identifier portion
  for _, q in ipairs (query_params) do         -- spin through the list of query parameters
   if param:match ('^' .. q) then          -- if the query string begins with one of the parameters
    found = true;             -- announce a find
    break;               -- and stop looking
   end
  end
 end

 if found then
  id = hdl;                -- found so replace id with the handle portion; this will be URL-encoded, suffix will not
 else
  suffix = '';               -- make sure suffix is empty string for concatenation else
 end

 local text = external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
   prefix = handler.prefix, id = id, suffix = suffix, separator = handler.separator, encode = handler.encode, access = access})

 if nil == id:match("^[^%s–]-/[^%s–]-[^%.,]$") then       -- HDL must contain a forward slash, must not contain spaces, endashes, and must not end with period or comma
  set_message ('err_bad_hdl' );
  options.coins_list_t['HDL'] = nil;          -- when error, unset so not included in COinS
 end

 return text;
end


--[[--------------------------< I S B N >----------------------------------------------------------------------

Determines whether an ISBN string is valid

]]

local function isbn (options)
 local isbn_str = options.id;
 local ignore_invalid = options.accept;
 local handler = options.handler;

 local function return_result (check, err_type)        -- local function to handle the various returns
  local ISBN = internal_link_id ({link = handler.link, label = handler.label, redirect = handler.redirect,
      prefix = handler.prefix, id = isbn_str, separator = handler.separator});
  if ignore_invalid then             -- if ignoring ISBN errors
   set_message ('maint_isbn_ignore');         -- add a maint category even when there is no error
  else                 -- here when not ignoring
   if not check then             -- and there is an error
    options.coins_list_t['ISBN'] = nil;        -- when error, unset so not included in COinS
    set_message ('err_bad_isbn', err_type);       -- set an error message
    return ISBN;              -- return id text
   end
  end
  return ISBN;               -- return id text
 end

 if nil ~= isbn_str:match ('[^%s-0-9X]') then
  return return_result (false, cfg.err_msg_supl.char);     -- fail if isbn_str contains anything but digits, hyphens, or the uppercase X
 end

 local id = isbn_str:gsub ('[%s-]', '');          -- remove hyphens and whitespace

 local len = id:len();
 
 if len ~= 10 and len ~= 13 then
  return return_result (false, cfg.err_msg_supl.length);     -- fail if incorrect length
 end

 if len == 10 then
  if id:match ('^%d*X?$') == nil then          -- fail if isbn_str has 'X' anywhere but last position
   return return_result (false, cfg.err_msg_supl.form);         
  end
  if not is_valid_isxn (id, 10) then          -- test isbn-10 for numerical validity
   return return_result (false, cfg.err_msg_supl.check);    -- fail if isbn-10 is not numerically valid
  end
  if id:find ('^63[<span class="ltr">01</span>]') then            -- 630xxxxxxx and 631xxxxxxx are (apparently) not valid isbn group ids but are used by amazon as numeric identifiers (asin)
   return return_result (false, cfg.err_msg_supl.group);    -- fail if isbn-10 begins with 630/1
  end
  return return_result (true, cfg.err_msg_supl.check);     -- pass if isbn-10 is numerically valid
 else
  if id:match ('^%d+$') == nil then
   return return_result (false, cfg.err_msg_supl.char);    -- fail if ISBN-13 is not all digits
  end
  if id:match ('^97[<span class="ltr">89</span>]%d*$') == nil then
   return return_result (false, cfg.err_msg_supl.prefix);    -- fail when ISBN-13 does not begin with 978 or 979
  end
  if id:match ('^9790') then
   return return_result (false, cfg.err_msg_supl.group);    -- group identifier '0' is reserved to ISMN
  end
  return return_result (is_valid_isxn_13 (<span class="ltr">id</span>), cfg.err_msg_supl.check);
 end
end


--[[--------------------------< A S I N >----------------------------------------------------------------------

Formats a link to Amazon.  Do simple error checking: ASIN must be mix of 10 numeric or uppercase alpha
characters.  If a mix, first character must be uppercase alpha; if all numeric, ASINs must be 10-digit
ISBN. If 10-digit ISBN, add a maintenance category so a bot or AWB script can replace |asin= with |isbn=.
Error message if not 10 characters, if not ISBN-10, if mixed and first character is a digit.

|asin=630....... and |asin=631....... are (apparently) not a legitimate ISBN though it checksums as one; these
do not cause this function to emit the maint_asin message

This function is positioned here because it calls isbn()

]]

local function asin (options)
 local id = options.id;
 local domain = options.ASINTLD;
 
 local err_flag;

 if not id:match("^[%d%u][%d%u][%d%u][%d%u][%d%u][%d%u][%d%u][%d%u][%d%u][%d%u]$") then
  err_flag = set_message ('err_bad_asin');        -- ASIN is not a mix of 10 uppercase alpha and numeric characters
 else
  if id:match("^%d%d%d%d%d%d%d%d%d[%dX]$") then       -- if 10-digit numeric (or 9 digits with terminal X)
   if is_valid_isxn (id, 10) then          -- see if ASIN value is or validates as ISBN-10
    if not id:find ('^63[<span class="ltr">01</span>]') then         -- 630xxxxxxx and 631xxxxxxx are (apparently) not a valid isbn prefixes but are used by amazon as a numeric identifier
     err_flag = set_message ('err_bad_asin');     -- ASIN has ISBN-10 form but begins with something other than 630/1 so probably an isbn 
    end
   elseif not is_set (err_flag) then
    err_flag = set_message ('err_bad_asin');      -- ASIN is not ISBN-10
   end
  elseif not id:match("^%u[%d%u]+$") then
   err_flag = set_message ('err_bad_asin');       -- asin doesn't begin with uppercase alpha
  end
 end
 if (not is_set (domain)) or in_array (domain, {'us'}) then     -- default: United States
  domain = "com";
 elseif in_array (domain, {'jp', 'uk'}) then         -- Japan, United Kingdom
  domain = "co." .. domain;
 elseif in_array (domain, {'z.cn'}) then          -- China
  domain = "cn";
 elseif in_array (domain, {'au', 'br', 'mx', 'sg', 'tr'}) then    -- Australia, Brazil, Mexico, Singapore, Turkey
  domain = "com." .. domain;
 elseif not in_array (domain, {'ae', 'ca', 'cn', 'de', 'es', 'fr', 'in', 'it', 'nl', 'pl', 'sa', 'se', 'co.jp', 'co.uk', 'com', 'com.au', 'com.br', 'com.mx', 'com.sg', 'com.tr'}) then -- Arabic Emirates, Canada, China, Germany, Spain, France, Indonesia, Italy, Netherlands, Poland, Saudi Arabia, Sweden (as of 2021-03 Austria (.at), Liechtenstein (.li) and Switzerland (.ch) still redirect to the German site (.de) with special settings, so don't maintain local ASINs for them)
  err_flag = set_message ('err_bad_asin_tld');       -- unsupported asin-tld value
 end
 local handler = options.handler;

 if not is_set (err_flag) then
  options.coins_list_t['ASIN'] = handler.prefix .. domain .. "/dp/" .. id; -- asin for coins
 else
  options.coins_list_t['ASIN'] = nil;          -- when error, unset so not included in COinS
 end
 
 return external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
  prefix = handler.prefix .. domain .. "/dp/",
  id = id, encode = handler.encode, separator = handler.separator})
end


--[[--------------------------< I S M N >----------------------------------------------------------------------

Determines whether an ISMN string is valid.  Similar to ISBN-13, ISMN is 13 digits beginning 979-0-... and uses the
same check digit calculations.  See https://www.ismn-international.org/download/Web_ISMN_Users_Manual_2008-6.pdf
section 2, pages 9–12.

ismn value not made part of COinS metadata because we don't have a url or isn't a COinS-defined identifier (rft.xxx)
or an identifier registered at info-uri.info (info:)

]]

local function ismn (options)
 local id = options.id;
 local handler = options.handler;
 local text;
 local valid_ismn = true;
 local id_copy;

 id_copy = id;                -- save a copy because this testing is destructive
 id = id:gsub ('[%s-]', '');             -- remove hyphens and white space

 if 13 ~= id:len() or id:match ("^9790%d*$" ) == nil then     -- ISMN must be 13 digits and begin with 9790
  valid_ismn = false;
 else
  valid_ismn=is_valid_isxn_13 (<span class="ltr">id</span>);          -- validate ISMN
 end

 -- text = internal_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,  -- use this (or external version) when there is some place to link to
 --  prefix = handler.prefix, id = id_copy, separator = handler.separator, encode = handler.encode})

 text = table.concat (              -- because no place to link to yet
  {
  make_wikilink (link_label_make (handler), handler.label),
  handler.separator,
  id_copy
  });

 if false == valid_ismn then
  options.coins_list_t['ISMN'] = nil;          -- when error, unset so not included in COinS; not really necessary here because ismn not made part of COinS
  set_message ('err_bad_ismn');           -- create an error message if the ISMN is invalid
 end 
 
 return text;
end


--[[--------------------------< I S S N >----------------------------------------------------------------------

Validate and format an ISSN.  This code fixes the case where an editor has included an ISSN in the citation but
has separated the two groups of four digits with a space.  When that condition occurred, the resulting link looked
like this:

 |issn=0819 4327 gives: [https://www.worldcat.org/issn/0819 4327 0819 4327] -- can't have spaces in an external link
 
This code now prevents that by inserting a hyphen at the ISSN midpoint.  It also validates the ISSN for length
and makes sure that the checkdigit agrees with the calculated value.  Incorrect length (8 digits), characters
other than 0-9 and X, or checkdigit / calculated value mismatch will all cause a check ISSN error message.  The
ISSN is always displayed with a hyphen, even if the ISSN was given as a single group of 8 digits.

]]

local function issn (options)
 local id = options.id;
 local handler = options.handler;
 local ignore_invalid = options.accept;

 local issn_copy = id;              -- save a copy of unadulterated ISSN; use this version for display if ISSN does not validate
 local text;
 local valid_issn = true;

 id = id:gsub ('[%s-]', '');             -- remove hyphens and whitespace

 if 8 ~= id:len() or nil == id:match ("^%d*X?$" ) then      -- validate the ISSN: 8 digits long, containing only 0-9 or X in the last position
  valid_issn = false;              -- wrong length or improper character
 else
  valid_issn = is_valid_isxn (id, 8);          -- validate ISSN
 end

 if true == valid_issn then
  id = string.sub (id, 1, 4 ) .. "-" .. string.sub (id, 5 );    -- if valid, display correctly formatted version
 else
  id = issn_copy;               -- if not valid, show the invalid ISSN with error message
 end

 text = external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
  prefix = handler.prefix, id = id, separator = handler.separator, encode = handler.encode})

 if ignore_invalid then
  set_message ('maint_issn_ignore');
 else
  if false == valid_issn then
   options.coins_list_t['ISSN'] = nil;         -- when error, unset so not included in COinS
   set_message ('err_bad_issn', (options.hkey == 'EISSN') and 'e' or ''); -- create an error message if the ISSN is invalid
  end 
 end
 
 return text;
end


--[[--------------------------< J F M >-----------------------------------------------------------------------

A numerical identifier in the form nn.nnnn.nn

]]

local function jfm (options)
 local id = options.id;
 local handler = options.handler;
 local id_num;

 id_num = id:match ('^[<span class="ltr">Jj</span>][<span class="ltr">Ff</span>][<span class="ltr">Mm</span>](.*)$');         -- identifier with jfm prefix; extract identifier

 if is_set (id_num) then
  set_message ('maint_jfm_format');
 else                  -- plain number without JFM prefix
  id_num = id;               -- if here id does not have prefix
 end

 if id_num and id_num:match('^%d%d%.%d%d%d%d%.%d%d$') then
  id = id_num;               -- jfm matches pattern
 else
  set_message ('err_bad_jfm' );           -- set an error message
  options.coins_list_t['JFM'] = nil;          -- when error, unset so not included in COinS
 end
 
 return external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
   prefix = handler.prefix, id = id, separator = handler.separator, encode = handler.encode});
end


--[[--------------------------< J S T O R >--------------------------------------------------------------------

Format a JSTOR with some error checking

]]

local function jstor (options)
 local id = options.id;
 local access = options.access;
 local handler = options.handler;

 if id:find ('[<span class="ltr">Jj</span>][<span class="ltr">Ss</span>][<span class="ltr">Tt</span>][<span class="ltr">Oo</span>][<span class="ltr">Rr</span>]') or id:find ('^https?://') or id:find ('%s') then
  set_message ('err_bad_jstor');           -- set an error message
  options.coins_list_t['JSTOR'] = nil;         -- when error, unset so not included in COinS
 end
 
 return external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
  prefix = handler.prefix, id = id, separator = handler.separator, encode = handler.encode, access = access});
end


--[[--------------------------< L C C N >----------------------------------------------------------------------

Format LCCN link and do simple error checking.  LCCN is a character string 8-12 characters long. The length of
the LCCN dictates the character type of the first 1-3 characters; the rightmost eight are always digits.
https://oclc-research.github.io/infoURI-Frozen/info-uri.info/info:lccn/reg.html

length = 8 then all digits
length = 9 then lccn[<span class="ltr">1</span>] is lowercase alpha
length = 10 then lccn[<span class="ltr">1</span>] and lccn[<span class="ltr">2</span>] are both lowercase alpha or both digits
length = 11 then lccn[<span class="ltr">1</span>] is lower case alpha, lccn[<span class="ltr">2</span>] and lccn[<span class="ltr">3</span>] are both lowercase alpha or both digits
length = 12 then lccn[<span class="ltr">1</span>] and lccn[<span class="ltr">2</span>] are both lowercase alpha

]]

local function lccn (options)
 local lccn = options.id;
 local handler = options.handler;
 local err_flag;                -- presume that LCCN is valid
 local id = lccn;               -- local copy of the LCCN

 id = normalize_lccn (<span class="ltr">id</span>);             -- get canonical form (no whitespace, hyphens, forward slashes)
 local len = id:len();              -- get the length of the LCCN

 if 8 == len then
  if id:match("[^%d]") then            -- if LCCN has anything but digits (nil if only digits)
   err_flag = set_message ('err_bad_lccn');       -- set an error message
  end
 elseif 9 == len then              -- LCCN should be adddddddd
  if nil == id:match("%l%d%d%d%d%d%d%d%d") then       -- does it match our pattern?
   err_flag = set_message ('err_bad_lccn');       -- set an error message
  end
 elseif 10 == len then              -- LCCN should be aadddddddd or dddddddddd
  if id:match("[^%d]") then            -- if LCCN has anything but digits (nil if only digits) ...
   if nil == id:match("^%l%l%d%d%d%d%d%d%d%d") then     -- ... see if it matches our pattern
    err_flag = set_message ('err_bad_lccn');      -- no match, set an error message
   end
  end
 elseif 11 == len then              -- LCCN should be aaadddddddd or adddddddddd
  if not (id:match("^%l%l%l%d%d%d%d%d%d%d%d") or id:match("^%l%d%d%d%d%d%d%d%d%d%d")) then -- see if it matches one of our patterns
   err_flag = set_message ('err_bad_lccn');       -- no match, set an error message
  end
 elseif 12 == len then              -- LCCN should be aadddddddddd
  if not id:match("^%l%l%d%d%d%d%d%d%d%d%d%d") then      -- see if it matches our pattern
   err_flag = set_message ('err_bad_lccn');       -- no match, set an error message
  end
 else
  err_flag = set_message ('err_bad_lccn');        -- wrong length, set an error message
 end

 if not is_set (err_flag) and nil ~= lccn:find ('%s') then
  err_flag = set_message ('err_bad_lccn');        -- lccn contains a space, set an error message
 end

 if is_set (err_flag) then
  options.coins_list_t['LCCN'] = nil;          -- when error, unset so not included in COinS
 end

 return external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
   prefix = handler.prefix, id = lccn, separator = handler.separator, encode = handler.encode});
end


--[[--------------------------< M E D R X I V >-----------------------------------------------------------------

Format medRxiv ID and do simple error checking.  Similar to later bioRxiv IDs, medRxiv IDs are prefixed with a
yyyy.mm.dd. date and suffixed with an optional version identifier.  Ealiest date accepted is 2020.01.01

The medRxiv ID is a date followed by an eight-digit number followed by an optional version indicator 'v' and one or more digits:
 https://www.medrxiv.org/content/10.1101/2020.11.16.20232009v2 -> 10.1101/2020.11.16.20232009v2

]]

local function medrxiv (options)
 local id = options.id;
 local handler = options.handler;
 local err_msg_flag = true;             -- flag; assume that there will be an error

 local patterns = {
  '%d%d%d%d%d%d%d%d$',             -- simple 8-digit identifier; these should be relatively rare
  '^10%.1101/(20%d%d)%.(%d%d)%.(%d%d)%.%d%d%d%d%d%d%d%dv%d+$',   -- y.m.d. date + 8-digit identifier + version (2020-01-01 and later)
  '^10%.1101/(20%d%d)%.(%d%d)%.(%d%d)%.%d%d%d%d%d%d%d%d$',    -- y.m.d. date + 8-digit identifier (2020-01-01 and later)
  }
 
 for _, pattern in ipairs (patterns) do          -- spin through the patterns looking for a match
  if id:match (pattern) then
   local y, m, d = id:match (pattern);         -- found a match, attempt to get year, month and date from the identifier

   if m then               -- m is nil when id is the 8-digit form
    if not is_valid_rxiv_date (y, m, d, 'b') then     -- validate the encoded date; 'b' for medrxiv limit
     break;              -- date fail; break out early so we don't unset the error message
    end
   end
   err_msg_flag = nil;             -- we found a match so unset the error message
   break;                -- and done
  end
 end                   -- <err_msg_flag> remains set here when no match

 if err_msg_flag then
  options.coins_list_t['MEDRXIV'] = nil;         -- when error, unset so not included in COinS
  set_message ('err_bad_medrxiv');          -- and set the error message
 end
 
 return external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
   prefix = handler.prefix, id = id, separator = handler.separator,
   encode = handler.encode, access = handler.access});
end


--[[--------------------------< M R >--------------------------------------------------------------------------

A seven digit number; if not seven digits, zero-fill leading digits to make seven digits.

]]

local function mr (options)
 local id = options.id;
 local handler = options.handler;
 local id_num;
 local id_len;

 id_num = id:match ('^[<span class="ltr">Mm</span>][<span class="ltr">Rr</span>](%d+)$');          -- identifier with mr prefix

 if is_set (id_num) then
  set_message ('maint_mr_format');          -- add maint cat
 else                  -- plain number without mr prefix
  id_num = id:match ('^%d+$');           -- if here id is all digits
 end

 id_len = id_num and id_num:len() or 0;
 if (7 >= id_len) and (0 ~= id_len) then
  id = string.rep ('0', 7-id_len) .. id_num;        -- zero-fill leading digits
 else
  set_message ('err_bad_mr');            -- set an error message
  options.coins_list_t['MR'] = nil;          -- when error, unset so not included in COinS
 end
 
 return external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
   prefix = handler.prefix, id = id, separator = handler.separator, encode = handler.encode});
end


--[[--------------------------< O C L C >----------------------------------------------------------------------

Validate and format an OCLC ID.  https://www.oclc.org/batchload/controlnumber.en.html {{dead link}}
archived at: https://web.archive.org/web/20161228233804/https://www.oclc.org/batchload/controlnumber.en.html

]]

local function oclc (options)
 local id = options.id;
 local handler = options.handler;
 local number;

 if id:match('^ocm%d%d%d%d%d%d%d%d$') then         -- ocm prefix and 8 digits; 001 field (12 characters)
  number = id:match('ocm(%d+)');           -- get the number
 elseif id:match('^ocn%d%d%d%d%d%d%d%d%d$') then        -- ocn prefix and 9 digits; 001 field (12 characters)
  number = id:match('ocn(%d+)');           -- get the number
 elseif id:match('^on%d%d%d%d%d%d%d%d%d%d+$') then       -- on prefix and 10 or more digits; 001 field (12 characters)
  number = id:match('^on(%d%d%d%d%d%d%d%d%d%d+)$');      -- get the number
 elseif id:match('^%(OCoLC%)[1-9]%d*$') then         -- (OCoLC) prefix and variable number digits; no leading zeros; 035 field
  number = id:match('%(OCoLC%)([1-9]%d*)');        -- get the number
  if 9 < number:len() then
   number = nil;              -- constrain to 1 to 9 digits; change this when OCLC issues 10-digit numbers
  end
 elseif id:match('^%d+$') then            -- no prefix
  number = id;               -- get the number
  if tonumber (<span class="ltr">id</span>) > handler.id_limit then
   number = nil;              -- unset when id value exceeds the limit
  end
 end

 if number then                -- proper format
  id = number;               -- exclude prefix, if any, from external link
 else
  set_message ('err_bad_oclc')           -- add an error message if the id is malformed
  options.coins_list_t['OCLC'] = nil;          -- when error, unset so not included in COinS
 end
 
 return external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
  prefix = handler.prefix, id = id, separator = handler.separator, encode = handler.encode});
end


--[[--------------------------< O P E N L I B R A R Y >--------------------------------------------------------

Formats an OpenLibrary link, and checks for associated errors.

]]

local function openlibrary (options)
 local id = options.id;
 local access = options.access;
 local handler = options.handler;
 local ident, code = id:gsub('^OL', ''):match("^(%d+([AMW]))$");    -- strip optional OL prefix followed immediately by digits followed by 'A', 'M', or 'W';
 local err_flag;
 local prefix = {               -- these are appended to the handler.prefix according to code
  ['A']='authors/OL',
  ['M']='books/OL',
  ['W']='works/OL',
  ['X']='OL'                -- not a code; spoof when 'code' in id is invalid
  };

 if not ident then
  code = 'X';                -- no code or id completely invalid
  ident = id;                -- copy id to ident so that we display the flawed identifier
  err_flag = set_message ('err_bad_ol');
 end

 if not is_set (err_flag) then
  options.coins_list_t['OL'] = handler.prefix .. prefix[code] .. ident; -- experiment for ol coins
 else
  options.coins_list_t['OL'] = nil;          -- when error, unset so not included in COinS
 end

 return external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
  prefix = handler.prefix .. prefix[code],
  id = ident, separator = handler.separator, encode = handler.encode,
  access = access});
end


--[[--------------------------< O S T I >----------------------------------------------------------------------

Format OSTI and do simple error checking. OSTIs are sequential numbers beginning at 1 and counting up.  This
code checks the OSTI to see that it contains only digits and is less than test_limit specified in the configuration;
the value in test_limit will need to be updated periodically as more OSTIs are issued.

NB. 1018 is the lowest OSTI number found in the wild (so far) and resolving OK on the OSTI site

]]

local function osti (options)
 local id = options.id;
 local access = options.access;
 local handler = options.handler;

 if id:match("[^%d]") then             -- if OSTI has anything but digits
  set_message ('err_bad_osti');           -- set an error message
  options.coins_list_t['OSTI'] = nil;          -- when error, unset so not included in COinS
 else                  -- OSTI is only digits
  local id_num = tonumber (<span class="ltr">id</span>);           -- convert id to a number for range testing
  if 1018 > id_num or handler.id_limit < id_num then      -- if OSTI is outside test limit boundaries
   set_message ('err_bad_osti');          -- set an error message
   options.coins_list_t['OSTI'] = nil;         -- when error, unset so not included in COinS
  end
 end
 
 return external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
   prefix = handler.prefix, id = id, separator = handler.separator, encode = handler.encode, access = access});
end


--[[--------------------------< P M C >------------------------------------------------------------------------

Format a PMC, do simple error checking, and check for embargoed articles.

The embargo parameter takes a date for a value. If the embargo date is in the future the PMC identifier will not
be linked to the article.  If the embargo date is today or in the past, or if it is empty or omitted, then the
PMC identifier is linked to the article through the link at cfg.id_handlers['PMC'].prefix.

PMC embargo date testing is done in function is_embargoed () which is called earlier because when the citation
has |pmc=<value> but does not have a |url= then |title= is linked with the PMC link.  Function is_embargoed ()
returns the embargo date if the PMC article is still embargoed, otherwise it returns an empty string.

PMCs are sequential numbers beginning at 1 and counting up.  This code checks the PMC to see that it contains only digits and is less
than test_limit; the value in local variable test_limit will need to be updated periodically as more PMCs are issued.

]]

local function pmc (options)
 local id = options.id;
 local embargo = options.Embargo;           -- TODO: lowercase?
 local handler = options.handler;
 local err_flag;
 local id_num;
 local text;

 id_num = id:match ('^[<span class="ltr">Pp</span>][<span class="ltr">Mm</span>][<span class="ltr">Cc</span>](%d+)$');         -- identifier with PMC prefix

 if is_set (id_num) then
  set_message ('maint_pmc_format');
 else                  -- plain number without PMC prefix
  id_num = id:match ('^%d+$');           -- if here id is all digits
 end

 if is_set (id_num) then              -- id_num has a value so test it
  id_num = tonumber (id_num);            -- convert id_num to a number for range testing
  if 1 > id_num or handler.id_limit < id_num then       -- if PMC is outside test limit boundaries
   err_flag = set_message ('err_bad_pmc');        -- set an error message
  else
   id = tostring (id_num);            -- make sure id is a string
  end
 else                  -- when id format incorrect
  err_flag = set_message ('err_bad_pmc');         -- set an error message
 end
 
 if is_set (embargo) and is_set (is_embargoed (embargo)) then    -- is PMC is still embargoed?
  text = table.concat (             -- still embargoed so no external link
   {
   make_wikilink (link_label_make (handler), handler.label),
   handler.separator,
   id,
   });
 else
  text = external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect, -- no embargo date or embargo has expired, ok to link to article
   prefix = handler.prefix, id = id, separator = handler.separator, encode = handler.encode, access = handler.access,
   auto_link = not err_flag and 'pmc' or nil       -- do not auto-link when PMC has error
   });
 end

 if err_flag then
  options.coins_list_t['PMC'] = nil;          -- when error, unset so not included in COinS
 end

 return text;
end


--[[--------------------------< P M I D >----------------------------------------------------------------------

Format PMID and do simple error checking.  PMIDs are sequential numbers beginning at 1 and counting up.  This
code checks the PMID to see that it contains only digits and is less than test_limit; the value in local variable
test_limit will need to be updated periodically as more PMIDs are issued.

]]

local function pmid (options)
 local id = options.id;
 local handler = options.handler;

 if id:match("[^%d]") then             -- if PMID has anything but digits
  set_message ('err_bad_pmid');           -- set an error message
  options.coins_list_t['PMID'] = nil;          -- when error, unset so not included in COinS
 else                  -- PMID is only digits
  local id_num = tonumber (<span class="ltr">id</span>);           -- convert id to a number for range testing
  if 1 > id_num or handler.id_limit < id_num then       -- if PMID is outside test limit boundaries
   set_message ('err_bad_pmid');          -- set an error message
   options.coins_list_t['PMID'] = nil;         -- when error, unset so not included in COinS
  end
 end
 
 return external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
   prefix = handler.prefix, id = id, separator = handler.separator, encode = handler.encode});
end


--[[--------------------------< R F C >------------------------------------------------------------------------

Format RFC and do simple error checking. RFCs are sequential numbers beginning at 1 and counting up.  This
code checks the RFC to see that it contains only digits and is less than test_limit specified in the configuration;
the value in test_limit will need to be updated periodically as more RFCs are issued.

An index of all RFCs is here: https://tools.ietf.org/rfc/

]]

local function rfc (options)
 local id = options.id;
 local handler = options.handler;

 if id:match("[^%d]") then             -- if RFC has anything but digits
  set_message ('err_bad_rfc');           -- set an error message
  options.coins_list_t['RFC'] = nil;          -- when error, unset so not included in COinS
 else                  -- RFC is only digits
  local id_num = tonumber (<span class="ltr">id</span>);           -- convert id to a number for range testing
  if 1 > id_num or handler.id_limit < id_num then       -- if RFC is outside test limit boundaries
   set_message ('err_bad_rfc');          -- set an error message
   options.coins_list_t['RFC'] = nil;         -- when error, unset so not included in COinS
  end
 end
 
 return external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
   prefix = handler.prefix, id = id, separator = handler.separator, encode = handler.encode, access = handler.access});
end


--[[--------------------------< S 2 C I D >--------------------------------------------------------------------

Format an S2CID, do simple error checking

S2CIDs are sequential numbers beginning at 1 and counting up.  This code checks the S2CID to see that it is only
digits and is less than test_limit; the value in local variable test_limit will need to be updated periodically
as more S2CIDs are issued.

]]

local function s2cid (options)
 local id = options.id;
 local access = options.access;
 local handler = options.handler;
 local id_num;
 local text;
 
 id_num = id:match ('^[1-9]%d*$');           -- id must be all digits; must not begin with 0; no open access flag

  if is_set (id_num) then              -- id_num has a value so test it
  id_num = tonumber (id_num);            -- convert id_num to a number for range testing
  if handler.id_limit < id_num then          -- if S2CID is outside test limit boundaries
   set_message ('err_bad_s2cid');          -- set an error message
   options.coins_list_t['S2CID'] = nil;        -- when error, unset so not included in COinS
  end
 else                  -- when id format incorrect
  set_message ('err_bad_s2cid');           -- set an error message
  options.coins_list_t['S2CID'] = nil;         -- when error, unset so not included in COinS
 end

 text = external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
  prefix = handler.prefix, id = id, separator = handler.separator, encode = handler.encode, access = access});

 return text;
end


--[[--------------------------< S B N >------------------------------------------------------------------------

9-digit form of ISBN-10; uses same check-digit validation when SBN is prefixed with an additional '0' to make 10 digits

sbn value not made part of COinS metadata because we don't have a url or isn't a COinS-defined identifier (rft.xxx)
or an identifier registered at info-uri.info (info:)

]]

local function sbn (options)
 local id = options.id;
 local ignore_invalid = options.accept;
 local handler = options.handler;
 local function return_result (check, err_type)        -- local function to handle the various returns
  local SBN = internal_link_id ({link = handler.link, label = handler.label, redirect = handler.redirect,
      prefix = handler.prefix, id = id, separator = handler.separator});
  if not ignore_invalid then            -- if not ignoring SBN errors
   if not check then
    options.coins_list_t['SBN'] = nil;        -- when error, unset so not included in COinS; not really necessary here because sbn not made part of COinS
    set_message ('err_bad_sbn', {err_type});      -- display an error message
    return SBN; 
   end
  else
   set_message ('maint_isbn_ignore');         -- add a maint category even when there is no error (ToDo: Possibly switch to separate message for SBNs only)
  end
  return SBN;
 end

 if id:match ('[^%s-0-9X]') then
  return return_result (false, cfg.err_msg_supl.char);     -- fail if SBN contains anything but digits, hyphens, or the uppercase X
 end

 local ident = id:gsub ('[%s-]', '');          -- remove hyphens and whitespace; they interfere with the rest of the tests

 if  9 ~= ident:len() then
  return return_result (false, cfg.err_msg_supl.length);     -- fail if incorrect length
 end

 if ident:match ('^%d*X?$') == nil then
  return return_result (false, cfg.err_msg_supl.form);     -- fail if SBN has 'X' anywhere but last position
 end

 return return_result (is_valid_isxn ('0' .. ident, 10), cfg.err_msg_supl.check);
end


--[[--------------------------< S S R N >----------------------------------------------------------------------

Format an SSRN, do simple error checking

SSRNs are sequential numbers beginning at 100? and counting up.  This code checks the SSRN to see that it is
only digits and is greater than 99 and less than test_limit; the value in local variable test_limit will need
to be updated periodically as more SSRNs are issued.

]]

local function ssrn (options)
 local id = options.id;
 local handler = options.handler;
 local id_num;
 local text;
 
 id_num = id:match ('^%d+$');            -- id must be all digits

 if is_set (id_num) then              -- id_num has a value so test it
  id_num = tonumber (id_num);            -- convert id_num to a number for range testing
  if 100 > id_num or handler.id_limit < id_num then      -- if SSRN is outside test limit boundaries
   set_message ('err_bad_ssrn');          -- set an error message
   options.coins_list_t['SSRN'] = nil;         -- when error, unset so not included in COinS
  end
 else                  -- when id format incorrect
  set_message ('err_bad_ssrn');           -- set an error message
  options.coins_list_t['SSRN'] = nil;          -- when error, unset so not included in COinS
 end
 
 text = external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
  prefix = handler.prefix, id = id, separator = handler.separator, encode = handler.encode, access = options.access});

 return text;
end


--[[--------------------------< U S E N E T _ I D >------------------------------------------------------------

Validate and format a usenet message id.  Simple error checking, looks for 'id-left@id-right' not enclosed in
'<' and/or '>' angle brackets.

]]

local function usenet_id (options)
 local id = options.id;
 local handler = options.handler;

 local text = external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
  prefix = handler.prefix, id = id, separator = handler.separator, encode = handler.encode})
 
 if not id:match('^.+@.+$') or not id:match('^[^<].*[^>]$') then    -- doesn't have '@' or has one or first or last character is '< or '>'
  set_message ('err_bad_usenet_id')          -- add an error message if the message id is invalid
  options.coins_list_t['USENETID'] = nil;         -- when error, unset so not included in COinS
 end 
 
 return text;
end


--[[--------------------------< Z B L >-----------------------------------------------------------------------

A numerical identifier in the form nnnn.nnnnn - leading zeros in the first quartet optional

format described here: http://emis.mi.sanu.ac.rs/ZMATH/zmath/en/help/search/

temporary format is apparently eight digits.  Anything else is an error

]]

local function zbl (options)
 local id = options.id;
 local handler = options.handler;

 if id:match('^%d%d%d%d%d%d%d%d$') then          -- is this identifier using temporary format?
  set_message ('maint_zbl');            -- yes, add maint cat
 elseif not id:match('^%d?%d?%d?%d%.%d%d%d%d%d$') then      -- not temporary, is it normal format?
  set_message ('err_bad_zbl');           -- no, set an error message
  options.coins_list_t['ZBL'] = nil;          -- when error, unset so not included in COinS
 end
 
 return external_link_id ({link = handler.link, label = handler.label, q = handler.q, redirect = handler.redirect,
   prefix = handler.prefix, id = id, separator = handler.separator, encode = handler.encode});
end


--============================<< I N T E R F A C E   F U N C T I O N S >>==========================================

--[[--------------------------< E X T R A C T _ I D S >------------------------------------------------------------

Populates ID table from arguments using configuration settings. Loops through cfg.id_handlers and searches args for
any of the parameters listed in each cfg.id_handlers['...'].parameters.  If found, adds the parameter and value to
the identifier list.  Emits redundant error message if more than one alias exists in args

]]

local function extract_ids (args)
 local id_list = {};               -- list of identifiers found in args
 for k, v in pairs (cfg.id_handlers) do          -- k is uppercase identifier name as index to cfg.id_handlers; e.g. cfg.id_handlers['ISBN'], v is a table
  v = select_one (args, v.parameters, 'err_redundant_parameters' );  -- v.parameters is a table of aliases for k; here we pick one from args if present
  if is_set (<span class="ltr">v</span>) then id_list[<span class="ltr">k</span>] = v; end         -- if found in args, add identifier to our list
 end
 return id_list;
end


--[[--------------------------< E X T R A C T _ I D _ A C C E S S _ L E V E L S >--------------------------------------

Fetches custom id access levels from arguments using configuration settings. Parameters which have a predefined access
level (e.g. arxiv) do not use this function as they are directly rendered as free without using an additional parameter.

returns a table of k/v pairs where k is same as the identifier's key in cfg.id_handlers and v is the assigned (valid) keyword

access-level values must match the case used in cfg.keywords_lists['id-access'] (lowercase unless there is some special reason for something else)

]]

local function extract_id_access_levels (args, id_list)
 local id_accesses_list = {};
 for k, v in pairs (cfg.id_handlers) do
  local access_param = v.custom_access;         -- name of identifier's access-level parameter
  if is_set (access_param) then
   local access_level = args[access_param];       -- get the assigned value if there is one
   if is_set (access_level) then
    if not in_array (access_level, cfg.keywords_lists['id-access']) then -- exact match required
     set_message ('err_invalid_param_val', {access_param, access_level}); 
     access_level = nil;           -- invalid so unset
    end
    if not is_set (id_list[<span class="ltr">k</span>]) then         -- identifier access-level must have a matching identifier
     set_message ('err_param_access_requires_param', {k:lower()}); -- parameter name is uppercase in cfg.id_handlers (<span class="ltr">k</span>); lowercase for error message
    end
    id_accesses_list[<span class="ltr">k</span>] = cfg.keywords_xlate[access_level];   -- get translated keyword
   end
  end
 end
 return id_accesses_list;
end


--[[--------------------------< B U I L D _ I D _ L I S T >----------------------------------------------------

render the identifiers into a sorted sequence table

<ID_list_coins_t> is a table of k/v pairs where k is same as key in cfg.id_handlers and v is the assigned value
<options_t> is a table of various k/v option pairs provided in the call to new_build_id_list();
 modified by this function and passed to all identifier rendering functions
<access_levels_t> is a table of k/v pairs where k is same as key in cfg.id_handlers and v is the assigned value (if valid)

returns a sequence table of sorted (by hkey - 'handler' key) rendered identifier strings

]]

local function build_id_list (ID_list_coins_t, options_t, access_levels_t)
 local ID_list_t = {};
 local accept;
 local func_map = {               --function map points to functions associated with hkey identifier
  ['ARXIV'] = arxiv,
  ['ASIN'] = asin,
  ['BIBCODE'] = bibcode,
  ['BIORXIV'] = biorxiv,
  ['CITESEERX'] = citeseerx,
  ['DOI'] = doi,
  ['EISSN'] = issn,
  ['HDL'] = hdl,
  ['ISBN'] = isbn,
  ['ISMN'] = ismn,
  ['ISSN'] = issn,
  ['JFM'] = jfm,
  ['JSTOR'] = jstor,
  ['LCCN'] = lccn,
  ['MEDRXIV'] = medrxiv,
  ['MR'] = mr,
  ['OCLC'] = oclc,
  ['OL'] = openlibrary,
  ['OSTI'] = osti,
  ['PMC'] = pmc,
  ['PMID'] = pmid,
  ['RFC']  = rfc,
  ['S2CID'] = s2cid,
  ['SBN'] = sbn,
  ['SSRN'] = ssrn,
  ['USENETID'] = usenet_id,
  ['ZBL'] = zbl,
  }

 for hkey, v in pairs (ID_list_coins_t) do
  v, accept = has_accept_as_written (<span class="ltr">v</span>);         -- remove accept-as-written markup if present; accept is boolean true when markup removed; false else
                    -- every function gets the options table with value v and accept boolean
  options_t.hkey = hkey;             -- ~/Configuration handler key
  options_t.id = v;              -- add that identifier value to the options table
  options_t.accept = accept;            -- add the accept boolean flag
  options_t.access = access_levels_t[hkey];        -- add the access level for those that have an |<identifier-access= parameter
  options_t.handler = cfg.id_handlers[hkey];
  options_t.coins_list_t = ID_list_coins_t;        -- pointer to ID_list_coins_t; for |asin= and |ol=; also to keep erroneous values out of the citation's metadata
  options_t.coins_list_t[hkey] = v;          -- id value without accept-as-written markup for metadata
  
  if options_t.handler.access and not in_array (options_t.handler.access, cfg.keywords_lists['id-access']) then
   error (cfg.messages['unknown_ID_access'] .. options_t.handler.access); -- here when handler access key set to a value not listed in list of allowed id access keywords
  end

  if func_map[hkey] then
   local id_text = func_map[hkey] (options_t);       -- call the function to get identifier text and any error message
   table.insert (ID_list_t, {hkey, id_text});       -- add identifier text to the output sequence table
  else
   error (cfg.messages['unknown_ID_key'] .. hkey);      -- here when func_map doesn't have a function for hkey
  end
 end

 local function comp (a, b)             -- used by following table.sort()
  return a[<span class="ltr">1</span>]:lower() < b[<span class="ltr">1</span>]:lower();          -- sort by hkey
 end

 table.sort (ID_list_t, comp);            -- sequence table of tables sort 
 for k, v in ipairs (ID_list_t) do           -- convert sequence table of tables to simple sequence table of strings
  ID_list_t[<span class="ltr">k</span>] = v[<span class="ltr">2</span>];             -- v[<span class="ltr">2</span>] is the identifier rendering from the call to the various functions in func_map{}
 end
 
 return ID_list_t;
end


--[[--------------------------< O P T I O N S _ C H E C K >----------------------------------------------------

check that certain option parameters have their associated identifier parameters with values

<ID_list_coins_t> is a table of k/v pairs where k is same as key in cfg.id_handlers and v is the assigned value
<ID_support_t> is a sequence table of tables created in citation0() where each subtable has four elements:
 [<span class="ltr">1</span>] is the support parameter's assigned value; empty string if not set
 [<span class="ltr">2</span>] is a text string same as key in cfg.id_handlers
 [<span class="ltr">3</span>] is cfg.error_conditions key used to create error message
 [<span class="ltr">4</span>] is original ID support parameter name used to create error message
 
returns nothing; on error emits an appropriate error message

]]

local function options_check (ID_list_coins_t, ID_support_t)
 for _, v in ipairs (ID_support_t) do
  if is_set (v[<span class="ltr">1</span>]) and not ID_list_coins_t[v[<span class="ltr">2</span>]] then      -- when support parameter has a value but matching identifier parameter is missing or empty
   set_message (v[<span class="ltr">3</span>], (v[<span class="ltr">4</span>]));           -- emit the appropriate error message
  end
 end
end


--[[--------------------------< I D E N T I F I E R _ L I S T S _ G E T >--------------------------------------

Creates two identifier lists: a k/v table of identifiers and their values to be used locally and for use in the
COinS metadata, and a sequence table of the rendered identifier strings that will be included in the rendered
citation.

]]

local function identifier_lists_get (args_t, options_t, ID_support_t)
 local ID_list_coins_t = extract_ids (args_t);          -- get a table of identifiers and their values for use locally and for use in COinS
 options_check (ID_list_coins_t, ID_support_t);          -- ID support parameters must have matching identifier parameters 
 local ID_access_levels_t = extract_id_access_levels (args_t, ID_list_coins_t);  -- get a table of identifier access levels
 local ID_list_t = build_id_list (ID_list_coins_t, options_t, ID_access_levels_t); -- get a sequence table of rendered identifier strings

 return ID_list_t, ID_list_coins_t;           -- return the tables
end


--[[--------------------------< S E T _ S E L E C T E D _ M O D U L E S >--------------------------------------

Sets local cfg table and imported functions table to same (live or sandbox) as that used by the other modules.

]]

local function set_selected_modules (cfg_table_ptr, utilities_page_ptr)
 cfg = cfg_table_ptr;

 has_accept_as_written = utilities_page_ptr.has_accept_as_written;   -- import functions from select Module:Citation/CS1/Utilities module
 is_set = utilities_page_ptr.is_set;        
 in_array = utilities_page_ptr.in_array;
 set_message = utilities_page_ptr.set_message;
 select_one = utilities_page_ptr.select_one;
 substitute = utilities_page_ptr.substitute;
 make_wikilink = utilities_page_ptr.make_wikilink;

 z = utilities_page_ptr.z;             -- table of tables in Module:Citation/CS1/Utilities
end


--[[--------------------------< E X P O R T E D   F U N C T I O N S >------------------------------------------
]]

return {
 auto_link_urls = auto_link_urls,           -- table of identifier URLs to be used when auto-linking |title=
 
 identifier_lists_get = identifier_lists_get,        -- experiment to replace individual calls to build_id_list(), extract_ids, extract_id_access_levels
 is_embargoed = is_embargoed;
 set_selected_modules = set_selected_modules;
 }
●