Module:Check isxn

--[[

This code is derived from the ISXN validation code at Module:Citation/CS1.  It allows validating ISBN,
ISMN, and ISSN without invoking a citation template.

]]

local p = {}


--[[--------------------------< E R R _ M S G _ S U P L _ T >--------------------------------------------------

error message supplements for check_isbn(); adapted from a similarly named table at Module:Citation/CS1/Configuration

]]

local err_msg_supl_t = {
 ['char'] = 'invalid character',
 ['check'] = 'checksum',
 ['form'] = 'invalid form',
 ['group'] = 'invalid group id',
 ['length'] = 'length',
 ['prefix'] = 'invalid prefix',
 }


--[[--------------------------< 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 check_isbn().
If the number is valid the result will be 0. Before calling this function, issbn/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(v) )*(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(v) );    -- 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


--[[--------------------------< C H E C K _ I S B N >------------------------------------------------------------

Determines whether an ISBN string is valid.  Implements an ISBN validity check for {{ISBN}}, {{ISBNT}}, {{SBN}}, and
{{Format ISBN}}.

]]

local function check_isbn (isbn_str, frame)
 local function return_result (check, err_type)        -- local function to render the various error returns
  if not check then              -- <check> false when there is an error
   local template = ((frame.args.template_name and '' ~= frame.args.template_name) and frame.args.template_name) or nil; -- get template name
   if not template then
    return '<span class="error" style="font-size:100%">&nbsp;calling template requires template_name parameter</span>';
   end

   local out_t = {'<span class="error" style="font-size:100%">'};  -- open the error message span
   table.insert (out_t, '&nbsp;Parameter error in {{[[Template:');  -- open 'template' markup; open wikilink with Template namespace
   table.insert (out_t, template);          -- template name wikilink
   table.insert (out_t, '|');           -- its pipe
   table.insert (out_t, template);          -- wikilink label
   table.insert (out_t, ']]}}:&nbsp;');        -- close wikilink; close 'template' markup
   table.insert (out_t, err_type);          -- type of isbn error
   table.insert (out_t, '</span>')          -- close the error message span
   if 0 == mw.title.getCurrentTitle().namespace then     -- categorize only when this template is used in mainspace
    local category = table.concat ({'[[Category:Pages with ISBN errors]]'});
    table.insert (out_t, category);
   end
   return table.concat (out_t);          -- make a big string and done
  end
 return '';                 -- no error, return an empty string
 end

 if nil ~= isbn_str:match ('[^%s-0-9X]') then
  return return_result (false, err_msg_supl_t.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, err_msg_supl_t.length);     -- fail if incorrect length
 end

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


--[[--------------------------< C H E C K _ I S M N >------------------------------------------------------------

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

]]

local function check_ismn (id, error_string)
 local text;
 local valid_ismn = true;

 id=id:gsub( "[%s-–]", "" );             -- strip spaces, hyphens, and endashes from the ismn

 if 13 ~= id:len() or id:match( "^9790%d*$" ) == nil then     -- ismn must be 13 digits and begin 9790
  valid_ismn = false;
 else
  valid_ismn=is_valid_isxn_13 (id);          -- validate ismn
 end

 return valid_ismn and '' or error_string
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: [http://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.

]]

local function check_issn(id, error_string)
 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;

 if not id:match ('^%d%d%d%d%-%d%d%d[%dX]$') then
  return error_string;
 end
 
 id=id:gsub( "[%s-–]", "" );         -- strip spaces, hyphens, and endashes from the issn

 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

 return valid_issn and '' or error_string
end


------------------------------< E N T R Y   P O I N T S >--------------------------------------------------====

function p.check_isbn(frame)
 return check_isbn(frame.args[1] or frame:getParent().args[1], frame)
end

function p.check_ismn(frame)
 return check_ismn(frame.args[1] or frame:getParent().args[1], frame.args['error'] or frame:getParent().args['error'] or 'error')
end

function p.check_issn(frame)
 return check_issn(frame.args[1] or frame:getParent().args[1], frame.args['error'] or frame:getParent().args['error'] or 'error')
end

return p