Module:Section link

-- This module implements {{section link}}.
require('strict');

local checkType = require('libraryUtil').checkType

local p = {}

local function makeSectionLink(page, section, display)
 display = display or section
 page = page or ''
 -- MediaWiki doesn't allow these in 'page', so only need to do for 'section'
 if type(section) == 'string' then
  section = string.gsub(section, "{", "{")
  section = string.gsub(section, "}", "}")
 end
 return string.format('[[%s#%s|%s]]', page, section, display)
end

local function normalizeTitle(title)
 title = mw.ustring.gsub(mw.ustring.gsub(title, "'", ""), '"', '')
 title = mw.ustring.gsub(title, "%b<>", "")
 return mw.title.new(title).prefixedText
end

function p._main(page, sections, options, title)
 -- Validate input.
 checkType('_main', 1, page, 'string', true)
 checkType('_main', 3, options, 'table', true)
 if sections == nil then
  sections = {}
 elseif type(sections) == 'string' then
  sections = {sections}
 elseif type(sections) ~= 'table' then
  error(string.format(
   "type error in argument #2 to '_main' " ..
   "(string, table or nil expected, got %s)",
   type(sections)
  ), 2)
 end
 options = options or {}
 title = title or mw.title.getCurrentTitle()

 -- Deal with blank page names elegantly
 if page and not page:find('%S') then
  page = nil
  options.nopage = true
 end

 -- Make the link(s).
 local isShowingPage = not options.nopage
 if #sections <= 1 then
  local linkPage = page or ''
  if options.permalink then            -- when oldid provided
   linkPage = 'Special:Permalink/' .. options.permalink;    -- make Special:Permalink/oldid wikilink
  end
  local section = sections[1];           -- sections[1] must have a value
  local display = '§&nbsp;' .. section
  if isShowingPage then
   page = page or title.prefixedText
   if options.display and options.display ~= '' then
    if normalizeTitle(options.display) == normalizeTitle(page) then
     display = options.display .. ' ' .. display
    else
     error(string.format(
      'Display title "%s" was ignored since it is ' ..
      "not equivalent to the page's actual title",
      options.display
     ), 0)
    end
   else
    display = page .. ' ' .. display
   end
  end
  return makeSectionLink(linkPage, section, display)
 else
  -- Multiple sections. First, make a list of the links to display.
  local ret = {}
  for i, section in ipairs(sections) do
   ret[i] = makeSectionLink(page, section)
  end

  -- Assemble the list of links into a string with mw.text.listToText.
  -- We use the default separator for mw.text.listToText, but a custom
  -- conjunction. There is also a special case conjunction if we only
  -- have two links.
  local conjunction
  if #sections == 2 then
   conjunction = '&#8203; and '
  else
   conjunction = ', and '
  end
  ret = mw.text.listToText(ret, nil, conjunction)

  -- Add the intro text.
  local intro = '§§&nbsp;'
  if isShowingPage then
   intro = (page or title.prefixedText) .. ' ' .. intro
  end
  ret = intro .. ret

  return ret
 end
end

function p.main(frame)
 local yesno = require('Module:Yesno')
 local args = require('Module:Arguments').getArgs(frame, {
  wrappers = 'Template:Section link',
  valueFunc = function (key, value)
   value = value:match('^%s*(.-)%s*$') -- Trim whitespace
   -- Allow blank first parameters, as the wikitext template does this.
   if value ~= '' or key == 1 then
    return value
   end
  end
 })

 for k, v in pairs(args) do             -- replace underscores in the positional parameter values
  if 'number' == type(k) then
   if not yesno (args['keep-underscores']) then      -- unless |keep-underscores=yes
    args[k] = mw.uri.decode (v, 'WIKI');       -- percent-decode; replace underscores with space characters
   else
    args[k] = mw.uri.decode (v, 'PATH');       -- percent-decode; retain underscores
   end
  end
 end

 -- Sort the arguments.
 local page
 local sections, options = {}, {}
 for k, v in pairs(args) do
  if k == 1 then
   -- Doing this in the loop because of a bug in [[Module:Arguments]]
   -- when using pairs with deleted arguments.
   page = mw.text.decode(v, true)
  elseif type(k) == 'number' then
   sections[k] = v
  else
   options[k] = v
  end
 end

 options.nopage = yesno (options.nopage);         -- make boolean
 
 -- Extract section from page, if present
 if page then
  local p, s = page:match('^(.-)#(.*)$')
  if p then page, sections[1] = p, s end
 end

 -- Compress the sections array.
 local function compressArray(t)
  local nums, ret = {}, {}
  for num in pairs(t) do
   nums[#nums + 1] = num
  end
  table.sort(nums)
  for i, num in ipairs(nums) do
   ret[i] = t[num]
  end
  return ret
 end
 sections = compressArray(sections)

 if not sections[1] then              -- empty section parameter makes {{Section link}} meaningless
  return ('<span style="color:#d33"><span style="font-family:monospace">{{[[Template:Section link|Section link]]}}</span>: required section parameter(s) missing</span>'); -- emit error message and abandon
 end

 return p._main(page, sections, options)
end

return p