-- This module implements {{Category main article}}.

local mHatnote = require('Module:Hatnote')
local mFormatLink = require('Module:Format link')
local yesno = require('Module:Yesno')
local mTableTools -- lazily initialise
local mArguments -- lazily initialise

local p = {}

-- Helper: true if the page is in Template: or Module: namespace
local function isTemplateOrModule(title)
	local t = (type(title) == 'string' and title) or (title and title.prefixedText) or ''
	if t == '' then
		return false
	end
	local ok, tt = pcall(mw.title.new, t)
	if not ok or not tt then
		return false
	end
	local ns = tt.namespace
	return ns == 10 or ns == 828
end

function p.catMain(frame)
	mTableTools = require('Module:TableTools')
	mArguments = require('Module:Arguments')

	-- Grab args
	local args = mArguments.getArgs(frame, {wrappers = 'Template:Category main article'})
	local pages = mTableTools.compressSparseArray(args)
	if #pages == 0 and args[1] then
		pages = { args[1] }
	end

	local options = {
		article = args.article,
		selfref = args.selfref,
		_rawPages = pages,
	}

	-- Determine the outer page (the page using the template)
	local thisTitle = frame and frame.getParent and frame:getParent() and frame:getParent().title or mw.title.getCurrentTitle()
	local titleText = thisTitle and thisTitle.prefixedText or ''
	local ns = thisTitle and thisTitle.namespace or nil

	-- Skip tracking categories on template/module pages
	local isTemplate = isTemplateOrModule(titleText)

	-- Remember original arg count
	local origCount = #pages

	-- Generate hatnote text
	local text, firstLink, usedAutoFill = p._catMain(options, thisTitle, unpack(pages))

	if isTemplate then
		-- On templates/modules, just return the hatnote (no tracking categories)
		return text
	end

	-- Add tracking categories
	local cats = {}

	-- Wrong namespace detection (Article, Draft)
	if ns == 0 or ns == 118 then
		table.insert(cats, '[[Category:Articles using category hatnotes]]')
	end

	-- Title mismatch detection
	if firstLink and (origCount == 1 or (origCount == 0 and usedAutoFill)) then
		local function normalizeTitle(s)
			return (s or ''):gsub('^%s+', ''):gsub('%s+$', ''):gsub('^[^:]*:', ''):gsub('%s+', ' '):gsub('^%l', string.upper):gsub('^[lL]ist%sof%s+', '')
		end
		local compareStr
		if usedAutoFill then
			compareStr = normalizeTitle(firstLink)
		else
			local raw = (options._rawPages and options._rawPages[1]) or firstLink
			compareStr = normalizeTitle(raw:gsub("|.*", ""))
		end
		local catName = normalizeTitle(thisTitle and thisTitle.text or '')
		if compareStr ~= catName then
			table.insert(cats, '[[Category:Category main article does not match category title]]')
		end
	end

	if #cats > 0 then
		text = text .. '\n' .. table.concat(cats, '\n')
	end

	return text
end

function p._catMain(options, thisTitle, ...)
	options = options or {}
	local pages = {...}

	thisTitle = thisTitle or mw.title.getCurrentTitle()
	local fullTitle = thisTitle and thisTitle.prefixedText or ''
	local thisText = thisTitle and thisTitle.text or (pages[1] or '')

	local isTemplate = isTemplateOrModule(fullTitle)

	-- Red link detection
	local rawLinks = mFormatLink.formatPages({
		categorizeMissing = not isTemplate and 'Categories with hatnote templates targeting a non-existent page' or nil
	}, pages)

	-- Convert to plain strings
	local links = {}
	for i, link in ipairs(rawLinks or {}) do
		links[i] = tostring(link)
	end

	-- Auto-fill if empty
	local firstOutputLink = nil
	local usedAutoFill = false

	if not links[1] or links[1] == '' then
		local title = mw.title.new(thisText)
		if title and title.isRedirect then
			title = title.redirectTarget
		end
		firstOutputLink = title and title.text or thisText
		usedAutoFill = true
		links[1] = tostring(mFormatLink._formatLink{
			link = firstOutputLink,
			categorizeMissing = not isTemplate and 'Categories with hatnote templates targeting a non-existent page' or nil
		})
		pages = { firstOutputLink }
	else
		local visible = links[1]
		visible = visible:gsub("^'''", ""):gsub("'''$", "")
		visible = visible:gsub("%[%[", ""):gsub("%]%]", "")
		visible = visible:gsub("|.*$", "")
		visible = visible:gsub("#.*$", "")
		firstOutputLink = visible
		usedAutoFill = false
	end

	-- Bold links
	for i, link in ipairs(links) do
		links[i] = string.format("'''%s'''", link)
	end

	-- Determine pagetype
	local pagetype
	if options.article ~= nil then
		pagetype = yesno(options.article) ~= false and 'article' or 'page'
	elseif pages and pages[1] then
		local page = pages[1]:gsub("|.*","")
		local tt = mw.title.new(page)
		pagetype = tt and tt.namespace == 0 and "article" or "page"
	else
		pagetype = "article"
	end

	-- Work out whether we need to be singular or plural
	local stringToFormat
	if #links > 1 then
		stringToFormat = 'The main %ss for this [[Help:Categories|category]] are %s.'
	else
		stringToFormat = 'The main %s for this [[Help:Categories|category]] is %s.'
	end

	-- Build hatnote text
	local text = string.format(
		stringToFormat,
		pagetype,
		mw.text.listToText(links)
	)

	-- Pass through Module:Hatnote
	local hnOptions = { selfref = options.selfref }
	text = mHatnote._hatnote(text, hnOptions)

	return text, firstOutputLink, usedAutoFill
end

return p