Editing Module:Infobox television season name

require('strict')
local match = require("Module:String")._match

local p = {}

--- Returns a formatted link to the list of episodes article.
--- @param listOfEpisodesArticle string
--- @return string
local function getListOfEpisodesLink(listOfEpisodesArticle)
	local listOfEpisodesPage = mw.title.new(listOfEpisodesArticle, 0)
	if listOfEpisodesPage and listOfEpisodesPage.exists and listOfEpisodesPage.redirectTarget ~= mw.title.getCurrentTitle() then
		return string.format("[[%s|List of episodes]]", listOfEpisodesArticle)
	end
end

--- Returns an article link.
--- @param article string The article's title.
--- @param pipedLink string The piped link.
--- @return string
local function getArticleLink(article, pipedLink)
	if not pipedLink or pipedLink == "" then
		return "[[" .. article .. "]]"
	end
	return "[[" .. article .. "|" .. pipedLink .. "]]"
end

--- Returns the show name and season number from a title.
--- @param showName string The show's title.
--- @return nil | number | string, nil | number | string
local function getShowNameAndSeasonNumberFromShowName(showName)
	local _, _, showNameModified, seasonNumber = string.find(showName, "(.*)%s+(%d+)$")
	return showNameModified, seasonNumber
end

--- Returns the current season number from the disambiguation.
--- @param disambiguation string The article's disambiguation.
--- @return string
local function getCurrentSeasonNumberFromDisambiguation(disambiguation)
	return match(disambiguation , "%d+", 1, -1, false, "")
end

--- Returns the type of word used for "season" in the title.
---
--- The returned value can be one of three options: "season", "series", "story arc" or "specials".
--- @param title string The article's title.
--- @return string
local function getSeasonType(title)
	for _, seasonType in pairs({"season", "series", "story arc", "specials"}) do
		if string.find(title, seasonType) then
			return seasonType
		end
	end
	return "season"
end

--- Returns the season number from the title.
--- @param title string The article's title.
--- @return string | nil
local function getSeasonNumber(title)
	return match(title , "%d+", 1, -1, false, "")
end

--- Returns the disambiguation from the title.
--- @param title string The article's title.
--- @return string | nil
local function getDisambiguation(title)
	local disambiguation = match(title, "%s%((.-)%)", 1, -1, false, "")
	if disambiguation and disambiguation == "" then
		return nil
	end
	return disambiguation
end

--- Returns the title without its disambiguation.
--- @param title string The article's title.
--- @return string | nil
local function getTitleWithoutDisambiguation(title)
	local disambiguation = getDisambiguation(title)
	if disambiguation then
		return string.gsub(title, "%(" .. disambiguation  .. "%)", "")
	end
	return title
end

--- Returns the TV program's disambiguation.
--- @param disambiguation string The disambiguation used in the season's article title.
--- @return string
local function getTVProgramDisambiguation(disambiguation)
	if not disambiguation then
		return ""
	end

	-- Check if the disambiguation is normal 'season #' or 'series #'.
	-- If so, remove disambiguation.
	if string.match(disambiguation, "^season %d*$") or string.match(disambiguation, "^series %d*$") then
		return ""
	end

	local disambiguationStyle = " (%s)"
	-- Check if the disambiguation is extended and has 'TV series' and isn't just season #.
	-- Only leave the TV series disambiguation, not including the season #.
	-- Example: Teenage Mutant Ninja Turtles (1987 TV series, season 5) will return '1987 TV series'.
	if string.find(disambiguation, "TV series") then
		local shortDisambiguation, _ = disambiguation:match("^(.*),")
		if shortDisambiguation then
			return string.format(disambiguationStyle, shortDisambiguation)
		end
	end

	-- Check if the disambiguation is extended with country adjective.
	-- Example: The Office (American season 2) will return "American season 2".
	-- Keep only country adjective.
	local countryDisambiguation = disambiguation:match("^(.*) season %d*") or disambiguation:match("^(.*) series %d*")
	local data = mw.loadData("Module:Country adjective")
	local valid_result = data.getCountryFromAdj[countryDisambiguation]
	-- Check if the country adjective is valid.
	if valid_result then
		-- Add 'TV series' suffix
		return string.format(disambiguationStyle, countryDisambiguation .. " TV series")
	end

	-- Not a known disambiguation style. Use whatever was used in the title or manually added.
	-- Note: might not be a valid style link.
	return string.format(disambiguationStyle, disambiguation)
end

--- Returns the show's name from the title.
--- @param title string The article's title.
--- @return string
local function getShowName(title)
	local name, _ = mw.ustring.gsub(title, "season %d*$", "")
	name, _ = mw.ustring.gsub(name, "series %d*$", "")
	name, _ = mw.ustring.gsub(name, "specials", "")
	name, _ = mw.ustring.gsub(name, "story arc %d*$", "")
	name = string.match(name, "^%s*(.-)%s*$") -- Trim spaces.
	return name
end

--- Returns "true" if the given link is valid; nil otherwise.
--- A link is valid in the following cases:
---	-- A season article exists.
---	-- A redirect exists to a season section.
---
--- A link is invalid in the following cases:
---	-- A season article or redirect do not exist.
---	-- A redirect exists, but it is a general redirect and not for any specific season section.
---
--- Note: Return values are not booleans as the returned value is used in template space.
--- @param title string The article's title.
--- @return string | nil
local function isLinkValid(title)
	local article = mw.title.new(title)

	-- Article or redirect do not exist; Not a valid link.
	if not article or not article.exists then
		return nil
	end

	local redirectTarget = article.redirectTarget

	-- Article exists and is not a redirect; Valid link.
	if not redirectTarget then
		return "true"
	end

	local fullLink = redirectTarget.fullText
	local isSection = fullLink:find("#")

	-- Article is a section redirect; Valid link.
	if isSection then
		return "true"
	end

	-- Article is a general redirect; Not a valid link.
	return nil
end

--- Returns a season article title and a piped link.
---
--- The following are the supported season naming styles:
---	--  Style: <showName> <seasonType> <seasonNumber>
---		Example: Lost season 2.
---		Example: Doctor Who series 2.
---	--  Style: <showName> (<country> TV series) <seasonType> <seasonNumber>
---		Example: The Office (American TV series) season 2.
---		Example: Teenage Mutant Ninja Turtles (1987 TV series) season 2
---		Example: X Factor (British TV series) series 2.
---		Example: Love Island (British TV series) series 2
---	--  Style: <showName> (<year> TV series) <seasonType> <seasonNumber>
---		Example: Love Island (2015 TV series) series 2
---	--  Style: <showName> (<country> <seasonType>)
---		Example: Big Brother 2 (American season).

--- @param title string The article's title.
--- @param seasonNumberDiff number The number difference between the current season and the other season.
--- @return string, string
local function getArticleTitleAndPipedLink(title, seasonNumberDiff)
	local seasonType = getSeasonType(title)
	local currentSeasonNumber = getSeasonNumber(title)
	if tonumber(currentSeasonNumber) == nil then
		return "", nil
	end
	local seasonNumber = currentSeasonNumber + seasonNumberDiff
	local modifiedTitle, numberOfReplacements = string.gsub(title, "%d+$", seasonNumber)
	local pipedLink = seasonType:gsub("^%l", string.upper) .. " " .. seasonNumber

	local disambiguation = getDisambiguation(title)
	-- Titles such as "Big Brother 2 (American season) and Teenage Mutant Ninja Turtles (1987 TV series) season 2".
	if disambiguation then
		local titleWithoutDisambiguation = string.gsub(title, disambiguation, "_DAB_")
		modifiedTitle, numberOfReplacements = string.gsub(titleWithoutDisambiguation, "%d+", seasonNumber)

		 -- Articles, such as "Hawaii Five-0 (2010 TV series) season 2", that have a number
		 -- as part of their title will need an additional fix in order for that number not to change.
		if numberOfReplacements > 1 then
			local titleFix = string.match(title, "%d+", 1)
			modifiedTitle = string.gsub(modifiedTitle, "%d+", titleFix, 1)
		end
	
		modifiedTitle = string.gsub(modifiedTitle, "_DAB_", disambiguation)
		return modifiedTitle, pipedLink

	-- Titles such as "Big Brother Brasil 2".
	elseif not string.find(title, seasonType) then
		return modifiedTitle, nil

	-- Invalid usages of TV series articles with the television season infobox.
	elseif disambiguation and string.find(disambiguation, "TV series") and not (string.find(disambiguation, ", season") or string.find(disambiguation, ", series"))  then
		return "", nil

	-- Standard titles such as "Lost season 1".
	else
		return modifiedTitle, pipedLink
	end
end

--- Returns the article's title either from args (usually from /testcases) or from the page itself.
--- @param frame table The frame invoking the module.
--- @return string
local function getTitle(frame)
	local getArgs = require("Module:Arguments").getArgs
	local args = getArgs(frame)
	if args.italic_title then
		return "no"
	end
	
	local title = args.title
	if not title then
		title = mw.title.getCurrentTitle().text
	end
	return title
end

--- Returns "true" if the given season link is valid; nil otherwise.
--- @param frame table The frame invoking the module.
--- @param seasonNumberDiff number The number difference between the current season and the other season.
--- @return string | nil
local function isSeasonLinkValid(frame, seasonNumberDiff)
	local title = getTitle(frame)
	local articleTitle, _ = getArticleTitleAndPipedLink(title, seasonNumberDiff)
	return isLinkValid(articleTitle)
end

--- Returns a season article link.
--- @param frame table The frame invoking the module.
--- @param seasonNumberDiff number The number difference between the current season and the other season.
--- @return string
local function getSeasonArticleLink(frame, seasonNumberDiff)
	local title = getTitle(frame)
	local articleTitle, pipedLink = getArticleTitleAndPipedLink(title, seasonNumberDiff)
	return getArticleLink(articleTitle, pipedLink)
end

--- Returns "true" if the season link for the next season is valid; nil otherwise.
--- @param frame table The frame invoking the module.
--- @return string | nil
function p.isNextSeasonLinkValid(frame)
	return isSeasonLinkValid(frame, 1)
end

--- Returns "true" if the season link for the previous season is valid; nil otherwise.
--- @param frame table The frame invoking the module.
--- @return string | nil
function p.isPrevSeasonLinkValid(frame)
	return isSeasonLinkValid(frame, -1)
end

--- Returns "true" if the season link for the previous or next season is valid; nil otherwise.
--- @param frame table The frame invoking the module.
--- @return string | nil
function p.isPrevOrNextSeasonLinkValid(frame)
	if p.isPrevSeasonLinkValid(frame) == "true" then
		return "true"
	end
	return p.isNextSeasonLinkValid(frame)
end

--- Returns the next season article title.
--- @param frame table The frame invoking the module.
--- @return string
function p.getNextSeasonArticle(frame)
	return getSeasonArticleLink(frame, 1)
end

--- Returns the previous season article title.
--- @param frame table The frame invoking the module.
--- @return string
function p.getPrevSeasonArticle(frame)
	return getSeasonArticleLink(frame, -1)
end

--- Returns the type of season word used - "season" or "series".
--- @param frame table The frame invoking the module.
--- @return string
function p.getSeasonWord(frame)
	local title = getTitle(frame)
	title = getTitleWithoutDisambiguation(title)
	local seasonType = getSeasonType(title)
	return seasonType
end

--- Returns an {{Italic title}} instance if title qualifies or a blank string.

--- @param frame table
--- @return string
function p.getItalicTitle(frame)
	local getArgs = require("Module:Arguments").getArgs
	local args = getArgs(frame)
	
	-- If italic_title is set then "no" is the only valid value.
	-- Don't set an italic title.
	if args.italic_title then
		return ""
	end

	local title = getTitle(frame)
	title = getShowName(getTitleWithoutDisambiguation(title))

	-- If the infobox is used on List of articles don't set an italic title.
	-- TODO: this can be fixed in the future but current usages use a manual display title.
	if string.find(title, "List of") then
		return ""
	end

	return frame:expandTemplate{title = "Italic title", args = {string = title}}
end

--- Returns the text used for the |above= field of the infobox.
---
--- @param frame table
--- @return string
function p.getAboveTitle(frame)
	local getArgs = require("Module:Arguments").getArgs
	local args = getArgs(frame)
	local title = getTitle(frame)
	title = getShowName(getTitleWithoutDisambiguation(title))
	return title
end

--- Returns the text used for the |subheader= field of the infobox.
---
--- The text is returned in the format of "Season #" or "Series #",
--- depending on either what the article disambiguation uses, or on the manually entered parameters of the infobox.
--- @param frame table The frame invoking the module.
--- @return string | nil
function p.getSubHeader(frame)
	local getArgs = require("Module:Arguments").getArgs
	local args = getArgs(frame)

	local seasonType
	local seasonNumber
	if args.season_number then
		seasonType = "Season"
		seasonNumber = args.season_number
	elseif args.series_number then
		seasonType = "Series"
		seasonNumber = args.series_number
	end

	if not seasonNumber then
		local title = getTitle(frame)
		local titleWithoutDisambiguation = getTitleWithoutDisambiguation(title)
		seasonNumber = getSeasonNumber(titleWithoutDisambiguation)
		seasonType = getSeasonType(titleWithoutDisambiguation)
		
		-- For pages like "Doctor Who specials (2008–2010)".
		if seasonType == "specials" then
			local disambiguation = getDisambiguation(title) or ""
			return disambiguation .. " " .. seasonType
		end
		seasonType = seasonType:sub(1, 1):upper() .. seasonType:sub(2)
	end

	if seasonNumber and seasonNumber ~= "" then
		return seasonType .. " " .. seasonNumber
	end

	return nil
end

--- Returns a formatted link to the list of episodes article.
---
--- The returned link is in the style of:
--- [List of <series name> <disambiguation, if present> episodes <range, if present>|List of episodes]
---
--- The link will only return if the page exists.
--- @param frame table The frame invoking the module.
--- @return string | nil
function p.getListOfEpisodes(frame)
	local getArgs = require("Module:Arguments").getArgs
	local args = getArgs(frame)

	if args.link then
		-- Parameter should be unformatted.
		if string.find(args.link, "%[") then
			local delink = require("Module:Delink")._delink
			args.link = delink({args.link, wikilinks = "target"})
		end

		return getListOfEpisodesLink(args.link)
	end

	local title = getTitle(frame)
	local showName = getShowName(getTitleWithoutDisambiguation(title))
	if showName then
		local disambiguation = getDisambiguation(title)
		if disambiguation then
			disambiguation = " (" .. disambiguation .. ")"
		end
		local listOfEpisodesArticle = string.format("List of %s%s episodes", showName, disambiguation or "")
		return getListOfEpisodesLink(listOfEpisodesArticle)
	end
end

return p