local getArgs = require('Module:Arguments').getArgs
local randomModule = require('Module:Random')
local yesno = require('Module:Yesno')
local slideshowModule = require('Module:Random slideshow')

p = {}

-- == Utility functions ==
local function getCleanArgs(frame)
	return getArgs(frame, {
		trim = true,
		removeBlanks = true
	})
end

local function wikiError(message)
	return mw.doc.create('div'):addClass('error'):wikitext(message)
end

-- replace all newlines in the string with break tags
-- slideshow only supports single line captions
local function replaceNewlines(s)
	return mw.ustring.gsub(s, '%c', '<br />')
end

-- == Argument preparation functions ==
-- Extracts dates, custom images, and subpages from args
local function extractPictures(args)
	local dates = {}
	local images = {}
	local subpages = {}
	for key, value in pairs(args) do
		if value then
			if type(key) == "number" then
				-- positional parameters correspond to POTD dates
				table.insert(dates, value)
			elseif string.sub(key, 1, 1) == "i" then
				-- named parameters with prefixes "i", "title", "credit", and "caption"
				-- correspond to custom images
				local num = string.sub(key, 2)
				local title = args["title" .. num]
				local credit = args["credit" .. num]
				local caption = args["caption" .. num] or ""
				local image = {
					file = value,
					title = title,
					credit = credit,
					caption = caption
				}
				table.insert(images, image)
			end
		end
	end
	local subpageMax = tonumber(args['subpagemax']) or 0
	if subpageMax > 0
	then
		local root = args['demoroot'] or (mw.title.getCurrentTitle().rootPageTitle.prefixedText)
		local picturesRoot = root .. '/' .. (args['subpage'] or 'Selected picture')
		for i = 1, subpageMax do
			table.insert(subpages, picturesRoot .. '/' .. tostring(i))
		end
	end
	return dates, images, subpages
end

local function getDefaultMoreLink(args)
	local root = args['demoroot'] or (mw.title.getCurrentTitle().rootPageTitle.prefixedText)
	local picturesPage = args['subpage'] or 'Selected picture'
	return "[[" .. root .. "/" .. picturesPage .. "|More selected pictures]]"
end

-- == Formatting functions ==
-- transclude [[Template:Portal POTD]]
local function formatPortalPotd(frame, potdDate)
	return frame:expandTemplate{
		title = "Portal POTD",
		args = {
			potdDate,
			more = 'no'
		}
	}
end

local function formatMoreHtml(more)
	if not yesno(more, true)
	then
		return ""
	end
	local moreHtml = mw.doc.create('div')
		:attr("class", "noprint")
		:attr("style", "margin-top:0.5em; font-weight:bold; width:100%; text-align:right;")
		:wikitext(more)
	return tostring(moreHtml)
end

-- manual recreation of the bottom half of [[Template:Portal POTD]]
local function formatPotdText(frame, titleText, creditText, captionText, moreHtml)
	local res = frame:expandTemplate{
		title = "POTD portal layout/text",
		args = {
			title = titleText,
			credit = creditText,
			caption = captionText,
			['margin-top']='0.5em'
		}
	}
	if moreHtml
	then
		-- ideally, the "more" text should be trancluded _once_ for the whole box
		-- but we do it for _every_ image for compatibility with portals, which use numbered subpages
		res = res .. moreHtml
	end
	return res
end

local function formatFile(filename)
	local doc = mw.doc.create('div')
		:attr("class", "center")
		:wikitext("[[File:" .. filename .. "|380px]]")
	return tostring(doc)
end

-- Extract value named "paramName" from a subpage of [[Template:POTD]]
local function getPotdPart(frame, potdSubpage, paramName)
	return frame:expandTemplate{
		title = potdSubpage,
		args = { paramName }
	}
end

-- bottom half of [[Template:Portal POTD]] for a POTD subpage
local function getPotdText(frame, potdDate, moreHtml)
	local potdText = getPotdPart(frame, "POTD/" .. potdDate, "portal layout/text")
	potdText = replaceNewlines(potdText)
	if moreHtml
	then
		potdText = potdText .. moreHtml
	end
	return potdText
end

-- prepare arguments for [[Module:Random slideshow]]
-- alternating: image1, text1, image2, text2, ...
local function makeSlideShowArgs(frame, dates, images, subpages, more, limit)
	local slideShowArgs = {}
	local moreHtml = formatMoreHtml(more)
	if #dates > 0 then
		local randomDates = randomModule.main('array', {t=dates, limit=limit})
		for _, potdDate in ipairs(randomDates) do
			local image = getPotdPart(frame, "POTD/" .. potdDate, "image")
			local image2 = ''
			if image == '{{{image}}}' then
				image = getPotdPart(frame, "POTD/" .. potdDate, "image1")
				image2 = '[[File:' .. getPotdPart(frame, "POTD/" .. potdDate, "image2") .. '|200px|center]]'
			end
			local text = image2 .. getPotdText(frame, potdDate, moreHtml)
			table.insert(slideShowArgs, image)
			table.insert(slideShowArgs, text)
		end
	end
	if #images > 0 then
		local randomImages = randomModule.main('array', {t=images, limit=limit})
		for _, image in pairs(randomImages) do
			table.insert(slideShowArgs, image['file'])
			local text = formatPotdText(frame, image['title'], image['credit'], image['caption'], moreHtml)
			table.insert(slideShowArgs, text)
		end
	end
	if #subpages > 0 then
		local randomSubpages = randomModule.main('array', {t=subpages, limit=math.floor(limit / 2)})
		for _, subpage in pairs(randomSubpages) do
			table.insert(slideShowArgs, 'Blank.png')
			local subpageContent = replaceNewlines(frame:expandTemplate{ title = subpage })
			table.insert(slideShowArgs, subpageContent)
		end
	end
	return slideShowArgs
end

-- == Main functions ==
-- Create a list gallery of all passed images
local function gallery(frame)
	local args = getCleanArgs(frame)
	local dates, images, subpages = extractPictures(args)
	local texts = {}

	for _, value in pairs(dates) do
		local topText = '<span id="Template:POTD/' .. value .. '"></span>' .. "[[Template:POTD/" .. value .. "]]\n\n"
		table.insert(texts,	topText .. formatPortalPotd(frame, value))
	end
	for _, image in pairs(images) do
		local topText = "[[:File:" .. image['file'] .. "]]\n\n"
		local bottomText = formatPotdText(frame, image['title'], image['credit'], image['caption'])
		table.insert(texts, topText .. formatFile(image['file']) .. "\n\n" .. bottomText)
	end
	for _, subpage in pairs(subpages) do
		local topText = "[[:" .. subpage .. "]]\n\n"
		local subpageContent = frame:expandTemplate{ title = subpage }
		table.insert(texts, topText .. subpageContent)
	end
	return frame:preprocess(table.concat(texts, "\n----\n"))
end

-- Create a slideshow of passed images using [[Module:Random slideshow]]
local function slideShow(frame)
	local args = getCleanArgs(frame)
	local more = args["more"] or getDefaultMoreLink(args)
	local dates, images, subpages = extractPictures(args)
	local limit = 15

	local slideShowArgs = makeSlideShowArgs(frame, dates, images, subpages, more, limit)

	local slideShow = slideshowModule._main(slideShowArgs, false, 'portalSlideshow-container')
	return frame:extensionTag{ name='templatestyles', args = { src='Module:Random slideshow/styles.css'} } .. frame:preprocess(slideShow)
end

-- entry point for the module
function main(frame)
	local title = mw.title.getCurrentTitle()
	if title.isSubpage
	then
		return gallery(frame)
	else
		return slideShow(frame)
	end
end

p.main = main
p.slideShow = slideShow
p.gallery = gallery

return p