-------------------------------------------------------------------------------
--                       Automatic archive navigator
--
-- This module produces a talk archive banner, together with an automatically-
-- generated list of navigation links to other archives of the talk page in
-- question. It implements {{Archive}}.
-------------------------------------------------------------------------------

local yesno = require('Module:Yesno')

-------------------------------------------------------------------------------
-- Helper functions
-------------------------------------------------------------------------------

local function makeWikilink(page, display)
	if display then
		return string.format('[[%s|%s]]', page, display)
	else
		return string.format('[[%s]]', page)
	end
end

local function escapePattern(s)
	-- Escape punctuation in a string so it can be used in a Lua pattern.
	s = s:gsub('%p', '%%%0')
	return s
end

local function makeTable(width)
	local archiveTable = mw.html.create('table')
	archiveTable
		:css({
			['max-width'] = width,
			['margin'] = '0 auto 0.5em',
			['text-align'] = 'center'
		})
		-- Set width so that the table doesn't spill out on narrower skins
		-- or when zooming in. It has to be defined multiple times because 
		-- "stretch" is experimental.
		:cssText('width:100%;width:-moz-available;width:-webkit-fill-available;width:stretch')
	return archiveTable
end


-------------------------------------------------------------------------------
-- Navigator class
-------------------------------------------------------------------------------

local Navigator = {}
Navigator.__index = Navigator

function Navigator.new(args, cfg, currentTitle)
	local obj = setmetatable({}, Navigator)
	
	-- Set inputs
	obj.args = args
	obj.cfg = cfg
	obj.currentTitle = currentTitle

	-- Archive prefix
	-- Decode HTML entities so users can enter things like "Archive " from
	-- wikitext.
	obj.archivePrefix = obj.args.prefix or obj:message('archive-prefix')
	obj.archivePrefix = mw.text.decode(obj.archivePrefix)

	-- Current archive number
	do
		local pattern = string.format(
			'^%s([1-9][0-9]*)$',
			escapePattern(obj.archivePrefix)
		)
		obj.currentArchiveNum = obj.currentTitle.subpageText:match(pattern)
		obj.currentArchiveNum = tonumber(obj.currentArchiveNum)
	end
	
	-- Highest archive number
	obj.highestArchiveNum = require('Module:Highest archive number')._main(
		 obj.currentTitle.nsText ..
		 	':' .. 
			obj.currentTitle.baseText .. 
			'/' .. 
			obj.archivePrefix,
		obj.currentArchiveNum
	)

	return obj
end

function Navigator:message(key, ...)
	local msg = self.cfg[key]
	if select('#', ...) > 0 then
		return mw.message.newRawMessage(msg, ...):plain()
	else
		return msg
	end
end

function Navigator:makeBlurb()
	local args = self.args
	local current = self.currentTitle
	local ret
	
	-- Skip if user provides their own blurb.
	if args.text then
		ret = args.text
	else
		-- Set parent talk page.
		local parentTalkPage = current.basePageTitle
		local talkPageTitle
		local pageUnderDiscussion
		
		-- If the parent talk page exists (and it's not the root talk page)
		-- we should link to it in both the "main talk page" and 
		-- "discussions about" parts of the blurb. 
		if args.prefix or (parentTalkPage.exists and parentTalkPage.isRedirect == false and current.baseText ~= current.rootText) then
			talkPageTitle = parentTalkPage.fullText
			pageUnderDiscussion = talkPageTitle
		-- If it doesn't, set "main talk page" to the root talk page
		-- and "discussions about" to the root subject.
		else
			talkPageTitle = current.nsText .. ':' .. parentTalkPage.rootText
			-- Set page under discussion.
			pageUnderDiscussion = current.subjectNsText .. ':' .. current.rootText
			
			-- Prepend colon for non-mainspace pages.
			if current.subjectNsText ~= '' then
				pageUnderDiscussion = ':' .. pageUnderDiscussion 
			end
		end
		
		-- Check current namespace for blurb.
		local namespace = 'main'
		if current.isTalkPage == true then
			namespace = 'talk'
		end
		
		-- Most talk pages are "about" an article. For user talk page archives
		-- use "with" instead as User:X will also be a participant. User talk
		-- archives will be found in both User and User talk namespaces (2,3).
		-- For noticeboards and wikiprojects use "on" as the discussions are
		-- typically not about the noticeboard itself (4,5).
		local namespacePreposition = "about"
		if current:inNamespaces(2, 3) == true then
			namespacePreposition = "with"
		elseif current:inNamespaces(4, 5) == true then
			namespacePreposition = "on"
		end
		
		if args.type == 'index' then
			-- For manually-indexed archives only
			ret = self:message('blurb-index', talkPageTitle, pageUnderDiscussion,
			args.type, namespace, namespacePreposition)
		elseif args.period then
			ret = self:message('blurb-period', talkPageTitle, pageUnderDiscussion,
				args.period, namespace, namespacePreposition)
		else
			ret = self:message('blurb-noperiod', talkPageTitle, pageUnderDiscussion,
				'', namespace, namespacePreposition)
		end
	end
	return ret
end

function Navigator:makeMessageBox()
	local args = self.args
	local image
	if args.image then
		image = args.image
	else
		local icon = args.icon or self:message('default-icon')
		image = string.format(
			'[[File:%s|%s|alt=|link=]]',
			icon,
			self:message('image-size')
		)
	end

	-- Hardcode tmbox style on the template's page.
	-- PS: Needs to be changed if the template is renamed!
	local mainTemplatePage = ''
	if self.currentTitle.fullText == 'Template:Archive' then
		mainTemplatePage = 'talk'
	end
	
	local mbox = require('Module:Message box').main('mbox', {
		demospace = args.demospace or mainTemplatePage,
		image = image,
		imageright = args.imageright,
		style = args.style or '',
		textstyle = args.textstyle or 'text-align:center',
		text = self:makeBlurb(),
	})

	return mbox
end

function Navigator:getArchiveNums()
	-- Returns an array of the archive numbers to format.
	local noLinks = tonumber(self.args.links) or self:message('default-link-count')
	noLinks = math.floor(noLinks)
	-- If |noredlinks is "yes", true or absent, don't allow red links. If it is 
	-- 'no' or false, allow red links.
	local allowRedLinks = yesno(self.args.noredlinks) == false
	
	local current = self.currentArchiveNum
	local highest = self.highestArchiveNum

	if not current or not highest or noLinks < 1 then
		return {}
	elseif noLinks == 1 then
		return {current}
	end

	local function getNum(i, current)
		-- Gets an archive number given i, the position in the array away from
		-- the current archive, and the current archive number. The first two
		-- offsets are consecutive; the third offset is rounded up to the
		-- nearest 5; and the fourth and subsequent offsets are rounded up to
		-- the nearest 10. The offsets are calculated in such a way that archive
		-- numbers will not be duplicated.
		if -2 <= i and i <= 2 then
			return current + i
		elseif -3 <= i and i <= 3 then
			return current + 2 - (current + 2) % 5 + (i / 3) * 5
		elseif 4 <= i then
			return current + 7 - (current + 7) % 10 + (i - 3) * 10
		else
			return current + 2 - (current + 2) % 10 + (i + 3) * 10
		end
	end

	local nums = {}

	-- Archive nums lower than the current page.
	for i = -1, -math.floor((noLinks - 1) / 2), -1 do
		local num = getNum(i, current)
		if num <= 1 then
			table.insert(nums, 1, 1)
			break
		else
			table.insert(nums, 1, num)
		end
	end

	-- Current page.
	if nums[#nums] < current then
		table.insert(nums, current)
	end

	-- Higher archive nums.
	for i = 1, math.ceil((noLinks - 1) / 2) do
		local num = getNum(i, current)
		if num <= highest then
			table.insert(nums, num)
		elseif allowRedLinks and (i <= 2 or i <= 3 and num == nums[#nums] + 1) then
			-- Only insert one red link, and only if it is consecutive.
			table.insert(nums, highest + 1)
			break
		elseif nums[#nums] < highest then
			-- Insert the highest archive number if it isn't already there.
			table.insert(nums, highest)
			break
		else
			break
		end
	end

	return nums
end

function Navigator:makeArchiveLinksWikitable()
	local args = self.args
	local lang = mw.language.getContentLanguage()
	local nums = self:getArchiveNums()
	local noLinks = #nums
	
	-- Skip number processing if |prev and |next are defined.
	if args.prev or args.next then
		local archives = {}
		if args.prev then archives[#archives + 1] = mw.title.new(args.prev) end
		archives[#archives + 1] = self.currentTitle
		if args.next then archives[#archives + 1] = mw.title.new(args.next) end
		
		local table = makeTable('30em')
		for _, title in ipairs(archives) do
			if tostring(title) == self.currentTitle.prefixedText then
				table:tag("td"):wikitext(string.format(
					'<span style="font-size:115%%;">%s</span>',
					makeWikilink(title.fullText, title.subpageText)
				))
			else
				table:tag("td"):wikitext(
					makeWikilink(title.fullText, title.subpageText)
				)
			end
		end
		return tostring(table)
	end
	if noLinks < 1 then
		return ''
	end

	-- Make the table of links.
	local links = {}
	local isCompact = noLinks > 7
	local currentIndex
	for i, num in ipairs(nums) do
		local subpage = self.archivePrefix .. tostring(num)
		local display
		if isCompact then
			display = tostring(num)
		else
			display = self:message('archive-link-display', num)
		end
		local link = makeWikilink('../' .. subpage, display)
		if num == self.currentArchiveNum then
			link = string.format('<span style="font-size:115%%;">%s</span>', link)
			currentIndex = i
		end
		table.insert(links, link)
	end

	-- Add the arrows.
	-- We must do the forwards arrow first as we are adding elements to the
	-- links table. If we did the backwards arrow first the index for the
	-- current archive would be wrong.
	currentIndex = currentIndex or math.ceil(#links / 2)
	for i = currentIndex + 1, #links do
		if nums[i] - nums[i - 1] > 1 then
			table.insert(links, i, lang:getArrow('forwards'))
			break
		end
	end
	for i = currentIndex - 1, 1, -1 do
		if nums[i + 1] - nums[i] > 1 then
			table.insert(links, i + 1, lang:getArrow('backwards'))
			break
		end
	end

	-- Output the wikitable.
	local width
	if noLinks <= 3 then
		width = string.format('%dem', noLinks * 10)
	elseif noLinks <= 7 then
		width = string.format('%dem', (noLinks + 3) * 5)
	else
		width = '37em'
	end
	local table = makeTable(width)
	for _, s in ipairs(links) do
		table:tag("td"):wikitext(s)
	end
	
	return tostring(table)
end

function Navigator:__tostring()
	local args = self.args
	local boxComponents
	
-- Is |omit filled? If not, make the whole box.
	if args.omit == nil then
		boxComponents = self:makeMessageBox() .. '\n' .. self:makeArchiveLinksWikitable()
	-- We're omitting the banner, so we should only make the links table.
	elseif args.omit == 'banner' then 
		boxComponents = self:makeArchiveLinksWikitable()
	-- We're omitting the archives, so we should only make the banner.
    elseif args.omit == 'archives' then
        boxComponents = self:makeMessageBox()
	end

	-- Allow for demo pages to be edited freely. 
	if not args.demospace then
		boxComponents = boxComponents .. ' __NONEWSECTIONLINK__ __NOEDITSECTION__ __ARCHIVEDTALK__'
	end

	return boxComponents
end

-------------------------------------------------------------------------------
-- Exports
-------------------------------------------------------------------------------

local p = {}

function p._exportClasses()
	return {
		Navigator = Navigator
	}
end

function p._aan(args, cfg, currentTitle)
	cfg = cfg or mw.loadData('Module:Archive/config')
	currentTitle = currentTitle or mw.title.getCurrentTitle()
	local aan = Navigator.new(args, cfg, currentTitle)
	return tostring(aan)
end

function p.aan(frame)
	local args = require('Module:Arguments').getArgs(frame, {
		wrappers = 'Template:Archive',
	})
	return p._aan(args)
end

return p