--------------------------------------------------------------------------------
--                              Module:Hatnote                                --
--                                                                            --
-- This module produces hatnote links and links to related articles. It       --
-- implements the {{hatnote}} and {{format link}} meta-templates and includes --
-- helper functions for other Lua hatnote modules.                            --
--------------------------------------------------------------------------------

local libraryUtil = require('libraryUtil')
local checkType = libraryUtil.checkType
local checkTypeForNamedArg = libraryUtil.checkTypeForNamedArg
local mArguments -- lazily initialise [[Module:Arguments]]
local yesno -- lazily initialise [[Module:Yesno]]

local p = {}

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

local function getArgs(frame)
	-- Fetches the arguments from the parent frame. Whitespace is trimmed and
	-- blanks are removed.
	mArguments = require('Module:Arguments')
	return mArguments.getArgs(frame, {parentOnly = true})
end

local function removeInitialColon(s)
	-- Removes the initial colon from a string, if present.
	return s:match('^:?(.*)')
end

function p.findNamespaceId(link, removeColon)
	-- Finds the namespace id (namespace number) of a link or a pagename. This
	-- function will not work if the link is enclosed in double brackets. Colons
	-- are trimmed from the start of the link by default. To skip colon
	-- trimming, set the removeColon parameter to false.
	checkType('findNamespaceId', 1, link, 'string')
	checkType('findNamespaceId', 2, removeColon, 'boolean', true)
	if removeColon ~= false then
		link = removeInitialColon(link)
	end
	local namespace = link:match('^(.-):')
	if namespace then
		local nsTable = mw.site.namespaces[namespace]
		if nsTable then
			return nsTable.id
		end
	end
	return 0
end

function p.formatPages(...)
	-- Formats a list of pages using formatLink and returns it as an array. Nil
	-- values are not allowed.
	local pages = {...}
	local ret = {}
	for i, page in ipairs(pages) do
		ret[i] = p._formatLink{link = page}
	end
	return ret
end

function p.formatPageTables(...)
	-- Takes a list of page/display tables and returns it as a list of
	-- formatted links. Nil values are not allowed.
	local pages = {...}
	local links = {}
	for i, t in ipairs(pages) do
		checkType('formatPageTables', i, t, 'table')
		local link = t[1]
		local display = t[2]
		links[i] = p._formatLink{link = link, display = display}
	end
	return links
end

function p.makeWikitextError(msg, helpLink, addTrackingCategory, title)
	-- Formats an error message to be returned to wikitext. If
	-- addTrackingCategory is not false after being returned from
	-- [[Module:Yesno]], and if we are not on a talk page, a tracking category
	-- is added.
	checkType('makeWikitextError', 1, msg, 'string')
	checkType('makeWikitextError', 2, helpLink, 'string', true)
	yesno = require('Module:Yesno')
	title = title or mw.title.getCurrentTitle()
	-- Make the help link text.
	local helpText
	if helpLink then
		helpText = ' ([[' .. helpLink .. '|help]])'
	else
		helpText = ''
	end
	-- Make the category text.
	local category
	if not title.isTalkPage -- Don't categorise talk pages
		and title.namespace ~= 2 -- Don't categorise userspace
		and yesno(addTrackingCategory) ~= false -- Allow opting out
	then
		category = 'Hatnote templates with errors'
		category = string.format(
			'[[%s:%s]]',
			mw.site.namespaces[14].name,
			category
		)
	else
		category = ''
	end
	return string.format(
		'<strong class="error">Error: %s%s.</strong>%s',
		msg,
		helpText,
		category
	)
end

function p.disambiguate(page, disambiguator)
	-- Formats a page title with a disambiguation parenthetical,
	-- i.e. "Example" → "Example (disambiguation)".
	checkType('disambiguate', 1, page, 'string')
	checkType('disambiguate', 2, disambiguator, 'string', true)
	disambiguator = disambiguator or 'disambiguation'
	return string.format('%s (%s)', page, disambiguator)
end

--------------------------------------------------------------------------------
-- Format link
--
-- Makes a wikilink from the given link and display values. Links are escaped
-- with colons if necessary, and links to sections are detected and displayed
-- with " § " as a separator rather than the standard MediaWiki "#". Used in
-- the {{format link}} template.
--------------------------------------------------------------------------------

function p.formatLink(frame)
	-- The formatLink export function, for use in templates.
	yesno = require('Module:Yesno')
	local args = getArgs(frame)
	local link = args[1]
	if not link then
		return p.makeWikitextError(
			'no link specified',
			'Template:Format link#Errors',
			args.category
		)
	end
	return p._formatLink{
		link = link,
		display = args[2],
		italicizePage = yesno(args.italicizepage),
		italicizeSection = yesno(args.italicizesection),
	}
end

local function italicize(s)
	-- Italicize a string.
	return '<i>' .. s .. '</i>'
end

local function maybeItalicize(s, shouldItalicize)
	-- italicize s if s is a string and the shouldItalicize parameter is true.
	if s and shouldItalicize then
		return italicize(s)
	else
		return s
	end
end

local function parseLink(link)
	-- Parse a link and return a table with the link's components.
	-- These components are:
	-- - link: the link, stripped of any initial colon (always present)
	-- - page: the page name (always present)
	-- - section: the page name (may be nil)
	-- - display: the display text, if manually entered after a pipe (may be nil)
	link = removeInitialColon(link)

	-- Find whether a faux display value has been added with the {{!}} magic
	-- word.
	local prePipe, display = link:match('^(.-)|(.*)$')
	link = prePipe or link

	-- Find the page, if it exists.
	-- For links like [[#Bar]], the page will be nil.
	local preHash, postHash = link:match('^(.-)#(.*)$')
	local page
	if not preHash then
		-- We have a link like [[Foo]].
		page = link
	elseif preHash ~= '' then
		-- We have a link like [[Foo#Bar]].
		page = preHash
	end

	-- Find the section, if it exists.
	local section
	if postHash and postHash ~= '' then
		section = postHash
	end
	
	return {
		link = link,
		page = page,
		section = section,
		display = display,
	}
end

function p._formatLink(options)
	-- The formatLink export function, for use in modules.
	checkType('_formatLink', 1, options, 'table')
	checkTypeForNamedArg('_formatLink', 'link', options.link, 'string', false)
	checkTypeForNamedArg(
		'_formatLink',
		'display',
		options.display,
		'string',
		true
	)
	checkTypeForNamedArg(
		'_formatLink',
		'italicizePage',
		options.italicizePage,
		'boolean',
		true
	)
	checkTypeForNamedArg(
		'_formatLink',
		'italicizeSection',
		options.italicizeSection,
		'boolean',
		true
	)

	local parsed = parseLink(options.link)
	local display = options.display or parsed.display
	
	-- Deal with the case where we don't have to pipe the link
	if not display and not parsed.section and not options.italicizePage then
		return string.format('[[:%s]]', parsed.link)
	end
	
	-- Find the display text for piped links
	if not display then
		local page = maybeItalicize(parsed.page, options.italicizePage)
		local section = maybeItalicize(parsed.section, options.italicizeSection)
		if not page then
			display = string.format('§&nbsp;%s', section)
		elseif section then
			display = string.format('%s §&nbsp;%s', page, section)
		else
			display = page
		end
	end
	
	return string.format('[[:%s|%s]]', parsed.link, display)
end

--------------------------------------------------------------------------------
-- Hatnote
--
-- Produces standard hatnote text. Implements the {{hatnote}} template.
--------------------------------------------------------------------------------

function p.hatnote(frame)
	local args = getArgs(frame)
	local s = args[1]
	local options = {}
	if not s then
		return p.makeWikitextError(
			'no text specified',
			'Template:Hatnote#Errors',
			args.category
		)
	end
	options.extraclasses = args.extraclasses
	options.selfref = args.selfref
	return p._hatnote(s, options)
end

function p._hatnote(s, options)
	checkType('_hatnote', 1, s, 'string')
	checkType('_hatnote', 2, options, 'table', true)
	options = options or {}
	local classes = {'hatnote', 'navigation-not-searchable'}
	local extraclasses = options.extraclasses
	local selfref = options.selfref
	if type(extraclasses) == 'string' then
		classes[#classes + 1] = extraclasses
	end
	if selfref then
		classes[#classes + 1] = 'selfref'
	end
	return string.format(
		'<div role="note" class="%s">%s</div>',
		table.concat(classes, ' '),
		s
	)
end

return p