require('strict')



-- Module to find commons galleries and categories based on wikidata entries

local getArgs = require('Module:Arguments').getArgs

local yesNo = require('Module:Yesno')

local p = {}



-- Check if string is a valid QID

-- Argument: QID to check

-- Returns: valid (bool)

local function _validQID(qid)

	return qid and mw.ustring.find(qid,"^[Qq]%d+$")

end



-- Check if string is a valid wikidata property string

-- Argument: property string to check

-- Returns: valid (bool)

local function _validProp(prop)

	return prop and mw.ustring.find(prop,"^[Pp]%d+$")

end



local function _lcfirst(s)

	return mw.ustring.lower(mw.ustring.sub(s,1,1))..mw.ustring.sub(s,2)

end



-- Format displayed linktext

-- Arguments:

--   s = string to display

--   formatting = formatting table:

--    formatting.linktext = if defined, override s

--    formatting.lcfirst = lower case the first letter in display

--    formatting.bold = whether to bold the display

--    formatting.italic = whether to italicize the display

--    formatting.nowrap = set nowrapping

-- Returns:

--   formatted string

local function _formatResult(s, formatting)

	local resultVal = formatting.linktext or s

	if formatting.lcfirst then

		resultVal = _lcfirst(resultVal)

	end

    local style = ""

	if formatting.italic then style = "font-style:italic; " end

	if formatting.bold then style = style.."font-weight:bold; " end

	if formatting.nowrap then style = style.."white-space:nowrap; " end

    if style ~= "" then

    	resultVal = '<span style="'..mw.text.trim(style)..'">'..resultVal..'</span>'

    end

	return resultVal

end



-- Get title, namespace, and QID for current page

-- Arguments:

--   qid = testing only: get title of alternative page with QID=qid

--   nsQid = whether to return the ns of the qid page or current

-- Returns:

--   title, namespace (string), qid of current page (or test page)

local function _getTitleQID(qid,nsQid)

	local titleObject = mw.title.getCurrentTitle()

	-- look up qid for current page (if not testing)

	local nsText = mw.ustring.gsub(titleObject.nsText,"_"," ") -- [[phab:T369784]]

	if not _validQID(qid) then

		qid = mw.wikibase.getEntityIdForCurrentPage()

		return titleObject.text, nsText, qid

	end

	-- testing-only path: given a qid, determine title

	-- always use namespace from current page (to suppress tracking cat)

	qid = qid:upper()

	local title = mw.wikibase.getSitelink(qid) or ""

	-- strip any namespace from sitelink

	local firstColon = mw.ustring.find(title,':',1,true)

	local qidNsText = ""

	if firstColon then

		qidNsText = mw.ustring.sub(title,1,firstColon-1)

		title = mw.ustring.sub(title,firstColon+1)

	end

	if nsQid then

		return title, qidNsText, qid

	end

	return title, nsText, qid

end



-- Lookup Commons gallery in Wikidata

-- Arguments:

--   qid = QID of current article

--   fetch = whether to lookup Commons sitelink (bool)

--   commonsSitelink = default value for Commons sitelink

-- Returns:

--   categoryLink = name of Commons category, nil if nothing is found

--   consistent = multiple wikidata fields are examined: are they consistent?

--   commonsSitelink = commons sitelink for current article

local function _lookupGallery(qid,fetch,commonsSitelink)

	if not _validQID(qid) then

		return nil, true, nil

	end

	qid = qid:upper()

	local galleryLink = nil

	local consistent = true

	-- look up commons sitelink for article, use if not category

	if fetch then

		commonsSitelink = mw.wikibase.getSitelink(qid,"commonswiki") or commonsSitelink

	end

	if commonsSitelink and mw.ustring.sub(commonsSitelink,1,9) ~= "Category:" then

		galleryLink = commonsSitelink

	end

	-- P935 is the "commons gallery" property for this article

	local P935 = mw.wikibase.getBestStatements(qid, "P935")[1

	if P935 and P935.mainsnak.datavalue then

		local gallery = P935.mainsnak.datavalue.value

		if galleryLink and galleryLink ~= gallery then

			consistent = false

		else

			galleryLink = gallery

		end

	end

	return galleryLink, consistent, commonsSitelink

end



-- Find fallback category by looking up Commons sitelink of different page

-- Arguments:

--    qid = QID for current article

--    property = property that refers to other article whose sitelink to return

-- Returns: either category-stripped name of article, or nil

local function _lookupFallback(qid,property)

	if not _validQID(qid) or not _validProp(property) then

		return nil

	end

	qid = qid:upper()

	property = property:upper()

	-- If property exists on current article, get value (other article qid)

	local value = mw.wikibase.getBestStatements(qid, property)[1

	if value and value.mainsnak.datavalue and value.mainsnak.datavalue.value.id then

		-- Look up Commons sitelink of other article

		local sitelink = mw.wikibase.getSitelink(value.mainsnak.datavalue.value.id,"commonswiki")

		-- Check to see if it starts with "Category:". If so, strip it and return

		if sitelink and mw.ustring.sub(sitelink,1,9) == "Category:" then

			return mw.ustring.sub(sitelink,10)

		end

	end

	return nil

end



-- Find Commons category by looking in wikidata

-- Arguments:

--   qid = QID of current article

--   fetch = whether to lookup Commons sitelink (bool)

--   commonsSitelink = default value for Commons sitelink

-- Returns:

--   categoryLink = name of Commons category, nil if nothing is found

--   consistent = multiple wikidata fields are examined: are they consistent?

--   commonsSitelink = commons sitelink for current article

local function _lookupCategory(qid, fetch, commonsSitelink)

	if not _validQID(qid) then

		return nil, true, nil

	end

	qid = qid:upper()

	local categoryLink = nil

	local consistent = true

	-- look up commons sitelink for article, use if starts with "Category:"

	if fetch then

		commonsSitelink = mw.wikibase.getSitelink(qid,"commonswiki") or commonsSitelink

	end

	if commonsSitelink and mw.ustring.sub(commonsSitelink,1,9) == "Category:" then

		categoryLink = mw.ustring.sub(commonsSitelink,10)

	end

	-- P910 is the "topic's main category". Look for commons sitelink there

	local fallback = _lookupFallback(qid,"P910")

	if fallback then

		if categoryLink and categoryLink ~= fallback then

			consistent = false

			qid = nil

		else

			categoryLink = fallback

		end

	end

	-- P1754 is the "list's main category". Look for commons sitelink there

	fallback = _lookupFallback(qid,"P1754")

	if fallback then

		if categoryLink and categoryLink ~= fallback then

			consistent = false

			qid = nil

		else

			categoryLink = fallback

		end

	end

    -- P373 is the "commons category" property for this article. This is

    -- a low-quality field, so should only be used as a last resort.

    if categoryLink == nil and _validQID(qid) then

	    local P373 = mw.wikibase.getBestStatements(qid, "P373")[1

	    if P373 and P373.mainsnak.datavalue then

		    categoryLink = P373.mainsnak.datavalue.value

		    consistent = true  -- P373 is never used if anything else is available

		end

	end

	return categoryLink, consistent, commonsSitelink

end



-- Does the article have a Commons gallery, and is it consistent?

-- Arguments:

--   qid = QID to lookup in wikidata (for testing only)

-- Returns:

--   filename at Commons, bool: is wikidata consistent for this article?

function p._hasGalleryConsistent(qid)

	local wp_title, wp_ns

	wp_title, wp_ns, qid = _getTitleQID(qid)

	return _lookupGallery(qid,true)

end



-- Does the article have a corresponding Commons gallery?

-- Arguments:

--   qid = QID to lookup in wikidata (for testing only)

-- Returns:

--   filename at Commons if so, false if not

function p._hasGallery(qid)

	local galleryLink, consistent = p._hasGalleryConsistent(qid)

	return consistent and galleryLink

end



-- Does the article have a Commons category? Is wikidata consistent for that?

-- Arguments:

--   qid = QID to lookup in wikidata (for testing only)

--   prefix = whether to add "Category:" to return string (default true)

-- Returns:

--   filename at Commons, bool: consistent

function p._hasCategoryConsistent(qid,prefix)

	if prefix == nil then

		prefix = true

	end

	local wp_title, wp_ns

	wp_title, wp_ns, qid = _getTitleQID(qid)

	local categoryLink, consistent = _lookupCategory(qid,true)

	if categoryLink and prefix then

		categoryLink = "Category:"..categoryLink

	end

	return categoryLink, consistent

end



-- Does the article have a corresponding Commons category?

-- Arguments:

--   qid = QID to lookup in wikidata (for testing only)

--   prefix = whether to add "Category:" to return string (default true)

-- Returns:

--   filename at Commons if so, blank if not

function p._hasCategory(qid,prefix)

	local categoryLink, consistent = p._hasCategoryConsistent(qid,prefix)

	return consistent and categoryLink

end



-- Create Commons link corresponding to current article

-- Arguments:

--   namespace = namespace in Commons ("" for galleries)

--   default = use as Commons link, don't access wikidata

--   search = string to search for

--   fallback = string to search for if wikidata fails

--   formatting = formatting parameters

--   qid = QID to lookup in wikidata (for testing only)

-- Returns:

--   formatted wikilink to Commons in specified namespace

function p._getCommons(namespace,default,search,fallback,formatting,qid)

	local nsColon

	if not namespace or namespace == "" then

		nsColon = ""

	else

		nsColon = namespace..":"

	end

	if default then

		return "[[Commons:"..nsColon..default.."|".._formatResult(default,formatting).."]]"

	end

	if search then

		return "[[Commons:Special:Search/"..nsColon..search.."|".._formatResult(search,formatting).."]]"

	end

	local wp_title, wp_ns

	wp_title, wp_ns, qid = _getTitleQID(qid)

	local commonsLink = nil

	local consistent = true

	if nsColon == "" then

		commonsLink, consistent = _lookupGallery(qid,true)

	elseif namespace:lower() == "category" then

		commonsLink, consistent = _lookupCategory(qid,true)

	end

	-- use wikidata if consistent

	if commonsLink and consistent then

		return "[[Commons:"..nsColon..commonsLink.."|".._formatResult(commonsLink,formatting).."]]"

	end

	-- if not consistent, fall back to search and add to tracking cat

	-- construct default result (which searches for title)

	local searchResult = "[[Commons:Special:Search/"..nsColon..(fallback or wp_title)

		.."|".._formatResult(fallback or wp_title,formatting).."]]"

	if not consistent and wp_ns == "" then

		local friendlyNS

		if nsColon == "" then

			friendlyNS = "gallery"

		else

			friendlyNS = namespace:lower()

		end

		searchResult = searchResult.."[[Category:Inconsistent wikidata for Commons "..friendlyNS.."]]"

	end

	return searchResult

end



-- Returns "best" Commons link: first look for gallery, then try category

-- Arguments:

--   default = use as Commons link, don't access wikidata

--   search = string to search for

--   fallback = string to search for if wikidata lookup fails

--   formatting = formatting parameters

--   qid = QID to lookup in wikidata (for testing only)

-- Returns:

--   formatted wikilink to Commons "best" landing page

function p._getGalleryOrCategory(default, search, fallback, formatting, qid)

	if default then

		return "[[Commons:"..default.."|".._formatResult(default,formatting).."]]"

	end

	if search then

		return "[[Commons:Special:Search/"..search.."|".._formatResult(search,formatting).."]]"

	end

	local wp_title, wp_ns

	wp_title, wp_ns, qid = _getTitleQID(qid)

	local trackingCats = ""

	local galleryLink, consistent, commonsSitelink = _lookupGallery(qid,true)

	-- use wikidata if either sitelink or P935 exist, and they both agree

	if galleryLink and consistent then

		return "[[Commons:"..galleryLink.."|".._formatResult(galleryLink,formatting).."]]"

	end

	if not consistent and wp_ns == "" then

		trackingCats = "[[Category:Inconsistent wikidata for Commons gallery]]"

	end

	-- if gallery is not good, fall back looking for category

	local categoryLink

	categoryLink, consistent = _lookupCategory(qid,false,commonsSitelink)

	if categoryLink and consistent then

		return "[[Commons:Category:"..categoryLink.."|".._formatResult(categoryLink,formatting).."]]"..trackingCats

	end

	if not consistent and wp_ns == "" then

		trackingCats = trackingCats.."[[Category:Inconsistent wikidata for Commons category]]"

	end

	-- return search result looking for title as last attempt

	return "[[Commons:Special:Search/" .. (fallback or wp_title) ..

		"|" .. _formatResult(fallback or wp_title,formatting) .. "]]" .. trackingCats

end



-- Return link(s) Commons gallery, or category, or both from wikidata

-- Arguments:

--   defaultGallery = default gallery link to use, instead of wikidata

--   defaultCategory = default category link to use, instead of wikidata

--   categoryText = if both gallery and category, text to use in category link ("category" by default)

--   oneSearch = only emit one search result

--   formatting = formatting parameters

--   qid = qid of page to lookup in wikidata (testing only)

function p._getGalleryAndCategory(defaultGallery, defaultCategory, 

	categoryText, oneSearch, formatting, qid

	)

	local wp_title, wp_ns

	wp_title, wp_ns, qid = _getTitleQID(qid)

	categoryText = categoryText or "category"

	local trackingCats = ""

	local galleryLink, galleryConsistent

	local commonsSitelink = nil

	if defaultGallery then

		galleryLink = defaultGallery

		galleryConsistent = true

	else

		galleryLink, galleryConsistent, commonsSitelink = _lookupGallery(qid,true)

	end

	local galleryGood = galleryLink and galleryConsistent

	if not galleryConsistent and wp_ns == "" then

		trackingCats = "[[Category:Inconsistent wikidata for Commons gallery]]"

	end

	local categoryLink, categoryConsistent

	if defaultCategory then

		categoryLink = defaultCategory

		categoryConsistent = true

	else

		categoryLink, categoryConsistent = _lookupCategory(qid,defaultGallery,commonsSitelink)

	end

	local categoryGood = categoryLink and categoryConsistent

	if not categoryConsistent and wp_ns == "" then

		trackingCats = trackingCats.."[[Category:Inconsistent wikidata for Commons category]]"

	end

	local firstLink

	-- construct default result (which searches for title)

	local searchResult = "[[Commons:Special:Search/"..wp_title.."|".._formatResult(wp_title,formatting).."]]"

	if not oneSearch then

		searchResult = searchResult.." ([[Commons:Special:Search/Category:"..wp_title.."|"..categoryText.."]])"

	end

	local linkText = nil

	if galleryGood then

		firstLink = galleryLink

		linkText = galleryLink

	elseif categoryGood then

		firstLink = "Category:"..categoryLink

		linkText = categoryLink

	else

		return searchResult..trackingCats

	end

	local resultVal = "[[Commons:"..firstLink.."|".._formatResult(linkText,formatting).."]]"

	if galleryGood and categoryGood then

		resultVal = resultVal.." ([[Commons:Category:"..categoryLink.."|"..categoryText.."]])"

	end

	return resultVal..trackingCats

end



-- Compare two titles with their namespaces stripped

local function titleMatch(s1,s2)

	s1 = s1 or ""

	s2 = s2 or ""

    s1 = mw.ustring.gsub(s1,"^[^:]+:","")

    s2 = mw.ustring.gsub(s2,"^[^:]+:","")

    return s1 == s2

end



local galleryTrackingCats = {

	commons_link_on_wikidata = '[[Category:Commons link is on Wikidata]]',

	commons_link_defined_as_pagename = '[[Category:Commons link is defined as the pagename]]',

	commons_link_locally_defined = '[[Category:Commons link is locally defined]]',

	commons_link_from_wikidata = '[[Category:Commons link from Wikidata]]',

	commons_link_is_pagename = '[[Category:Commons link is the pagename]]',

	inconsistent = '[[Category:Inconsistent wikidata for Commons gallery]]'

}



local categoryTrackingCats = {

		commons_link_on_wikidata = '[[Category:Commons category link is on Wikidata]]',

		commons_link_defined_as_pagename = '[[Category:Commons category link is defined as the pagename]]',

		commons_link_locally_defined = '[[Category:Commons category link is locally defined]]',

		commons_link_from_wikidata = '[[Category:Commons category link from Wikidata]]',

		commons_link_is_pagename = '[[Category:Commons category link is the pagename]]',

		inconsistent = '[[Category:Inconsistent wikidata for Commons category]]'

	}



local function selectTrackingCat(trackingCats,wikidata,consistent,default,title)

	if not consistent then

		return trackingCats.inconsistent

	end

	if default then

	-- construct warning message

		if default == wikidata then

			return trackingCats.commons_link_on_wikidata

		end

		local warning = ""

		if wikidata then

			local generateWarning = require('Module:If preview')._warning

			warning = generateWarning({

					"Commons link does not match Wikidata – [[Template:Commons_category#Resolving_discrepancies|please check]]"

				})

		end

		if titleMatch(default,title) then

			return trackingCats.commons_link_defined_as_pagename .. warning

		end

		return trackingCats.commons_link_locally_defined .. warning

	end

	if wikidata then

		return trackingCats.commons_link_from_wikidata

	end

	return trackingCats.commons_link_is_pagename

end



-- Figure out tracking categories and editor warnings

-- Arguments:

--   default = Commons link argument passed to template

--   fetchGallery = whether to fetch a gallery from Wikidata

--   fetchCategory = whether to fetch a category from Wikidata

--   qid = force a qid for testing

-- Returns:

--   tracking category and possible user warning

--

-- Note: the logic for the tracking is quite different than the logic

-- for generating Commons links (above). Thus, it is separated into another

-- function for code clarity and maintainability. This should not seriously 

-- affect performance: server time is dominated by fetching wikidata entities,

-- and those entities should be cached and shared between the Commons generating

-- code and this tracking code.

function p._tracking(default, fetchGallery, fetchCategory, qid)

	local title, wp_ns, wp_qid = _getTitleQID(qid,true)

	if wp_ns ~= "" then

		title = wp_ns..":"..title

	end

	-- only track if test or namespace=article or namespace=category

	if not (qid or wp_ns == "" or wp_ns == "Category") then

		return ""

	end

	

	-- determine title and namespace of wikidata and wp article

	local wikidata = nil

	local consistent = nil

	-- Tracking code works for all 4 cases of states of fetchGallery/Category

	-- fetchGallery takes precedence

	if fetchGallery then

		wikidata, consistent = p._hasGalleryConsistent(qid)

		if default or not fetchCategory or (consistent and wikidata) then

			return selectTrackingCat(galleryTrackingCats,wikidata,consistent,

				                     default,title)

		end

	end

    if fetchCategory then

		local cat_wikidata, cat_consistent = p._hasCategoryConsistent(qid,true)

		if not fetchGallery or (cat_consistent and cat_wikidata) then

			return selectTrackingCat(categoryTrackingCats,cat_wikidata,

			                    	 cat_consistent,default,title)

		end

		return selectTrackingCat(galleryTrackingCats,wikidata,consistent,

			                     default,title)

    end

	return "" -- nothing fetched, nothing tracked

end



local function _createFormatting(args)

	local formatting = {}

	formatting.linktext = args.linktext

	formatting.lcfirst = yesNo(args.lcfirst)

	formatting.bold = yesNo(args.bold)

	formatting.italic = yesNo(args.italic)

	formatting.nowrap = yesNo(args.nowrap)

	return formatting

end



-- Testing-only entry point for _getTitleQID

function p.getTitleQID(frame)

	local args = getArgs(frame,{frameOnly=true,parentOnly=false,parentFirst=false})

	local text, ns, qid = _getTitleQID(args1],args2])

	return text..","..ns..","..(qid or "nil")

end



-- Testing-only entry point for _lookupFallback

function p.lookupFallback(frame)

	local args = getArgs(frame,{frameOnly=true,parentOnly=false,parentFirst=false})

	local fallback = _lookupFallback(args1],args2])

	return fallback or "nil"

end



-- Find the Commons gallery page associated with article

function p.getGallery(frame)

	local args = getArgs(frame,{frameOnly=true,parentOnly=false,parentFirst=false})

	return p._getCommons("",args1],args.search,args.fallback,_createFormatting(args),args.qid)

end



-- Find the Commons category page associated with article

function p.getCategory(frame)

	local args = getArgs(frame,{frameOnly=true,parentOnly=false,parentFirst=false})

	local retval = p._getCommons("Category", args1], 

		args.search, args.fallback, _createFormatting(args), args.qid

	)

	if args.tracking then

		local default = nil

		if args1 then

			default = "Category:"..args1

		end

		retval = retval..p._tracking(default, false, true, args.qid)

	end

	return retval

end



function p.getGalleryOrCategory(frame)

	local args = getArgs(frame,{frameOnly=true,parentOnly=false,parentFirst=false})

	local retval = p._getGalleryOrCategory(

		args1], args.search, args.fallback, _createFormatting(args), args.qid

	)

	if args.tracking then

		retval = retval..p._tracking(args1],true,true,args.qid)

	end

	return retval

end



function p.hasGallery(frame)

	local args = getArgs(frame,{frameOnly=true,parentOnly=false,parentFirst=false})

	return p._hasGallery(args.qid) or ""

end



function p.hasCategory(frame)

	local args = getArgs(frame,{frameOnly=true,parentOnly=false,parentFirst=false})

	return p._hasCategory(args.qid) or ""

end



function p.hasGalleryOrCategory(frame)

	local args = getArgs(frame,{frameOnly=true,parentOnly=false,parentFirst=false})

	return p._hasGallery(args.qid) or p._hasCategory(args.qid) or ""

end



function p.getGalleryAndCategory(frame)

	local args = getArgs(frame,{frameOnly=true,parentOnly=false,parentFirst=false})

	return p._getGalleryAndCategory(args1], args2], 

		args.categoryText, args.oneSearch, _createFormatting(args), args.qid)

end



function p.tracking(frame)

	local args = getArgs(frame,{frameOnly=true,parentOnly=false,parentFirst=false})

	return p._tracking(args1], args.fetchGallery, args.fetchCategory, args.qid)

end



return p