POINT_IN_TIME_PID = "P585"

YT_CHAN_ID_PID= "P2397"

SUB_COUNT_PID = "P8687"



local p = {} 



-- taken from /info/en/?search=Module:Wd

function parseDate(dateStr, precision)

	precision = precision or "d"



	local i, j, index, ptr

	local parts = {nil, nil, nil}



	if dateStr == nil then

		return parts1], parts2], parts3  -- year, month, day

	end



	-- 'T' for snak values, '/' for outputs with '/Julian' attached

	i, j = dateStr:find("[T/]")



	if i then

		dateStr = dateStr:sub(1, i-1)

	end



	local from = 1



	if dateStr:sub(1,1) == "-" then

		-- this is a negative number, look further ahead

		from = 2

	end



	index = 1

	ptr = 1



	i, j = dateStr:find("-", from)



	if i then

		-- year

		partsindex = tonumber(mw.ustring.gsub(dateStr:sub(ptr, i-1), "^%+(.+)$", "%1"), 10)  -- remove '+' sign (explicitly give base 10 to prevent error)



		if partsindex == -0 then

			partsindex = tonumber("0")  -- for some reason, 'parts[index] = 0' may actually store '-0', so parse from string instead

		end



		if precision == "y" then

			-- we're done

			return parts1], parts2], parts3  -- year, month, day

		end



		index = index + 1

		ptr = i + 1



		i, j = dateStr:find("-", ptr)



		if i then

			-- month

			partsindex = tonumber(dateStr:sub(ptr, i-1), 10)



			if precision == "m" then

				-- we're done

				return parts1], parts2], parts3  -- year, month, day

			end



			index = index + 1

			ptr = i + 1

		end

	end



	if dateStr:sub(ptr) ~= "" then

		-- day if we have month, month if we have year, or year

		partsindex = tonumber(dateStr:sub(ptr), 10)

	end



	return parts1], parts2], parts3  -- year, month, day

end



-- taken from /info/en/?search=Module:Wd

local function datePrecedesDate(aY, aM, aD, bY, bM, bD)

	if aY == nil or bY == nil then

		return nil

	end

	aM = aM or 1

	aD = aD or 1

	bM = bM or 1

	bD = bD or 1



	if aY < bY then

		return true

	elseif aY > bY then

		return false

	elseif aM < bM then

		return true

	elseif aM > bM then

		return false

	elseif aD < bD then

		return true

	end



	return false

end



function getClaimDate(claim)

	if claim'qualifiers' and claim'qualifiers'][POINT_IN_TIME_PID then 

		local pointsInTime = claim'qualifiers'][POINT_IN_TIME_PID

		if #pointsInTime ~= 1 then

			-- be conservative in what we accept

			error("Encountered a statement with zero or multiple point in time (P85) qualifiers. Please add or remove point in time information so each statement has exactly one")

		end

		local pointInTime = pointsInTime1

		if pointInTime and 

		   pointInTime'datavalue' and 

		   pointInTime'datavalue']['value' and 

		   pointInTime'datavalue']['value']['time' 

		then

			return parseDate(pointInTime'datavalue']['value']['time'])

		end

	end

	return nil

end



-- for a given list of statements find the newest one with a matching qual

function newestMatchingStatement(statements, qual, targetQualValue)

	local newestStatement = nil

	local newestStatementYr = nil

	local newestStatementMo = nil

	local newestStatementDay = nil

    for k, v in pairs(statements) do

    	if v'rank' ~= "deprecated" and v'qualifiers' and v'qualifiers'][qual then

    		local quals = v'qualifiers'][qual

    		-- should only have one instance of the qualifier on a statement

    		if #quals == 1 then

    			local qual = quals1

    			if qual'datavalue' and qual'datavalue']['value' then

    				local qualValue = qual'datavalue']['value'

    				if qualValue == targetQualValue then

	    				local targetYr, targetMo, targetDay = getClaimDate(v)

	    				if targetYr then

	    					local older = datePrecedesDate(targetYr, targetMo, targetDay, newestStatementYr, newestStatementMo, newestStatementDay)

	    					if older == nil or not older then

	    						newestStatementYr, newestStatementMo, newestStatementDay = targetYr, targetMo, targetDay

	    						newestStatement = v

	    					end

	    				end

    				end

    			end

    		end

    	end

    end

	return newestStatement

end



-- for a given property and qualifier pair returns the newest statement that matches

function newestMatching(e, prop, qual, targetQualValue)

	-- first check the best statements

	local statements = e:getBestStatements(prop)

	local newestStatement = newestMatchingStatement(statements, qual, targetQualValue)

	if newestStatement then

		return newestStatement

	end

	-- try again with all statements if nothing so far

	statements = e:getAllStatements(prop)

	newestStatement = newestMatchingStatement(statements, qual, targetQualValue)

	if newestStatement then

		return newestStatement

	end

	return nil

end



function getEntity ( frame )

	local qid = nil

	if frame.args then

		qid = frame.args"qid"

	end

	if not qid then

		qid = mw.wikibase.getEntityIdForCurrentPage()

	end

	if not qid then

		local e = nil

		return e

	end

	local e = mw.wikibase.getEntity(qid)

	assert(e, "No such item found: " .. qid)

	return e

end



-- find the channel ID we are going to be getting the sub counts for

function getBestYtChanId(e) 

	local chanIds = e:getBestStatements(YT_CHAN_ID_PID)

	if #chanIds == 1 then

		local chan = chanIds1

		if chan and 

		   chan"mainsnak" and 

		   chan"mainsnak"]["datavalue" and 

		   chan"mainsnak"]["datavalue"]["value" 

		then

			return chan"mainsnak"]["datavalue"]["value"

		end

	end

	return nil

end



function returnError(frame, eMessage)

	return frame:expandTemplate{ title = 'error', args = { eMessage } } .. "[[Category:Pages with YouTubeSubscribers module errors]]"

end



-- the date of the current YT subscriber count

function p.date( frame )

	local e = getEntity(frame)

	assert(e, "No qid found for page. Please make a Wikidata item for this article")

	local chanId = getBestYtChanId(e)

	assert(chanId, "Could not find a single best YouTube channel ID for this item. Add a YouTube channel ID or set the rank of one channel ID to be preferred")

	local s = newestMatching(e, SUB_COUNT_PID, YT_CHAN_ID_PID, chanId)

	if s then

		local yt_year, yt_month, yt_day = getClaimDate(s)

		if not yt_year then

			return nil

		end

		local dateString = yt_year .. "|"

		-- construct YYYY|mm|dd date string

		if yt_month and yt_month ~= 0 then

			dateString = dateString .. yt_month .. "|"

			-- truncate the day of month

			--if yt_day and yt_day ~= 0 then

			--	dateString = dateString .. yt_day

			--end

		end

		return frame:expandTemplate{title="Format date", args = {yt_year, yt_month, yd_day}}

	end

	error("Could not find a date for YouTube subscriber information. Is there a social media followers statement (P8687) qualified with good values for P585 and P2397?")

end



function p.dateNice( frame )

	local status, obj = pcall(p.date, frame)

	if status then

		return obj

	else 

		return returnError(frame, obj)

	end

end



-- the most up to date number of subscribers

function p.subCount( frame )

	local subCount = nil

	local e = getEntity(frame)

	if not e then

		subCount = -424

    	return tonumber(subCount)

	end

	local chanId = getBestYtChanId(e)

	if chanId then

		local s = newestMatching(e, SUB_COUNT_PID, YT_CHAN_ID_PID, chanId)

		if s and 

		   s"mainsnak" and 

		   s'mainsnak']["datavalue" and 

		   s'mainsnak']["datavalue"]["value" and 

		   s'mainsnak']["datavalue"]['value']['amount'

		then

			subCount = s'mainsnak']["datavalue"]['value']['amount'

		end

	else 

		subCount = -404

	end

    if subCount then

    	return tonumber(subCount)

    else

		subCount = -412

    	return tonumber(subCount)

    end

end



function p.subCountNice( frame )

	local status, obj = pcall(p.subCount, frame)

	if status then

		if obj >= 0 then

			return frame:expandTemplate{title="Format price", args = {obj}}

		else

			return obj

		end

	else 

		return returnError(frame, obj)

	end

end



return p