local defaultFormat = {
	[0] = "Y",				-- precision: billion years
	[1] = "Y",				-- precision: hundred million years
	[2] = "Y",				-- precision: ten million years
	[3] = "Y",				-- precision: million years
	[4] = "Y",				-- precision: hundred thousand years
	[5] = "Y",				-- precision: ten thousand years
	[6] = "Y",				-- precision: millennium
	[7] = "Y",				-- precision: century
	[8] = "Y",				-- precision: decade
	[9]  = "Y",				-- precision: year
	[10] = "M Y",			-- precision: month
	[11] = "j F Y",			-- precision: day
	[12] = "j F Y ga",		-- precision: hour
	[13] = "j F Y g:ia",	-- precision: minute
	[14] = "j F Y g:i:sa"	-- precision: second
}

local p = {}

function p.plot(frame)
	local property = frame.args[1] or error("Wikidata property to chart required")
	local xQualifier = frame.args[2] or error("Wikidata qualifier for x axis required")
	local yIds = mw.text.split(frame.args["pageIds"] or "", ",", true)
	local xStart = frame.args["xStart"]
	local xEnd = frame.args["xEnd"]
	local precision = tonumber(frame.args["precision"])
	local xAxisFormat = defaultFormat[precision or 9]	
	
	-- Collect data
	local series = { captions = {}, points = {} }
	for seriesIdx, id in ipairs(yIds) do
		if id == "" then id = nil end
		local entity = mw.wikibase.getEntity(id)
		
		local labels = entity.labels or {}
		series.captions[seriesIdx] = (labels.en or labels.de or {}).value or id

		local property = entity.claims[property]
		for _, item in ipairs(property) do
			if item.qualifiers and item.qualifiers[xQualifier] and item.qualifiers[xQualifier][1] then
				local qualifier = item.qualifiers[xQualifier][1]
				if qualifier.snaktype ~= "value" or qualifier.datatype ~= "time" then
					error("'xQualifier' parameter must be a time")
				end
				local x = applyPrecision(mw.text.trim(qualifier.datavalue.value.time, "+"), precision)
				
				if (not xStart or x >= xStart) and (not xEnd or string.sub(x, 1, #xEnd) <= xEnd) and qualifier.datavalue.value.precision >= (precision or 0) then
					local mainsnak = item.mainsnak
					if mainsnak.snaktype ~= "value" or mainsnak.datatype ~= "quantity" then
						error("'property' parameter must be numeric")
					end
					local y = tonumber(mainsnak.datavalue.value.amount)
	
					if not series.points[x] then series.points[x] = {} end
					series.points[x][seriesIdx] = y
				end
			end
		end
	end

	-- Sort x values
	local xValues = {}
	for k in pairs(series.points) do table.insert(xValues, k) end
	table.sort(xValues)

    -- default values, can be overwritten
	local chartArgs =
	{
		type = "line",
		xType = "date",
		x = table.concat(xValues, ","),
		yType = "number",
		
		-- these are not supported anymore with new chart extension as of now..
--		xAxisTitle = mw.wikibase.label(xQualifier),		
--		yAxisTitle = mw.wikibase.label(property)
	}
	-- Set legends / series titles
	for seriesIdx, caption in ipairs(series.captions) do
		chartArgs["y" .. seriesIdx] = ""
		chartArgs["y" .. seriesIdx .. "Title"] = caption
	end
	-- Set values
	local seriesCount = #series.captions
	for _, x in ipairs(xValues) do
		yValues = series.points[x]
		for seriesIdx = 1, seriesCount do
			chartArgs["y" .. seriesIdx] = chartArgs["y" .. seriesIdx] .. "," .. (yValues[seriesIdx] or "")
		end
	end
	-- Remove separators at the beginning
	for seriesIdx, _ in ipairs(series.captions) do
		chartArgs["y" .. seriesIdx] = mw.ustring.sub(chartArgs["y" .. seriesIdx], 2)
	end
	-- Transfer diagram parameters (all parameters that start with chart_ are transferred directly to the Graph module without a prefix)
	for k, v in pairs(frame.args) do
		local chartParam = string.match(k, "^chart_(.+)")
		if chartParam then chartArgs[chartParam] = v end
	end

 	
	--workaround, to better show dates since the extension doesn't support them yet properly
	if chartArgs["xType"]=="date" then
		xValuesCutted = {}
		for _, k in pairs(xValues) do
			table.insert(xValuesCutted,string.sub( k, 1, 10))
		end
		chartArgs["x"] = table.concat(xValuesCutted, ",")
	end
	-- if number, use precision to round (default 9=years)
	if chartArgs["xType"]=="number" then
		xValuesCutted = {}
		for _, k in pairs(xValues) do
			table.insert(xValuesCutted,mw.getContentLanguage():formatDate(xAxisFormat, k))
		end
		chartArgs["x"] = table.concat(xValuesCutted, ",")
	end
	
	-- create the plot
	local resultplot
	resultplot = mw.getCurrentFrame():expandTemplate {
		title = 'Template:ChartDirect',
		args = chartArgs
		}
		
	return resultplot
end

function p.plotWrapper(frame)
	return p.plot(frame:getParent())
end

function applyPrecision(date, precision)
	if not precision then precision = math.huge end

	local _, _, year, month, day, hour, minute, second, timezone = string.find(date, "^(.?%d+)-(%d+)-(%d+)T(%d+):(%d+):(%d+)(.+)$")
	if precision < 14 then second = "00" end
	if precision < 13 then minute = "00" end
	if precision < 12 then hour = "00" end
	if precision < 11 or day == "00" then day = "01" end
	if precision < 10 or month == "00" then month = "01" end
	return year .. "-" .. month .. "-" .. day .. "T" .. hour .. ":" .. minute .. ":" .. second .. timezone
end

return p