local p={}

local function split(text, pattern, plain)
    local ret = {}
    local s, l = 1, string.len( text )
    while s do
    	local e, n = string.find( text, pattern, s, plain )
    	if not e then
    		table.insert(ret, string.sub ( text, s ))
    		s = nil
    	elseif n < e then
    		-- Empty separator!
    		table.insert(ret, string.sub ( text, s, e ))
    		if e < l then
    			s = e + 1
    		else
    			s = nil
    		end
    	else
    		table.insert(ret, e > s and string.sub( text, s, e - 1 ) or '')
    		s = n + 1
    	end
    end
    return ret
end

function p._parse(index, template, frame)
	if not frame then frame = mw.getCurrentFrame() end
	local error = ' when using {{tl|Inflation/' .. template .. '}}.{{main other|[[Category:Pages with errors in inflation template]]}}</span>'
	if index and index ~= 'ERR' then
		local tempTitle = "Inflation/" .. index .. "/dataset"
		local dataset = mw.title.new(tempTitle, "Template"):getContent()
		if dataset then
			local redirect = mw.ustring.match(dataset, "#REDIRECT%s*%[%[Template:Inflation/(.*)/dataset%]%]")
			if redirect then return p._parse(redirect, template, frame)	end
			dataset = mw.ustring.gsub(mw.ustring.gsub(dataset, "<!%-%-.-%-%->", ""), "\n?%s*|%s*#default%s*", "")
			local datatable = {}
			local data = split(dataset, "\n", true)
			for _, row in ipairs(data) do
				local year, value = mw.ustring.match(row, "%s*|%s*(%d%d%d%d)%s*=%s*([^=]+)%s*")
				if year and value and tonumber(year) then
					year = tonumber(year)
					if tonumber(value) then
						datatable[year] = tonumber(value)
					elseif mw.ustring.sub(value,1,8) == '{{#expr:' and mw.ustring.sub(value,-2) == '}}' then
						value = mw.ustring.sub(value, 3, -3)
						datatable[year] = tonumber(frame:callParserFunction( value ))
					end
				end
			end
			if table.maxn(datatable) > 0 then
				return datatable
			else
				error = '<span class="error">Error: unable to parse "Template:' .. tempTitle .. '"' .. error
			end
		else
			error = '<span class="error">Error: undefined index "' .. index .. '"' .. error
		end
	else
		error = '<span class="error">Error: no index specified' .. error
	end
	return frame:preprocess(error)
end

function p.year(frame)
	local index = frame.args.index or frame.args[1] or frame:getParent().args.index or frame:getParent().args[1]
	local result = p._parse(index, 'year', frame)
	if type(result) == "table" then
		return table.maxn(result)
	else
		return result
	end
end

return p