Module:Template parameter value

Implements {{Template parameter value}}

---

local p = {}
local escape = require("Module:String")._escapePattern
function trimspaces(s)
	return string.gsub(s, "^%s*(.-)%s*$", "%1")
end

local function getTitle(title)
	local success, titleObj = pcall(mw.title.new, title)
	if success then return titleObj
	else return nil end
end

function p.main(frame)
	local args = require('Module:Arguments').getArgs(frame, {
		wrappers = 'Template:Template parameter value'
	})
	local template = escape(args[2])
	local parameter = escape(args[4])
	local numberedParameter = (tonumber(parameter) ~= nil)
	
	local templateCount = 0
	local parameterCount = 0
	local pipemarker = '~_~TPVPIPEMARKER~_~'
	local templateMatch = tonumber(args[3] or 1)
	local parameterMatch = tonumber(args[5] or 1)*(numberedParameter and parameter or 1)
	
	local targettitle = getTitle(args[1])
	if targettitle == nil then return "" end
    local content = string.gsub(targettitle:getContent() or "", "[\r\n]", "")
	
	-- Escape some pipes
	content = string.gsub(content, '(%[%[[^%[{}]*)|([^%[%]{}]*%]%])', '%1' .. pipemarker ..'%2')
	
	while templateCount ~= templateMatch do
		if content == nil then return "" end
		content = string.match(content, '{{' .. template .. "(.+)")
		templateCount = templateCount + 1
	end
	
	while parameterCount ~= parameterMatch do
		if content == nil then return "" end
		content = string.match(content, '|%s*' .. (numberedParameter and "" or parameter .. '%s*=%s*') .. '([^|].*)')
		parameterCount = parameterCount + 1
	end
	
	if content == nil then return "" end
	
	content = string.gsub(content, "</?%a*include%a*>", "")
	content = string.match(content, '^([^|}]*{{[^}]+}}[^|}]*)|') or string.match(content, '([^|}]+)')
	content = string.gsub(content, pipemarker, '|')
	content = frame:preprocess{text = content}
	content = trimspaces(content)
	
	return content
end

return p