Module:Item

local p = {}

local function escape(str)
	return str:gsub("[|\\]", function (c) return string.format("\\%03d", c:byte()) end)
end

local function unescape(str)
	return str:gsub("\\(%d%d%d)", function (d) return string.char(d) end)
end

-- Implements [[Template:Item]]
function p.pack(frame)
	local parent = frame:getParent()
	local result = ''
	for key, value in pairs(parent.args) do
		result = result .. "|" .. escape(tostring(key)) .. "|" .. escape(value)
	end
	return result .. "|";
end

local function unpack(str)
	local result = { }
	for key, value in str:gfind("|([^|]*)|([^|]*)") do
		result[unescape(key)] = unescape(value)
	end
	return result
end

-- Implements [[Template:Component]]
function p.component(frame)
	return unpack(frame.args[1])[frame.args[2]]
end

local function getItems(frame)
	return frame:getParent().args
end

local function invert(tbl)
	local result = { }
	for key, value in pairs(tbl) do
		result[value] = key
	end
	return result
end

-- Add args into item as appropriate (see [[Template:Format item]])
local function addArgs(
	item,   -- unpacked item to modify
	args,   -- arguments for adding into item
	ignore, -- pass in invert{keys to ignore}
	shift   -- for numbered arguments, args[key+shift] is assigned to item[key]
	-- returns: item
)
	for key, value in pairs(args) do
		if not ignore[key] then
			local _, _, paramKey = string.find(key, "^param (.*)")
			local _, _, importantKey = string.find(key, "^important (.*)")
			paramKey = paramKey or importantKey or key
			if shift and type(paramKey) == "number" then
				paramKey = paramKey - shift
				if paramKey < 1 then paramKey = nil end
			end
			if paramKey and (importantKey or item[paramKey] == nil) then
				item[paramKey] = value
			end
		end
	end
	
	return item
end

-- Implements [[Template:Format item]]
function p.format(frame)
	local args = frame:getParent().args
	local ignore = invert{ "template", "item" }
	local templateArgs = addArgs(unpack(args.item), args, ignore)
	
	return frame:expandTemplate{ title = args.template, args = templateArgs }
end

-- See [[Template:Item#Format each item using a template]]
function p.each(frame)
	local args = frame.args
	local items = getItems(frame)
	local separator = args[1] or ""
	local prepend = args[2] or ""
	local append = args[3] or ""
	local ignore = invert{ "template" }
	local shift = 3

	local result = ""
	for i, item in ipairs(items) do
		local templateArgs = addArgs(unpack(item), args, ignore, shift)
		result = result .. prepend .. frame:expandTemplate{ title = args.template, args = templateArgs } .. append
		if items[i + 1] then
			result = result .. separator
		end
	end
	return result
end

-- See [[Template:Item#Gather given parameter from all items]]
function p.gather(frame)
	local args = frame.args
	local items = getItems(frame)
	local parameter = args.parameter or "1"
	
	local templateArgs = { }
	for i, item in ipairs(items) do
		templateArgs[i] = unpack(item)[parameter]
	end
	
	return frame:expandTemplate{ title = args.template, args = templateArgs }
end

return p