--[[
	Various functional programming bits and bobs
	Function signatures:
		fn.curry(func,...) 		:: 		function(...)	::	any
		fn.map(tbl,func) 		:: 		table
		fn.compose(...) 		:: 		function(...)	::	any
		fn.filter(tbl,func) 	:: 		table
		fn.zip(...) 			:: 		table
		fn.fill(arg,times) 		:: 		table
		fn.amalg(...)			::		function(...)	::	any
		fn.cycle(tbl)			::		table
		fn.fold(tbl)			::		function(func(T1,T2)::T)	::	T
		fn.flatten(tbl)			::		table
]]
--AddCSLuaFile()
local fn = {}

if table.Copy == nil then
	function table.Copy(tbl)
		local ntbl = {}
		for k,v in pairs(tbl) do ntbl[k] = v end
		return ntbl
	end
end

--[[
	Puts some arguments "in" a function so that it can be called with some number fewer arguments.
	Ex:
		local f = include("nightz/gamemode/utility/functional.lua")
		local debugprint = f.curry(print,"[DEBUG]")
		debugprint("Hello, world!")
		--Is the same as
		print("[DEBUG]","Hello, world!")
]]
function fn.curry(func,...)
	local nargs = {...}
	return function(...)
		for k,v in pairs({...}) do
			nargs[k + #nargs] = v
		end
		func(unpack(nargs))
	end
end

--[[
	calls each function from first to last on every element of tbl, and returns a table with the function called.
	Ex:
		local f = include("nightz/gamemode/utility/functional.lua")
		local playerents = {
			Player(1),
			Player(2),
			Player(3)
		}
		local getname = function(ply) return ply:Nick() end
		local playernames = f.map(playerents)
		--playernames is now a table {
			"Player1_name",
			"Player2_name",
			"Player3_name"
		}
]]
function fn.map(tbl,...)
	local nfuncs = {...}
	local ntbl = table.Copy(tbl)
	for i,j in pairs(nfuncs) do
		for k,v in pairs(tbl) do
			ntbl[k] = j(v)
		end
	end
	return ntbl
end

--[[
	Calls a list of functions, starting with the last, going to the first, and passes the arguments as whatever was outputed from the previous function.
	Ex:
		local f = include("nightz/gamemode/utility/functional.lua")
		local printf = f.compose(print,string.format)
		printf("Thanks, I love %d",5)
		--Is the same as
		print(string.format("Thanks, I love %d", 5))
]]
function fn.compose(...)
	local nargs = {...}
	local n = #nargs
	local lastresult
	return function(...)
		lastresult = {...}
		while n > 0 do
			lastresult = {nargs[n](unpack(lastresult))}
			n = n - 1
		end
	end
end

--[[
	Removes elements from tbl for which func returns nil or false (returns new table). this WILL mess up order for arrays.
	Ex:
		local f = include("nightz/gamemode/utility/functional.lua")
		local sometable = {
			1,3,4,5,5,6,7,8,9
		}
		for k,v in pairs(sometable) do print(k,":",v) end
		--this will print:
			1:1
			2:3
			3:4
			4:5
			5:5
			6:6
			7:7
			8:8
			9:9
		local function iseven(k) return k%2 == 0 end
		local evens = f.filter(sometable,iseven)
		for k,v in pairs(evens) do print(k,":",v) end
		--this will print:
			3:4
			6:6
			8:8
]]
function fn.filter(tbl,func)
	local ntbl = table.Copy(tbl)
	for k,v in pairs(ntbl) do
		if not func(v) then
			ntbl[k] = nil
		end
	end
end

--Takes n tables that have the same indexes, and returns a table that for every index, it's value is {tbl1[index],tbl2[index],...,tbln[index]}
function fn.zip(...)
	local nargs = {...}
	local ntbl = table.Copy(nargs[1])
	for k,v in pairs(ntbl) do
		local ttbl = {}
		for i,j in pairs(nargs) do
			ttbl[#ttbl + 1] = v[i]
		end
		ntbl[k] = ttbl
	end
	return ntbl
end

--Creates a table filled with <times> number of arg
function fn.fill(arg,times)
	local ret = {}
	for i = 1,times do
		ret[i] = arg
	end
	return ret
end

--Calls all functions passed in order, and returns all results for all functions called.S
function fn.amalg(...)
	local nargs = {...}
	return function(...)
		local nret = {}
		for k,v in pairs(nargs) do
			local tret = {v(unpack({...}))}
			for i,j in pairs(tret) do
				nret[#nret + 1] = j
			end
		end
		return unpack(nret)
	end
end

--[[
Cycles a table infinitely
	Ex:
		local sometbl = {1,2,3}
		fn.cycle(sometbl)
		for i = 1, 100 do
			print(sometbl[i])
		end
	Outputs:
		1
		2
		3
		1
		2
		:
		:
		:
]]
function fn.cycle(tbl)
	local ntbl = table.Copy(tbl)
	local tbllen = #tbl
	local mt = {
		__index = function(self, ind)
			local id = (ind % tbllen) + 1
			return tbl[id]
		end
	}
	setmetatable(ntbl,mt)
	return ntbl
end

--[[
	Iterates over a table applying a function to each item
	Ex:
		local sometbl = {1,4,5,6,7,10}
		local add = function(a,b) return a + b end
		local sum = fn.fold(sometbl)(add)
		print(sum)
	Output:
		33
]]
function fn.fold(tbl)
	return function(func)
		local running = tbl[1]
		for k = 2, #tbl do
			running = func(running,tbl[k])
		end
		return running
	end
end

--[[
	Returns an array-type table
]]
function fn.flatten(tbl)
	local ret = {}
	for k,v in pairs(tbl) do
		ret[#ret + 1] = v
	end
	return ret
end

return fn