local CXX = "clang++"

local config = {
	["buildmode"]="debug",
	["target"]="x86_64-windows",
	["max_parallel"]=1
}

local program_output = "build/lbs"
local source_dirs = {"src", "thirdparty/uniproc/src"}
local include_dirs = {"include", "src", "thirdparty/luajit/src", "thirdparty/uniproc/include"}
local library_dirs = {"thirdparty/luajit/src"}
local linker_inputs = {"lua51", "luajit"}
local defines = {}
local additional_arguments = {"-std=c++20"}

local function load_config(cfg_table, args)
	for i=1,#args,1 do
		k = args[i]	
		if (k:sub(1,2) == "-j") then
			if (tonumber(k:sub(3,-1),10) > 0) then
				cfg_table.max_parallel = tonumber(k:sub(3,-1),10)
			elseif (tonumber(args[i+1],10) > 0) then
				cfg_table.max_parallel = tonumber(args[i+1],10)
				i = i + 1
			else
				print("ERROR: -j option must be formatted as -j<num> or -j <num>. Numbers must be positive integers greater than 0")
				return -1
			end
		else
			cfg_table.buildmode = k
		end
	end
	return cfg_table
end

function table.shallow_copy(tbl)
	local new = {}
	for k,v in pairs(tbl) do
		new[k] = v
	end
	return new
end

local function get_required_objects(dirs, src_extension, obj_prefix, obj_postfix)
	obj_prefix = obj_prefix or "obj/"
	obj_postfix = obj_postfix or ".o"
	local objs = {}
	local new_src = {}
	for fsobj in fs.forall(dirs) do
		-- Get all files in the directory
		local src_files
		if fs.is_dir(fsobj) then src_files = fs.list_alldirs(fsobj)
		else src_files = {fsobj} end
		-- For each of the files,
		for _, src_file in pairs(src_files) do repeat
			-- Skip files that don't end in the provided extension
			if (fs.extension(src_file) ~= src_extension) then break end
			local obj_file = obj_prefix .. src_file .. obj_postfix
			-- Skip old files that do not need to be recompiled
			if not fs.is_newer(src_file) then break end
			-- Add the src and obj file to a table that will be returned
			objs[#objs+1] = obj_file
			new_src[#new_src+1] = src_file
		until true end
	end
	return objs, new_src
end

local function compile(CXX, src_dirs, include_dirs, defines, additional_arguments)
	local base_argv = {}
	
	additional_arguments[#additional_arguments+1] = "-c"
	for _,v in pairs(additional_arguments) do base_argv[#base_argv+1] = v end
	for _,v in pairs(include_dirs) do base_argv[#base_argv+1] = "-I\"" .. v .. "\"" end
	for k,v in pairs(defines) do base_argv[#base_argv+1] = "-D" .. k .. "=" .. v end

	local obj_files, src_files = get_required_objects(src_dirs, ".cpp")
	local argv = {}
	for k,obj_file in pairs(obj_files) do
		local args = table.shallow_copy(base_argv)
		args[#args+1] = src_files[k]
		args[#args+1] = "-o\"" .. obj_file .. "\""
		argv[#argv+1] = args
	end

	local ec, stdout, stderr = platform.exec_parallel(CXX, config.max_parallel, argv)
	for i,ec in pairs(ec) do
		if (ec ~= 0) then
			print("Command \"" .. CXX .. " " .. table.concat(argv[i], " ") .. "\" failed with exit code " .. tostring(ec) .. " and output;")
			if (#stderr ~= 0) then print(stderr[i]) else print(stdout[i]) end
			print()
		end
	end
end

local function link(LNK, obj_dirs, library_dirs, linker_inputs, additional_arguments)
	local argv = {}
	for _,v in pairs(library_dirs) do argv[#argv+1] = "-L\"" .. v .. "\"" end
	for _,v in pairs(linker_inputs) do argv[#argv+1] = "-l\"" .. v .. "\"" end
	for _,v in pairs(additional_arguments) do argv[#argv+1] = v end
	
	local ec, stdout, stderr = platform.exec(LNK, argv)
	if (ec ~= 0) then
		print("Command \"" .. LNK .. " " .. table.concat(argv) .. "\" failed with exit code " .. tostring(ec) .. " and output;")
		if (#stderr ~= 0) then print(stderr[i]) else print(stdout[i]) end
		print()
	end
end

function build(...)
	local args = {...}
	config = load_config(config, args)
	print("Building " .. config.buildmode .. " with up to " .. tostring(config.max_parallel) .. " concurrent jobs")
	
	compile(CXX, source_dirs, include_dirs, defines, additional_arguments)
	link(CXX, "obj", library_dirs, linker_inputs, {})
end

return 0