--[[
	Copyright (C) 2023
	Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted.

	THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE
]]

local function read(fn)
	local fd = io.open(fn, "r")
	
	if not fd then return nil end
	
	local ret = fd:read("*all")
	fd:close()
	return ret
end

local function compile(src, name)
	local code = {"RETURN_STRINGS={} "}
	
	name = name or "Lyre Render"
	
	while true do
		local startI = select(2, src:find("{[{%%]", 1, false))
		local endI
		local isstmt = false
		
		if startI then
			isstmt = src:byte(startI) == string.byte("%")
			endI = select(2, src:find(isstmt and "%%}" or "}}", 1, false))
		end
		
		if startI and endI then
			if endI < startI then
				table.insert(code, ";RETURN_STRINGS[#RETURN_STRINGS+1]="..string.format("%q", src:sub(1, startI - 2)))
				src = src:sub(startI - 1)
			else
				table.insert(code, ";RETURN_STRINGS[#RETURN_STRINGS+1]="..string.format("%q", src:sub(1, startI - 2)))
				
				if isstmt then
					table.insert(code, src:sub(startI + 1, endI - 2))
				else
					table.insert(code, "RETURN_STRINGS[#RETURN_STRINGS+1]=tostring("..src:sub(startI + 1, endI - 2)..")")
				end
				
				table.insert(code, ret)
				
				src = src:sub(endI + 1)
			end
		else
			table.insert(code, "RETURN_STRINGS[#RETURN_STRINGS+1]="..string.format("%q", src)..";return table.concat(RETURN_STRINGS)")
			break
		end
	end

	local env = setmetatable({table = table, tostring = tostring, tonumber = tonumber, pairs = pairs, ipairs = ipairs, string = string, math = math, RETURN_STRINGS = {}, type = type}, {})
	
	local chu, err
	if _ENV then
		chu, err = load(table.concat(code), name, "t", env)
		if err then error(err) end
	else
		chu, err = loadstring(table.concat(code), name)
		if err then error(err) end
		setfenv(chu, env)
	end
	
	return {chu = chu, env = env}
end

local function render(tmpl, envOverride, strongEnv)
	local mt = getmetatable(tmpl.env)
	mt.__index = envOverride
	if strongEnv then mt.__newindex = envOverride end
	return tmpl.chu()
end

return {
	render = render,
	compile = compile,
	compilef = function(fn) return compile(read(fn), fn) end
}