local magic = 0x5f7d
local magic_rev = 0x7d5f
local header = "I2I2I2I2I2I6I6"

local function read_header(dat)
	local e = "<"
	local m = string.unpack("<I2", dat)
	if m ~= magic and m ~= magic_rev then return nil, "bad magic" end
	if m ~= magic then
		e = ">"
	end
	local ent = {}
	ent.magic, ent.namesize, ent.mode, ent.uid, ent.gid, ent.filesize, ent.mtime = string.unpack(e..header_fmt, dat)
	return ent
end

local arc = {}

function arc:read(path)
	for i=1, #self.tbl do
		if (self.tbl[i].name == path and self.tbl[i].mode & 32768 > 0) then
			self.seek(self.tbl[i].pos-self.seek(0))
			return self.read(self.tbl[i].filesize), self.tbl[i]
		end
	end
	return nil, "file not found"
end

function arc:exists(path)
	for i=1, #self.tbl do
		if (self.tbl[i].name == path) then
			return true
		end
	end
	return false
end

function arc:list(path)
	if path:sub(#path) ~= "/" then path = path .. "/" end
	local ent = {}
	for i=1, #self.tbl do
		if (self.tbl[i].name:sub(1, #path) == path and not self.tbl[i].name:find("/", #path+1, false)) then
			ent[#ent+1] = self.tbl[i].name
		end
	end
	return ent
end

function arc:meta(path)
	for i=1, #self.tbl do
		if (self.tbl[i].name == path) then
			return self.tbl[i]
		end
	end
	return nil, "file not found"
end

function arc:stream(path)
	for i=1, #self.tbl do
		if (self.tbl[i].name == path) then
			return kio.create_stream({dev=self.dev, start=self.tbl[i].pos, size=self.tbl[i].filesize, pos=1}, {
				read = function(self, amt)
					self.dev:seek("set", self.pos+self.start-1)
					if (self.pos+amt-1 > self.size) then
						amt = self.size-self.pos
					end
					local dat = self.dev:read(amt)
					self.pos = self.pos + #dat
					return dat
				end,
				seek = function(self, whence, amt)
					self.pos = kio.calc_seek(whence, amt, self.size, self.pos)
					return self.pos
				end,
				write = function(self)
					return kio.get_error(kio.errno.UNSUPPORTED_OPERATION)
				end,
				close = function(self)
					
				end
			})
		end
	end
end

function arc:trailer()
	self.dev:seek("set", self.tbl.trailer.pos)
	return self.dev:read(self.tbl.trailer.filesize)
end

function arc:close()
	self.close()
end

return {
	read = function(dev)
		local function read(a)
			return dev:read(a)
		end
		local function seek(a)
			return dev:seek("cur", a)
		end
		local function close()
			return dev:close()
		end
		local start = seek(0)
		local tbl = {}
		local lname = ""
		while lname ~= "TRAILER!!!" do
			local dat = read(22)
			local et = read_header(dat)
			et.name = read(et.namesize)
			et.pos = seek(et.namesize & 1)
			seek(et.filesize + (et.filesize & 1))
			lname = et.name
			if lname ~= "TRAILER!!!" then
				tbl[#tbl+1] = et
			else
				tbl.trailer = et
			end
		end
		return setmetatable({tbl = tbl, read = read, seek = seek, close = close, dev=dev, start=true}, {__index=arc})
	end
}