local tonumber = tonumber;

local assert = assert;

local url_parse = require "socket.url".parse;

local urldecode = require "util.http".urldecode;

local dbuffer = require "util.dbuffer";

local function preprocess_path(path)

	path = urldecode((path:gsub("//+", "/")));

	if path:sub(1,1) ~= "/" then

		path = "/"..path;

	end

	local level = 0;

	for component in path:gmatch("([^/]+)/") do

		if component == ".." then

			level = level - 1;

		elseif component ~= "." then

			level = level + 1;

		end

		if level < 0 then

			return nil;

		end

	end

	return path;

end

local httpstream = {};

function httpstream.new(success_cb, error_cb, parser_type, options_cb)

	local client = true;

	if not parser_type or parser_type == "server" then client = false; else assert(parser_type == "client", "Invalid parser type"); end

	local bodylimit = tonumber(options_cb and options_cb().body_size_limit) or 10*1024*1024;

	-- https://stackoverflow.com/a/686243

	-- Individual headers can be up to 16k? What madness?

	local headlimit = tonumber(options_cb and options_cb().head_size_limit) or 10*1024;

	local buflimit = tonumber(options_cb and options_cb().buffer_size_limit) or bodylimit * 2;

	local buffer = dbuffer.new(buflimit);

	local chunked;

	local state = nil;

	local packet;

	local len;

	local have_body;

	local error;

	return {

		feed = function(_, data)

			if error then return nil, "parse has failed"; end

			if not data then -- EOF

				if state and client and not len then -- reading client body until EOF

					buffer:collapse();

					packet.body = buffer:read_chunk() or "";

					packet.partial = nil;

					success_cb(packet);

					state = nil;

				elseif buffer:length() ~= 0 then -- unexpected EOF

					error = true; return error_cb("unexpected-eof");

				end

				return;

			end

			if not buffer:write(data) then error = true; return error_cb("max-buffer-size-exceeded"); end

			while buffer:length() > 0 do

				if state == nil then -- read request

					local index = buffer:sub(1, headlimit):find("\r\n\r\n", nil, true);

					if not index then return; end -- not enough data

					-- FIXME was reason_phrase meant to be passed on somewhere?

					local method, path, httpversion, status_code, reason_phrase; -- luacheck: ignore reason_phrase

					local first_line;

					local headers = {};

					for line in buffer:read(index+3):gmatch("([^\r\n]+)\r\n") do -- parse request

						if first_line then

							local key, val = line:match("^([^%s:]+): *(.*)$");

							if not key then error = true; return error_cb("invalid-header-line"); end -- TODO handle multi-line and invalid headers

							key = key:lower();

							headers[key] = headers[key] and headers[key]..","..val or val;

						else

							first_line = line;

							if client then

								httpversion, status_code, reason_phrase = line:match("^HTTP/(1%.[01]) (%d%d%d) (.*)$");

								status_code = tonumber(status_code);

								if not status_code then error = true; return error_cb("invalid-status-line"); end

								have_body = not

									 ( (options_cb and options_cb().method == "HEAD")

									or (status_code == 204 or status_code == 304 or status_code == 301)

									or (status_code >= 100 and status_code < 200) );

							else

								method, path, httpversion = line:match("^(%w+) (%S+) HTTP/(1%.[01])$");

								if not method then error = true; return error_cb("invalid-status-line"); end

							end

						end

					end

					if not first_line then error = true; return error_cb("invalid-status-line"); end

					chunked = have_body and headers["transfer-encoding"] == "chunked";

					len = tonumber(headers["content-length"]); -- TODO check for invalid len

					if client then

						-- FIXME handle '100 Continue' response (by skipping it)

						if not have_body then len = 0; end

						packet = {

							code = status_code;

							httpversion = httpversion;

							headers = headers;

							body = false;

							body_length = len;

							chunked = chunked;

							partial = true;

							-- COMPAT the properties below are deprecated

							responseversion = httpversion;

							responseheaders = headers;

						};

					else

						local parsed_url;

						if path:byte() == 47 then -- starts with /

							local _path, _query = path:match("([^?]*).?(.*)");

							if _query == "" then _query = nil; end

							parsed_url = { path = _path, query = _query };

						else

							parsed_url = url_parse(path);

							if not(parsed_url and parsed_url.path) then error = true; return error_cb("invalid-url"); end

						end

						path = preprocess_path(parsed_url.path);

						headers.host = parsed_url.host or headers.host;

						len = len or 0;

						packet = {

							method = method;

							url = parsed_url;

							path = path;

							httpversion = httpversion;

							headers = headers;

							body = false;

							body_sink = nil;

							chunked = chunked;

							partial = true;

						};

					end

					if len and len > bodylimit then

						-- Early notification, for redirection

						success_cb(packet);

						if not packet.body_sink then error = true; return error_cb("content-length-limit-exceeded"); end

					end

					if chunked and not packet.body_sink then

						success_cb(packet);

						if not packet.body_sink then

							packet.body_buffer = dbuffer.new(buflimit);

						end

					end

					state = true;

				end

				if state then -- read body

					if chunked then

						local chunk_header = buffer:sub(1, 512); -- XXX How large do chunk headers grow?

						local chunk_size, chunk_start = chunk_header:match("^(%x+)[^\r\n]*\r\n()");

						if not chunk_size then return; end

						chunk_size = chunk_size and tonumber(chunk_size, 16);

						if not chunk_size then error = true; return error_cb("invalid-chunk-size"); end

						if chunk_size == 0 and chunk_header:find("\r\n\r\n", chunk_start-2, true) then

							local body_buffer = packet.body_buffer;

							if body_buffer then

								packet.body_buffer = nil;

								body_buffer:collapse();

								packet.body = body_buffer:read_chunk() or "";

							end

							buffer:collapse();

							local buf = buffer:read_chunk();

							buf = buf:gsub("^.-\r\n\r\n", ""); -- This ensure extensions and trailers are stripped

							buffer:write(buf);

							state, chunked = nil, nil;

							packet.partial = nil;

							success_cb(packet);

						elseif buffer:length() - chunk_start - 2 >= chunk_size then -- we have a chunk

							buffer:discard(chunk_start - 1); -- TODO verify that it's not off-by-one

							(packet.body_sink or packet.body_buffer):write(buffer:read(chunk_size));

							buffer:discard(2); -- CRLF

						else -- Partial chunk remaining

							break;

						end

					elseif packet.body_sink then

						local chunk = buffer:read_chunk(len);

						while chunk and len > 0 do

							if packet.body_sink:write(chunk) then

								len = len - #chunk;

								chunk = buffer:read_chunk(len);

							else

								error = true;

								return error_cb("body-sink-write-failure");

							end

						end

						if len == 0 then

							state = nil;

							packet.partial = nil;

							success_cb(packet);

						end

					elseif buffer:length() >= len then

						assert(not chunked)

						packet.body = buffer:read(len) or "";

						state = nil;

						packet.partial = nil;

						success_cb(packet);

					else

						break;

					end

				else

					break;

				end

			end

		end;

	};

end

return httpstream;