// Copyright (c) 2022 Nadeen Udantha <me@nadeen.lk>. All rights reserved.

package boihttp

import (
	"bufio"
	"context"
	"errors"
	"fmt"
	"io"
	"net"
	"os"
)

type Handler func(req *Message, reqbody io.Reader, res *Message) (resbody io.Reader)

func Listen(addr string, ctx context.Context, handler Handler) (err error) {
	var lc net.ListenConfig
	l, err := lc.Listen(ctx, "tcp", addr)
	if err != nil {
		return
	}
	return Serve(l, handler)
}

func Serve(l net.Listener, handler Handler) (err error) {
	for {
		c, err := l.Accept()
		if err != nil {
			return err
		}
		go handler2(c, handler)
	}
}

func handler2(c net.Conn, handler Handler) {
	defer c.Close()
	err := Handle(bufio.NewReadWriter(bufio.NewReader(c), bufio.NewWriter(c)), handler)
	if err != nil {
		if errors.Is(err, io.EOF) {
			return
		}
		if _, z := err.(net.Error); z {
			return
		}
		fmt.Fprintf(os.Stderr, "boihttp error: %s\n", err)
	}
}

func Handle(c *bufio.ReadWriter, handler Handler) (err error) {
	for {
		more, err := handle(c, handler)
		if err != nil {
			return err
		}
		if !more {
			break
		}
	}
	return
}

func handle(c *bufio.ReadWriter, handler Handler) (more bool, err error) {
	req := new(Message)
	err = req.ReadRequest(c.Reader)
	if err != nil {
		return
	}
	reqbody := req.body(c.Reader)
	res := new(Message)
	res.Headers = make(Headers)
	res.SetKeepAlive(req.KeepAlive() || (req.Version == VersionHTTP1_1 && !req.Has("Connection")))
	res.Version = req.Version
	resbody := handler(req, reqbody, res)
	_, err = io.Copy(io.Discard, reqbody)
	if err != nil {
		return
	}
	more = res.KeepAlive()
	err = res.WriteResponse(c.Writer)
	if err != nil {
		return
	}
	err = c.Writer.Flush()
	if err != nil {
		return
	}
	_, err = c.Writer.ReadFrom(resbody)
	if err != nil {
		return
	}
	err = c.Writer.Flush()
	if err != nil {
		return
	}
	return
}