package v2raywebsocket

import (
	"bufio"
	"context"
	"encoding/base64"
	"io"
	"net"
	"os"
	"sync"
	"time"

	C "github.com/sagernet/sing-box/constant"
	"github.com/sagernet/sing/common"
	"github.com/sagernet/sing/common/buf"
	"github.com/sagernet/sing/common/debug"
	E "github.com/sagernet/sing/common/exceptions"
	"github.com/sagernet/ws"
	"github.com/sagernet/ws/wsutil"
)

type WebsocketConn struct {
	net.Conn
	*Writer
	state          ws.State
	reader         *wsutil.Reader
	controlHandler wsutil.FrameHandlerFunc
	remoteAddr     net.Addr
}

func NewConn(conn net.Conn, br *bufio.Reader, remoteAddr net.Addr, state ws.State) *WebsocketConn {
	controlHandler := wsutil.ControlFrameHandler(conn, state)
	var reader io.Reader
	if br != nil && br.Buffered() > 0 {
		reader = br
	} else {
		reader = conn
	}
	return &WebsocketConn{
		Conn:  conn,
		state: state,
		reader: &wsutil.Reader{
			Source:          reader,
			State:           state,
			SkipHeaderCheck: !debug.Enabled,
			OnIntermediate:  controlHandler,
		},
		controlHandler: controlHandler,
		remoteAddr:     remoteAddr,
		Writer:         NewWriter(conn, state),
	}
}

func (c *WebsocketConn) Close() error {
	c.Conn.SetWriteDeadline(time.Now().Add(C.TCPTimeout))
	frame := ws.NewCloseFrame(ws.NewCloseFrameBody(
		ws.StatusNormalClosure, "",
	))
	if c.state == ws.StateClientSide {
		frame = ws.MaskFrameInPlace(frame)
	}
	ws.WriteFrame(c.Conn, frame)
	c.Conn.Close()
	return nil
}

func (c *WebsocketConn) Read(b []byte) (n int, err error) {
	var header ws.Header
	for {
		n, err = c.reader.Read(b)
		if n > 0 {
			err = nil
			return
		}
		if !E.IsMulti(err, io.EOF, wsutil.ErrNoFrameAdvance) {
			return
		}
		header, err = c.reader.NextFrame()
		if err != nil {
			return
		}
		if header.OpCode.IsControl() {
			err = c.controlHandler(header, c.reader)
			if err != nil {
				return
			}
			continue
		}
		if header.OpCode&ws.OpBinary == 0 {
			err = c.reader.Discard()
			if err != nil {
				return
			}
			continue
		}
	}
}

func (c *WebsocketConn) Write(p []byte) (n int, err error) {
	err = wsutil.WriteMessage(c.Conn, c.state, ws.OpBinary, p)
	if err != nil {
		return
	}
	n = len(p)
	return
}

func (c *WebsocketConn) RemoteAddr() net.Addr {
	if c.remoteAddr != nil {
		return c.remoteAddr
	}
	return c.Conn.RemoteAddr()
}

func (c *WebsocketConn) SetDeadline(t time.Time) error {
	return os.ErrInvalid
}

func (c *WebsocketConn) SetReadDeadline(t time.Time) error {
	return os.ErrInvalid
}

func (c *WebsocketConn) SetWriteDeadline(t time.Time) error {
	return os.ErrInvalid
}

func (c *WebsocketConn) NeedAdditionalReadDeadline() bool {
	return true
}

func (c *WebsocketConn) Upstream() any {
	return c.Conn
}

type EarlyWebsocketConn struct {
	*Client
	ctx    context.Context
	conn   *WebsocketConn
	access sync.Mutex
	create chan struct{}
	err    error
}

func (c *EarlyWebsocketConn) Read(b []byte) (n int, err error) {
	if c.conn == nil {
		<-c.create
		if c.err != nil {
			return 0, c.err
		}
	}
	return c.conn.Read(b)
}

func (c *EarlyWebsocketConn) writeRequest(content []byte) error {
	var (
		earlyData []byte
		lateData  []byte
		conn      *WebsocketConn
		err       error
	)
	if len(content) > int(c.maxEarlyData) {
		earlyData = content[:c.maxEarlyData]
		lateData = content[c.maxEarlyData:]
	} else {
		earlyData = content
	}
	if len(earlyData) > 0 {
		earlyDataString := base64.RawURLEncoding.EncodeToString(earlyData)
		if c.earlyDataHeaderName == "" {
			requestURL := c.requestURL
			requestURL.Path += earlyDataString
			conn, err = c.dialContext(c.ctx, &requestURL, c.headers)
		} else {
			headers := c.headers.Clone()
			headers.Set(c.earlyDataHeaderName, earlyDataString)
			conn, err = c.dialContext(c.ctx, &c.requestURL, headers)
		}
	} else {
		conn, err = c.dialContext(c.ctx, &c.requestURL, c.headers)
	}
	if err != nil {
		return err
	}
	if len(lateData) > 0 {
		_, err = conn.Write(lateData)
		if err != nil {
			return err
		}
	}
	c.conn = conn
	return nil
}

func (c *EarlyWebsocketConn) Write(b []byte) (n int, err error) {
	if c.conn != nil {
		return c.conn.Write(b)
	}
	c.access.Lock()
	defer c.access.Unlock()
	if c.err != nil {
		return 0, c.err
	}
	if c.conn != nil {
		return c.conn.Write(b)
	}
	err = c.writeRequest(b)
	c.err = err
	close(c.create)
	if err != nil {
		return
	}
	return len(b), nil
}

func (c *EarlyWebsocketConn) WriteBuffer(buffer *buf.Buffer) error {
	if c.conn != nil {
		return c.conn.WriteBuffer(buffer)
	}
	c.access.Lock()
	defer c.access.Unlock()
	if c.conn != nil {
		return c.conn.WriteBuffer(buffer)
	}
	if c.err != nil {
		return c.err
	}
	err := c.writeRequest(buffer.Bytes())
	c.err = err
	close(c.create)
	return err
}

func (c *EarlyWebsocketConn) Close() error {
	if c.conn == nil {
		return nil
	}
	return c.conn.Close()
}

func (c *EarlyWebsocketConn) LocalAddr() net.Addr {
	if c.conn == nil {
		return nil
	}
	return c.conn.LocalAddr()
}

func (c *EarlyWebsocketConn) RemoteAddr() net.Addr {
	if c.conn == nil {
		return nil
	}
	return c.conn.RemoteAddr()
}

func (c *EarlyWebsocketConn) SetDeadline(t time.Time) error {
	return os.ErrInvalid
}

func (c *EarlyWebsocketConn) SetReadDeadline(t time.Time) error {
	return os.ErrInvalid
}

func (c *EarlyWebsocketConn) SetWriteDeadline(t time.Time) error {
	return os.ErrInvalid
}

func (c *EarlyWebsocketConn) NeedAdditionalReadDeadline() bool {
	return true
}

func (c *EarlyWebsocketConn) Upstream() any {
	return common.PtrOrNil(c.conn)
}

func (c *EarlyWebsocketConn) LazyHeadroom() bool {
	return c.conn == nil
}