// Copyright 2021, Chef.  All rights reserved.
// https://github.com/q191201771/lal
//
// Use of this source code is governed by a MIT-style license
// that can be found in the License file.
//
// Author: joestarzxh

package base

import (
	"crypto/sha1"
	"encoding/base64"
	"math"

	"github.com/q191201771/naza/pkg/bele"
)

// The WebSocket Protocol
// https://tools.ietf.org/html/rfc6455
//
// 0                   1                   2                   3
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
// +-+-+-+-+-------+-+-------------+-------------------------------+
// |F|R|R|R| opcode|M| Payload len |    Extended payload length    |
// |I|S|S|S|  (4)  |A|     (7)     |             (16/64)           |
// |N|V|V|V|       |S|             |   (if payload len==126/127)   |
// | |1|2|3|       |K|             |                               |
// +-+-+-+-+-------+-+-------------+ - - - - - - - - - - - - - - - +
// |     Extended payload length continued, if payload len == 127  |
// + - - - - - - - - - - - - - - - +-------------------------------+
// |                               |Masking-key, if MASK set to 1  |
// +-------------------------------+-------------------------------+
// | Masking-key (continued)       |          Payload Data         |
// +-------------------------------- - - - - - - - - - - - - - - - +
// :                     Payload Data continued ...                :
// + - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - +
// |                     Payload Data continued ...                |
// +---------------------------------------------------------------+
// opcode:
// *  %x0 denotes a continuation frame
// *  %x1 denotes a text frame
// *  %x2 denotes a binary frame
// *  %x3-7 are reserved for further non-control frames
// *  %x8 denotes a connection close
// *  %x9 denotes a ping
// *  %xA denotes a pong
// *  %xB-F are reserved for further control frames
// Payload length:  7 bits, 7+16 bits, or 7+64 bits
// Masking-key:  0 or 4 bytes
// mark 加密
// for i := 0; i < datalen; i {
//     m := markingkeys[i%4]
//     data[i] = msg[i] ^ m
// }
type WsOpcode = uint8

const (
	Wso_Continuous WsOpcode = iota //连续消息片断
	Wso_Text                       //文本消息片断,
	Wso_Binary                     //二进制消息片断,
	//非控制消息片断保留的操作码,
	Wso_Rsv3
	Wso_Rsv4
	Wso_Rsv5
	Wso_Rsv6
	Wso_Rsv7
	Wso_Close //连接关闭,
	Wso_Ping  //心跳检查的ping,
	Wso_Pong  //心跳检查的pong,
	//为将来的控制消息片断的保留操作码
	Wso_RsvB
	Wso_RsvC
	Wso_RsvD
	Wso_RsvE
	Wso_RsvF
)

type WsHeader struct {
	Fin    bool
	Rsv1   bool
	Rsv2   bool
	Rsv3   bool
	Opcode WsOpcode

	PayloadLength uint64

	Masked  bool
	MaskKey uint32
}

const WsMagicStr = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"

func MakeWsFrameHeader(wsHeader WsHeader) (buf []byte) {
	headerSize := 2
	payload := uint64(0)
	switch {
	case wsHeader.PayloadLength < 126:
		payload = wsHeader.PayloadLength
	case wsHeader.PayloadLength <= math.MaxUint16:
		payload = 126
		headerSize += 2
	case wsHeader.PayloadLength > math.MaxUint16:
		payload = 127
		headerSize += 8
	}
	if wsHeader.Masked {
		headerSize += 4
	}
	buf = make([]byte, headerSize, headerSize)
	if wsHeader.Fin {
		buf[0] |= 1 << 7
	}
	if wsHeader.Rsv1 {
		buf[0] |= 1 << 6
	}
	if wsHeader.Rsv2 {
		buf[0] |= 1 << 5
	}
	if wsHeader.Rsv3 {
		buf[0] |= 1 << 4
	}
	buf[0] |= wsHeader.Opcode

	if wsHeader.Masked {
		buf[1] |= 1 << 7
	}
	buf[1] |= (uint8(payload) & 0x7F)
	if payload == 126 {
		bele.BePutUint16(buf[2:], uint16(wsHeader.PayloadLength))
	} else if payload == 127 {
		bele.BePutUint64(buf[2:], wsHeader.PayloadLength)
	}

	if wsHeader.Masked {
		bele.LePutUint32(buf[headerSize-4:], wsHeader.MaskKey)
	}
	return buf
}
func UpdateWebSocketHeader(secWebSocketKey string) []byte {
	firstLine := "HTTP/1.1 101 Switching Protocol\r\n"
	sha1Sum := sha1.Sum([]byte(secWebSocketKey + WsMagicStr))
	secWebSocketAccept := base64.StdEncoding.EncodeToString(sha1Sum[:])
	webSocketResponseHeaderStr := firstLine +
		"Server: " + LalHttpflvSubSessionServer + "\r\n" +
		"Sec-WebSocket-Accept:" + secWebSocketAccept + "\r\n" +
		"Keep-Alive: timeout=15, max=100\r\n" +
		"Connection: Upgrade\r\n" +
		"Upgrade: websocket\r\n" +
		"Access-Control-Allow-Credentials: true\r\n" +
		"Access-Control-Allow-Origin: *\r\n" +
		"\r\n"
	return []byte(webSocketResponseHeaderStr)
}