package server

import (
	"bytes"
	"encoding/binary"
	"errors"
	"fmt"
	"io"
	"net"
	"strings"
	"time"

	"github.com/tidwall/resp"
	"github.com/tidwall/tile38/core"
	"github.com/tidwall/tile38/internal/log"
)

// This phrase is copied nearly verbatim from Redis.
var deniedMessage = []byte(strings.Replace(strings.TrimSpace(`
-DENIED Tile38 is running in protected mode because protected mode is enabled,
no bind address was specified, no authentication password is requested to
clients. In this mode connections are only accepted from the loopback
interface. If you want to connect from external computers to Tile38 you may
adopt one of the following solutions: 1) Just disable protected mode sending
the command 'CONFIG SET protected-mode no' from the loopback interface by
connecting to Tile38 from the same host the server is running, however MAKE
SURE Tile38 is not publicly accessible from internet if you do so. Use CONFIG
REWRITE to make this change permanent. 2) Alternatively you can just disable
the protected mode by editing the Tile38 configuration file, and setting the
protected mode option to 'no', and then restarting the server. 3) If you
started the server manually just for testing, restart it with the
'--protected-mode no' option. 4) Setup a bind address or an authentication
password. NOTE: You only need to do one of the above things in order for the
server to start accepting connections from the outside.
`), "\n", " ", -1) + "\r\n")

// Conn represents a server connection.
type Conn struct {
	net.Conn
	Authenticated bool
}

// SetKeepAlive sets the connection keepalive
func (conn Conn) SetKeepAlive(period time.Duration) error {
	if tcp, ok := conn.Conn.(*net.TCPConn); ok {
		if err := tcp.SetKeepAlive(true); err != nil {
			return err
		}
		return tcp.SetKeepAlivePeriod(period)
	}
	return nil
}

var errCloseHTTP = errors.New("close http")

// ListenAndServe starts a tile38 server at the specified address.
func ListenAndServe(
	host string, port int,
	protected func() bool,
	handler func(conn *Conn, msg *Message, rd *PipelineReader, w io.Writer, websocket bool) error,
	opened func(conn *Conn),
	closed func(conn *Conn),
	lnp *net.Listener,
	http bool,
) error {
	ln, err := net.Listen("tcp", fmt.Sprintf("%s:%d", host, port))
	if err != nil {
		return err
	}
	if lnp != nil {
		*lnp = ln
	}
	log.Infof("The server is now ready to accept connections on port %d", port)
	for {
		conn, err := ln.Accept()
		if err != nil {
			log.Error(err)
			return err
		}
		go handleConn(&Conn{Conn: conn}, protected, handler, opened, closed, http)
	}
}

func handleConn(
	conn *Conn,
	protected func() bool,
	handler func(conn *Conn, msg *Message, rd *PipelineReader, w io.Writer, websocket bool) error,
	opened func(conn *Conn),
	closed func(conn *Conn),
	http bool,
) {
	addr := conn.RemoteAddr().String()
	opened(conn)
	if core.ShowDebugMessages {
		log.Debugf("opened connection: %s", addr)
	}
	defer func() {
		conn.Close()
		closed(conn)
		if core.ShowDebugMessages {
			log.Debugf("closed connection: %s", addr)
		}
	}()
	if !strings.HasPrefix(addr, "127.0.0.1:") && !strings.HasPrefix(addr, "[::1]:") {
		if protected() {
			// This is a protected server. Only loopback is allowed.
			conn.Write(deniedMessage)
			return
		}
	}

	wr := &bytes.Buffer{}
	outputType := Null
	rd := NewPipelineReader(conn)
	for {
		wr.Reset()
		ok := func() bool {
			msgs, err := rd.ReadMessages()
			if err != nil {
				errstr := err.Error()
				if err == errCloseHTTP ||
					err == io.EOF ||
					strings.Contains(errstr, "use of closed network connection") ||
					strings.Contains(errstr, "connection reset by peer") {
					return false
				}
				log.Error(err)
				return false
			}
			for _, msg := range msgs {
				// Just closing connection if we have deprecated HTTP or WS connection,
				// And --http-transport = false
				if !http && (msg.ConnType == WebSocket || msg.ConnType == HTTP) {
					return false
				}
				if msg != nil && msg.Command != "" {
					if outputType != Null {
						msg.OutputType = outputType
					}
					if msg.Command == "quit" {
						if msg.OutputType == RESP {
							io.WriteString(wr, "+OK\r\n")
						}
						return false
					}
					err := handler(conn, msg, rd, wr, msg.ConnType == WebSocket)
					if err != nil {
						log.Error(err)
						return false
					}
					outputType = msg.OutputType
				} else {
					wr.Write([]byte("HTTP/1.1 500 Bad Request\r\nConnection: close\r\n\r\n"))
					return false
				}
				if msg.ConnType == HTTP || msg.ConnType == WebSocket {
					return false
				}
			}
			return true
		}()
		conn.Write(wr.Bytes())
		if !ok {
			break
		}
	}
	// all done
}

// WriteWebSocketMessage write a websocket message to an io.Writer.
func WriteWebSocketMessage(w io.Writer, data []byte) error {
	var msg []byte
	buf := make([]byte, 10+len(data))
	buf[0] = 129 // FIN + TEXT
	if len(data) <= 125 {
		buf[1] = byte(len(data))
		copy(buf[2:], data)
		msg = buf[:2+len(data)]
	} else if len(data) <= 0xFFFF {
		buf[1] = 126
		binary.BigEndian.PutUint16(buf[2:], uint16(len(data)))
		copy(buf[4:], data)
		msg = buf[:4+len(data)]
	} else {
		buf[1] = 127
		binary.BigEndian.PutUint64(buf[2:], uint64(len(data)))
		copy(buf[10:], data)
		msg = buf[:10+len(data)]
	}
	_, err := w.Write(msg)
	return err
}

// OKMessage returns a default OK message in JSON or RESP.
func OKMessage(msg *Message, start time.Time) resp.Value {
	switch msg.OutputType {
	case JSON:
		return resp.StringValue(`{"ok":true,"elapsed":"` + time.Now().Sub(start).String() + "\"}")
	case RESP:
		return resp.SimpleStringValue("OK")
	}
	return resp.SimpleStringValue("")
}

// NOMessage is no message
var NOMessage = resp.SimpleStringValue("")