// Package redcon implements a Redis compatible server framework
package redcon

import (
	"bufio"
	"context"
	"crypto/tls"
	"errors"
	"fmt"
	"io"
	"net"
	"strings"
	"sync"
	"time"

	"github.com/tidwall/btree"
	"github.com/tidwall/match"
)

var (
	errUnbalancedQuotes       = &errProtocol{"unbalanced quotes in request"}
	errInvalidBulkLength      = &errProtocol{"invalid bulk length"}
	errInvalidMultiBulkLength = &errProtocol{"invalid multibulk length"}
	errDetached               = errors.New("detached")
	errIncompleteCommand      = errors.New("incomplete command")
	errTooMuchData            = errors.New("too much data")
	errContextDone            = errors.New("context done")
)

type errProtocol struct {
	msg string
}

func (err *errProtocol) Error() string {
	return "Protocol error: " + err.msg
}

// Conn represents a client connection
type Conn interface {
	// RemoteAddr returns the remote address of the client connection.
	RemoteAddr() string
	// Close closes the connection.
	Close() error
	// WriteError writes an error to the client.
	WriteError(msg string)
	// WriteString writes a string to the client.
	WriteString(str string)
	// WriteBulk writes bulk bytes to the client.
	WriteBulk(bulk []byte)
	// WriteBulkString writes a bulk string to the client.
	WriteBulkString(bulk string)
	// WriteInt writes an integer to the client.
	WriteInt(num int)
	// WriteInt64 writes a 64-bit signed integer to the client.
	WriteInt64(num int64)
	// WriteUint64 writes a 64-bit unsigned integer to the client.
	WriteUint64(num uint64)
	// WriteArray writes an array header. You must then write additional
	// sub-responses to the client to complete the response.
	// For example to write two strings:
	//
	//   c.WriteArray(2)
	//   c.WriteBulk("item 1")
	//   c.WriteBulk("item 2")
	WriteArray(count int)
	// WriteNull writes a null to the client
	WriteNull()
	// WriteRaw writes raw data to the client.
	WriteRaw(data []byte)
	// WriteAny writes any type to the client.
	//   nil             -> null
	//   error           -> error (adds "ERR " when first word is not uppercase)
	//   string          -> bulk-string
	//   numbers         -> bulk-string
	//   []byte          -> bulk-string
	//   bool            -> bulk-string ("0" or "1")
	//   slice           -> array
	//   map             -> array with key/value pairs
	//   SimpleString    -> string
	//   SimpleInt       -> integer
	//   everything-else -> bulk-string representation using fmt.Sprint()
	WriteAny(any interface{})
	// Context returns a user-defined context
	Context() interface{}
	// SetContext sets a user-defined context
	SetContext(v interface{})
	// SetReadBuffer updates the buffer read size for the connection
	SetReadBuffer(bytes int)
	// Detach return a connection that is detached from the server.
	// Useful for operations like PubSub.
	//
	//   dconn := conn.Detach()
	//   go func(){
	//       defer dconn.Close()
	//       cmd, err := dconn.ReadCommand()
	//       if err != nil{
	//           fmt.Printf("read failed: %v\n", err)
	//	         return
	//       }
	//       fmt.Printf("received command: %v", cmd)
	//       hconn.WriteString("OK")
	//       if err := dconn.Flush(); err != nil{
	//           fmt.Printf("write failed: %v\n", err)
	//	         return
	//       }
	//   }()
	Detach() DetachedConn
	// ReadPipeline returns all commands in current pipeline, if any
	// The commands are removed from the pipeline.
	ReadPipeline() []Command
	// PeekPipeline returns all commands in current pipeline, if any.
	// The commands remain in the pipeline.
	PeekPipeline() []Command
	// NetConn returns the base net.Conn connection
	NetConn() net.Conn
}

// NewServer returns a new Redcon server configured on "tcp" network net.
func NewServer(
	ctx context.Context,
	addr string,
	handler func(conn Conn, cmd Command),
	accept func(conn Conn) bool,
	closed func(conn Conn, err error),
) *Server {
	return NewServerNetwork(ctx, "tcp", addr, handler, accept, closed)
}

// NewServerTLS returns a new Redcon TLS server configured on "tcp" network net.
func NewServerTLS(ctx context.Context,
	addr string,
	handler func(conn Conn, cmd Command),
	accept func(conn Conn) bool,
	closed func(conn Conn, err error),
	config *tls.Config,
) *TLSServer {
	return NewServerNetworkTLS(ctx, "tcp", addr, handler, accept, closed, config)
}

// NewServerNetwork returns a new Redcon server. The network net must be
// a stream-oriented network: "tcp", "tcp4", "tcp6", "unix" or "unixpacket"
func NewServerNetwork(
	ctx context.Context,
	net, laddr string,
	handler func(conn Conn, cmd Command),
	accept func(conn Conn) bool,
	closed func(conn Conn, err error),
) *Server {
	if handler == nil {
		panic("handler is nil")
	}
	s := &Server{
		ctx:     ctx,
		net:     net,
		laddr:   laddr,
		handler: handler,
		accept:  accept,
		closed:  closed,
		conns:   make(map[*conn]bool),
	}
	return s
}

// NewServerNetworkTLS returns a new TLS Redcon server. The network net must be
// a stream-oriented network: "tcp", "tcp4", "tcp6", "unix" or "unixpacket"
func NewServerNetworkTLS(
	ctx context.Context,
	net, laddr string,
	handler func(conn Conn, cmd Command),
	accept func(conn Conn) bool,
	closed func(conn Conn, err error),
	config *tls.Config,
) *TLSServer {
	if handler == nil {
		panic("handler is nil")
	}
	s := Server{
		ctx:     ctx,
		net:     net,
		laddr:   laddr,
		handler: handler,
		accept:  accept,
		closed:  closed,
		conns:   make(map[*conn]bool),
	}

	tls := &TLSServer{
		config: config,
		Server: &s,
	}
	return tls
}

// Close stops listening on the TCP address.
// Already Accepted connections will be closed.
func (s *Server) Close() error {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.ln == nil {
		return errors.New("not serving")
	}
	s.done = true
	return s.ln.Close()
}

// ListenAndServe serves incoming connections.
func (s *Server) ListenAndServe() error {
	return s.ListenServeAndSignal(nil)
}

// Addr returns server's listen address
func (s *Server) Addr() net.Addr {
	return s.ln.Addr()
}

// Close stops listening on the TCP address.
// Already Accepted connections will be closed.
func (s *TLSServer) Close() error {
	s.mu.Lock()
	defer s.mu.Unlock()
	if s.ln == nil {
		return errors.New("not serving")
	}
	s.done = true
	return s.ln.Close()
}

// ListenAndServe serves incoming connections.
func (s *TLSServer) ListenAndServe() error {
	return s.ListenServeAndSignal(nil)
}

// Serve creates a new server and serves with the given net.Listener.
func Serve(ln net.Listener,
	handler func(conn Conn, cmd Command),
	accept func(conn Conn) bool,
	closed func(conn Conn, err error),
) error {
	s := &Server{
		net:     ln.Addr().Network(),
		laddr:   ln.Addr().String(),
		ln:      ln,
		handler: handler,
		accept:  accept,
		closed:  closed,
		conns:   make(map[*conn]bool),
	}

	return serve(s)
}

// ListenAndServe creates a new server and binds to addr configured on "tcp" network net.
func ListenAndServe(
	ctx context.Context,
	addr string,
	handler func(conn Conn, cmd Command),
	accept func(conn Conn) bool,
	closed func(conn Conn, err error),
) error {
	return ListenAndServeNetwork(ctx, "tcp", addr, handler, accept, closed)
}

// ListenAndServeTLS creates a new TLS server and binds to addr configured on "tcp" network net.
func ListenAndServeTLS(
	ctx context.Context,
	addr string,
	handler func(conn Conn, cmd Command),
	accept func(conn Conn) bool,
	closed func(conn Conn, err error),
	config *tls.Config,
) error {
	return ListenAndServeNetworkTLS(ctx, "tcp", addr, handler, accept, closed, config)
}

// ListenAndServeNetwork creates a new server and binds to addr. The network net must be
// a stream-oriented network: "tcp", "tcp4", "tcp6", "unix" or "unixpacket"
func ListenAndServeNetwork(
	ctx context.Context,
	net, laddr string,
	handler func(conn Conn, cmd Command),
	accept func(conn Conn) bool,
	closed func(conn Conn, err error),
) error {
	return NewServerNetwork(ctx, net, laddr, handler, accept, closed).ListenAndServe()
}

// ListenAndServeNetworkTLS creates a new TLS server and binds to addr. The network net must be
// a stream-oriented network: "tcp", "tcp4", "tcp6", "unix" or "unixpacket"
func ListenAndServeNetworkTLS(
	ctx context.Context,
	net, laddr string,
	handler func(conn Conn, cmd Command),
	accept func(conn Conn) bool,
	closed func(conn Conn, err error),
	config *tls.Config,
) error {
	return NewServerNetworkTLS(ctx, net, laddr, handler, accept, closed, config).ListenAndServe()
}

// ListenServeAndSignal serves incoming connections and passes nil or error
// when listening. signal can be nil.
func (s *Server) ListenServeAndSignal(signal chan error) error {
	//var lc net.ListenConfig
	//ln, err := lc.Listen(s.ctx, s.net, s.laddr)
	ln, err := net.Listen(s.net, s.laddr)
	if err != nil {
		if signal != nil {
			signal <- err
		}
		return err
	}
	s.ln = ln
	if signal != nil {
		signal <- nil
	}
	return serve(s)
}

// Serve serves incoming connections with the given net.Listener.
func (s *Server) Serve(ln net.Listener) error {
	s.ln = ln
	s.net = ln.Addr().Network()
	s.laddr = ln.Addr().String()
	return serve(s)
}

// ListenServeAndSignal serves incoming connections and passes nil or error
// when listening. signal can be nil.
func (s *TLSServer) ListenServeAndSignal(signal chan error) error {
	ln, err := tls.Listen(s.net, s.laddr, s.config)
	if err != nil {
		if signal != nil {
			signal <- err
		}
		return err
	}
	s.ln = ln
	if signal != nil {
		signal <- nil
	}
	return serve(s.Server)
}

func serve(s *Server) error {
	defer func() {
		s.ln.Close()
		func() {
			s.mu.Lock()
			defer s.mu.Unlock()
			for c := range s.conns {
				c.Close()
			}
			s.conns = nil
		}()
	}()

	go func() {
		select {
		case <-s.ctx.Done():
			s.Close()
		}
	}()

	for {
		lnconn, err := s.ln.Accept()
		if err != nil {
			s.mu.Lock()
			done := s.done
			s.mu.Unlock()
			if done {
				select {
				case <-s.ctx.Done():
					return errContextDone
				default:
				}
				return nil
			}
			if s.AcceptError != nil {
				s.AcceptError(err)
			}
			continue
		}
		c := &conn{
			conn: lnconn,
			addr: lnconn.RemoteAddr().String(),
			wr:   NewWriter(lnconn),
			rd:   NewReader(lnconn),
		}
		s.mu.Lock()
		c.idleClose = s.idleClose
		s.conns[c] = true
		s.mu.Unlock()
		if s.accept != nil && !s.accept(c) {
			s.mu.Lock()
			delete(s.conns, c)
			s.mu.Unlock()
			c.Close()
			continue
		}
		go handle(s, c)
	}
}

// handle manages the server connection.
func handle(s *Server, c *conn) {
	var err error
	defer func() {
		if err != errDetached {
			// do not close the connection when a detach is detected.
			c.conn.Close()
		}
		func() {
			// remove the conn from the server
			s.mu.Lock()
			defer s.mu.Unlock()
			delete(s.conns, c)
			if s.closed != nil {
				if err == io.EOF {
					err = nil
				}
				s.closed(c, err)
			}
		}()
	}()

	err = func() error {
		// read commands and feed back to the client
		for {
			// read pipeline commands
			if c.idleClose != 0 {
				c.conn.SetReadDeadline(time.Now().Add(c.idleClose))
			}
			cmds, err := c.rd.readCommands(nil)
			if err != nil {
				if err, ok := err.(*errProtocol); ok {
					// All protocol errors should attempt a response to
					// the client. Ignore write errors.
					c.wr.WriteError("ERR " + err.Error())
					c.wr.Flush()
				}
				return err
			}
			c.cmds = cmds
			for len(c.cmds) > 0 {
				cmd := c.cmds[0]
				if len(c.cmds) == 1 {
					c.cmds = nil
				} else {
					c.cmds = c.cmds[1:]
				}
				s.handler(c, cmd)
			}
			if c.detached {
				// client has been detached
				return errDetached
			}
			if c.closed {
				return nil
			}
			if err := c.wr.Flush(); err != nil {
				return err
			}
		}
	}()
}

// conn represents a client connection
type conn struct {
	conn      net.Conn
	wr        *Writer
	rd        *Reader
	addr      string
	ctx       interface{}
	detached  bool
	closed    bool
	cmds      []Command
	idleClose time.Duration
}

func (c *conn) Close() error {
	c.wr.Flush()
	c.closed = true
	return c.conn.Close()
}
func (c *conn) Context() interface{}        { return c.ctx }
func (c *conn) SetContext(v interface{})    { c.ctx = v }
func (c *conn) SetReadBuffer(n int)         {}
func (c *conn) WriteString(str string)      { c.wr.WriteString(str) }
func (c *conn) WriteBulk(bulk []byte)       { c.wr.WriteBulk(bulk) }
func (c *conn) WriteBulkString(bulk string) { c.wr.WriteBulkString(bulk) }
func (c *conn) WriteInt(num int)            { c.wr.WriteInt(num) }
func (c *conn) WriteInt64(num int64)        { c.wr.WriteInt64(num) }
func (c *conn) WriteUint64(num uint64)      { c.wr.WriteUint64(num) }
func (c *conn) WriteError(msg string)       { c.wr.WriteError(msg) }
func (c *conn) WriteArray(count int)        { c.wr.WriteArray(count) }
func (c *conn) WriteNull()                  { c.wr.WriteNull() }
func (c *conn) WriteRaw(data []byte)        { c.wr.WriteRaw(data) }
func (c *conn) WriteAny(v interface{})      { c.wr.WriteAny(v) }
func (c *conn) RemoteAddr() string          { return c.addr }
func (c *conn) ReadPipeline() []Command {
	cmds := c.cmds
	c.cmds = nil
	return cmds
}
func (c *conn) PeekPipeline() []Command {
	return c.cmds
}
func (c *conn) NetConn() net.Conn {
	return c.conn
}

// BaseWriter returns the underlying connection writer, if any
func BaseWriter(c Conn) *Writer {
	if c, ok := c.(*conn); ok {
		return c.wr
	}
	return nil
}

// DetachedConn represents a connection that is detached from the server
type DetachedConn interface {
	// Conn is the original connection
	Conn
	// ReadCommand reads the next client command.
	ReadCommand() (Command, error)
	// Flush flushes any writes to the network.
	Flush() error
}

// Detach removes the current connection from the server loop and returns
// a detached connection. This is useful for operations such as PubSub.
// The detached connection must be closed by calling Close() when done.
// All writes such as WriteString() will not be written to the client
// until Flush() is called.
func (c *conn) Detach() DetachedConn {
	c.detached = true
	cmds := c.cmds
	c.cmds = nil
	return &detachedConn{conn: c, cmds: cmds}
}

type detachedConn struct {
	*conn
	cmds []Command
}

// Flush writes and Write* calls to the client.
func (dc *detachedConn) Flush() error {
	return dc.conn.wr.Flush()
}

// ReadCommand read the next command from the client.
func (dc *detachedConn) ReadCommand() (Command, error) {
	if len(dc.cmds) > 0 {
		cmd := dc.cmds[0]
		if len(dc.cmds) == 1 {
			dc.cmds = nil
		} else {
			dc.cmds = dc.cmds[1:]
		}
		return cmd, nil
	}
	cmd, err := dc.rd.ReadCommand()
	if err != nil {
		return Command{}, err
	}
	return cmd, nil
}

// Command represent a command
type Command struct {
	// Raw is a encoded RESP message.
	Raw []byte
	// Args is a series of arguments that make up the command.
	Args [][]byte
}

// Server defines a server for clients for managing client connections.
type Server struct {
	ctx       context.Context
	mu        sync.Mutex
	net       string
	laddr     string
	handler   func(conn Conn, cmd Command)
	accept    func(conn Conn) bool
	closed    func(conn Conn, err error)
	conns     map[*conn]bool
	ln        net.Listener
	done      bool
	idleClose time.Duration

	// AcceptError is an optional function used to handle Accept errors.
	AcceptError func(err error)
}

// TLSServer defines a server for clients for managing client connections.
type TLSServer struct {
	*Server
	config *tls.Config
}

// Writer allows for writing RESP messages.
type Writer struct {
	w io.Writer
	b []byte
}

// NewWriter creates a new RESP writer.
func NewWriter(wr io.Writer) *Writer {
	return &Writer{
		w: wr,
	}
}

// WriteNull writes a null to the client
func (w *Writer) WriteNull() {
	w.b = AppendNull(w.b)
}

// WriteArray writes an array header. You must then write additional
// sub-responses to the client to complete the response.
// For example to write two strings:
//
//   c.WriteArray(2)
//   c.WriteBulk("item 1")
//   c.WriteBulk("item 2")
func (w *Writer) WriteArray(count int) {
	w.b = AppendArray(w.b, count)
}

// WriteBulk writes bulk bytes to the client.
func (w *Writer) WriteBulk(bulk []byte) {
	w.b = AppendBulk(w.b, bulk)
}

// WriteBulkString writes a bulk string to the client.
func (w *Writer) WriteBulkString(bulk string) {
	w.b = AppendBulkString(w.b, bulk)
}

// Buffer returns the unflushed buffer. This is a copy so changes
// to the resulting []byte will not affect the writer.
func (w *Writer) Buffer() []byte {
	return append([]byte(nil), w.b...)
}

// SetBuffer replaces the unflushed buffer with new bytes.
func (w *Writer) SetBuffer(raw []byte) {
	w.b = w.b[:0]
	w.b = append(w.b, raw...)
}

// Flush writes all unflushed Write* calls to the underlying writer.
func (w *Writer) Flush() error {
	if _, err := w.w.Write(w.b); err != nil {
		return err
	}
	w.b = w.b[:0]
	return nil
}

// WriteError writes an error to the client.
func (w *Writer) WriteError(msg string) {
	w.b = AppendError(w.b, msg)
}

// WriteString writes a string to the client.
func (w *Writer) WriteString(msg string) {
	w.b = AppendString(w.b, msg)
}

// WriteInt writes an integer to the client.
func (w *Writer) WriteInt(num int) {
	w.WriteInt64(int64(num))
}

// WriteInt64 writes a 64-bit signed integer to the client.
func (w *Writer) WriteInt64(num int64) {
	w.b = AppendInt(w.b, num)
}

// WriteUint64 writes a 64-bit unsigned integer to the client.
func (w *Writer) WriteUint64(num uint64) {
	w.b = AppendUint(w.b, num)
}

// WriteRaw writes raw data to the client.
func (w *Writer) WriteRaw(data []byte) {
	w.b = append(w.b, data...)
}

// WriteAny writes any type to client.
//   nil             -> null
//   error           -> error (adds "ERR " when first word is not uppercase)
//   string          -> bulk-string
//   numbers         -> bulk-string
//   []byte          -> bulk-string
//   bool            -> bulk-string ("0" or "1")
//   slice           -> array
//   map             -> array with key/value pairs
//   SimpleString    -> string
//   SimpleInt       -> integer
//   everything-else -> bulk-string representation using fmt.Sprint()
func (w *Writer) WriteAny(v interface{}) {
	w.b = AppendAny(w.b, v)
}

// Reader represent a reader for RESP or telnet commands.
type Reader struct {
	rd    *bufio.Reader
	buf   []byte
	start int
	end   int
	cmds  []Command
}

// NewReader returns a command reader which will read RESP or telnet commands.
func NewReader(rd io.Reader) *Reader {
	return &Reader{
		rd:  bufio.NewReader(rd),
		buf: make([]byte, 4096),
	}
}

func parseInt(b []byte) (int, bool) {
	if len(b) == 1 && b[0] >= '0' && b[0] <= '9' {
		return int(b[0] - '0'), true
	}
	var n int
	var sign bool
	var i int
	if len(b) > 0 && b[0] == '-' {
		sign = true
		i++
	}
	for ; i < len(b); i++ {
		if b[i] < '0' || b[i] > '9' {
			return 0, false
		}
		n = n*10 + int(b[i]-'0')
	}
	if sign {
		n *= -1
	}
	return n, true
}

func (rd *Reader) readCommands(leftover *int) ([]Command, error) {
	var cmds []Command
	b := rd.buf[rd.start:rd.end]
	if rd.end-rd.start == 0 && len(rd.buf) > 4096 {
		rd.buf = rd.buf[:4096]
		rd.start = 0
		rd.end = 0
	}
	if len(b) > 0 {
		// we have data, yay!
		// but is this enough data for a complete command? or multiple?
	next:
		switch b[0] {
		default:
			// just a plain text command
			for i := 0; i < len(b); i++ {
				if b[i] == '\n' {
					var line []byte
					if i > 0 && b[i-1] == '\r' {
						line = b[:i-1]
					} else {
						line = b[:i]
					}
					var cmd Command
					var quote bool
					var quotech byte
					var escape bool
				outer:
					for {
						nline := make([]byte, 0, len(line))
						for i := 0; i < len(line); i++ {
							c := line[i]
							if !quote {
								if c == ' ' {
									if len(nline) > 0 {
										cmd.Args = append(cmd.Args, nline)
									}
									line = line[i+1:]
									continue outer
								}
								if c == '"' || c == '\'' {
									if i != 0 {
										return nil, errUnbalancedQuotes
									}
									quotech = c
									quote = true
									line = line[i+1:]
									continue outer
								}
							} else {
								if escape {
									escape = false
									switch c {
									case 'n':
										c = '\n'
									case 'r':
										c = '\r'
									case 't':
										c = '\t'
									}
								} else if c == quotech {
									quote = false
									quotech = 0
									cmd.Args = append(cmd.Args, nline)
									line = line[i+1:]
									if len(line) > 0 && line[0] != ' ' {
										return nil, errUnbalancedQuotes
									}
									continue outer
								} else if c == '\\' {
									escape = true
									continue
								}
							}
							nline = append(nline, c)
						}
						if quote {
							return nil, errUnbalancedQuotes
						}
						if len(line) > 0 {
							cmd.Args = append(cmd.Args, line)
						}
						break
					}
					if len(cmd.Args) > 0 {
						// convert this to resp command syntax
						var wr Writer
						wr.WriteArray(len(cmd.Args))
						for i := range cmd.Args {
							wr.WriteBulk(cmd.Args[i])
							cmd.Args[i] = append([]byte(nil), cmd.Args[i]...)
						}
						cmd.Raw = wr.b
						cmds = append(cmds, cmd)
					}
					b = b[i+1:]
					if len(b) > 0 {
						goto next
					} else {
						goto done
					}
				}
			}
		case '*':
			// resp formatted command
			marks := make([]int, 0, 16)
		outer2:
			for i := 1; i < len(b); i++ {
				if b[i] == '\n' {
					if b[i-1] != '\r' {
						return nil, errInvalidMultiBulkLength
					}
					count, ok := parseInt(b[1 : i-1])
					if !ok || count <= 0 {
						return nil, errInvalidMultiBulkLength
					}
					marks = marks[:0]
					for j := 0; j < count; j++ {
						// read bulk length
						i++
						if i < len(b) {
							if b[i] != '$' {
								return nil, &errProtocol{"expected '$', got '" +
									string(b[i]) + "'"}
							}
							si := i
							for ; i < len(b); i++ {
								if b[i] == '\n' {
									if b[i-1] != '\r' {
										return nil, errInvalidBulkLength
									}
									size, ok := parseInt(b[si+1 : i-1])
									if !ok || size < 0 {
										return nil, errInvalidBulkLength
									}
									if i+size+2 >= len(b) {
										// not ready
										break outer2
									}
									if b[i+size+2] != '\n' ||
										b[i+size+1] != '\r' {
										return nil, errInvalidBulkLength
									}
									i++
									marks = append(marks, i, i+size)
									i += size + 1
									break
								}
							}
						}
					}
					if len(marks) == count*2 {
						var cmd Command
						if rd.rd != nil {
							// make a raw copy of the entire command when
							// there's a underlying reader.
							cmd.Raw = append([]byte(nil), b[:i+1]...)
						} else {
							// just assign the slice
							cmd.Raw = b[:i+1]
						}
						cmd.Args = make([][]byte, len(marks)/2)
						// slice up the raw command into the args based on
						// the recorded marks.
						for h := 0; h < len(marks); h += 2 {
							cmd.Args[h/2] = cmd.Raw[marks[h]:marks[h+1]]
						}
						cmds = append(cmds, cmd)
						b = b[i+1:]
						if len(b) > 0 {
							goto next
						} else {
							goto done
						}
					}
				}
			}
		}
	done:
		rd.start = rd.end - len(b)
	}
	if leftover != nil {
		*leftover = rd.end - rd.start
	}
	if len(cmds) > 0 {
		return cmds, nil
	}
	if rd.rd == nil {
		return nil, errIncompleteCommand
	}
	if rd.end == len(rd.buf) {
		// at the end of the buffer.
		if rd.start == rd.end {
			// rewind the to the beginning
			rd.start, rd.end = 0, 0
		} else {
			// must grow the buffer
			newbuf := make([]byte, len(rd.buf)*2)
			copy(newbuf, rd.buf)
			rd.buf = newbuf
		}
	}
	n, err := rd.rd.Read(rd.buf[rd.end:])
	if err != nil {
		return nil, err
	}
	rd.end += n
	return rd.readCommands(leftover)
}

// ReadCommands reads the next pipeline commands.
func (rd *Reader) ReadCommands() ([]Command, error) {
	for {
		if len(rd.cmds) > 0 {
			cmds := rd.cmds
			rd.cmds = nil
			return cmds, nil
		}
		cmds, err := rd.readCommands(nil)
		if err != nil {
			return []Command{}, err
		}
		rd.cmds = cmds
	}
}

// ReadCommand reads the next command.
func (rd *Reader) ReadCommand() (Command, error) {
	if len(rd.cmds) > 0 {
		cmd := rd.cmds[0]
		rd.cmds = rd.cmds[1:]
		return cmd, nil
	}
	cmds, err := rd.readCommands(nil)
	if err != nil {
		return Command{}, err
	}
	rd.cmds = cmds
	return rd.ReadCommand()
}

// Parse parses a raw RESP message and returns a command.
func Parse(raw []byte) (Command, error) {
	rd := Reader{buf: raw, end: len(raw)}
	var leftover int
	cmds, err := rd.readCommands(&leftover)
	if err != nil {
		return Command{}, err
	}
	if leftover > 0 {
		return Command{}, errTooMuchData
	}
	return cmds[0], nil

}

// A Handler responds to an RESP request.
type Handler interface {
	ServeRESP(conn Conn, cmd Command)
}

// The HandlerFunc type is an adapter to allow the use of
// ordinary functions as RESP handlers. If f is a function
// with the appropriate signature, HandlerFunc(f) is a
// Handler that calls f.
type HandlerFunc func(conn Conn, cmd Command)

// ServeRESP calls f(w, r)
func (f HandlerFunc) ServeRESP(conn Conn, cmd Command) {
	f(conn, cmd)
}

// ServeMux is an RESP command multiplexer.
type ServeMux struct {
	handlers map[string]Handler
}

// NewServeMux allocates and returns a new ServeMux.
func NewServeMux() *ServeMux {
	return &ServeMux{
		handlers: make(map[string]Handler),
	}
}

// HandleFunc registers the handler function for the given command.
func (m *ServeMux) HandleFunc(command string, handler func(conn Conn, cmd Command)) {
	if handler == nil {
		panic("redcon: nil handler")
	}
	m.Handle(command, HandlerFunc(handler))
}

// Handle registers the handler for the given command.
// If a handler already exists for command, Handle panics.
func (m *ServeMux) Handle(command string, handler Handler) {
	if command == "" {
		panic("redcon: invalid command")
	}
	if handler == nil {
		panic("redcon: nil handler")
	}
	if _, exist := m.handlers[command]; exist {
		panic("redcon: multiple registrations for " + command)
	}

	m.handlers[command] = handler
}

// ServeRESP dispatches the command to the handler.
func (m *ServeMux) ServeRESP(conn Conn, cmd Command) {
	command := strings.ToLower(string(cmd.Args[0]))

	if handler, ok := m.handlers[command]; ok {
		handler.ServeRESP(conn, cmd)
	} else {
		conn.WriteError("ERR unknown command '" + command + "'")
	}
}

// PubSub is a Redis compatible pub/sub server
type PubSub struct {
	mu     sync.RWMutex
	nextid uint64
	initd  bool
	chans  *btree.BTree
	conns  map[Conn]*pubSubConn
}

// Subscribe a connection to PubSub
func (ps *PubSub) Subscribe(conn Conn, channel string) {
	ps.subscribe(conn, false, channel)
}

// Psubscribe a connection to PubSub
func (ps *PubSub) Psubscribe(conn Conn, channel string) {
	ps.subscribe(conn, true, channel)
}

// Publish a message to subscribers
func (ps *PubSub) Publish(channel, message string) int {
	ps.mu.RLock()
	defer ps.mu.RUnlock()
	if !ps.initd {
		return 0
	}
	var sent int
	// write messages to all clients that are subscribed on the channel
	pivot := &pubSubEntry{pattern: false, channel: channel}
	ps.chans.Ascend(pivot, func(item interface{}) bool {
		entry := item.(*pubSubEntry)
		if entry.channel != pivot.channel || entry.pattern != pivot.pattern {
			return false
		}
		entry.sconn.writeMessage(entry.pattern, "", channel, message)
		sent++
		return true
	})

	// match on and write all psubscribe clients
	pivot = &pubSubEntry{pattern: true}
	ps.chans.Ascend(pivot, func(item interface{}) bool {
		entry := item.(*pubSubEntry)
		if match.Match(channel, entry.channel) {
			entry.sconn.writeMessage(entry.pattern, entry.channel, channel,
				message)
		}
		sent++
		return true
	})

	return sent
}

type pubSubConn struct {
	id      uint64
	mu      sync.Mutex
	conn    Conn
	dconn   DetachedConn
	entries map[*pubSubEntry]bool
}

type pubSubEntry struct {
	pattern bool
	sconn   *pubSubConn
	channel string
}

func (sconn *pubSubConn) writeMessage(pat bool, pchan, channel, msg string) {
	sconn.mu.Lock()
	defer sconn.mu.Unlock()
	if pat {
		sconn.dconn.WriteArray(4)
		sconn.dconn.WriteBulkString("pmessage")
		sconn.dconn.WriteBulkString(pchan)
		sconn.dconn.WriteBulkString(channel)
		sconn.dconn.WriteBulkString(msg)
	} else {
		sconn.dconn.WriteArray(3)
		sconn.dconn.WriteBulkString("message")
		sconn.dconn.WriteBulkString(channel)
		sconn.dconn.WriteBulkString(msg)
	}
	sconn.dconn.Flush()
}

// bgrunner runs in the background and reads incoming commands from the
// detached client.
func (sconn *pubSubConn) bgrunner(ps *PubSub) {
	defer func() {
		// client connection has ended, disconnect from the PubSub instances
		// and close the network connection.
		ps.mu.Lock()
		defer ps.mu.Unlock()
		for entry := range sconn.entries {
			ps.chans.Delete(entry)
		}
		delete(ps.conns, sconn.conn)
		sconn.mu.Lock()
		defer sconn.mu.Unlock()
		sconn.dconn.Close()
	}()
	for {
		cmd, err := sconn.dconn.ReadCommand()
		if err != nil {
			return
		}
		if len(cmd.Args) == 0 {
			continue
		}
		switch strings.ToLower(string(cmd.Args[0])) {
		case "psubscribe", "subscribe":
			if len(cmd.Args) < 2 {
				func() {
					sconn.mu.Lock()
					defer sconn.mu.Unlock()
					sconn.dconn.WriteError(fmt.Sprintf("ERR wrong number of "+
						"arguments for '%s'", cmd.Args[0]))
					sconn.dconn.Flush()
				}()
				continue
			}
			command := strings.ToLower(string(cmd.Args[0]))
			for i := 1; i < len(cmd.Args); i++ {
				if command == "psubscribe" {
					ps.Psubscribe(sconn.conn, string(cmd.Args[i]))
				} else {
					ps.Subscribe(sconn.conn, string(cmd.Args[i]))
				}
			}
		case "unsubscribe", "punsubscribe":
			pattern := strings.ToLower(string(cmd.Args[0])) == "punsubscribe"
			if len(cmd.Args) == 1 {
				ps.unsubscribe(sconn.conn, pattern, true, "")
			} else {
				for i := 1; i < len(cmd.Args); i++ {
					channel := string(cmd.Args[i])
					ps.unsubscribe(sconn.conn, pattern, false, channel)
				}
			}
		case "quit":
			func() {
				sconn.mu.Lock()
				defer sconn.mu.Unlock()
				sconn.dconn.WriteString("OK")
				sconn.dconn.Flush()
				sconn.dconn.Close()
			}()
			return
		case "ping":
			var msg string
			switch len(cmd.Args) {
			case 1:
			case 2:
				msg = string(cmd.Args[1])
			default:
				func() {
					sconn.mu.Lock()
					defer sconn.mu.Unlock()
					sconn.dconn.WriteError(fmt.Sprintf("ERR wrong number of "+
						"arguments for '%s'", cmd.Args[0]))
					sconn.dconn.Flush()
				}()
				continue
			}
			func() {
				sconn.mu.Lock()
				defer sconn.mu.Unlock()
				sconn.dconn.WriteArray(2)
				sconn.dconn.WriteBulkString("pong")
				sconn.dconn.WriteBulkString(msg)
				sconn.dconn.Flush()
			}()
		default:
			func() {
				sconn.mu.Lock()
				defer sconn.mu.Unlock()
				sconn.dconn.WriteError(fmt.Sprintf("ERR Can't execute '%s': "+
					"only (P)SUBSCRIBE / (P)UNSUBSCRIBE / PING / QUIT are "+
					"allowed in this context", cmd.Args[0]))
				sconn.dconn.Flush()
			}()
		}
	}
}

// byEntry is a "less" function that sorts the entries in a btree. The tree
// is sorted be (pattern, channel, conn.id). All pattern=true entries are at
// the end (right) of the tree.
func byEntry(a, b interface{}) bool {
	aa := a.(*pubSubEntry)
	bb := b.(*pubSubEntry)
	if !aa.pattern && bb.pattern {
		return true
	}
	if aa.pattern && !bb.pattern {
		return false
	}
	if aa.channel < bb.channel {
		return true
	}
	if aa.channel > bb.channel {
		return false
	}
	var aid uint64
	var bid uint64
	if aa.sconn != nil {
		aid = aa.sconn.id
	}
	if bb.sconn != nil {
		bid = bb.sconn.id
	}
	return aid < bid
}

func (ps *PubSub) subscribe(conn Conn, pattern bool, channel string) {
	ps.mu.Lock()
	defer ps.mu.Unlock()

	// initialize the PubSub instance
	if !ps.initd {
		ps.conns = make(map[Conn]*pubSubConn)
		ps.chans = btree.New(byEntry)
		ps.initd = true
	}

	// fetch the pubSubConn
	sconn, ok := ps.conns[conn]
	if !ok {
		// initialize a new pubSubConn, which runs on a detached connection,
		// and attach it to the PubSub channels/conn btree
		ps.nextid++
		dconn := conn.Detach()
		sconn = &pubSubConn{
			id:      ps.nextid,
			conn:    conn,
			dconn:   dconn,
			entries: make(map[*pubSubEntry]bool),
		}
		ps.conns[conn] = sconn
	}
	sconn.mu.Lock()
	defer sconn.mu.Unlock()

	// add an entry to the pubsub btree
	entry := &pubSubEntry{
		pattern: pattern,
		channel: channel,
		sconn:   sconn,
	}
	ps.chans.Set(entry)
	sconn.entries[entry] = true

	// send a message to the client
	sconn.dconn.WriteArray(3)
	if pattern {
		sconn.dconn.WriteBulkString("psubscribe")
	} else {
		sconn.dconn.WriteBulkString("subscribe")
	}
	sconn.dconn.WriteBulkString(channel)
	var count int
	for ient := range sconn.entries {
		if ient.pattern == pattern {
			count++
		}
	}
	sconn.dconn.WriteInt(count)
	sconn.dconn.Flush()

	// start the background client operation
	if !ok {
		go sconn.bgrunner(ps)
	}
}

func (ps *PubSub) unsubscribe(conn Conn, pattern, all bool, channel string) {
	ps.mu.Lock()
	defer ps.mu.Unlock()
	// fetch the pubSubConn. This must exist
	sconn := ps.conns[conn]
	sconn.mu.Lock()
	defer sconn.mu.Unlock()

	removeEntry := func(entry *pubSubEntry) {
		if entry != nil {
			ps.chans.Delete(entry)
			delete(sconn.entries, entry)
		}
		sconn.dconn.WriteArray(3)
		if pattern {
			sconn.dconn.WriteBulkString("punsubscribe")
		} else {
			sconn.dconn.WriteBulkString("unsubscribe")
		}
		if entry != nil {
			sconn.dconn.WriteBulkString(entry.channel)
		} else {
			sconn.dconn.WriteNull()
		}
		var count int
		for ient := range sconn.entries {
			if ient.pattern == pattern {
				count++
			}
		}
		sconn.dconn.WriteInt(count)
	}
	if all {
		// unsubscribe from all (p)subscribe entries
		var entries []*pubSubEntry
		for ient := range sconn.entries {
			if ient.pattern == pattern {
				entries = append(entries, ient)
			}
		}
		if len(entries) == 0 {
			removeEntry(nil)
		} else {
			for _, entry := range entries {
				removeEntry(entry)
			}
		}
	} else {
		// unsubscribe single channel from (p)subscribe.
		for ient := range sconn.entries {
			if ient.pattern == pattern && ient.channel == channel {
				removeEntry(ient)
				break
			}
		}
	}
	sconn.dconn.Flush()
}

// SetIdleClose will automatically close idle connections after the specified
// duration. Use zero to disable this feature.
func (s *Server) SetIdleClose(dur time.Duration) {
	s.mu.Lock()
	s.idleClose = dur
	s.mu.Unlock()
}