package client

import (
	"bufio"
	"bytes"
	"crypto/tls"
	"encoding/base64"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"net"
	"net/http"
	"net/url"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	olog "git.loafle.net/overflow/log-go"
	"git.loafle.net/overflow/server-go/socket"
	"git.loafle.net/overflow/server-go/socket/client"
	"git.loafle.net/overflow/server-go/socket/web"
)

var errMalformedURL = errors.New("malformed ws or wss URL")

type Connectors struct {
	client.Connectors

	URL string `json:"url,omitempty"`

	RequestHeader func() http.Header `json:"-"`

	Subprotocols []string `json:"subprotocols,omitempty"`
	// Jar specifies the cookie jar.
	// If Jar is nil, cookies are not sent in requests and ignored
	// in responses.
	CookieJar http.CookieJar `json:"-"`

	ResponseHandler func(*http.Response) `json:"-"`

	// NetDial specifies the dial function for creating TCP connections. If
	// NetDial is nil, net.Dial is used.
	NetDial func(network, addr string) (net.Conn, error) `json:"-"`

	// Proxy specifies a function to return a proxy for a given
	// Request. If the function returns a non-nil error, the
	// request is aborted with the provided error.
	// If Proxy is nil or returns a nil *URL, no proxy is used.
	Proxy func(*http.Request) (*url.URL, error) `json:"-"`

	serverURL *url.URL

	stopChan chan struct{}
	stopWg   sync.WaitGroup

	readChan  chan socket.SocketMessage
	writeChan chan socket.SocketMessage

	disconnectedChan chan struct{}
	reconnectedChan  chan socket.Conn

	crw socket.ClientReadWriter

	validated atomic.Value
}

func (c *Connectors) Connect() (readChan <-chan socket.SocketMessage, writeChan chan<- socket.SocketMessage, err error) {
	var (
		conn socket.Conn
		res  *http.Response
	)

	if c.stopChan != nil {
		return nil, nil, fmt.Errorf("%s already connected", c.logHeader())
	}

	conn, res, err = c.connect()
	if nil != err {
		return nil, nil, err
	}
	resH := c.ResponseHandler
	if nil != resH {
		resH(res)
	}

	c.readChan = make(chan socket.SocketMessage, 256)
	c.writeChan = make(chan socket.SocketMessage, 256)
	c.disconnectedChan = make(chan struct{})
	c.reconnectedChan = make(chan socket.Conn)
	c.stopChan = make(chan struct{})

	c.crw.ReadwriteHandler = c
	c.crw.ReadChan = c.readChan
	c.crw.WriteChan = c.writeChan
	c.crw.ClientStopChan = c.stopChan
	c.crw.ClientStopWg = &c.stopWg
	c.crw.DisconnectedChan = c.disconnectedChan
	c.crw.ReconnectedChan = c.reconnectedChan

	c.stopWg.Add(1)
	go c.handleReconnect()
	c.stopWg.Add(1)
	go c.crw.HandleConnection(conn)

	return c.readChan, c.writeChan, nil
}

func (c *Connectors) Disconnect() error {
	if c.stopChan == nil {
		return fmt.Errorf("%s must be connected before disconnection it", c.logHeader())
	}
	close(c.stopChan)
	c.stopWg.Wait()

	c.stopChan = nil

	return nil
}

func (c *Connectors) logHeader() string {
	return fmt.Sprintf("Connector[%s]:", c.Name)
}

func (c *Connectors) onDisconnected() {
	close(c.readChan)
	close(c.writeChan)

	c.reconnectedChan <- nil

	onDisconnected := c.OnDisconnected
	if nil != onDisconnected {
		go func() {
			onDisconnected(c)
		}()
	}
}

func (c *Connectors) handleReconnect() {
	defer func() {
		c.stopWg.Done()
	}()

RC_LOOP:
	for {
		select {
		case <-c.disconnectedChan:
		case <-c.stopChan:
			return
		}

		if 0 >= c.GetReconnectTryTime() {
			c.onDisconnected()
			return
		}

		olog.Logger().Debugf("%s connection lost", c.logHeader())

		for indexI := 0; indexI < c.GetReconnectTryTime(); indexI++ {
			olog.Logger().Debugf("%s trying reconnect[%d]", c.logHeader(), indexI)

			conn, res, err := c.connect()
			if nil == err {
				resH := c.ResponseHandler
				if nil != resH {
					resH(res)
				}

				olog.Logger().Debugf("%s reconnected", c.logHeader())
				c.reconnectedChan <- conn
				continue RC_LOOP
			}
			time.Sleep(c.GetReconnectInterval())
		}
		olog.Logger().Debugf("%s reconnecting has been failed", c.logHeader())

		c.onDisconnected()
		return
	}
}

func (c *Connectors) connect() (socket.Conn, *http.Response, error) {
	conn, res, err := c.dial()
	if nil != err {
		return nil, nil, err
	}

	conn.SetCloseHandler(func(code int, text string) error {
		olog.Logger().Debugf("%s close", c.logHeader())
		return nil
	})
	return conn, res, nil
}

func (c *Connectors) dial() (socket.Conn, *http.Response, error) {
	var (
		err          error
		challengeKey string
		netConn      net.Conn
	)

	challengeKey, err = web.GenerateChallengeKey()
	if err != nil {
		return nil, nil, err
	}

	req := &http.Request{
		Method:     "GET",
		URL:        c.serverURL,
		Proto:      "HTTP/1.1",
		ProtoMajor: 1,
		ProtoMinor: 1,
		Header:     make(http.Header),
		Host:       c.serverURL.Host,
	}

	cookieJar := c.CookieJar
	// Set the cookies present in the cookie jar of the dialer
	if nil != cookieJar {
		for _, cookie := range cookieJar.Cookies(c.serverURL) {
			req.AddCookie(cookie)
		}
	}

	// Set the request headers using the capitalization for names and values in
	// RFC examples. Although the capitalization shouldn't matter, there are
	// servers that depend on it. The Header.Set method is not used because the
	// method canonicalizes the header names.
	req.Header["Upgrade"] = []string{"websocket"}
	req.Header["Connection"] = []string{"Upgrade"}
	req.Header["Sec-WebSocket-Key"] = []string{challengeKey}
	req.Header["Sec-WebSocket-Version"] = []string{"13"}

	subprotocols := c.Subprotocols

	if len(subprotocols) > 0 {
		req.Header["Sec-WebSocket-Protocol"] = []string{strings.Join(subprotocols, ", ")}
	}

	for k, vs := range c.RequestHeader() {
		switch {
		case k == "Host":
			if len(vs) > 0 {
				req.Host = vs[0]
			}
		case k == "Upgrade" ||
			k == "Connection" ||
			k == "Sec-Websocket-Key" ||
			k == "Sec-Websocket-Version" ||
			k == "Sec-Websocket-Extensions" ||
			(k == "Sec-Websocket-Protocol" && len(subprotocols) > 0):
			return nil, nil, fmt.Errorf("%s duplicate header not allowed: %s", c.logHeader(), k)
		default:
			req.Header[k] = vs
		}
	}

	if c.IsEnableCompression() {
		req.Header.Set("Sec-Websocket-Extensions", "permessage-deflate; server_no_context_takeover; client_no_context_takeover")
	}

	hostPort, hostNoPort := hostPortNoPort(c.serverURL)

	var proxyURL *url.URL
	// Check wether the proxy method has been configured
	proxy := c.Proxy
	if nil != proxy {
		proxyURL, err = proxy(req)
		if err != nil {
			return nil, nil, err
		}
	}

	var targetHostPort string
	if proxyURL != nil {
		targetHostPort, _ = hostPortNoPort(proxyURL)
	} else {
		targetHostPort = hostPort
	}

	var deadline time.Time
	handshakeTimeout := c.GetHandshakeTimeout()
	if 0 != handshakeTimeout {
		deadline = time.Now().Add(handshakeTimeout)
	}

	netDial := c.NetDial
	if netDial == nil {
		netDialer := &net.Dialer{Deadline: deadline}
		netDial = netDialer.Dial
	}

	netConn, err = netDial("tcp", targetHostPort)
	if err != nil {
		return nil, nil, err
	}

	defer func() {
		if nil != netConn {
			netConn.Close()
		}
	}()

	err = netConn.SetDeadline(deadline)
	if nil != err {
		return nil, nil, err
	}

	if nil != proxyURL {
		connectHeader := make(http.Header)
		if user := proxyURL.User; nil != user {
			proxyUser := user.Username()
			if proxyPassword, passwordSet := user.Password(); passwordSet {
				credential := base64.StdEncoding.EncodeToString([]byte(proxyUser + ":" + proxyPassword))
				connectHeader.Set("Proxy-Authorization", "Basic "+credential)
			}
		}
		connectReq := &http.Request{
			Method: "CONNECT",
			URL:    &url.URL{Opaque: hostPort},
			Host:   hostPort,
			Header: connectHeader,
		}

		connectReq.Write(netConn)

		// Read response.
		// Okay to use and discard buffered reader here, because
		// TLS server will not speak until spoken to.
		br := bufio.NewReader(netConn)
		resp, err := http.ReadResponse(br, connectReq)
		if err != nil {
			return nil, nil, err
		}
		if resp.StatusCode != 200 {
			f := strings.SplitN(resp.Status, " ", 2)
			return nil, nil, errors.New(f[1])
		}
	}

	if "https" == c.serverURL.Scheme {
		cfg := cloneTLSConfig(c.GetTLSConfig())
		if cfg.ServerName == "" {
			cfg.ServerName = hostNoPort
		}
		tlsConn := tls.Client(netConn, cfg)
		netConn = tlsConn
		if err := tlsConn.Handshake(); err != nil {
			return nil, nil, err
		}
		if !cfg.InsecureSkipVerify {
			if err := tlsConn.VerifyHostname(cfg.ServerName); err != nil {
				return nil, nil, err
			}
		}
	}

	conn := socket.NewConn(netConn, false, c.GetReadBufferSize(), c.GetWriteBufferSize())

	if err := req.Write(netConn); err != nil {
		return nil, nil, err
	}

	resp, err := http.ReadResponse(conn.BuffReader, req)
	if err != nil {
		return nil, nil, err
	}

	if nil != cookieJar {
		if rc := resp.Cookies(); len(rc) > 0 {
			cookieJar.SetCookies(c.serverURL, rc)
		}
	}

	if resp.StatusCode != 101 ||
		!strings.EqualFold(resp.Header.Get("Upgrade"), "websocket") ||
		!strings.EqualFold(resp.Header.Get("Connection"), "upgrade") ||
		resp.Header.Get("Sec-Websocket-Accept") != web.ComputeAcceptKey(challengeKey) {
		// Before closing the network connection on return from this
		// function, slurp up some of the response to aid application
		// debugging.
		buf := make([]byte, 1024)
		n, _ := io.ReadFull(resp.Body, buf)
		resp.Body = ioutil.NopCloser(bytes.NewReader(buf[:n]))
		return nil, resp, socket.ErrBadHandshake
	}

	for _, ext := range web.HttpParseExtensions(resp.Header) {
		if ext[""] != "permessage-deflate" {
			continue
		}
		_, snct := ext["server_no_context_takeover"]
		_, cnct := ext["client_no_context_takeover"]
		if !snct || !cnct {
			return nil, resp, socket.ErrInvalidCompression
		}
		conn.SetNewCompressionWriter(socket.CompressNoContextTakeover)
		conn.SetNewDecompressionReader(socket.DecompressNoContextTakeover)
		break
	}

	resp.Body = ioutil.NopCloser(bytes.NewReader([]byte{}))
	conn.SetSubprotocol(resp.Header.Get("Sec-Websocket-Protocol"))

	netConn.SetDeadline(time.Time{})
	netConn = nil // to avoid close in defer.

	return conn, resp, nil
}

// parseURL parses the URL.
//
// This function is a replacement for the standard library url.Parse function.
// In Go 1.4 and earlier, url.Parse loses information from the path.
func parseURL(s string) (*url.URL, error) {
	// From the RFC:
	//
	// ws-URI = "ws:" "//" host [ ":" port ] path [ "?" query ]
	// wss-URI = "wss:" "//" host [ ":" port ] path [ "?" query ]
	var u url.URL
	switch {
	case strings.HasPrefix(s, "ws://"):
		u.Scheme = "ws"
		s = s[len("ws://"):]
	case strings.HasPrefix(s, "wss://"):
		u.Scheme = "wss"
		s = s[len("wss://"):]
	default:
		return nil, errMalformedURL
	}

	if i := strings.Index(s, "?"); i >= 0 {
		u.RawQuery = s[i+1:]
		s = s[:i]
	}

	if i := strings.Index(s, "/"); i >= 0 {
		u.Opaque = s[i:]
		s = s[:i]
	} else {
		u.Opaque = "/"
	}

	u.Host = s

	if strings.Contains(u.Host, "@") {
		// Don't bother parsing user information because user information is
		// not allowed in websocket URIs.
		return nil, errMalformedURL
	}

	return &u, nil
}

func hostPortNoPort(u *url.URL) (hostPort, hostNoPort string) {
	hostPort = u.Host
	hostNoPort = u.Host
	if i := strings.LastIndex(u.Host, ":"); i > strings.LastIndex(u.Host, "]") {
		hostNoPort = hostNoPort[:i]
	} else {
		switch u.Scheme {
		case "wss":
			hostPort += ":443"
		case "https":
			hostPort += ":443"
		default:
			hostPort += ":80"
		}
	}
	return hostPort, hostNoPort
}

func cloneTLSConfig(cfg *tls.Config) *tls.Config {
	if cfg == nil {
		return &tls.Config{}
	}
	return cfg.Clone()
}

func (c *Connectors) Clone() client.Connector {
	return &Connectors{
		Connectors:      *c.Connectors.Clone(),
		URL:             c.URL,
		RequestHeader:   c.RequestHeader,
		Subprotocols:    c.Subprotocols,
		CookieJar:       c.CookieJar,
		ResponseHandler: c.ResponseHandler,
		NetDial:         c.NetDial,
		Proxy:           c.Proxy,
		serverURL:       c.serverURL,
		validated:       c.validated,
	}
}

func (c *Connectors) Validate() error {
	if nil != c.validated.Load() {
		return nil
	}
	c.validated.Store(true)

	if err := c.Connectors.Validate(); nil != err {
		return err
	}

	if "" == c.URL {
		return fmt.Errorf("URL is not valid")
	}

	u, err := parseURL(c.URL)
	if nil != err {
		return err
	}
	switch u.Scheme {
	case "ws":
		u.Scheme = "http"
	case "wss":
		u.Scheme = "https"
	default:
		return errMalformedURL
	}
	if nil != u.User {
		// User name and password are not allowed in websocket URIs.
		return errMalformedURL
	}

	c.serverURL = u

	if nil == c.Proxy {
		c.Proxy = http.ProxyFromEnvironment
	}

	return nil
}