// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package rpc

import (
	"bufio"
	"context"
	"encoding/gob"
	"errors"
	"io"
	"log"
	"net"
	"sync"
	"sync/atomic"
	"time"

	"go-common/library/conf/env"
	"go-common/library/ecode"
	xlog "go-common/library/log"
	"go-common/library/net/metadata"
	"go-common/library/net/netutil/breaker"
	"go-common/library/net/trace"
	"go-common/library/stat"
	xtime "go-common/library/time"

	perr "github.com/pkg/errors"
)

const (
	_family       = "gorpc"
	_pingDuration = time.Second * 1
)

var (
	stats = stat.RPCClient

	// ErrShutdown shutdown error.
	ErrShutdown = errors.New("connection is shut down")
	// ErrNoClient current no rpc client.
	ErrNoClient = errors.New("no rpc client")

	errClient = new(client)
)

// ServerError represents an error that has been returned from
// the remote side of the RPC connection.
type ServerError string

func (e ServerError) Error() string {
	return string(e)
}

// Call represents an active RPC.
type Call struct {
	ServiceMethod string      // The name of the service and method to call.
	Args          interface{} // The argument to the function (*struct).
	Reply         interface{} // The reply from the function (*struct).
	Trace         trace.Trace
	Color         string
	RemoteIP      string
	Timeout       time.Duration
	Error         error      // After completion, the error status.
	Done          chan *Call // Strobes when call is complete.
}

// client represents an RPC Client.
// There may be multiple outstanding Calls associated
// with a single Client, and a Client may be used by
// multiple goroutines simultaneously.
type client struct {
	codec *clientCodec

	reqMutex sync.Mutex // protects following
	request  Request

	mutex    sync.Mutex // protects following
	seq      uint64
	pending  map[uint64]*Call
	closing  bool // user has called Close
	shutdown bool // server has told us to stop

	timeout    time.Duration // call timeout
	remoteAddr string        // server address
}

func (client *client) send(call *Call) {
	client.reqMutex.Lock()
	defer client.reqMutex.Unlock()

	// Register this call.
	client.mutex.Lock()
	if client.shutdown || client.closing {
		call.Error = ErrShutdown
		client.mutex.Unlock()
		call.done()
		return
	}
	seq := client.seq
	client.seq++
	client.mutex.Unlock()

	// Encode and send the request.
	client.request.Seq = seq
	client.request.ServiceMethod = call.ServiceMethod
	client.request.Color = call.Color
	client.request.RemoteIP = call.RemoteIP
	client.request.Timeout = call.Timeout
	if call.Trace != nil {
		trace.Inject(call.Trace, nil, &client.request.Trace)
	} else {
		client.request.Trace = TraceInfo{}
	}
	err := client.codec.WriteRequest(&client.request, call.Args)
	if err != nil {
		err = perr.WithStack(err)
		if call != nil {
			call.Error = err
			call.done()
		}
	} else {
		client.mutex.Lock()
		client.pending[seq] = call
		client.mutex.Unlock()
	}
}

func (client *client) input() {
	var err error
	var response Response
	for err == nil {
		response = Response{}
		err = client.codec.ReadResponseHeader(&response)
		if err != nil {
			break
		}
		seq := response.Seq
		client.mutex.Lock()
		call := client.pending[seq]
		delete(client.pending, seq)
		client.mutex.Unlock()

		switch {
		case call == nil:
			// We've got no pending call. That usually means that
			// WriteRequest partially failed, and call was already
			// removed; response is a server telling us about an
			// error reading request body. We should still attempt
			// to read error body, but there's no one to give it to.
			err = client.codec.ReadResponseBody(nil)
			if err != nil {
				err = errors.New("reading error body: " + err.Error())
			}
		case response.Error != "":
			// We've got an error response. Give this to the request;
			// any subsequent requests will get the ReadResponseBody
			// error if there is one.
			call.Error = ServerError(response.Error)
			err = client.codec.ReadResponseBody(nil)
			if err != nil {
				err = errors.New("reading error body: " + err.Error())
			}
			call.done()
		default:
			err = client.codec.ReadResponseBody(call.Reply)
			if err != nil {
				call.Error = errors.New("reading body " + err.Error())
			}
			call.done()
		}
	}
	// Terminate pending calls.
	client.reqMutex.Lock()
	client.mutex.Lock()
	client.shutdown = true
	closing := client.closing
	if err == io.EOF {
		if closing {
			err = ErrShutdown
		} else {
			err = io.ErrUnexpectedEOF
		}
	}
	for _, call := range client.pending {
		call.Error = err
		call.done()
	}
	client.mutex.Unlock()
	client.reqMutex.Unlock()
	if err != io.EOF && !closing {
		log.Println("rpc: client protocol error:", err)
	}
}

func (call *Call) done() {
	select {
	case call.Done <- call:
		// ok
	default:
		// We don't want to block here. It is the caller's responsibility to make
		// sure the channel has enough buffer space. See comment in Go().
		log.Println("rpc: discarding Call reply due to insufficient Done chan capacity")
	}
}

// Finish must called after Go.
func (call *Call) Finish() {
	if call.Trace != nil {
		call.Trace.Finish(&call.Error)
	}
}

// newClient returns a new Client to handle requests to the
// set of services at the other end of the connection.
// It adds a buffer to the write side of the connection so
// the header and payload are sent as a unit.
func newClient(timeout time.Duration, conn net.Conn) (*client, error) {
	encBuf := bufio.NewWriter(conn)
	client := &clientCodec{conn, gob.NewDecoder(conn), gob.NewEncoder(encBuf), encBuf}
	c := newClientWithCodec(client)
	c.timeout = timeout
	c.remoteAddr = conn.RemoteAddr().String()
	// handshake
	c.Call(_authServiceMethod, &Auth{User: env.AppID}, &struct{}{})
	return c, nil
}

// newClientWithCodec is like newClient but uses the specified
// codec to encode requests and decode responses.
func newClientWithCodec(codec *clientCodec) *client {
	client := &client{
		codec:   codec,
		pending: make(map[uint64]*Call),
	}
	go client.input()
	return client
}

type clientCodec struct {
	rwc    io.ReadWriteCloser
	dec    *gob.Decoder
	enc    *gob.Encoder
	encBuf *bufio.Writer
}

func (c *clientCodec) WriteRequest(r *Request, body interface{}) (err error) {
	if err = c.enc.Encode(r); err != nil {
		return perr.WithStack(err)
	}
	if err = c.enc.Encode(body); err != nil {
		return perr.WithStack(err)
	}
	return perr.WithStack(c.encBuf.Flush())
}

func (c *clientCodec) ReadResponseHeader(r *Response) error {
	return perr.WithStack(c.dec.Decode(r))
}

func (c *clientCodec) ReadResponseBody(body interface{}) error {
	return perr.WithStack(c.dec.Decode(body))
}

func (c *clientCodec) Close() error {
	return perr.WithStack(c.rwc.Close())
}

// dial connects to an RPC server at the specified network address.
func dial(network, addr string, timeout time.Duration) (*client, error) {
	// TODO dial timeout
	conn, err := net.Dial(network, addr)
	if err != nil {
		err = perr.WithStack(err)
		return nil, err
	}
	return newClient(timeout, conn)
}

// Close close the rpc client.
func (client *client) Close() error {
	client.mutex.Lock()
	if client.closing {
		client.mutex.Unlock()
		return ErrShutdown
	}
	client.closing = true
	client.mutex.Unlock()
	return client.codec.Close()
}

func (client *client) do(call *Call, done chan *Call) {
	if done == nil {
		done = make(chan *Call, 10) // buffered.
	} else {
		// If caller passes done != nil, it must arrange that
		// done has enough buffer for the number of simultaneous
		// RPCs that will be using that channel. If the channel
		// is totally unbuffered, it's best not to run at all.
		if cap(done) == 0 {
			log.Panic("rpc: done channel is unbuffered")
		}
	}
	call.Done = done
	client.send(call)
}

// Go invokes the function asynchronously. It returns the Call structure representing
// the invocation. The done channel will signal when the call is complete by returning
// the same Call object. If done is nil, Go will allocate a new channel.
// If non-nil, done must be buffered or Go will deliberately crash.
// Must call Finish() after call Go.
func (client *client) Go(serviceMethod string, args interface{}, reply interface{}, done chan *Call) *Call {
	call := new(Call)
	call.ServiceMethod = serviceMethod
	call.Args = args
	call.Reply = reply
	client.do(call, done)
	return call
}

// Call invokes the named function, waits for it to complete, and returns its error status.
func (client *client) Call(serviceMethod string, args interface{}, reply interface{}) (err error) {
	call := <-client.Go(serviceMethod, args, reply, make(chan *Call, 1)).Done
	return call.Error
}

// Do do a rpc call.
func (client *client) Do(call *Call) {
	client.do(call, make(chan *Call, 1))
}

type td struct {
	path    string
	timeout time.Duration
}

// Client wrapper is a client holder with implements pinger.
type Client struct {
	addr    string
	timeout xtime.Duration

	client atomic.Value
	quit   chan struct{}

	breaker *breaker.Group
}

// Dial connects to an RPC server at the specified network address.
func Dial(addr string, timeout xtime.Duration, bkc *breaker.Config) *Client {
	client := &Client{
		addr:    addr,
		timeout: timeout,
		quit:    make(chan struct{}),
	}
	// breaker
	client.breaker = breaker.NewGroup(bkc)
	// timeout
	if timeout <= 0 {
		client.timeout = xtime.Duration(300 * time.Millisecond)
	}
	client.timeout = timeout
	// dial
	rc, err := dial("tcp", addr, time.Duration(timeout))
	if err != nil {
		xlog.Error("dial(%s, %s) error(%v)", "tcp", addr, err)
	} else {
		client.client.Store(rc)
	}
	go client.ping()
	return client
}

// Call invokes the named function, waits for it to complete, and returns its error status.
func (c *Client) Call(ctx context.Context, serviceMethod string, args interface{}, reply interface{}) (err error) {
	var (
		ok      bool
		code    string
		rc      *client
		call    *Call
		cancel  func()
		t       trace.Trace
		timeout = time.Duration(c.timeout)
	)
	if rc, ok = c.client.Load().(*client); !ok || rc == errClient {
		xlog.Error("client is errClient (no rpc client) by ping addr(%s) error", c.addr)
		return ErrNoClient
	}
	if t, ok = trace.FromContext(ctx); !ok {
		t = trace.New(serviceMethod)
	}
	t = t.Fork(_family, serviceMethod)
	t.SetTag(trace.String(trace.TagAddress, rc.remoteAddr))
	defer t.Finish(&err)
	// breaker
	brk := c.breaker.Get(serviceMethod)
	if err = brk.Allow(); err != nil {
		code = "breaker"
		stats.Incr(serviceMethod, code)
		return
	}
	defer c.onBreaker(brk, &err)
	// stat
	now := time.Now()
	defer func() {
		stats.Timing(serviceMethod, int64(time.Since(now)/time.Millisecond))
		if code != "" {
			stats.Incr(serviceMethod, code)
		}
	}()
	// timeout: get from conf
	// if context > conf use conf else context
	deliver := true
	if deadline, ok := ctx.Deadline(); ok {
		if ctimeout := time.Until(deadline); ctimeout < timeout {
			timeout = ctimeout
			deliver = false
		}
	}
	if deliver {
		ctx, cancel = context.WithTimeout(ctx, timeout)
		defer cancel()
	}
	color := metadata.String(ctx, metadata.Color)
	remoteIP := metadata.String(ctx, metadata.RemoteIP)
	// call
	call = &Call{
		ServiceMethod: serviceMethod,
		Args:          args,
		Reply:         reply,
		Trace:         t,
		Color:         color,
		RemoteIP:      remoteIP,
		Timeout:       timeout,
	}
	rc.Do(call)
	select {
	case call = <-call.Done:
		err = call.Error
		code = ecode.Cause(err).Error()
	case <-ctx.Done():
		err = ecode.Deadline
		code = "timeout"
	}
	return
}

func (c *Client) onBreaker(breaker breaker.Breaker, err *error) {
	if err != nil && *err != nil && (*err == ErrShutdown || *err == io.ErrUnexpectedEOF || ecode.Deadline.Equal(*err) || ecode.ServiceUnavailable.Equal(*err) || ecode.ServerErr.Equal(*err)) {
		breaker.MarkFailed()
	} else {
		breaker.MarkSuccess()
	}
}

// ping ping the rpc connect and re connect when has an error.
func (c *Client) ping() {
	var (
		err       error
		cancel    func()
		call      *Call
		ctx       context.Context
		client, _ = c.client.Load().(*client)
	)
	for {
		select {
		case <-c.quit:
			c.client.Store(errClient)
			if client != nil {
				client.Close()
			}
			return
		default:
		}
		if client == nil || err != nil {
			if client, err = dial("tcp", c.addr, time.Duration(c.timeout)); err != nil {
				xlog.Error("dial(%s, %s) error(%v)", "tcp", c.addr, err)
				time.Sleep(_pingDuration)
				continue
			}
			c.client.Store(client)
		}
		ctx, cancel = context.WithTimeout(context.Background(), time.Duration(c.timeout))
		select {
		case call = <-client.Go(_pingServiceMethod, _pingArg, _pingArg, make(chan *Call, 1)).Done:
			err = call.Error
		case <-ctx.Done():
			err = ecode.Deadline
		}
		cancel()
		if err != nil {
			if err == ErrShutdown || err == io.ErrUnexpectedEOF || ecode.Deadline.Equal(err) {
				xlog.Error("rpc ping error beiTle addr(%s)", c.addr)
				c.client.Store(errClient)
				client.Close()
			} else {
				err = nil // never touch here
			}
		}
		time.Sleep(_pingDuration)
	}
}

// Close close client connection.
func (c *Client) Close() {
	close(c.quit)
}