package krpc

import (
	"bufio"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"log"
	"net"
	"net/http"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	"krwu.top/krpc.v1/codec"
)

type Call struct {
	Seq           uint64
	ServiceMethod string
	Args          interface{}
	Reply         interface{}
	Error         error
	Done          chan *Call
}

func (call *Call) done() {
	call.Done <- call
}

type Client struct {
	cc       codec.Codec
	opt      *Options
	sending  sync.Mutex
	header   codec.Header
	mu       sync.Mutex
	seq      uint64
	pending  map[uint64]*Call
	closing  bool
	shutdown bool
}

type clientResult struct {
	client *Client
	err    error
}

type newClientFunc func(conn net.Conn, opts ...Option) (client *Client, err error)

var _ io.Closer = (*Client)(nil)

var ErrShutdown = errors.New("connection is shutdown")

func NewClient(conn net.Conn, opts ...Option) (*Client, error) {
	for i := range opts {
		opts[i](DefaultOptions)
	}
	f := codec.NewCodecFuncMap[DefaultOptions.CodecType]
	if f == nil {
		err := fmt.Errorf("invalid codec type %s", DefaultOptions.CodecType)
		log.Println("rpc client: codec error: ", err)
		return nil, err
	}

	if err := json.NewEncoder(conn).Encode(DefaultOptions); err != nil {
		log.Println("rpc client: options error:", err)
		_ = conn.Close()
		return nil, err
	}
	return newClientCodec(f(conn), DefaultOptions), nil
}

func Dial(network, address string, opts ...Option) (client *Client, err error) {
	return dialTimeout(NewClient, network, address, opts...)
}

func newClientCodec(cc codec.Codec, opts *Options) *Client {
	client := &Client{
		seq:     1,
		cc:      cc,
		opt:     opts,
		pending: make(map[uint64]*Call),
	}
	go client.receive()
	return client
}

func (client *Client) Close() error {
	client.mu.Lock()
	defer client.mu.Unlock()
	if client.closing {
		return ErrShutdown
	}
	client.closing = true
	return client.cc.Close()
}

func (client *Client) IsAvailable() bool {
	client.mu.Lock()
	defer client.mu.Unlock()
	return !client.shutdown && !client.closing
}

func (client *Client) registerCall(call *Call) (uint64, error) {
	client.mu.Lock()
	defer client.mu.Unlock()
	if client.closing || client.shutdown {
		return 0, ErrShutdown
	}
	call.Seq = client.seq
	client.pending[call.Seq] = call
	atomic.StoreUint64(&client.seq, client.seq+1)
	return call.Seq, nil
}

func (client *Client) removeCall(seq uint64) *Call {
	client.mu.Lock()
	defer client.mu.Unlock()
	call := client.pending[seq]
	delete(client.pending, seq)
	return call
}

func (client *Client) terminateCalls(err error) {
	client.sending.Lock()
	defer client.sending.Unlock()
	client.mu.Lock()
	defer client.mu.Unlock()
	client.shutdown = true
	for i := range client.pending {
		client.pending[i].Error = err
		client.pending[i].done()
	}
}

func (client *Client) receive() {
	var err error
	for err == nil {
		var h codec.Header
		if err = client.cc.ReadHeader(&h); err != nil {
			break
		}
		call := client.removeCall(h.Seq)
		switch {
		case call == nil:
			err = client.cc.ReadBody(nil)
		case h.Error != "":
			call.Error = fmt.Errorf(h.Error)
			err = client.cc.ReadBody(nil)
			call.done()
		default:
			err = client.cc.ReadBody(call.Reply)
			if err != nil {
				call.Error = fmt.Errorf("read body %s", err.Error())
			}
			call.done()
		}
	}
	client.terminateCalls(err)
}

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

	seq, err := client.registerCall(call)
	if err != nil {
		call.Error = err
		call.done()
		return
	}

	client.header.ServiceMethod = call.ServiceMethod
	client.header.Seq = seq
	client.header.Error = ""

	if err := client.cc.Write(&client.header, call.Args); err != nil {
		call := client.removeCall(seq)
		if call != nil {
			call.Error = err
			call.done()
		}
	}
}

func (client *Client) Go(serviceMethod string,
	args, reply interface{}, done chan *Call) *Call {
	if done == nil {
		done = make(chan *Call, 10)
	} else if cap(done) == 0 {
		log.Panic("rpc client: done channel is unbuffered")
	}
	call := &Call{
		ServiceMethod: serviceMethod,
		Args:          args,
		Reply:         reply,
		Done:          done,
	}
	go client.send(call)
	return call
}

func (client *Client) Call(ctx context.Context, serviceMethod string, args, reply interface{}) error {
	call := client.Go(serviceMethod, args, reply, make(chan *Call, 1))
	select {
	case <-ctx.Done():
		client.removeCall(call.Seq)
		return fmt.Errorf("rpc: client call failed: %v", ctx.Err())
	case c := <-call.Done:
		return c.Error
	}
}

func dialTimeout(f newClientFunc, network, address string,
	opts ...Option) (client *Client, err error) {

	o := apply(DefaultOptions, opts...)
	conn, err := net.DialTimeout(network, address, o.ConnectTimeout)
	if err != nil {
		return nil, err
	}
	defer func() {
		if err != nil {
			_ = conn.Close()
		}
	}()

	ch := make(chan clientResult)
	go func() {
		client, err := f(conn, opts...)
		ch <- clientResult{client: client, err: err}
	}()
	if o.ConnectTimeout == 0 {
		result := <-ch
		return result.client, result.err
	}
	select {
	case <-time.After(o.ConnectTimeout):
		return nil, fmt.Errorf("rpc: client connection timeout after %s", o.ConnectTimeout)
	case result := <-ch:
		return result.client, result.err
	}
}

func NewHTTPClient(conn net.Conn, opts ...Option) (*Client, error) {
	_, _ = fmt.Fprintf(conn,
	"CONNECT %s HTTP/1.0\n\n", defaultRPCPath)

	resp, err := http.ReadResponse(bufio.NewReader(conn),
		&http.Request{Method: http.MethodConnect})
	if err == nil && resp.Status == connected {
		return NewClient(conn, opts...)
	}
	return nil, err
}

func DialHTTP(network, address string, opts ...Option) (*Client, error) {
	return dialTimeout(NewHTTPClient, network, address, opts...)
}

func XDial(rpcAddr string, opts ...Option) (*Client, error) {
	parts := strings.Split(rpcAddr, "://")
	if len(parts) != 2 {
		return nil, fmt.Errorf("rpc: client wrong format '%s', expect protocol://addr", rpcAddr)
	}
	protocol, addr := parts[0], parts[1]

	switch protocol {
	case "http":
		return DialHTTP("tcp", addr, opts...)
	default:
		return Dial(protocol, addr, opts...)
	}
}