package core

import (
	"errors"
	"fmt"
	"git.noahlan.cn/noahlan/nnet/entity"
	"git.noahlan.cn/noahlan/nnet/packet"
	"git.noahlan.cn/noahlan/nnet/scheduler"
	"git.noahlan.cn/noahlan/ntools-go/core/nlog"
	"git.noahlan.cn/noahlan/ntools-go/core/pool"
	"net"
	"sync/atomic"
)

var (
	ErrCloseClosedSession = errors.New("close closed session")
	// ErrBrokenPipe represents the low-level connection has broken.
	ErrBrokenPipe = errors.New("broken low-level pipe")
)

const (
	// StatusStart 开始阶段
	StatusStart int32 = iota + 1
	// StatusPrepare 准备阶段
	StatusPrepare
	// StatusPending 等待工作阶段
	StatusPending
	// StatusWorking 工作阶段
	StatusWorking
	// StatusClosed 连接关闭
	StatusClosed
)

type (
	connection struct {
		session *session // Session
		ngin    *engine  // engine

		status int32    // 连接状态
		conn   net.Conn // low-level conn fd
		isWS   bool     // 是否为websocket

		packer packet.Packer // 封包、拆包器

		lastMid uint64 // 最近一次消息ID

		chDie   chan struct{}       // 停止通道
		chSend  chan PendingMessage // 消息发送通道（结构化消息）
		chWrite chan []byte         // 消息发送通道（二进制消息）
	}

	PendingMessage struct {
		header  interface{}
		payload interface{}
	}
)

func newConnection(server *engine, conn net.Conn) *connection {
	r := &connection{
		ngin: server,

		status: StatusStart,
		conn:   conn,
		packer: server.packerFn(),

		chDie:   make(chan struct{}),
		chSend:  make(chan PendingMessage, 128),
		chWrite: make(chan []byte, 128),
	}
	_, r.isWS = conn.(*WSConn)

	// binding session
	r.session = newSession(r)
	return r
}

func (r *connection) Send(header, payload interface{}) (err error) {
	defer func() {
		if e := recover(); e != nil {
			err = ErrBrokenPipe
		}
	}()
	r.chSend <- PendingMessage{
		header:  header,
		payload: payload,
	}
	return err
}

func (r *connection) SendBytes(data []byte) (err error) {
	defer func() {
		if e := recover(); e != nil {
			err = ErrBrokenPipe
		}
	}()
	r.chWrite <- data
	return err
}

func (r *connection) Status() int32 {
	return atomic.LoadInt32(&r.status)
}

func (r *connection) SetStatus(s int32) {
	atomic.StoreInt32(&r.status, s)
}

func (r *connection) Conn() (net.Conn, bool) {
	return r.conn, r.isWS
}

func (r *connection) ID() int64 {
	return r.session.ID()
}

func (r *connection) Session() entity.Session {
	return r.session
}

func (r *connection) LastMID() uint64 {
	return r.lastMid
}

func (r *connection) SetLastMID(mid uint64) {
	atomic.StoreUint64(&r.lastMid, mid)
}

func (r *connection) serve() {
	_ = pool.Submit(func() {
		r.write()
	})

	_ = pool.Submit(func() {
		r.read()
	})
}

func (r *connection) write() {
	defer func() {
		close(r.chSend)
		close(r.chWrite)
		_ = r.Close()

		nlog.Debugf("[writeLoop] connection write goroutine exit, ConnID=%d, SessionUID=%s", r.ID(), r.session.UID())
	}()

	for {
		select {
		case data := <-r.chSend:
			// marshal packet body (data)
			if r.ngin.serializer == nil {
				if _, ok := data.payload.([]byte); !ok {
					nlog.Errorf("serializer is nil, but payload type not []byte")
					break
				}
			} else {
				payload, err := r.ngin.serializer.Marshal(data.payload)
				if err != nil {
					nlog.Errorf("message body marshal err: %v", err)
					break
				}
				data.payload = payload
			}

			// invoke pipeline
			if pipe := r.ngin.pipeline; pipe != nil {
				err := pipe.Outbound().Process(r, data)
				if err != nil {
					nlog.Errorf("pipeline err: %s", err.Error())
				}
			}

			// packet pack data
			p, err := r.packer.Pack(data.header, data.payload.([]byte))
			if err != nil {
				nlog.Error(err.Error())
				break
			}
			r.chWrite <- p
		case data := <-r.chWrite:
			// 回写数据
			if _, err := r.conn.Write(data); err != nil {
				nlog.Error(err.Error())
				break
			}
			//nlog.Debugf("write data %v", data)
		case <-r.chDie: // connection close signal
			return
		case <-r.ngin.dieChan: // application quit signal
			return
		}
	}
}

func (r *connection) read() {
	defer func() {
		_ = r.Close()
	}()

	buf := make([]byte, 4096)
	for {
		n, err := r.conn.Read(buf)
		//nlog.Debugf("receive data %v", buf[:n])
		if err != nil {
			nlog.Errorf("[readLoop] Read message error: %s, session will be closed immediately", err.Error())
			return
		}

		if r.packer == nil {
			nlog.Errorf("[readLoop] unexpected error: packer is nil")
			return
		}

		// warning: 为性能考虑，复用slice处理数据，buf传入后必须要copy再处理
		packets, err := r.packer.Unpack(buf[:n])
		if err != nil {
			nlog.Error(err.Error())
		}
		// packets 处理
		for _, p := range packets {
			if err := r.processPacket(p); err != nil {
				nlog.Error(err.Error())
				continue
			}
		}
	}
}

func (r *connection) processPacket(packet packet.IPacket) error {
	if pipe := r.ngin.pipeline; pipe != nil {
		err := pipe.Inbound().Process(r, packet)
		if err != nil {
			return errors.New(fmt.Sprintf("pipeline process failed: %v", err.Error()))
		}
	}

	if r.Status() == StatusWorking {
		// HandleFunc
		_ = pool.Submit(func() {
			r.ngin.handler.Handle(r, packet)
		})
	}
	return nil
}

func (r *connection) Close() error {
	if r.Status() == StatusClosed {
		return ErrCloseClosedSession
	}
	r.SetStatus(StatusClosed)

	nlog.Debugf("close connection, ID: %d", r.ID())

	select {
	case <-r.chDie:
	default:
		close(r.chDie)
		scheduler.PushTask(func() { Lifetime.Close(r) })
	}
	r.session.Close()

	return r.conn.Close()
}