package core

import (
	"errors"
	"fmt"
	"git.noahlan.cn/northlan/nnet/internal/pool"
	"git.noahlan.cn/northlan/nnet/log"
	"git.noahlan.cn/northlan/nnet/packet"
	"git.noahlan.cn/northlan/nnet/scheduler"
	"git.noahlan.cn/northlan/nnet/session"
	"net"
	"sync/atomic"
	"time"
)

var (
	ErrCloseClosedSession = errors.New("close closed session")
	// ErrBrokenPipe represents the low-level connection has broken.
	ErrBrokenPipe = errors.New("broken low-level pipe")
	// ErrBufferExceed indicates that the current session buffer is full and
	// can not receive more data.
	ErrBufferExceed = errors.New("session send buffer exceed")
)

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 // Session
		ngin    *engine          // engine

		conn    net.Conn // low-level conn fd
		status  int32    // 连接状态
		lastMid uint64   // 最近一次消息ID
		// TODO 考虑独立出去作为一个中间件
		lastHeartbeatAt int64 // 最近一次心跳时间

		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 newConn(server *engine, conn net.Conn) *Connection {
	r := &Connection{
		conn:   conn,
		ngin:   server,
		status: StatusStart,

		lastHeartbeatAt: time.Now().Unix(),

		chDie:   make(chan struct{}),
		chSend:  make(chan pendingMessage, 128),
		chWrite: make(chan []byte, 128),
	}

	// binding session
	r.session = session.NewSession()
	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 {
	return r.conn
}

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

func (r *Connection) SetLastHeartbeatAt(t int64) {
	atomic.StoreInt64(&r.lastHeartbeatAt, t)
}

func (r *Connection) Session() *session.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.SubmitConn(func() {
		r.write()
	})

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

func (r *Connection) write() {
	ticker := time.NewTicker(r.ngin.heartbeatInterval)

	defer func() {
		ticker.Stop()
		close(r.chSend)
		close(r.chWrite)
		_ = r.Close()

		log.Debugf("Connection write goroutine exit, ConnID=%d, SessionUID=%s", r.ID(), r.session.UID())
	}()

	for {
		select {
		case <-ticker.C:
			// TODO heartbeat enable control
			deadline := time.Now().Add(-2 * r.ngin.heartbeatInterval).Unix()
			if atomic.LoadInt64(&r.lastHeartbeatAt) < deadline {
				log.Debugf("Session heartbeat timeout, LastTime=%d, Deadline=%d", atomic.LoadInt64(&r.lastHeartbeatAt), deadline)
				return
			}
			// TODO heartbeat data
			r.chWrite <- []byte{}
		case data := <-r.chSend:
			// marshal packet body (data)
			if r.ngin.serializer == nil {
				if _, ok := data.payload.([]byte); !ok {
					log.Errorf("serializer is nil, but payload type not []byte")
					break
				}
			} else {
				payload, err := r.ngin.serializer.Marshal(data.payload)
				if err != nil {
					log.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 {
					log.Errorf("broken pipeline err: %s", err.Error())
					break
				}
			}

			// packet pack data
			p, err := r.ngin.packer.Pack(data.header, data.payload.([]byte))
			if err != nil {
				log.Error(err.Error())
				break
			}
			r.chWrite <- p
		case data := <-r.chWrite:
			// 回写数据
			if _, err := r.conn.Write(data); err != nil {
				log.Error(err.Error())
				return
			}
		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)
		if err != nil {
			log.Errorf("Read message error: %s, session will be closed immediately", err.Error())
			return
		}

		if r.ngin.packer == nil {
			log.Errorf("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.ngin.packer.Unpack(buf[:n])
		if err != nil {
			log.Error(err.Error())
		}
		// packets 处理
		for _, p := range packets {
			if err := r.processPacket(p); err != nil {
				log.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()))
		}
	}

	// packet processor
	err := r.ngin.processor.Process(r, packet)
	if err != nil {
		return err
	}

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

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

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

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