package notify

import (
	"fmt"
	"log"
	"net"
	"runtime"
	"sync"

	"git.loafle.net/commons_go/rpc/client"
)

func New(nh NotifyHandler) Notifier {
	n := &notify{
		nh: nh,
	}
	return n
}

type Notifier interface {
	Start(conn net.Conn)
	Close()

	Notify(method string, args ...interface{}) (err error)
}

type notify struct {
	nh NotifyHandler

	conn net.Conn

	notifyQueueChan chan *client.CallState

	stopChan chan struct{}
	stopWg   sync.WaitGroup
}

func (n *notify) Start(conn net.Conn) {
	n.nh.Validate()

	if n.stopChan != nil {
		panic("RPC Notify: the given notify is already started. Call Notifier.Stop() before calling Notifier.Start(conn) again!")
	}

	n.conn = conn

	n.stopChan = make(chan struct{})
	n.notifyQueueChan = make(chan *client.CallState, n.nh.GetPendingNotifies())

	go n.handleRPC()
}

func (n *notify) Close() {
	if n.stopChan == nil {
		panic("RPC Notify: the notify must be started before stopping it")
	}
	close(n.stopChan)
	n.stopWg.Wait()
	n.stopChan = nil
}

func (n *notify) Notify(method string, args ...interface{}) (err error) {
	var cs *client.CallState
	if cs, err = n.send(method, args...); nil != err {
		return
	}

	select {
	case <-cs.DoneChan:
		err = cs.Error
		client.ReleaseCallState(cs)
	}

	return
}

func (n *notify) send(method string, args ...interface{}) (cs *client.CallState, err error) {
	cs = client.RetainCallState()

	cs.Method = method
	cs.Args = args
	cs.DoneChan = make(chan *client.CallState, 1)

	select {
	case n.notifyQueueChan <- cs:
		return cs, nil
	default:
		client.ReleaseCallState(cs)
		return nil, getClientOverflowError(n)
	}
}

func (n *notify) handleRPC() {
	subStopChan := make(chan struct{})

	writerDone := make(chan error, 1)
	go n.rpcWriter(subStopChan, writerDone)

	var err error

	select {
	case err = <-writerDone:
		close(subStopChan)
	case <-n.stopChan:
		close(subStopChan)
		<-writerDone
	}

	if err != nil {
		//n.LogError("%s", err)
		log.Printf("handleRPC: %v", err)
		err = &client.ClientError{
			Connection: true,
			Err:        err,
		}
	}
}

func (n *notify) rpcWriter(stopChan <-chan struct{}, writerDone chan<- error) {
	var err error
	defer func() {
		writerDone <- err
	}()

	for {
		var cs *client.CallState

		select {
		case cs = <-n.notifyQueueChan:
		default:
			// Give the last chance for ready goroutines filling n.requestsChan :)
			runtime.Gosched()

			select {
			case <-stopChan:
				return
			case cs = <-n.notifyQueueChan:
			}
		}

		if cs.IsCanceled() {
			client.ReleaseCallState(cs)
			continue
		}

		err = n.nh.GetCodec().Write(n.conn, cs.Method, cs.Args, nil)
		cs.Error = err
		cs.Done()
		if nil != err {
			err = fmt.Errorf("RPC Notify: Cannot send notify to wire: [%s]", err)
			return
		}
	}
}

func getClientOverflowError(n *notify) error {
	err := fmt.Errorf("RPC Notify: Notifies' queue with size=%d is overflown. Try increasing NotifyHandler.PendingNotifies value", cap(n.notifyQueueChan))
	//c.LogError("%s", err)
	return &client.ClientError{
		Overflow: true,
		Err:      err,
	}
}