/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package util

import (
	"golang.org/x/net/context"
	"sync"
	"time"
)

var GlobalPoolConfig = &PoolConfig{
	Concurrent:  1000,
	WaitTimeout: time.Second,
	IdleTimeout: 60 * time.Second,
}

type PoolConfig struct {
	Concurrent  int
	WaitTimeout time.Duration
	IdleTimeout time.Duration
}

type GoRoutine struct {
	ctx        context.Context
	cancel     context.CancelFunc
	wg         sync.WaitGroup
	mux        sync.RWMutex
	closed     bool
	task       chan func(ctx context.Context)
	concurrent chan struct{}
}

func (g *GoRoutine) execute(f func(ctx context.Context)) {
	defer RecoverAndReport()
	f(g.ctx)
}

func (g *GoRoutine) Do(f func(context.Context)) {
	defer RecoverAndReport()
	select {
	case g.task <- f:
		return
	case g.concurrent <- struct{}{}:
		go g.loop(f)
	}
}

func (g *GoRoutine) loop(f func(context.Context)) {
	g.wg.Add(1)
	defer g.wg.Done()
	defer func() { <-g.concurrent }()

	timer := time.NewTimer(GlobalPoolConfig.IdleTimeout)
	defer timer.Stop()
	for {
		g.execute(f)

		select {
		case <-timer.C:
			return
		case f = <-g.task:
			if f == nil {
				return
			}
			ResetTimer(timer, GlobalPoolConfig.IdleTimeout)
		}
	}
}

func (g *GoRoutine) Close(wait bool) {
	g.mux.Lock()
	if g.closed {
		g.mux.Unlock()
		return
	}
	g.closed = true
	g.mux.Unlock()

	close(g.task)
	close(g.concurrent)
	g.cancel()
	if wait {
		g.Wait()
	}
}

func (g *GoRoutine) Wait() {
	g.wg.Wait()
}

var defaultGo *GoRoutine

func init() {
	defaultGo = NewGo(context.Background())
}

func Go(f func(context.Context)) {
	defaultGo.Do(f)
}

func GoCloseAndWait() {
	defaultGo.Close(true)
	Logger().Debugf("all goroutines exited")
}

func NewGo(ctx context.Context) *GoRoutine {
	ctx, cancel := context.WithCancel(ctx)
	gr := &GoRoutine{
		ctx:        ctx,
		cancel:     cancel,
		task:       make(chan func(context.Context)),
		concurrent: make(chan struct{}, GlobalPoolConfig.Concurrent),
	}
	return gr
}