// Copyright 2019 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.

package queue

import (
	"context"
	"fmt"
	"reflect"
	"time"

	"code.gitea.io/gitea/modules/log"
)

// ChannelQueueType is the type for channel queue
const ChannelQueueType Type = "channel"

// ChannelQueueConfiguration is the configuration for a ChannelQueue
type ChannelQueueConfiguration struct {
	QueueLength  int
	BatchLength  int
	Workers      int
	MaxWorkers   int
	BlockTimeout time.Duration
	BoostTimeout time.Duration
	BoostWorkers int
	Name         string
}

// ChannelQueue implements
type ChannelQueue struct {
	pool     *WorkerPool
	exemplar interface{}
	workers  int
	name     string
}

// NewChannelQueue create a memory channel queue
func NewChannelQueue(handle HandlerFunc, cfg, exemplar interface{}) (Queue, error) {
	configInterface, err := toConfig(ChannelQueueConfiguration{}, cfg)
	if err != nil {
		return nil, err
	}
	config := configInterface.(ChannelQueueConfiguration)
	if config.BatchLength == 0 {
		config.BatchLength = 1
	}
	dataChan := make(chan Data, config.QueueLength)

	ctx, cancel := context.WithCancel(context.Background())
	queue := &ChannelQueue{
		pool: &WorkerPool{
			baseCtx:            ctx,
			cancel:             cancel,
			batchLength:        config.BatchLength,
			handle:             handle,
			dataChan:           dataChan,
			blockTimeout:       config.BlockTimeout,
			boostTimeout:       config.BoostTimeout,
			boostWorkers:       config.BoostWorkers,
			maxNumberOfWorkers: config.MaxWorkers,
		},
		exemplar: exemplar,
		workers:  config.Workers,
		name:     config.Name,
	}
	queue.pool.qid = GetManager().Add(queue, ChannelQueueType, config, exemplar, queue.pool)
	return queue, nil
}

// Run starts to run the queue
func (c *ChannelQueue) Run(atShutdown, atTerminate func(context.Context, func())) {
	atShutdown(context.Background(), func() {
		log.Warn("ChannelQueue: %s is not shutdownable!", c.name)
	})
	atTerminate(context.Background(), func() {
		log.Warn("ChannelQueue: %s is not terminatable!", c.name)
	})
	go func() {
		_ = c.pool.AddWorkers(c.workers, 0)
	}()
}

// Push will push data into the queue
func (c *ChannelQueue) Push(data Data) error {
	if c.exemplar != nil {
		// Assert data is of same type as r.exemplar
		t := reflect.TypeOf(data)
		exemplarType := reflect.TypeOf(c.exemplar)
		if !t.AssignableTo(exemplarType) || data == nil {
			return fmt.Errorf("Unable to assign data: %v to same type as exemplar: %v in queue: %s", data, c.exemplar, c.name)
		}
	}
	c.pool.Push(data)
	return nil
}

// Name returns the name of this queue
func (c *ChannelQueue) Name() string {
	return c.name
}

func init() {
	queuesMap[ChannelQueueType] = NewChannelQueue
}