// SiYuan - Build Your Eternal Digital Garden
// Copyright (c) 2020-present, b3log.org
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

package task

import (
	"reflect"
	"sync"
	"time"

	"github.com/siyuan-note/logging"
)

var (
	taskQueue       []*Task
	taskQueueStatus int
	queueLock       = sync.Mutex{}
	taskLock        = sync.Mutex{}
)

const (
	QueueStatusRunning = iota
	QueueStatusClosing
)

type Task struct {
	Action  string
	Handler reflect.Value
	Args    []interface{}
	Created time.Time
}

func PrependTask(action string, handler interface{}, args ...interface{}) {
	queueLock.Lock()
	defer queueLock.Unlock()

	if QueueStatusRunning != taskQueueStatus {
		logging.LogWarnf("task queue is paused, action [%s] will be ignored", action)
		return
	}

	cancelTask(action)
	taskQueue = append([]*Task{newTask(action, handler, args...)}, taskQueue...)
}

func AppendTask(action string, handler interface{}, args ...interface{}) {
	queueLock.Lock()
	defer queueLock.Unlock()

	if QueueStatusRunning != taskQueueStatus {
		logging.LogWarnf("task queue is paused, action [%s] will be ignored", action)
		return
	}

	cancelTask(action)
	taskQueue = append(taskQueue, newTask(action, handler, args...))
}

func CancelTask(actions ...string) {
	queueLock.Lock()
	defer queueLock.Unlock()

	cancelTask(actions...)
}

func cancelTask(actions ...string) {
	for i := len(taskQueue) - 1; i >= 0; i-- {
		task := taskQueue[i]
		for _, action := range actions {
			if action == task.Action {
				taskQueue = append(taskQueue[:i], taskQueue[i+1:]...)
				break
			}
		}
	}
}

func newTask(action string, handler interface{}, args ...interface{}) *Task {
	return &Task{
		Action:  action,
		Handler: reflect.ValueOf(handler),
		Args:    args,
		Created: time.Now(),
	}
}

const (
	CloudSync               = "task.cloud.sync"                // 数据同步
	RepoCheckout            = "task.repo.checkout"             // 从快照中检出
	DatabaseIndexFull       = "task.database.index.full"       // 重建索引
	DatabaseIndex           = "task.database.index"            // 数据库所以队列
	DatabaseIndexFix        = "task.database.index.fix"        // 数据库索引订正
	OCRImage                = "task.ocr.image"                 // 图片 OCR 提取文本
	DatabaseIndexEmbedBlock = "task.database.index.embedblock" // 数据库索引嵌入块
)

func Loop() {
	for {
		time.Sleep(10 * time.Millisecond)
		task := popTask()
		if nil == task {
			continue
		}

		execTask(task)
	}
}

func CloseWait() {
	queueLock.Lock()
	defer queueLock.Unlock()

	taskQueueStatus = QueueStatusClosing
	for {
		time.Sleep(10 * time.Millisecond)
		if 1 > len(taskQueue) {
			break
		}
	}
}

func popTask() (ret *Task) {
	queueLock.Lock()
	defer queueLock.Unlock()

	if 0 == len(taskQueue) {
		return
	}

	ret = taskQueue[0]
	taskQueue = taskQueue[1:]
	return
}

func execTask(task *Task) {
	taskLock.Lock()
	defer taskLock.Unlock()
	defer logging.Recover()

	args := make([]reflect.Value, len(task.Args))
	for i, v := range task.Args {
		if nil == v {
			args[i] = reflect.New(task.Handler.Type().In(i)).Elem()
		} else {
			args[i] = reflect.ValueOf(v)
		}
	}
	task.Handler.Call(args)
}