import {Injectable} from "@angular/core";
import {GalleryCacheService} from "./cache.gallery.service";
import {Photo} from "./Photo";
import {IconPhoto} from "./IconPhoto";
import {PhotoDTO} from "../../../common/entities/PhotoDTO";
import {Config} from "../../../common/config/public/Config";

export enum ThumbnailLoadingPriority{
  high, medium, low
}

@Injectable()
export class ThumbnailLoaderService {

  que: Array<ThumbnailTask> = [];
  runningRequests: number = 0;

  constructor(private galleryChacheService: GalleryCacheService) {
  }

  removeTasks() {
    this.que = [];
  }

  removeTask(taskEntry: ThumbnailTaskEntity) {

    for (let i = 0; i < this.que.length; i++) {
      let index = this.que[i].taskEntities.indexOf(taskEntry);
      if (index == -1) {
        this.que[i].taskEntities.splice(index, 1);
        if (this.que[i].taskEntities.length == 0) {
          this.que.splice(i, 1);

        }
        return;
      }
    }

  }

  loadIcon(photo: IconPhoto, priority: ThumbnailLoadingPriority, listener: ThumbnailLoadingListener): ThumbnailTaskEntity {
    let tmp: ThumbnailTask = null;
    //is image already qued?
    for (let i = 0; i < this.que.length; i++) {
      if (this.que[i].path == photo.getIconPath()) {
        tmp = this.que[i];
        break;
      }
    }

    let thumbnailTaskEntity = {priority: priority, listener: listener};
    //add to previous
    if (tmp != null) {
      tmp.taskEntities.push(thumbnailTaskEntity);
      if (tmp.inProgress == true) {
        listener.onStartedLoading();
      }


    } else {//create new task
      this.que.push(<ThumbnailTask>{
        photo: photo.photo,
        inProgress: false,
        taskEntities: [thumbnailTaskEntity],
        onLoaded: () => {
          photo.iconLoaded();
        },
        path: photo.getIconPath()
      });
    }
    setTimeout(this.run, 0);
    return thumbnailTaskEntity;
  }

  loadImage(photo: Photo, priority: ThumbnailLoadingPriority, listener: ThumbnailLoadingListener): ThumbnailTaskEntity {

    let tmp: ThumbnailTask = null;
    //is image already qued?
    for (let i = 0; i < this.que.length; i++) {
      if (this.que[i].path == photo.getThumbnailPath()) {
        tmp = this.que[i];
        break;
      }
    }

    let thumbnailTaskEntity = {priority: priority, listener: listener};
    //add to previous
    if (tmp != null) {
      tmp.taskEntities.push(thumbnailTaskEntity);
      if (tmp.inProgress == true) {
        listener.onStartedLoading();
      }


    } else {//create new task
      this.que.push({
        photo: photo.photo,
        inProgress: false,
        taskEntities: [thumbnailTaskEntity],
        onLoaded: () => {
          photo.thumbnailLoaded();
        },
        path: photo.getThumbnailPath()
      });
    }
    setTimeout(this.run, 0);
    return thumbnailTaskEntity;

  }


  private getNextTask(): ThumbnailTask {
    if (this.que.length === 0) {
      return null;
    }

    for (let i = 0; i < this.que.length; i++) {
      for (let j = 0; j < this.que[i].taskEntities.length; j++) {
        if (this.que[i].inProgress == false && this.que[i].taskEntities[j].priority === ThumbnailLoadingPriority.high) {
          return this.que[i];
        }
      }
    }

    for (let i = 0; i < this.que.length; i++) {
      for (let j = 0; j < this.que[i].taskEntities.length; j++) {
        if (this.que[i].inProgress == false && this.que[i].taskEntities[j].priority === ThumbnailLoadingPriority.medium) {
          return this.que[i];
        }
      }
    }


    for (let i = 0; i < this.que.length; i++) {
      if (this.que[i].inProgress == false) {
        return this.que[i];
      }

    }

    return null;
  }

  private taskReady(task: ThumbnailTask) {
    let i = this.que.indexOf(task);
    if (i == -1) {
      if (task.taskEntities.length !== 0) {
        console.error("ThumbnailLoader: can't find task to remove");
      }
      return;
    }
    this.que.splice(i, 1);
  }


  run = () => {
    if (this.que.length === 0 || this.runningRequests >= Config.Client.concurrentThumbnailGenerations) {
      return;
    }
    let task = this.getNextTask();

    if (task === null) {
      return;
    }

    this.runningRequests++;
    task.taskEntities.forEach(te => te.listener.onStartedLoading());
    task.inProgress = true;

    let curImg = new Image();
    curImg.onload = () => {
      task.onLoaded();
      this.galleryChacheService.photoUpdated(task.photo);
      task.taskEntities.forEach((te: ThumbnailTaskEntity) => te.listener.onLoad());

      this.taskReady(task);
      this.runningRequests--;
      this.run();
    };

    curImg.onerror = (error) => {
      task.taskEntities.forEach((te: ThumbnailTaskEntity) => te.listener.onError(error));

      this.taskReady(task);
      this.runningRequests--;
      this.run();
    };

    curImg.src = task.path;
  };
}


export interface ThumbnailLoadingListener {
  onStartedLoading: () => void;
  onLoad: () => void;
  onError: (error: any) => void;
}


export interface ThumbnailTaskEntity {
  priority: ThumbnailLoadingPriority;
  listener: ThumbnailLoadingListener;
}

interface ThumbnailTask {
  photo: PhotoDTO;
  inProgress: boolean;
  taskEntities: Array<ThumbnailTaskEntity>;
  path: string;
  onLoaded: Function;
}