import {EventEmitter} from '@angular/core';
import {Observable} from 'rxjs/Observable';
import {Subscription} from 'rxjs/Subscription';
import {Subscriber} from 'rxjs/Subscriber';
import 'rxjs/add/observable/merge';
import 'rxjs/add/observable/from';
import 'rxjs/add/operator/mergeAll';
import 'rxjs/add/operator/combineLatest';

export enum UploadStatus {
    Queue,
    Uploading,
    Done,
    Canceled
}

export interface UploadProgress {
    status: UploadStatus;
    data?: {
        percentage: number;
        speed: number;
        speedHuman: string;
        startTime: number | null;
        endTime: number | null;
    };
}

export interface UploadFile {
    id: string;
    fileIndex: number;
    lastModifiedDate: Date;
    name: string;
    size: number;
    type: string;
    progress: UploadProgress;
    response?: any;
}

export interface UploadOutput {
    type: 'addedToQueue' | 'allAddedToQueue' | 'uploading' | 'done' | 'removed' | 'start' | 'cancelled' | 'dragOver' | 'dragOut' | 'drop' | 'clearedAll';
    file?: UploadFile;
}

export interface UploadInput {
    type: 'uploadAll' | 'uploadFile' | 'cancel' | 'cancelAll' | 'clearAll';
    url?: string;
    method?: string;
    id?: string;
    fieldName?: string;
    fileIndex?: number;
    file?: UploadFile;
    data?: { [key: string]: string | Blob };
    headers?: { [key: string]: string };
    concurrency?: number;
    withCredentials?: boolean;
}

export function humanizeBytes(bytes: number): string {
    if (bytes === 0) {
        return '0 Byte';
    }

    const k = 1024;
    const sizes: string[] = ['Bytes', 'KB', 'MB', 'GB', 'TB', 'PB'];
    const i: number = Math.floor(Math.log(bytes) / Math.log(k));

    return parseFloat((bytes / Math.pow(k, i)).toFixed(2)) + ' ' + sizes[i];
}

export class NgUploaderService {
    fileList: FileList;
    files: UploadFile[];
    uploads: { file?: UploadFile, files?: UploadFile[], sub: { instance: Subscription } }[];
    serviceEvents: EventEmitter<UploadOutput>;

    constructor() {
        this.files = [];
        this.serviceEvents = new EventEmitter<any>();
        this.uploads = [];
    }

    handleFiles(files: FileList): void {
        this.fileList = files;

        this.files = [].map.call(files, (file: File, i: number) => {
            const uploadFile: UploadFile = {
                fileIndex: i,
                id: this.generateId(),
                name: file.name,
                size: file.size,
                type: file.type,
                progress: {
                    status: UploadStatus.Queue,
                    data: {
                        percentage: 0,
                        speed: null,
                        speedHuman: null,
                        startTime: null,
                        endTime: null
                    }
                },
                lastModifiedDate: file.lastModifiedDate
            };

            this.serviceEvents.emit({type: 'addedToQueue', file: uploadFile});
            return uploadFile;
        });
        /*FORCING ONLY last file on the queue*/
        if (this.files.length > 1) {
            this.files = [this.files[this.files.length - 1]];
        }
        this.serviceEvents.emit({type: 'allAddedToQueue', file: this.files[0]});
    }

    initInputEvents(input: EventEmitter<UploadInput>): void {
        input.subscribe((event: UploadInput) => {
            switch (event.type) {
                case 'uploadFile':
                    this.serviceEvents.emit({type: 'start', file: event.file});

                    let sub: { instance: Subscription } = {instance: null};

                    this.uploads.push({file: event.file, sub: sub});

                    sub.instance = this.uploadFile(event.file, event).subscribe(data => {
                        this.serviceEvents.emit(data);
                    });
                    break;
                case 'uploadAll':
                    const concurrency = event.concurrency > 0 ? event.concurrency : Number.POSITIVE_INFINITY;

                    const subscriber = Subscriber.create((data: UploadOutput) => {
                        this.serviceEvents.emit(data);
                    });

                    this.uploads = this.uploads.concat(this.files.map(file => {
                        return {file: file, sub: null};
                    }));

                    const subscription = Observable.from(this.files.map(file => this.uploadFile(file, event)))
                        .mergeAll(concurrency)
                        .combineLatest(data => data)
                        .subscribe(subscriber);
                    break;
                case 'cancel':
                    const id = event.id || null;
                    if (!id) {
                        return;
                    }

                    const index = this.uploads.findIndex(upload => upload.file.id === id);
                    if (index !== -1) {
                        if (this.uploads[index].sub && this.uploads[index].sub.instance) {
                            this.uploads[index].sub.instance.unsubscribe();
                        }

                        this.serviceEvents.emit({type: 'cancelled', file: this.uploads[index].file});
                        this.uploads[index].file.progress.status = UploadStatus.Canceled;
                    }
                    break;
                case 'cancelAll':
                    this.uploads.forEach(upload => {
                        upload.file.progress.status = UploadStatus.Canceled;
                        this.serviceEvents.emit({type: 'cancelled', file: upload.file});
                    });
                    break;
                case 'clearAll':
                    this.files = [];
                    this.fileList = null;
                    this.serviceEvents.emit({type: 'clearedAll'});
                    break
            }
        });
    }

    uploadFile(file: UploadFile, event: UploadInput): Observable<UploadOutput> {
        return new Observable(observer => {
            const url = event.url;
            const method = event.method || 'POST';
            const data = event.data || {};
            const headers = event.headers || {};

            const reader = new FileReader();
            const xhr = new XMLHttpRequest();
            let time: number = new Date().getTime();
            let speed = 0;

            xhr.upload.addEventListener('progress', (e: ProgressEvent) => {
                if (e.lengthComputable) {
                    const percentage = Math.round((e.loaded * 100) / e.total);
                    const diff = new Date().getTime() - time;
                    speed = Math.round(e.loaded / diff * 1000);

                    file.progress = {
                        status: UploadStatus.Uploading,
                        data: {
                            percentage: percentage,
                            speed: speed,
                            speedHuman: `${humanizeBytes(speed)}/s`,
                            startTime: file.progress.data.startTime || new Date().getTime(),
                            endTime: null
                        }
                    };

                    observer.next({type: 'uploading', file: file});
                }
            }, false);

            xhr.upload.addEventListener('error', (e: Event) => {
                observer.error(e);
                observer.complete();
            });

            xhr.onreadystatechange = () => {
                if (xhr.readyState === XMLHttpRequest.DONE) {
                    const speedAverage = Math.round(file.size / (new Date().getTime() - file.progress.data.startTime) * 1000);
                    file.progress = {
                        status: UploadStatus.Done,
                        data: {
                            percentage: 100,
                            speed: speedAverage,
                            speedHuman: `${humanizeBytes(speedAverage)}/s`,
                            startTime: file.progress.data.startTime,
                            endTime: new Date().getTime()
                        }
                    };

                    try {
                        file.response = JSON.parse(xhr.response);
                    } catch (e) {
                        file.response = xhr.response;
                    }

                    observer.next({type: 'done', file: file});
                    observer.complete();
                }
            };

            xhr.open(method, url, true);
            xhr.withCredentials = event.withCredentials ? true : false;

            const form = new FormData();
            try {
                const uploadFile = this.fileList.item(file.fileIndex);
                const uploadIndex = this.uploads.findIndex(upload => upload.file.size === uploadFile.size);
                if (this.uploads[uploadIndex].file.progress.status === UploadStatus.Canceled) {
                    observer.complete();
                }

                form.append(event.fieldName || 'file', uploadFile, uploadFile.name);

                Object.keys(data).forEach(key => form.append(key, data[key]));
                Object.keys(headers).forEach(key => xhr.setRequestHeader(key, headers[key]));

                this.serviceEvents.emit({type: 'start', file: file});
                xhr.send(form);
            } catch (e) {
                observer.complete();
            }

            return () => {
                xhr.abort();
                reader.abort();
            };
        });
    }

    generateId(): string {
        return Math.random().toString(36).substring(7);
    }
}