import {
    AfterViewInit,
    Directive,
    ElementRef,
    EventEmitter,
    HostBinding,
    HostListener,
    Input,
    OnChanges,
    OnDestroy,
    Output,
    Renderer2,
    SimpleChanges,
} from '@angular/core';
import { isInternetExplorer } from '@uipath/angular/utilities';

/**
 * A directive that facilitates `file inputs` and `file drop regions`.
 *
 * @export
 */
@Directive({
    selector: '[uiDragAndDropFile]',
})
export class UiDragAndDropFileDirective implements OnChanges, AfterViewInit, OnDestroy {
    /**
     * The accepted `file-type`.
     *
     */
    @Input()
    fileType?: string;

    /**
     * The element reference that triggers file `browsing`.
     *
     */
    @Input()
    fileBrowseRef?: Element;

    /**
     * The element reference that serve as a `clear` trigger for the selected files.
     *
     */
    @Input()
    fileClearRef?: Element;

    /**
     * Configures if the `file area` accepts multiple files.
     *
     */
    @Input()
    multiple = false;

    /**
     * Configures the `disabled` state of the `file area`.
     *
     */
    @Input()
    disabled = false;

    /**
     * An event that emits when the file selection state `changes`.
     *
     */
    @Output()
    fileChange = new EventEmitter<File[]>();

    /**
     * An event that emits when the file selection is `cleared`.
     *
     */
    @Output()
    fileClear = new EventEmitter();

    @HostBinding('class.file-dragging')
    protected _isDragging = false;

    private _disposalCallbacks: (() => void)[] = [];
    private _fileInput: HTMLInputElement;

    /**
     * @ignore
     */
    constructor(
        private _elementRef: ElementRef,
        private _renderer: Renderer2,
    ) {
        this._fileInput = this._renderer.createElement('input') as HTMLInputElement;
        this._renderer.setProperty(this._fileInput, 'type', 'file');
        this._renderer.setProperty(this._fileInput, 'value', null);
        this._renderer.setAttribute(this._fileInput, 'hidden', '');
        this._renderer.appendChild(this._elementRef.nativeElement, this._fileInput);
    }

    /**
     * @ignore
     */
    ngOnChanges(changes: SimpleChanges) {
        if (changes.fileType) {
            const fileType = changes.fileType.currentValue;
            this._renderer.setProperty(this._fileInput, 'accept', fileType || '');
        }
    }

    /**
     * @ignore
     */
    ngAfterViewInit() {
        if (this.multiple) {
            this._renderer.setProperty(this._fileInput, 'multiple', 'true');
        }

        this._preventEnterOnChildren(this._elementRef.nativeElement);

        if (!this.fileBrowseRef) {
            this.fileBrowseRef = this._elementRef.nativeElement;
        }

        this._renderer.setStyle(this.fileBrowseRef, 'cursor', 'pointer');

        ['click', 'keydown.enter', 'keydown.space'].forEach(eventName => {
            const browse = this._renderer
                .listen(this.fileBrowseRef, eventName, () => {
                    if (this.disabled) { return; }
                    this._fileInput.click();
                });
            this._disposalCallbacks.push(browse);
        });

        const change = this._renderer.listen(this._fileInput, 'change', (ev) => {
            this._preventAll(ev);
            if (this.disabled) { return; }
            const target = ev.target as HTMLInputElement;
            if (target.files) {
                this._emitFiles(target.files);
                this._renderer.setProperty(this._fileInput, 'value', null);
            }
        });
        this._disposalCallbacks.push(change);

        if (this.fileClearRef) {
            const clear = this._renderer
                .listen(this.fileClearRef, 'click', () => {
                    if (this.disabled) { return; }
                    this._renderer.setProperty(this._fileInput, 'value', null);
                    this.fileClear.emit();
                });
            this._disposalCallbacks.push(clear);
        }
    }

    /**
     * @ignore
     */
    ngOnDestroy() {
        this._disposalCallbacks.forEach(dispose => {
            dispose();
        });
    }

    /**
     * Reacts to `drop` events.
     *
     * @param ev The `DragEvent` data associated to the `drop`.
     */
    @HostListener('drop', ['$event'])
    protected _onDrop(ev: DragEvent) {
        this._preventAll(ev);
        if (this.disabled) { return; }
        this._isDragging = false;
        this._emitFiles(ev.dataTransfer!.files);
    }

    /**
     * Marks the `state` as `dragging` when a `dragover` event occurs.
     *
     * @param ev The `DragEvent` data associated to the `dragover`.
     */
    @HostListener('dragover', ['$event'])
    protected _onDragOver(ev: DragEvent) {
        this._preventAll(ev);
        if (
            this.disabled ||
            !this.multiple &&
            ev.dataTransfer &&
            ev.dataTransfer.items &&
            ev.dataTransfer.items.length > 1
        ) { return; }
        this._isDragging = true;
    }

    /**
     * Clears the `dragging` `state` when a `dragleave` event occurs.
     *
     * @param ev The `DragEvent` data associated to the `dragover`.
     */
    @HostListener('dragleave', ['$event'])
    protected _onDragLeave(ev: DragEvent) {
        this._preventAll(ev);
        if (this.disabled) { return; }
        this._isDragging = false;
    }

    /**
     * Clears the `dragging` `state` when a `dragleave` event occurs.
     *
     * @param ev The `DragEvent` data associated to the `dragend`.
     */
    @HostListener('dragend')
    protected _onDragEnd() {
        if (this.disabled) { return; }
        this._isDragging = false;
    }

    /**
     * Prevents weird flickering `cross-browser`.
     *
     * @param ev The `DragEvent` data associated to the `dragenter`.
     */
    @HostListener('dragenter', ['$event'])
    protected _onDragEnter(ev: DragEvent) {
        this._preventAll(ev);
        if (this.disabled) { return; }
    }

    private _emitFiles(files: FileList) {
        if (
            !files?.length ||
            this.disabled
        ) { return; }

        const acceptedExtensions = (this.fileType ?? '')
            .split(',')
            .map(e => e.trim().toLowerCase());
        const isAccepted = (file: File) => this.fileType
            ? acceptedExtensions.some(extension => file.name.toLowerCase().endsWith(extension))
            : true;
        const emittedFiles = Array.from(files).filter(isAccepted);

        if (
            !emittedFiles.length ||
            emittedFiles.length > 1 && !this.multiple
        ) { return; }

        this.fileChange.emit(emittedFiles);
    }

    private _preventEnterOnChildren(element: Element) {
        if (!isInternetExplorer()) { return; }

        if (element.children.length) {
            const children: Element[] = Array.from(element.children);

            for (const child of children) {
                const dragenter = this._renderer.listen(child, 'dragenter', this._preventAll);
                const dragleave = this._renderer.listen(child, 'dragleave', this._preventAll);

                this._disposalCallbacks.push(
                    dragenter,
                    dragleave,
                );
            }
        }
    }

    private _preventAll(ev: Event) {
        ev.preventDefault();
        ev.stopPropagation();
    }
}