import {
    Component,
    ElementRef,
    EventEmitter,
    HostListener,
    Input,
    OnChanges,
    OnInit,
    Output,
    SimpleChanges,
    ViewChild
} from "@angular/core";
import {File} from "../../../../../models/File";
import {FileGridEntryComponent} from "./file-grid-entry/file-grid-entry.component";
import {GridEntry} from "./file-grid-entry/GridEntry";
import {CdkVirtualScrollViewport} from "@angular/cdk/scrolling";
import {TabService} from "../../../../../services/tab/tab.service";
import {FileService} from "../../../../../services/file/file.service";

@Component({
    selector: "app-file-grid",
    templateUrl: "./file-grid.component.html",
    styleUrls: ["./file-grid.component.scss"]
})
export class FileGridComponent implements OnChanges, OnInit {

    @Input() files: File[] = [];
    @Input() columns: number = 6;
    @Input() preselectedFile: File | undefined;
    @Output() fileOpenEvent = new EventEmitter<File>();
    @Output() fileSelectEvent = new EventEmitter<File[]>();

    @ViewChild("virtualScrollGrid") virtualScroll!: CdkVirtualScrollViewport;
    @ViewChild("galleryWrapper") galleryWrapper!: ElementRef<HTMLDivElement>;

    selectedEntries: GridEntry[] = [];
    partitionedGridEntries: GridEntry[][] = [];
    private shiftClicked = false;
    private ctrlClicked = false;
    private gridEntries: GridEntry[] = []

    constructor(
        private tabService: TabService,
        private fileService: FileService,
    ) {
        tabService.selectedTab.subscribe(() => this.adjustElementSizes());
    }

    public ngOnInit(): void {
        this.gridEntries = this.files.map(file => {
            return {file, selected: false}
        });
        this.setPartitionedGridEntries();
    }

    ngOnChanges(changes: SimpleChanges): void {
        if (changes["files"]) {
            this.gridEntries = this.files.map(file => {
                return {file, selected: false}
            });
            this.refreshFileSelections();
            this.setPartitionedGridEntries();
        }
    }

    /**
     * File selector logic
     * @param {FileGridEntryComponent} clickedEntry
     */
    setSelectedFile(clickedEntry: GridEntry) {
        if (!(this.shiftClicked || this.ctrlClicked) && this.selectedEntries.length > 0) {
            this.selectedEntries.forEach(entry => {
                if (entry !== clickedEntry) entry.selected = false
            });
            this.selectedEntries = [];
        }
        if (this.shiftClicked && this.selectedEntries.length > 0) {
            this.handleShiftSelect(clickedEntry);
        } else {
            clickedEntry.selected = !clickedEntry.selected;
            if (!clickedEntry.selected) {
                const index = this.selectedEntries.indexOf(clickedEntry);
                if (index > -1) {
                    this.selectedEntries.splice(index, 1);
                }
            } else {
                this.selectedEntries.push(clickedEntry);
            }
        }
        this.fileSelectEvent.emit(this.selectedEntries.map(g => g.file));
    }

    public adjustElementSizes(): void {
        if (this.virtualScroll) {
            this.virtualScroll.checkViewportSize();
        }
    }

    public async regenerateThumbnail(file: File) {
        await this.fileService.deleteThumbnails(file);
    }

    private setPartitionedGridEntries() {
        this.partitionedGridEntries = [];
        let scrollToIndex = -1;
        let selectedEntry: GridEntry | undefined = undefined;

        for (let i = 0; i < (Math.ceil(
            this.gridEntries.length / this.columns)); i++) {
            const entries = this.gridEntries.slice(i * this.columns,
                Math.min(this.gridEntries.length, (i + 1) * this.columns));
            this.partitionedGridEntries.push(entries);
            const preselectedEntry = entries.find(
                e => e.file.hash == this.preselectedFile?.hash);

            if (preselectedEntry) {
                scrollToIndex = i;
                selectedEntry = preselectedEntry;
            }
        }
        if (scrollToIndex >= 0 && this.preselectedFile && this.selectedEntries.length == 0) {
            setTimeout(() => {  // add timeout to avoid being stuck in the update loop
                if (this.virtualScroll) {
                    this.virtualScroll?.scrollToIndex(scrollToIndex);
                    if (selectedEntry) {
                        selectedEntry.selected = true;
                        this.selectedEntries.push(selectedEntry);
                    }
                }
            }, 0);
        }
    }

    private refreshFileSelections() {
        const newSelection: GridEntry[] = this.gridEntries.filter(
            entry => this.selectedEntries.findIndex(
                e => e.file.id == entry.file.id) >= 0);
        newSelection.forEach(entry => entry.selected = true);
        this.selectedEntries = newSelection;
    }

    private handleShiftSelect(clickedEntry: GridEntry): void {
        const lastEntry = this.selectedEntries[this.selectedEntries.length - 1];
        let found = false;
        if (clickedEntry == lastEntry) {
            return;
        }

        for (const gridEntry of this.gridEntries) {
            if (found) {
                gridEntry.selected = true;
                this.selectedEntries.push(gridEntry);
                if (gridEntry === clickedEntry || gridEntry == lastEntry) {
                    return;
                }
            } else if (gridEntry === lastEntry || gridEntry === clickedEntry) {
                found = true;
                if (gridEntry === clickedEntry) {
                    gridEntry.selected = true;
                    this.selectedEntries.push(gridEntry);
                }
            }
        }
    }

    @HostListener("window:keydown", ["$event"])
    private handleKeydownEvent(event: KeyboardEvent) {
        switch (event.key) {
            case "Shift":
                this.shiftClicked = true;
                break;
            case "Control":
                this.ctrlClicked = true;
                break;
        }
    }

    @HostListener("window:keyup", ["$event"])
    private handleKeyupEvent(event: KeyboardEvent) {
        switch (event.key) {
            case "Shift":
                this.shiftClicked = false;
                break;
            case "Control":
                this.ctrlClicked = false;
                break;
        }
    }
}