/**
 * 文章归档模块
 */
export class Archive {
    private static _instance: Archive | null = null;
    private _loading: boolean = false;
    private _hasMore: boolean = true;
    private _pageIndex: number = 1;
    private _pageSize: number = 50;
    private _totalCount: number = 0;
    private _scrollHandler: ((this: Window, ev: Event) => void) | null = null;
    private _isInitialized: boolean = false;
    private _archiveContainer: HTMLElement | null = null;
    private _loadingElement: HTMLElement | null = null;
    private _endElement: HTMLElement | null = null;

    public constructor() {
        if (Archive._instance) {
            Archive._instance.destroy();
        }

        this._loading = false;
        this._hasMore = true;
        this._pageIndex = 1;
        this._pageSize = 50;
        this._totalCount = 0;
        this._scrollHandler = null;
        this._isInitialized = false;

        Archive._instance = this;
        this.init();
    }

    public init(): void {
        const archiveContainer = document.querySelector<HTMLElement>('.archive');

        if (!archiveContainer) {
            return;
        }

        this._pageIndex = parseInt(archiveContainer.dataset.pageIndex as string) || 1;
        this._pageSize = parseInt(archiveContainer.dataset.pageSize as string) || 50;
        this._totalCount = parseInt(archiveContainer.dataset.totalCount as string) || 0;
        this._hasMore = archiveContainer.dataset.hasMore === 'true';

        this._archiveContainer = archiveContainer;
        this._loadingElement = document.querySelector<HTMLElement>('.archive__loading');
        this._endElement = document.querySelector<HTMLElement>('.archive__end');

        this.setupScrollListener();

        if (this._loadingElement) {
            this._loadingElement.style.display = this._hasMore ? 'flex' : 'none';
        }

        this._isInitialized = true;
    }

    public destroy(): void {
        if (this._scrollHandler) {
            window.removeEventListener('scroll', this._scrollHandler);
            this._scrollHandler = null;
        }
        this._isInitialized = false;

        if (Archive._instance === this) {
            Archive._instance = null;
        }
    }

    public setupScrollListener(): void {
        let ticking = false;

        const checkScroll = (): void => {
            const scrollTop = window.pageYOffset || document.documentElement.scrollTop;
            const windowHeight = window.innerHeight;
            const documentHeight = document.documentElement.scrollHeight;

            const threshold = 500;
            const distanceToBottom = documentHeight - (scrollTop + windowHeight);

            if (distanceToBottom < threshold && this._hasMore && !this._loading) {
                void this.loadMore();
            }

            ticking = false;
        };

        this._scrollHandler = () => {
            if (!ticking) {
                window.requestAnimationFrame(checkScroll);
                ticking = true;
            }
        };

        window.addEventListener('scroll', this._scrollHandler, { passive: true });
    }

    public async loadMore(): Promise<void> {
        if (this._loading || !this._hasMore) {
            return;
        }

        this._loading = true;

        if (this._loadingElement) {
            this._loadingElement.style.display = 'flex';
        }

        try {
            const nextPage = this._pageIndex + 1;
            const url = `/Article/ArchiveLoadMore?pageIndex=${nextPage}&pageSize=${this._pageSize}`;

            const response = await fetch(url);

            if (!response.ok) {
                throw new Error('Network response was not ok');
            }

            const html = await response.text();

            if (html.trim() === '') {
                this._hasMore = false;
                this.showEndMessage();
                return;
            }

            const tempDiv = document.createElement('div');
            tempDiv.innerHTML = html;

            const newYears = tempDiv.querySelectorAll<HTMLElement>('.archive__year');

            if (newYears.length === 0) {
                this._hasMore = false;
                this.showEndMessage();
                return;
            }

            newYears.forEach((year) => {
                if (this._archiveContainer) {
                    this._archiveContainer.appendChild(year);
                }
            });

            this._pageIndex = nextPage;

            const loadedSoFar = this._pageIndex * this._pageSize;
            if (loadedSoFar >= this._totalCount) {
                this._hasMore = false;
                this.showEndMessage();
            }
        } catch (error) {
            console.error('加载归档失败:', error);
        } finally {
            this._loading = false;
            if (this._loadingElement) {
                this._loadingElement.style.display = 'none';
            }
        }
    }

    public showEndMessage(): void {
        if (this._loadingElement) {
            this._loadingElement.style.display = 'none';
        }
        if (this._endElement) {
            this._endElement.style.display = 'flex';
        }
    }
}