/**
 * TOC (Table of Contents) 工具类
 * 用于 SidebarTOC 和 FloatingTOC 的共享逻辑
 */

export interface TOCConfig {
	contentId: string;
	indicatorId: string;
	maxLevel?: number;
	scrollOffset?: number;
}

export class TOCManager {
	private tocItems: HTMLElement[] = [];
	private observer: IntersectionObserver | null = null;
	private minDepth = 10;
	private maxLevel: number;
	private scrollTimeout: number | null = null;
	private contentId: string;
	private indicatorId: string;
	private scrollOffset: number;

	constructor(config: TOCConfig) {
		this.contentId = config.contentId;
		this.indicatorId = config.indicatorId;
		this.maxLevel = config.maxLevel || 3;
		this.scrollOffset = config.scrollOffset || 80;
	}

	/**
	 * 查找文章内容容器
	 */
	private getContentContainer(): Element | null {
		return (
			document.querySelector(".custom-md") ||
			document.querySelector(".prose") ||
			document.querySelector(".markdown-content")
		);
	}

	/**
	 * 查找所有标题
	 */
	private getAllHeadings(): NodeListOf<HTMLElement> {
		const contentContainer = this.getContentContainer();
		if (contentContainer) {
			return contentContainer.querySelectorAll("h1, h2, h3, h4, h5, h6");
		}
		return document.querySelectorAll("h1, h2, h3, h4, h5, h6");
	}

	/**
	 * 计算最小深度
	 */
	private calculateMinDepth(headings: NodeListOf<HTMLElement>): number {
		let minDepth = 10;
		headings.forEach((heading) => {
			const depth = Number.parseInt(heading.tagName.charAt(1), 10);
			minDepth = Math.min(minDepth, depth);
		});
		return minDepth;
	}

	/**
	 * 过滤标题
	 */
	private filterHeadings(headings: NodeListOf<HTMLElement>): HTMLElement[] {
		return Array.from(headings).filter((heading) => {
			const depth = Number.parseInt(heading.tagName.charAt(1), 10);
			return depth < this.minDepth + this.maxLevel;
		});
	}

	/**
	 * 生成徽章内容
	 */
	private generateBadgeContent(depth: number, heading1Count: number): string {
		if (depth === this.minDepth) {
			return heading1Count.toString();
		}
		if (depth === this.minDepth + 1) {
			return '<div class="transition w-2 h-2 rounded-[0.1875rem] bg-(--toc-badge-bg)"></div>';
		}
		return '<div class="transition w-1.5 h-1.5 rounded-xs bg-black/5 dark:bg-white/10"></div>';
	}

	/**
	 * 生成TOC HTML
	 */
	public generateTOCHTML(): string {
		const headings = this.getAllHeadings();

		if (headings.length === 0) {
			return '<div class="text-center py-8 text-gray-500 dark:text-gray-400"><p>当前页面没有目录</p></div>';
		}

		this.minDepth = this.calculateMinDepth(headings);
		const filteredHeadings = this.filterHeadings(headings);

		if (filteredHeadings.length === 0) {
			return '<div class="text-center py-8 text-gray-500 dark:text-gray-400"><p>当前页面没有目录</p></div>';
		}

		let tocHTML = "";
		let heading1Count = 1;

		filteredHeadings.forEach((heading) => {
			const depth = Number.parseInt(heading.tagName.charAt(1), 10);
			const depthClass =
				depth === this.minDepth
					? ""
					: depth === this.minDepth + 1
						? "pl-4"
						: "pl-8";

			if (!heading.id) {
				return;
			}

			const badgeContent = this.generateBadgeContent(depth, heading1Count);
			if (depth === this.minDepth) {
				heading1Count++;
			}

			let headingText = (heading.textContent || "")
				.replace(/#+\s*$/, "")
				.trim();

			// Fallback for empty text (e.g. dynamic subtitle)
			if (!headingText) {
				const dataSubtitles = heading.getAttribute("data-subtitles");
				if (dataSubtitles) {
					try {
						const subtitles = JSON.parse(dataSubtitles);
						headingText = Array.isArray(subtitles) ? subtitles[0] : subtitles;
					} catch {
						// ignore
					}
				}
			}

			if (!headingText) {
				headingText =
					heading.id === "banner-subtitle"
						? "Banner Subtitle"
						: heading.id || "Heading";
			}

			tocHTML += `
        <a 
          href="#${heading.id}" 
          class="px-2 flex gap-2 relative transition w-full min-h-9 rounded-xl hover:bg-(--toc-btn-hover) active:bg-(--toc-btn-active) py-2 ${depthClass}"
          data-heading-id="${heading.id}"
          aria-label="${headingText}"
        >
          <div class="transition w-5 h-5 shrink-0 rounded-lg text-xs flex items-center justify-center font-bold ${depth === this.minDepth ? "bg-(--toc-badge-bg) text-(--btn-content)" : ""}">
            ${badgeContent}
          </div>
          <div class="transition text-sm ${depth <= this.minDepth + 1 ? "text-50" : "text-30"} flex-1 min-w-0 overflow-hidden text-ellipsis whitespace-nowrap">${headingText}</div>
        </a>
      `;
		});

		tocHTML += `<div id="${this.indicatorId}" style="opacity: 0;" class="-z-10 absolute bg-(--toc-btn-hover) left-0 right-0 rounded-xl transition-all"></div>`;

		return tocHTML;
	}

	/**
	 * 更新TOC内容
	 */
	public updateTOCContent(): void {
		const tocContent = document.getElementById(this.contentId);
		if (!tocContent) return;

		tocContent.innerHTML = this.generateTOCHTML();
		this.tocItems = Array.from(
			document.querySelectorAll(`#${this.contentId} a`),
		);
	}

	/**
	 * 获取可见的标题ID
	 */
	private getVisibleHeadingIds(): string[] {
		const headings = this.getAllHeadings();
		const visibleHeadingIds: string[] = [];

		headings.forEach((heading) => {
			if (heading.id) {
				const rect = heading.getBoundingClientRect();
				const isVisible = rect.top < window.innerHeight && rect.bottom > 0;

				if (isVisible) {
					visibleHeadingIds.push(heading.id);
				}
			}
		});

		// 如果没有可见标题，选择最接近屏幕顶部的标题
		if (visibleHeadingIds.length === 0 && headings.length > 0) {
			let closestHeading: string | null = null;
			let minDistance = Number.POSITIVE_INFINITY;

			headings.forEach((heading) => {
				if (heading.id) {
					const rect = heading.getBoundingClientRect();
					const distance = Math.abs(rect.top);

					if (distance < minDistance) {
						minDistance = distance;
						closestHeading = heading.id;
					}
				}
			});

			if (closestHeading) {
				visibleHeadingIds.push(closestHeading);
			}
		}

		return visibleHeadingIds;
	}

	/**
	 * 更新活动状态
	 */
	public updateActiveState(): void {
		if (!this.tocItems || this.tocItems.length === 0) return;

		// 移除所有活动状态
		this.tocItems.forEach((item) => {
			item.classList.remove("visible");
		});

		const visibleHeadingIds = this.getVisibleHeadingIds();

		// 找到对应的TOC项并添加活动状态
		const activeItems = this.tocItems.filter((item) => {
			const headingId = item.dataset.headingId;
			return headingId && visibleHeadingIds.includes(headingId);
		});

		// 添加活动状态
		activeItems.forEach((item) => {
			item.classList.add("visible");
		});

		// 更新活动指示器
		this.updateActiveIndicator(activeItems);
	}

	/**
	 * 更新活动指示器
	 */
	private updateActiveIndicator(activeItems: HTMLElement[]): void {
		const indicator = document.getElementById(this.indicatorId);
		if (!indicator || !this.tocItems.length) return;

		if (activeItems.length === 0) {
			indicator.style.opacity = "0";
			return;
		}

		const tocContent = document.getElementById(this.contentId);
		if (!tocContent) return;

		const contentRect = tocContent.getBoundingClientRect();
		const firstActive = activeItems[0];
		const lastActive = activeItems[activeItems.length - 1];

		const firstRect = firstActive.getBoundingClientRect();
		const lastRect = lastActive.getBoundingClientRect();

		const top = firstRect.top - contentRect.top;
		const height = lastRect.bottom - firstRect.top;

		indicator.style.top = `${top}px`;
		indicator.style.height = `${height}px`;
		indicator.style.opacity = "1";

		// 自动滚动到活动项
		if (firstActive) {
			this.scrollToActiveItem(firstActive);
		}
	}

	/**
	 * 滚动到活动项
	 */
	private scrollToActiveItem(activeItem: HTMLElement): void {
		if (!activeItem) return;

		const tocContainer = document
			.querySelector(`#${this.contentId}`)
			?.closest(".toc-scroll-container");
		if (!tocContainer) return;

		// 清除之前的定时器
		if (this.scrollTimeout) {
			clearTimeout(this.scrollTimeout);
		}

		// 使用节流机制
		this.scrollTimeout = window.setTimeout(() => {
			const containerRect = tocContainer.getBoundingClientRect();
			const itemRect = activeItem.getBoundingClientRect();

			// 只在元素不在可视区域时才滚动
			const isVisible =
				itemRect.top >= containerRect.top &&
				itemRect.bottom <= containerRect.bottom;

			if (!isVisible) {
				const itemOffsetTop = (activeItem as HTMLElement).offsetTop;
				const containerHeight = tocContainer.clientHeight;
				const itemHeight = activeItem.clientHeight;

				// 计算目标滚动位置，将元素居中显示
				const targetScroll =
					itemOffsetTop - containerHeight / 2 + itemHeight / 2;

				tocContainer.scrollTo({
					top: targetScroll,
					behavior: "smooth",
				});
			}
		}, 100);
	}

	/**
	 * 处理点击事件
	 */
	public handleClick(event: Event): void {
		event.preventDefault();
		const target = event.currentTarget as HTMLAnchorElement;
		const id = decodeURIComponent(
			target.getAttribute("href")?.substring(1) || "",
		);
		const targetElement = document.getElementById(id);

		if (targetElement) {
			const targetTop =
				targetElement.getBoundingClientRect().top +
				window.pageYOffset -
				this.scrollOffset;

			window.scrollTo({
				top: targetTop,
				behavior: "smooth",
			});
		}
	}

	/**
	 * 设置IntersectionObserver
	 */
	public setupObserver(): void {
		const headings = this.getAllHeadings();

		if (this.observer) {
			this.observer.disconnect();
		}

		this.observer = new IntersectionObserver(
			() => {
				this.updateActiveState();
			},
			{
				rootMargin: "0px 0px 0px 0px",
				threshold: 0,
			},
		);

		headings.forEach((heading) => {
			if (heading.id) {
				this.observer?.observe(heading);
			}
		});
	}

	/**
	 * 绑定点击事件
	 */
	public bindClickEvents(): void {
		this.tocItems.forEach((item) => {
			item.addEventListener("click", this.handleClick.bind(this));
		});
	}

	/**
	 * 清理
	 */
	public cleanup(): void {
		if (this.observer) {
			this.observer.disconnect();
			this.observer = null;
		}
		if (this.scrollTimeout) {
			clearTimeout(this.scrollTimeout);
			this.scrollTimeout = null;
		}
	}

	/**
	 * 初始化
	 */
	public init(): void {
		this.updateTOCContent();
		this.bindClickEvents();
		this.setupObserver();
		this.updateActiveState();
	}
}

/**
 * 检查是否为文章页面
 */
export function isPostPage(): boolean {
	return window.location.pathname.includes("/posts/");
}