import type { MarkdownIt, Token } from "markdown-it";

const YOUTUBE_RE =
	/^(?:https?:\/\/)?(?:www\.)?(?:youtube\.com\/watch\?v=|youtu\.be\/|youtube\.com\/embed\/)([a-zA-Z0-9_-]{11})(?:[?&]\S*)?$/;

const TWEET_RE = /^https?:\/\/(?:www\.)?(?:x|twitter)\.com\/[^/]+\/status\/\d+/;

// A lone image is the shape Obsidian embeds with; anything alongside it is a real image.
function loneImage(inline: Token): Token | null {
	const only = inline.children?.length === 1 ? inline.children[0] : null;
	return only?.type === "image" ? only : null;
}

// videoId is regex-bound to 11 url-safe chars, so the interpolated iframe src can't break out.
function iframeHtml(videoId: string): string {
	return `<div class="youtube-embed aspect-video my-4"><iframe class="w-full h-full border-0" title="YouTube video player" src="https://www.youtube-nocookie.com/embed/${videoId}" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen loading="lazy"></iframe></div>\n`;
}

// Obsidian embeds a video with the image form, `![](https://youtu.be/…)`; a bare URL alone
// in a paragraph is Lichen's own syntax. Both mean the same thing, so both become the
// iframe. Tweets deliberately become a plain link instead: an x.com embed is a third-party
// frame, and `frame-src` (src/lib/response.ts) allows youtube-nocookie only.
export function embedPlugin(mdi: MarkdownIt): void {
	mdi.core.ruler.push("embed", (state) => {
		const tokens = state.tokens;
		for (let i = 0; i < tokens.length; i++) {
			const token = tokens[i];
			if (token?.type !== "paragraph_open") continue;

			const inline = tokens[i + 1];
			const close = tokens[i + 2];
			if (inline?.type !== "inline" || close?.type !== "paragraph_close")
				continue;

			const image = loneImage(inline);
			const url = String(image?.attrGet("src") ?? inline.content.trim());

			const match = YOUTUBE_RE.exec(url);
			if (match) {
				const htmlToken = new state.Token("html_block", "", 0);
				htmlToken.content = iframeHtml(match[1] as string);
				tokens.splice(i, 3, htmlToken); // p_open + inline + p_close → html_block
				continue;
			}

			if (image && TWEET_RE.test(url)) {
				const linkOpen = new state.Token("link_open", "a", 1);
				linkOpen.attrSet("href", url);
				const text = new state.Token("text", "", 0);
				text.content = url;
				inline.children = [
					linkOpen,
					text,
					new state.Token("link_close", "a", -1),
				];
			}
		}
	});
}