import type { RichContent } from "../../model/interfaces.ts";
import type { RichContentProvider } from "../rich-content-service.ts";
import {
  extractBestIcon,
  extractFirstContentImage,
  extractJsonLd,
  extractLargeImage,
  extractMaskIconColor,
  extractMetaName,
  extractOgTag,
  extractPageTitle,
  extractThemeColor,
  fetchWithTimeout,
  normalizeCssColor,
} from "../rich-content-service.ts";

export const genericProvider: RichContentProvider = {
  name: "generic",

  matches(_url: string): boolean {
    return true; // fallback — always matches
  },

  async fetch(url: string): Promise<RichContent> {
    const res = await fetchWithTimeout(url);
    const contentType = res.headers.get("content-type") ?? "";

    if (!contentType.startsWith("text/html")) {
      return { type: "generic", url };
    }

    const html = await res.text();
    const ld = extractJsonLd(html);

    // If og:url is present but points to a different page (e.g. the homepage),
    // the og: block is a site-level fallback, not page-specific metadata.
    // In that case skip og:title and og:image so page-level signals win.
    const ogUrl = extractOgTag(html, "url");
    const useOg = !ogUrl || (() => {
      try {
        const ogPath = new URL(ogUrl).pathname.replace(/\/+$/, "") || "/";
        const pagePath = new URL(url).pathname.replace(/\/+$/, "") || "/";
        return ogPath === pagePath;
      } catch {
        return true;
      }
    })();

    // Title: og:title (page-matched) → twitter:title → JSON-LD → <title>
    const title = (useOg ? extractOgTag(html, "title") : undefined) ??
      extractMetaName(html, "twitter:title") ??
      ld.title ??
      extractPageTitle(html);

    // Site name: og:site_name → hostname
    const siteName = extractOgTag(html, "site_name") ??
      new URL(url).hostname.replace(/^www\./, "");

    // Description: og:description → twitter:description → JSON-LD → <meta name="description">
    const description = extractOgTag(html, "description") ??
      extractMetaName(html, "twitter:description") ??
      ld.description ??
      extractMetaName(html, "description");

    // Image: og:image (page-matched) → twitter:image → JSON-LD → large <img> →
    // first content <img>. The chain deliberately stops there: a favicon is not
    // artwork, and pretending otherwise means every art-less page gets a 16×16
    // icon cover-cropped into a 128×72 box. No match here means "no artwork",
    // and the frontend draws a generated placeholder instead.
    const thumbnailUrl = (useOg ? extractOgTag(html, "image") : undefined) ??
      extractMetaName(html, "twitter:image") ??
      ld.thumbnailUrl ??
      extractLargeImage(html, url) ??
      extractFirstContentImage(html, url);

    // Icon and brand color are independent facts about the page, so they're
    // collected whether or not there's artwork. `/favicon.ico` is a guess; when
    // it 404s the placeholder falls back to the site's initial.
    const faviconUrl = extractBestIcon(html, url) ??
      `${new URL(url).origin}/favicon.ico`;

    const accentColor = normalizeCssColor(
      extractThemeColor(html) ??
        extractMetaName(html, "msapplication-TileColor") ??
        extractMaskIconColor(html),
    );

    return {
      type: "generic",
      url,
      title,
      description,
      thumbnailUrl,
      faviconUrl,
      accentColor,
      siteName,
    };
  },
};