/**
 * OG Image metadata utilities.
 *
 * Builds the /api/og URL with appropriate query params for dynamic
 * Open Graph image generation. Used by page-level metadata exports.
 */

import { BOOK_NAMES, CC_LILAS } from "@/lib/constants";

const SITE_URL =
  process.env.NEXT_PUBLIC_SITE_URL || "https://prabhupadasays.org";

// ---------------------------------------------------------------------------
// Types
// ---------------------------------------------------------------------------

export type OgParams = {
  title: string;
  detail?: string;
  quote?: string;
};

// ---------------------------------------------------------------------------
// Build the /api/og image URL
// ---------------------------------------------------------------------------

/**
 * Build a fully-qualified URL to the /api/og image endpoint.
 *
 * The URL is kept as short as possible — only non-empty params are included.
 * The quote is truncated to 260 chars to keep URL length reasonable.
 */
export function buildOgImageUrl(params: OgParams): string {
  const url = new URL("/api/og", SITE_URL);

  url.searchParams.set("title", params.title);

  if (params.detail) {
    url.searchParams.set("detail", params.detail);
  }

  if (params.quote) {
    const truncated =
      params.quote.length > 260
        ? params.quote.slice(0, 257) + "..."
        : params.quote;
    url.searchParams.set("quote", truncated);
  }

  return url.toString();
}

/**
 * Build OG metadata object for use in Next.js page `metadata` exports.
 *
 * Returns the `openGraph` and `twitter` fields to spread into `Metadata`.
 */
export function buildOgMeta(params: OgParams & { description?: string }) {
  const imageUrl = buildOgImageUrl(params);
  const description =
    params.description ||
    params.quote ||
    `${params.title}${params.detail ? ` — ${params.detail}` : ""}`;

  return {
    openGraph: {
      title: params.title,
      description,
      images: [
        {
          url: imageUrl,
          width: 1200,
          height: 630,
          alt: params.title,
        },
      ],
      siteName: "Prabhupāda Says",
    },
    twitter: {
      card: "summary_large_image" as const,
      title: params.title,
      description,
      images: [imageUrl],
    },
  };
}

// ---------------------------------------------------------------------------
// Helpers for common page types
// ---------------------------------------------------------------------------

/** OG metadata for a book page. */
export function ogForBook(code: string) {
  const title = BOOK_NAMES[code] || code.toUpperCase();
  return buildOgMeta({ title });
}

/** OG metadata for a verse page. */
export function ogForVerse(
  code: string,
  parts: { division?: string; chapter: number; verse: number },
) {
  const title = BOOK_NAMES[code] || code.toUpperCase();
  let detail: string;

  if (code === "sb" && parts.division) {
    detail = `Canto ${parts.division}, Chapter ${parts.chapter}, Verse ${parts.verse}`;
  } else if (code === "cc" && parts.division) {
    const lila = CC_LILAS[parts.division] || parts.division;
    detail = `${lila}, Chapter ${parts.chapter}, Verse ${parts.verse}`;
  } else {
    detail = `Chapter ${parts.chapter}, Verse ${parts.verse}`;
  }

  return buildOgMeta({ title, detail });
}

/** OG metadata for a prose chapter. */
export function ogForChapter(code: string, chapterTitle: string) {
  const bookTitle = BOOK_NAMES[code] || code.toUpperCase();
  return buildOgMeta({ title: bookTitle, detail: chapterTitle });
}

/** OG metadata for an essay. */
export function ogForEssay(title: string) {
  return buildOgMeta({
    title,
    detail: "Essay by Śrīla Prabhupāda",
  });
}

/** OG metadata for a letter. */
export function ogForLetter(recipient: string, meta?: string) {
  return buildOgMeta({
    title: `Letter to ${recipient}`,
    detail: meta || undefined,
  });
}

/** OG metadata for a journal entry. */
export function ogForJournal(journalTitle: string, entryTitle?: string) {
  return buildOgMeta({
    title: journalTitle,
    detail: entryTitle || undefined,
  });
}

/** OG metadata for a magazine issue. */
export function ogForMagazine(magazineTitle: string, issueTitle?: string) {
  return buildOgMeta({
    title: magazineTitle,
    detail: issueTitle || undefined,
  });
}

/** OG metadata for an other document chapter. */
export function ogForOtherDocument(docTitle: string, chapterTitle?: string) {
  return buildOgMeta({
    title: docTitle,
    detail: chapterTitle || undefined,
  });
}

/** Default OG metadata for the site. */
export function ogDefault() {
  return buildOgMeta({
    title: "Prabhupāda Says",
    description:
      "Browse the books and teachings of His Divine Grace A.C. Bhaktivedanta Swami Prabhupāda",
  });
}