/**
 * 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";
import { decodeTextFragment, extractMatchedText } from "@/lib/text-highlight";

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

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

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

// ---------------------------------------------------------------------------
// Fallback descriptions — used when no quote/description is provided
// ---------------------------------------------------------------------------

const SITE_DESCRIPTION =
  "Browse the original, unedited books, letters, and teachings of His Divine Grace A.C. Bhaktivedanta Swami Prabhupāda — presented as they are.";

const BOOK_DESCRIPTIONS: Record<string, string> = {
  bg: "The definitive guide to the science of self-realization, spoken by Lord Śrī Kṛṣṇa to His devotee Arjuna on the Battlefield of Kurukṣetra.",
  sb: "The ripened fruit of the tree of Vedic literature — 18,000 verses describing the pastimes of the Supreme Lord and His devotees.",
  cc: "The life and teachings of Śrī Caitanya Mahāprabhu, the most munificent incarnation of Godhead who distributed love of God freely to all.",
  sb1962:
    "The original 1962 edition of Śrīmad-Bhāgavatam — Śrīla Prabhupāda's first major literary contribution in English.",
  iso: "Eighteen mantras revealing the essential teachings of the Vedas — the relationship between God, the living entity, and the material world.",
  noi: "Eleven verses by Śrīla Rūpa Gosvāmī providing essential instructions for serious practitioners of devotional service.",
  nod: "A comprehensive guide to the science of bhakti-yoga, summarizing Śrīla Rūpa Gosvāmī's Bhakti-rasāmṛta-sindhu.",
  bs: "The prayers of Lord Brahmā glorifying the Supreme Lord Govinda — with translation and commentary by Śrīla Prabhupāda.",
  mm: "Devotional prayers of King Kulaśekhara expressing the purest sentiments of surrender to Lord Kṛṣṇa.",
  nbs: "The eternal principles of devotional service as taught by the great sage Nārada Muni.",
  kb: "The enchanting pastimes of Lord Śrī Kṛṣṇa in Vṛndāvana and Dvārakā — the Supreme Personality of Godhead in His original form.",
  tlc: "The sublime teachings of Lord Śrī Caitanya Mahāprabhu to Śrīla Sanātana Gosvāmī, Śrīla Rūpa Gosvāmī, and others.",
  ej: "A scientific presentation of the anti-material world and how the soul can travel there.",
  ek: "How to elevate consciousness from the material to the spiritual platform through the practice of Kṛṣṇa consciousness.",
  mg: "An introduction to the unmatched gift of Kṛṣṇa consciousness — the path to eternal happiness and self-realization.",
  bbd: "A concise exploration of the soul's journey through repeated birth and death, and the path to liberation.",
  owk: "Practical guidance on the journey toward Kṛṣṇa — developing love of God through devotional service.",
  rv: "The king of knowledge — understanding the supreme science of devotional service as taught in the Bhagavad-gītā.",
  poy: "The perfection of the yoga system — how bhakti-yoga surpasses all other forms of yoga and meditation.",
  pqpa: "Conversations between Śrīla Prabhupāda and Bob Cohen — answering life's most fundamental questions.",
  ttp: "The teachings of Lord Kapila to His mother Devahūti on the science of God realization and devotional service.",
  ochkm:
    "The transcendental vibration of the Hare Kṛṣṇa mahā-mantra — its meaning, potency, and practice.",
  hkh: "A practical handbook for understanding and practicing Kṛṣṇa consciousness in daily life.",
  lcl: "Morning walks with Śrīla Prabhupāda — challenging the fundamental assumptions of modern science.",
  lob: "Meditations on the beauty of nature as a reflection of the Supreme Lord's transcendental opulence.",
  tlk: "Lord Kapila's instructions on Sāṅkhya philosophy and the path of devotional service.",
  tqk: "The prayers and teachings of Queen Kuntī — exemplifying pure devotion in the face of adversity.",
  gg: "Bengali poetic renderings of the Bhagavad-gītā by Śrīla Prabhupāda.",
  mog: "Śrīla Prabhupāda's message of Godhead — presenting the Absolute Truth for the modern world.",
  cbhc: "Commentary on the Śrī Caitanya-bhāgavata — the pastimes of Lord Caitanya by Vṛndāvana dāsa Ṭhākura.",
  bk: "Bhagavāner Kathā — Bengali narration of the pastimes of the Supreme Lord.",
  pk: "Prabhupāda-Kṛpā — the mercy of Śrīla Prabhupāda preserved in his writings.",
  ssr: "Conversations and essays illuminating the timeless science of self-realization for the modern reader.",
  ds: "Śrīla Prabhupāda's critique of Western philosophy from Socrates to Sartre — in light of Vedic wisdom.",
  sva: "Sacred songs of the great Vaiṣṇava ācāryas — prayers and bhajanas with translations and purports.",
  va: "Śrīla Prabhupāda's commentary on the Vedānta-sūtra — the conclusion of all Vedic knowledge.",
};

const CONTENT_TYPE_DESCRIPTIONS: Record<string, string> = {
  letters:
    "Personal correspondence by Śrīla Prabhupāda — guiding disciples, Godbrothers, and well-wishers in the science of Kṛṣṇa consciousness.",
  essays:
    "Foundational essays on the science of Kṛṣṇa consciousness by His Divine Grace A.C. Bhaktivedanta Swami Prabhupāda.",
  glossary:
    "A comprehensive glossary of Sanskrit and Vedic terms from the books of Śrīla Prabhupāda.",
  disciples:
    "A directory of disciples initiated by Śrīla Prabhupāda between 1966 and 1977.",
  journals:
    "From the personal journals of Śrīla Prabhupāda — a window into the daily life and mission of the Founder-Ācārya of ISKCON.",
  magazines:
    "Back to Godhead — the magazine founded by Śrīla Prabhupāda in 1944 to present the timeless science of Kṛṣṇa consciousness.",
  "other-documents":
    "Writings and analyses by His Divine Grace A.C. Bhaktivedanta Swami Prabhupāda.",
};

function getFallbackQuote(title: string, code?: string): string {
  // Book-specific description
  if (code && BOOK_DESCRIPTIONS[code]) {
    return BOOK_DESCRIPTIONS[code];
  }

  // Content-type descriptions
  if (title.startsWith("Letter to")) {
    return CONTENT_TYPE_DESCRIPTIONS.letters;
  }
  for (const [key, desc] of Object.entries(CONTENT_TYPE_DESCRIPTIONS)) {
    if (title.toLowerCase().includes(key)) {
      return desc;
    }
  }

  // Generic fallback
  return SITE_DESCRIPTION;
}

// ---------------------------------------------------------------------------
// 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,
    quote: getFallbackQuote(title, code),
  });
}

/** 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,
    quote: getFallbackQuote(title, code),
  });
}

/** 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,
    quote: getFallbackQuote(bookTitle, code),
  });
}

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

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

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

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

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

/** OG metadata for the disciples directory. */
export function ogForDisciples() {
  return buildOgMeta({
    title: "Disciples of Śrīla Prabhupāda",
    quote: CONTENT_TYPE_DESCRIPTIONS.disciples,
  });
}

/** OG metadata for letters filtered by year. */
export function ogForLettersByYear(year: number, count: number) {
  return buildOgMeta({
    title: `Letters from ${year}`,
    detail: `${count} ${count === 1 ? "letter" : "letters"}`,
    quote: `Śrīla Prabhupāda's correspondence from ${year} — personal letters guiding disciples and well-wishers in the science of Kṛṣṇa consciousness.`,
  });
}

/** OG metadata for letters filtered by recipient. */
export function ogForLettersByRecipient(name: string, count: number) {
  return buildOgMeta({
    title: `Letters to ${name}`,
    detail: `${count} ${count === 1 ? "letter" : "letters"}`,
    quote: `Śrīla Prabhupāda's personal correspondence to ${name} — instructions, blessings, and guidance in devotional service.`,
  });
}

/** OG metadata for letters filtered by location. */
export function ogForLettersByLocation(location: string, count: number) {
  return buildOgMeta({
    title: `Letters from ${location}`,
    detail: `${count} ${count === 1 ? "letter" : "letters"}`,
    quote: `Śrīla Prabhupāda's letters written from ${location} — chronicling the worldwide mission of the Hare Kṛṣṇa movement.`,
  });
}

// ---------------------------------------------------------------------------
// hl= query param → OG quote extraction
// ---------------------------------------------------------------------------

/**
 * Extract a display quote from the `?hl=` search param.
 *
 * When `paragraphs` are provided (from the database), the full matched text
 * is extracted by searching the content — giving the OG image the actual
 * selected quote, not just the prefix/suffix.
 *
 * When `paragraphs` are not provided, falls back to reconstructing a
 * readable snippet from prefix + suffix: "first few words ... last few words"
 *
 * Returns null if hl is missing or invalid.
 */
export function extractQuoteFromHl(
  searchParams: Record<string, string | string[] | undefined> | URLSearchParams,
  paragraphs?: string[],
): string | null {
  const raw =
    searchParams instanceof URLSearchParams
      ? searchParams.get("hl")
      : typeof searchParams.hl === "string"
        ? searchParams.hl
        : null;

  if (!raw) return null;

  const fragment = decodeTextFragment(raw);
  if (!fragment) return null;

  // If paragraphs are available, extract the full matched text
  if (paragraphs && paragraphs.length > 0) {
    const fullMatch = extractMatchedText(fragment, paragraphs);
    if (fullMatch) {
      // Truncate at word boundary if too long for OG image
      if (fullMatch.length > 280) {
        const truncated = fullMatch.slice(0, 277);
        const lastSpace = truncated.lastIndexOf(" ");
        return (
          (lastSpace > 200 ? truncated.slice(0, lastSpace) : truncated) + "..."
        );
      }
      return fullMatch;
    }
  }

  // Fallback: reconstruct from prefix + suffix
  const { prefix, suffix } = fragment;
  if (!prefix) return null;

  if (suffix && suffix !== prefix) {
    return `${prefix} ... ${suffix}`;
  }

  return prefix;
}

/** Default OG metadata for the site. */
export function ogDefault() {
  return buildOgMeta({
    title: "Prabhupāda Says",
    description: SITE_DESCRIPTION,
    quote: SITE_DESCRIPTION,
  });
}