/**
 * Data access layer for Śrī Īśopaniṣad (ISO).
 *
 * Reads from MongoDB via Prisma.
 * ISO is unique — it has BOTH verses (in the `verses` collection)
 * AND prose intro segments (in the `prose_chapters` collection).
 *
 * Verses were seeded with:
 *   - book: "iso", division: null
 *   - chapter = mantra number (0 for Invocation, 1-18 for mantras)
 *   - verse = always 1
 *
 * Intro segments were seeded with:
 *   - book: "iso", volume: 0, type: "intro-segment"
 *   - slugs like "intro-front-pages", "intro-introduction", "intro-about-the-author"
 */

import { prisma } from "@/lib/db";
import type { JsonValue } from "@prisma/client/runtime/library";

// ---------------------------------------------------------------------------
// Constants
// ---------------------------------------------------------------------------

const BOOK = "iso";
const NO_VOLUME = 0;

// ---------------------------------------------------------------------------
// Mantra title lookup
// ---------------------------------------------------------------------------

const MANTRA_TITLES: Record<number, string> = {
  0: "Invocation",
  1: "Mantra One",
  2: "Mantra Two",
  3: "Mantra Three",
  4: "Mantra Four",
  5: "Mantra Five",
  6: "Mantra Six",
  7: "Mantra Seven",
  8: "Mantra Eight",
  9: "Mantra Nine",
  10: "Mantra Ten",
  11: "Mantra Eleven",
  12: "Mantra Twelve",
  13: "Mantra Thirteen",
  14: "Mantra Fourteen",
  15: "Mantra Fifteen",
  16: "Mantra Sixteen",
  17: "Mantra Seventeen",
  18: "Mantra Eighteen",
};

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

export type IsoMeta = {
  book: string;
  title: string;
  author: string;
  year: number;
  description: string;
  totalMantras: number;
  mantras: IsoMantraEntry[];
};

export type IsoMantraEntry = {
  number: number;
  title: string;
  slug: string;
};

export type IsoIntroSegment = {
  slug: string;
  title: string;
  type: string;
  book: string;
  order: number;
  paragraphs: string[];
};

export type IsoVerse = {
  book: string;
  book_title: string;
  mantra: number;
  title: string;
  reference: string;
  devanagari: string;
  transliteration: string;
  synonyms: { word: string; meanings: string[] }[];
  translation: string;
  purport: string[];
};

/** Union type used in sidebar / table-of-contents navigation. */
export type IsoSidebarItem = {
  /** URL-safe slug: "intro-front-pages", "invocation", "1", "intro-about-the-author" */
  slug: string;
  /** Human-readable label for the sidebar */
  label: string;
  /** "intro-segment" | "verse" */
  type: string;
  /** Mantra number (0 for invocation), or null for non-verse items */
  mantra: number | null;
};

// ---------------------------------------------------------------------------
// HTML sanitisation (mirrors lib/nod.ts)
// ---------------------------------------------------------------------------

function sanitizeHtml(html: string): string {
  let clean = html.replace(/<script[\s>][\s\S]*?<\/script>/gi, "");
  clean = clean.replace(/<style[\s>][\s\S]*?<\/style>/gi, "");
  clean = clean.replace(/<iframe[\s>][\s\S]*?<\/iframe>/gi, "");
  clean = clean.replace(
    /<\/?(?:script|style|iframe|object|embed|form|input|textarea|select|button)[^>]*>/gi,
    "",
  );
  clean = clean.replace(/\s+on\w+\s*=\s*(?:"[^"]*"|'[^']*'|[^\s>]+)/gi, "");
  clean = clean.replace(/href\s*=\s*"javascript:[^"]*"/gi, 'href=""');
  clean = clean.replace(/href\s*=\s*'javascript:[^']*'/gi, "href=''");
  return clean;
}

/** Normalize paragraphs — handles both native arrays and stringified JSON. */
function normalizeParagraphs(paragraphs: string[] | JsonValue): string[] {
  let result: string[];

  if (typeof paragraphs === "string") {
    try {
      const parsed = JSON.parse(paragraphs);
      result = Array.isArray(parsed) ? parsed : [paragraphs];
    } catch {
      result = [paragraphs];
    }
  } else if (Array.isArray(paragraphs)) {
    result = paragraphs as string[];
  } else {
    result = [];
  }

  return result.map(sanitizeHtml);
}

/** Normalize purport (string[] from Prisma) via normalizeParagraphs. */
function normalizePurport(purport: string[] | JsonValue): string[] {
  return normalizeParagraphs(purport);
}

// ---------------------------------------------------------------------------
// Book meta
// ---------------------------------------------------------------------------

/**
 * Book-level metadata (title, author, mantras list, etc.)
 */
export async function getIsoMeta(): Promise<IsoMeta | null> {
  const meta = await prisma.bookMeta.findUnique({ where: { book: BOOK } });
  if (!meta) return null;
  return meta.data as unknown as IsoMeta;
}

// ---------------------------------------------------------------------------
// Intro segments (from prose_chapters collection)
// ---------------------------------------------------------------------------

/**
 * All intro segments, ordered by their `order` field.
 */
export async function getIsoIntroSegments(): Promise<IsoIntroSegment[]> {
  const results = await prisma.proseChapter.findMany({
    where: { book: BOOK, volume: NO_VOLUME, type: "intro-segment" },
    orderBy: { order: "asc" },
  });

  return results.map((doc) => ({
    slug: doc.slug,
    title: doc.title,
    type: doc.type,
    book: doc.book,
    order: doc.order,
    paragraphs: normalizeParagraphs(doc.paragraphs),
  }));
}

/**
 * A single intro segment by slug.
 * Accepts both "intro-front-pages" (URL slug) and "front-pages" (raw slug).
 */
export async function getIsoIntroSegment(
  slug: string,
): Promise<IsoIntroSegment | null> {
  // DB stores with "intro-" prefix; accept either form
  const dbSlug = slug.startsWith("intro-") ? slug : `intro-${slug}`;

  const doc = await prisma.proseChapter.findUnique({
    where: {
      book_volume_slug: { book: BOOK, volume: NO_VOLUME, slug: dbSlug },
    },
  });
  if (!doc) return null;

  return {
    slug: doc.slug,
    title: doc.title,
    type: doc.type,
    book: doc.book,
    order: doc.order,
    paragraphs: normalizeParagraphs(doc.paragraphs),
  };
}

// ---------------------------------------------------------------------------
// Verses (from verses collection)
// ---------------------------------------------------------------------------

/**
 * A single verse/mantra by slug.
 *
 * - "invocation" → chapter=0, verse=1
 * - "1"-"18"     → chapter=1–18, verse=1
 */
export async function getIsoVerse(slug: string): Promise<IsoVerse | null> {
  let mantraNum: number;

  if (slug === "invocation") {
    mantraNum = 0;
  } else {
    const num = Number(slug);
    if (!Number.isInteger(num) || num < 1 || num > 18) return null;
    mantraNum = num;
  }

  const doc = await prisma.verse.findFirst({
    where: { book: BOOK, division: null, chapter: mantraNum, verse: 1 },
  });
  if (!doc) return null;

  return {
    book: doc.book,
    book_title: doc.bookTitle,
    mantra: doc.chapter, // chapter field stores the mantra number
    title: MANTRA_TITLES[doc.chapter] ?? `Mantra ${doc.chapter}`,
    reference: doc.reference,
    devanagari: doc.devanagari,
    transliteration: doc.transliteration,
    synonyms: doc.synonyms as { word: string; meanings: string[] }[],
    translation: sanitizeHtml(doc.translation),
    purport: normalizePurport(doc.purport),
  };
}

// ---------------------------------------------------------------------------
// Unified content accessor
// ---------------------------------------------------------------------------

/**
 * Get content by URL slug.
 *
 *   "intro-front-pages"         → intro segment
 *   "intro-introduction"        → intro segment
 *   "intro-about-the-author"    → intro segment
 *   "invocation"                → invocation verse
 *   "1" … "18"                  → mantra verse
 */
export async function getIsoContent(
  slug: string,
): Promise<IsoVerse | IsoIntroSegment | null> {
  if (slug.startsWith("intro-")) {
    return getIsoIntroSegment(slug);
  }

  if (slug === "invocation") {
    return getIsoVerse("invocation");
  }

  const num = Number(slug);
  if (!Number.isNaN(num) && Number.isInteger(num) && num >= 1 && num <= 18) {
    return getIsoVerse(String(num));
  }

  return null;
}

// ---------------------------------------------------------------------------
// Sidebar navigation
// ---------------------------------------------------------------------------

/**
 * Build the full sidebar navigation list.
 *
 * Order: front-pages → introduction → invocation → mantras 1-18 → about-the-author
 */
export async function getIsoSidebarItems(): Promise<IsoSidebarItem[]> {
  const meta = await getIsoMeta();
  if (!meta) return [];

  const items: IsoSidebarItem[] = [];

  // 1. Front pages intro segment
  items.push({
    slug: "intro-front-pages",
    label: "Back Cover & Front Pages",
    type: "intro-segment",
    mantra: null,
  });

  // 2. Introduction (Teachings of the Vedas)
  items.push({
    slug: "intro-introduction",
    label: "Introduction (Teachings of the Vedas)",
    type: "intro-segment",
    mantra: null,
  });

  // 3. Invocation + Mantras 1-18 (from meta.mantras)
  for (const m of meta.mantras) {
    if (m.number === 0) {
      items.push({
        slug: "invocation",
        label: "Invocation",
        type: "verse",
        mantra: 0,
      });
    } else {
      items.push({
        slug: String(m.number),
        label: `${m.number}. ${m.title}`,
        type: "verse",
        mantra: m.number,
      });
    }
  }

  // 4. About the Author intro segment (at the end)
  items.push({
    slug: "intro-about-the-author",
    label: "About the Author",
    type: "intro-segment",
    mantra: null,
  });

  return items;
}