/**
 * Data access layer for Perfect Questions Perfect Answers (PQPA).
 *
 * Reads from MongoDB via Prisma, same as the rest of the app.
 * PQPA is a prose/dialogue book with no volume structure —
 * we use volume=0 as the sentinel for "no volumes".
 *
 * Collections used:
 *   - book_meta (via Prisma BookMeta model)
 *   - prose_chapters (via Prisma ProseChapter model)
 */

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

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

/** Volume sentinel for books without volumes. */
const NO_VOLUME = 0;

const BOOK = "pqpa";

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

export type PqpaMeta = {
  book: string;
  title: string;
  author: string;
  year: number;
  description: string;
  totalChapters: number;
  chapters: PqpaChapterEntry[];
};

export type PqpaChapterEntry = {
  number: number;
  title: string;
};

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

export type PqpaChapter = {
  book: string;
  chapter: number | null;
  title: string;
  type: string;
  slug?: string;
  paragraphs: string[];
};

/** Union type used in sidebar / table-of-contents navigation. */
export type PqpaSidebarItem = {
  /** URL-safe slug: "intro-front-pages", "1", "9", "concluding-words" */
  slug: string;
  /** Human-readable label for the sidebar */
  label: string;
  /** "intro-segment" | "chapter" | "conclusion" */
  type: string;
  /** Chapter number, or null for non-chapter items */
  chapter: number | null;
};

// ---------------------------------------------------------------------------
// HTML sanitisation (mirrors lib/api.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);
}

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

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

// ---------------------------------------------------------------------------
// Intro segments
// ---------------------------------------------------------------------------

/**
 * All intro segments, ordered by their `order` field.
 */
export async function getPqpaIntroSegments(): Promise<PqpaIntroSegment[]> {
  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-introduction" (URL slug) and "introduction" (raw slug).
 */
export async function getPqpaIntroSegment(
  slug: string,
): Promise<PqpaIntroSegment | 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),
  };
}

// ---------------------------------------------------------------------------
// Chapters
// ---------------------------------------------------------------------------

/**
 * A numbered chapter (1–9).
 */
export async function getPqpaChapter(
  chapterNum: number,
): Promise<PqpaChapter | null> {
  if (chapterNum < 1 || chapterNum > 9 || !Number.isInteger(chapterNum)) {
    return null;
  }

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

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

/**
 * The concluding words section.
 */
export async function getPqpaConcludingWords(): Promise<PqpaChapter | null> {
  const doc = await prisma.proseChapter.findUnique({
    where: {
      book_volume_slug: {
        book: BOOK,
        volume: NO_VOLUME,
        slug: "concluding-words",
      },
    },
  });
  if (!doc) return null;

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

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

/**
 * Get content by URL slug.
 *
 *   "intro-front-pages"       → intro segment
 *   "intro-introduction"      → intro segment
 *   "intro-about-the-author"  → intro segment
 *   "1" … "9"                 → chapter
 *   "concluding-words"        → concluding section
 */
export async function getPqpaContent(
  slug: string,
): Promise<PqpaChapter | PqpaIntroSegment | null> {
  if (slug.startsWith("intro-")) {
    return getPqpaIntroSegment(slug);
  }

  if (slug === "concluding-words") {
    return getPqpaConcludingWords();
  }

  const num = Number(slug);
  if (!Number.isNaN(num) && Number.isInteger(num) && num >= 1 && num <= 9) {
    return getPqpaChapter(num);
  }

  return null;
}

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

/**
 * Build the full sidebar navigation list.
 *
 * Order: front-pages → introduction → chapters 1–9 → concluding-words → about-the-author
 */
export async function getPqpaSidebarItems(): Promise<PqpaSidebarItem[]> {
  const [meta, allDocs] = await Promise.all([
    getPqpaMeta(),
    prisma.proseChapter.findMany({
      where: { book: BOOK, volume: NO_VOLUME },
      orderBy: { order: "asc" },
      select: { slug: true, title: true, type: true, chapter: true, order: true },
    }),
  ]);

  if (!meta) return [];

  const items: PqpaSidebarItem[] = [];

  // Intro segments that come BEFORE chapters (order < 99)
  for (const doc of allDocs) {
    if (doc.type === "intro-segment" && (doc.order ?? 0) < 99) {
      items.push({
        slug: doc.slug,
        label: doc.title,
        type: "intro-segment",
        chapter: null,
      });
    }
  }

  // Chapters 1–9 (use meta.chapters for consistent title/ordering)
  for (const ch of meta.chapters) {
    items.push({
      slug: String(ch.number),
      label: `Chapter ${ch.number}: ${ch.title}`,
      type: "chapter",
      chapter: ch.number,
    });
  }

  // Concluding words
  const cw = allDocs.find((d) => d.type === "conclusion");
  if (cw) {
    items.push({
      slug: cw.slug,
      label: cw.title,
      type: "conclusion",
      chapter: null,
    });
  }

  // Intro segments that come AFTER chapters (order >= 99, e.g. about-the-author)
  for (const doc of allDocs) {
    if (doc.type === "intro-segment" && (doc.order ?? 0) >= 99) {
      items.push({
        slug: doc.slug,
        label: doc.title,
        type: "intro-segment",
        chapter: null,
      });
    }
  }

  return items;
}