const path = require("path");

const { fetchWpMangaChapterLinks } = require("./mangareadFetchChapters.js");
const { chapterUrlToCbz, sanitizeComicDirName, stemForCbzFilename } = require("./downloadChapterCbz.js");

/**
 * @typedef {object} ParsedCli
 * @property {boolean} [help] - When set from `--help`, print usage and exit.
 * @property {string|undefined} listingUrl - Page containing `li.wp-manga-chapter` links.
 * @property {boolean} listOnly - Print numbered chapters and exit.
 * @property {boolean} allChapters - Queue every chapter in list order.
 * @property {string|undefined} selectSpec - Comma-separated **list indices** on the printed menu (oldest first: row 1 ≈ Chapter 1), e.g. `1,3,5-7`.
 * @property {string|undefined} numbersSpec - Comma-separated **chapter numbers** from titles, e.g. `22,23,24` or `22-24`.
 * @property {string} outDir - Directory for `.cbz` files.
 */

/**
 * Parses CLI arguments after `node .../downloadChaptersQueue.js`.
 * @param {string[]} argv - `process.argv`.
 * @returns {ParsedCli} Parsed options.
 */
function parseCli(argv) {
  /** @type {ParsedCli} */
  const result = {
    help: false,
    listingUrl: undefined,
    listOnly: false,
    allChapters: false,
    selectSpec: undefined,
    numbersSpec: undefined,
    outDir: path.join(process.cwd(), "data", "comics"),
  };

  for (let i = 2; i < argv.length; i += 1) {
    const a = argv[i];
    if (a === "--help" || a === "-h") {
      result.help = true;
    } else if (a === "--list-only" || a === "-l") {
      result.listOnly = true;
    } else if (a === "--all") {
      result.allChapters = true;
    } else if (a === "--select" || a === "-s") {
      const next = argv[i + 1];
      if (next === undefined || next.startsWith("-")) {
        throw new Error("Missing value for --select");
      }
      result.selectSpec = next;
      i += 1;
    } else if (a === "--numbers" || a === "-n") {
      const next = argv[i + 1];
      if (next === undefined || next.startsWith("-")) {
        throw new Error("Missing value for --numbers");
      }
      result.numbersSpec = next;
      i += 1;
    } else if (a === "--out" || a === "-o") {
      const next = argv[i + 1];
      if (next === undefined || next.startsWith("-")) {
        throw new Error("Missing value for --out");
      }
      result.outDir = path.resolve(next);
      i += 1;
    } else if (!a.startsWith("-")) {
      if (result.listingUrl) {
        throw new Error(`Unexpected extra argument: ${a}`);
      }
      result.listingUrl = a;
    } else {
      throw new Error(`Unknown option: ${a}`);
    }
  }

  return result;
}

/**
 * WP‑Manga lists chapters **newest first** in the HTML. We reverse so the numbered
 * menu and `--select` indices match reading order (line 1 ≈ Chapter 1).
 * @param {import("./mangareadFetchChapters.js").ChapterLink[]} chapters - Fetched in site order.
 * @returns {import("./mangareadFetchChapters.js").ChapterLink[]} New array, oldest chapter first.
 */
function chaptersInReadingOrder(chapters) {
  return [...chapters].reverse();
}

/**
 * Builds sorted unique 1-based indices from a spec like `1`, `1,3`, `5-10,2`.
 * @param {string} spec - Selection string.
 * @param {number} count - Number of chapters (max index).
 * @returns {number[]} Ascending unique indices in [1, count].
 */
function parseChapterSelection(spec, count) {
  if (count <= 0) {
    throw new Error("Chapter list is empty; cannot select indices.");
  }

  const trimmed = spec.trim();
  if (trimmed.length === 0) {
    throw new Error("--select value is empty.");
  }

  /** @type {Set<number>} */
  const seen = new Set();

  for (const rawPart of trimmed.split(",")) {
    const part = rawPart.trim();
    if (part.length === 0) {
      continue;
    }

    if (/^\d+$/.test(part)) {
      const n = Number.parseInt(part, 10);
      if (n < 1 || n > count) {
        throw new Error(
          `Index ${String(n)} is out of range (valid: 1–${String(count)}).`,
        );
      }
      seen.add(n);
      continue;
    }

    const rangeMatch = /^(\d+)\s*-\s*(\d+)$/.exec(part);
    if (rangeMatch) {
      const lo = Number.parseInt(rangeMatch[1], 10);
      const hi = Number.parseInt(rangeMatch[2], 10);
      const a = Math.min(lo, hi);
      const b = Math.max(lo, hi);
      for (let i = a; i <= b; i += 1) {
        if (i < 1 || i > count) {
          throw new Error(
            `Range ${part} includes invalid index ${String(i)} (valid: 1–${String(count)}).`,
          );
        }
        seen.add(i);
      }
      continue;
    }

    throw new Error(`Invalid --select segment: "${part}"`);
  }

  if (seen.size === 0) {
    throw new Error("No indices parsed from --select.");
  }

  return [...seen].sort((x, y) => x - y);
}

/**
 * Parses "Chapter 22" / "chapter 160.5" style titles from WP‑Manga lists.
 * @param {string} title - Anchor text.
 * @returns {string|null} Numeric suffix or null.
 */
function chapterNumberFromWpTitle(title) {
  const m = /^Chapter\s+([\d.]+)\s*$/iu.exec(title.trim().replace(/\s+/g, " "));
  return m ? m[1] : null;
}

/**
 * Expands `"22,23,24"` or `"22-24"` into ordered chapter-number strings.
 * Integer ranges only (22-24 → 22,23,24). Use explicit `160.5` for decimals.
 * @param {string} spec - User `--numbers` argument.
 * @returns {string[]} Ordered unique chapter numbers to resolve.
 */
function parseMangaChapterNumbersSpec(spec) {
  const trimmed = spec.trim();
  if (trimmed.length === 0) {
    throw new Error("--numbers value is empty.");
  }

  /** @type {string[]} */
  const ordered = [];
  /** @type {Set<string>} */
  const seen = new Set();

  for (const rawPart of trimmed.split(",")) {
    const part = rawPart.trim();
    if (part.length === 0) {
      continue;
    }

    const rangeMatch = /^(\d+)\s*-\s*(\d+)$/.exec(part);
    if (rangeMatch) {
      const lo = Number.parseInt(rangeMatch[1], 10);
      const hi = Number.parseInt(rangeMatch[2], 10);
      const a = Math.min(lo, hi);
      const b = Math.max(lo, hi);
      for (let n = a; n <= b; n += 1) {
        const k = String(n);
        if (!seen.has(k)) {
          seen.add(k);
          ordered.push(k);
        }
      }
      continue;
    }

    if (/^\d+(\.\d+)?$/.test(part)) {
      if (!seen.has(part)) {
        seen.add(part);
        ordered.push(part);
      }
      continue;
    }

    throw new Error(`Invalid --numbers segment: "${part}"`);
  }

  if (ordered.length === 0) {
    throw new Error("No chapter numbers parsed from --numbers.");
  }

  return ordered;
}

/**
 * Resolves chapter rows by numeric title (e.g. Chapter 22).
 * @param {string[]} orderedNums - From {@link parseMangaChapterNumbersSpec}.
 * @param {import("./mangareadFetchChapters.js").ChapterLink[]} chapters - Full list.
 * @returns {Array<{ url: string, title: string, pickLabel: string, chapterNumber: string }>} Queue rows with URLs and labels.
 */
function queueItemsByChapterNumbers(orderedNums, chapters) {
  /** @type {Map<string, import("./mangareadFetchChapters.js").ChapterLink>} */
  const first = new Map();
  for (const ch of chapters) {
    const num = chapterNumberFromWpTitle(ch.title);
    if (num !== null && !first.has(num)) {
      first.set(num, ch);
    }
  }

  return orderedNums.map((num) => {
    const ch = first.get(num);
    if (!ch) {
      throw new Error(
        `No chapter titled "Chapter ${num}" in the listing.` +
          " Use --list-only and check spelling (decimals like 160.5 must be listed explicitly).",
      );
    }
    return {
      url: ch.url,
      title: ch.title,
      pickLabel: `Ch.${num}`,
      chapterNumber: num,
    };
  });
}

/**
 * Prints numbered chapters for manual `--select` choice.
 * @param {import("./mangareadFetchChapters.js").ChapterLink[]} chapters - Chapter rows.
 * @returns {void}
 */
function printChapterMenu(chapters) {
  const digits = String(chapters.length).length;
  for (let i = 0; i < chapters.length; i += 1) {
    const n = i + 1;
    const pad = String(n).padStart(digits, " ");
    const title = chapters[i].title.replace(/\s+/g, " ").trim();
    console.log(`${pad}. ${title}`);
    console.log(`     ${chapters[i].url}`);
  }
}

/**
 * @param {number[]} indices1 - Sorted unique 1-based indices.
 * @param {import("./mangareadFetchChapters.js").ChapterLink[]} chapters - Full list.
 * @returns {Array<{ url: string, title: string, index: number, pickLabel: string }>} One item per requested index.
 */
function chaptersByIndices(indices1, chapters) {
  return indices1.map((idx) => ({
    index: idx,
    title: chapters[idx - 1].title,
    url: chapters[idx - 1].url,
    pickLabel: `#${String(idx)}`,
  }));
}

/**
 * Fetches chapter list, queues selected chapters, downloads one `.cbz` at a time.
 * @returns {Promise<void>}
 */
async function main() {
  let parsed;
  try {
    parsed = parseCli(process.argv);
  } catch (err) {
    console.error(err instanceof Error ? err.message : err);
    process.exitCode = 1;
    return;
  }

  if (parsed.help) {
    console.log(`Usage:
  node src/downloadChaptersQueue.js <listing-page-url> [--list-only|-l]
  node src/downloadChaptersQueue.js <listing-page-url> --numbers|-n <spec> [--out|-o <dir>]
  node src/downloadChaptersQueue.js <listing-page-url> --select|-s <spec> [--out|-o <dir>]
  node src/downloadChaptersQueue.js <listing-page-url> --all [--out|-o <dir>]

Any chapter URL for that manga usually works as <listing-page-url> (same HTML includes the chapter list).

--numbers spec: chapter numbers from link titles ("Chapter 22"), e.g. 22,23,24 or 22-24
  Decimals (e.g. 160.5) must be listed explicitly; integer ranges expand to whole numbers only.

--select spec: 1-based row numbers on the **printed list** (oldest first; row 1 is Chapter 1),
  e.g. 1,3,5-10. This is the menu index, not a substring of the title (use --numbers for that).

Chapters are processed in list order for --select/--all, or in the order given for --numbers.
Default --out: data/comics/<comic title>/ (under current working directory).`);
    return;
  }

  if (!parsed.listingUrl) {
    console.error(
      "Usage: node src/downloadChaptersQueue.js <listing-page-url> [options]\nTry --help for details.",
    );
    process.exitCode = 1;
    return;
  }

  let chapters;
  let comicTitle;
  try {
    ({ chapters, comicTitle } = await fetchWpMangaChapterLinks(parsed.listingUrl));
    chapters = chaptersInReadingOrder(chapters);
  } catch (err) {
    console.error(err instanceof Error ? err.message : err);
    process.exitCode = 1;
    return;
  }

  console.log(`Found ${String(chapters.length)} chapter link(s) on listing page.`);
  printChapterMenu(chapters);

  if (parsed.listOnly) {
    return;
  }

  const wantsAll = parsed.allChapters;
  const wantsSelect = Boolean(parsed.selectSpec);
  const wantsNumbers = Boolean(parsed.numbersSpec);
  const pickModes = [wantsAll, wantsSelect, wantsNumbers].filter(Boolean).length;
  if (pickModes === 0) {
    console.error(
      "Choose: --numbers <spec>, --select <spec>, or --all  (or use --list-only to exit after listing).",
    );
    process.exitCode = 1;
    return;
  }
  if (pickModes > 1) {
    console.error("Use only one of --all, --select, or --numbers.");
    process.exitCode = 1;
    return;
  }

  /** @type {Array<{ url: string, title: string, pickLabel: string }>} */
  let queue;
  try {
    if (wantsAll) {
      const indices = Array.from({ length: chapters.length }, (_, i) => i + 1);
      queue = chaptersByIndices(indices, chapters);
    } else if (wantsSelect) {
      const indices = parseChapterSelection(
        /** @type {string} */ (parsed.selectSpec),
        chapters.length,
      );
      queue = chaptersByIndices(indices, chapters);
    } else {
      const orderedNums = parseMangaChapterNumbersSpec(
        /** @type {string} */ (parsed.numbersSpec),
      );
      queue = queueItemsByChapterNumbers(orderedNums, chapters);
    }
  } catch (err) {
    console.error(err instanceof Error ? err.message : err);
    process.exitCode = 1;
    return;
  }
  const outDir = path.join(parsed.outDir, sanitizeComicDirName(comicTitle));
  console.log(`Comic: ${comicTitle}`);
  console.log(`Output directory: ${outDir}`);

  let failedCount = 0;
  let done = 0;
  for (const item of queue) {
    done += 1;
    const stem = stemForCbzFilename(item.url);
    const targetPath = path.join(outDir, `${stem}.cbz`);
    console.log(
      `\n[${String(done)}/${String(queue.length)}] ${item.pickLabel} ${item.title}`,
    );
    console.log(`  → ${item.url}`);
    try {
      const { imageCount, outputPath } = await chapterUrlToCbz(item.url, targetPath);
      console.log(`  ✓ ${String(imageCount)} page(s) → ${outputPath}`);
    } catch (err) {
      console.error(`  ✗ ${err instanceof Error ? err.message : err}`);
      failedCount += 1;
    }
  }

  if (failedCount > 0) {
    console.error(
      `\n${String(failedCount)} chapter(s) failed (${String(queue.length - failedCount)} succeeded).`,
    );
    process.exitCode = 1;
  }
}

module.exports = {
  chapterNumberFromWpTitle,
  chaptersByIndices,
  chaptersInReadingOrder,
  parseChapterSelection,
  parseCli,
  parseMangaChapterNumbersSpec,
  printChapterMenu,
  queueItemsByChapterNumbers,
};

if (require.main === module) {
  main().catch((err) => {
    console.error(err);
    process.exitCode = 1;
  });
}