// ==UserScript==
// @name         Book Links
// @namespace    http://tampermonkey.net/
// @version      1.0
// @description  Show Anna's Archive and Waterstones links when browsing books
// @match        https://bookshop.org/p/books/*
// @match        https://www.waterstones.com/book/*
// @match        https://www.amazon.fr/dp/*
// @match        https://www.amazon.fr/*/dp/*
// @match        https://www.amazon.com/dp/*
// @match        https://www.amazon.com/*/dp/*
// @connect      annas-archive.gl
// @connect      www.waterstones.com
// @updateURL    https://raw.githubusercontent.com/alexture/book-links/main/book-links.user.js
// @downloadURL  https://raw.githubusercontent.com/alexture/book-links/main/book-links.user.js
// @grant        GM_xmlhttpRequest
// ==/UserScript==

(function () {
  'use strict';

  function isbn10to13(isbn10) {
    const base = '978' + isbn10.slice(0, 9);
    let sum = 0;
    for (let i = 0; i < 12; i++) {
      sum += parseInt(base[i]) * (i % 2 === 0 ? 1 : 3);
    }
    return base + String((10 - (sum % 10)) % 10);
  }

  function extractISBN() {
    const url = window.location.href;
    const host = window.location.hostname;

    if (host.includes('waterstones.com')) {
      const m = url.match(/\/(97[89]\d{10})(?:[/?#]|$)/);
      return m ? m[1] : null;
    }

    if (host.includes('amazon.')) {
      // Numeric ASIN in URL = ISBN-10
      const asinMatch = url.match(/\/dp\/(\d{10})(?:[/?#]|$)/);
      if (asinMatch) return isbn10to13(asinMatch[1]);

      const text = document.body?.innerText || '';

      // ISBN-13 in product details
      const m13 = text.match(/ISBN-?13[\s:‎‏ ]+([0-9][-0-9 ]{11,16}[0-9])/);
      if (m13) {
        const cleaned = m13[1].replace(/[-\s]/g, '');
        if (/^97[89]\d{10}$/.test(cleaned)) return cleaned;
      }

      // ISBN-10 in product details
      const m10 = text.match(/ISBN-?10[\s:‎‏ ]+(\d{9}[\dX])/);
      if (m10 && /^\d{9}[\dX]$/.test(m10[1])) return isbn10to13(m10[1]);

      return null;
    }

    if (host.includes('bookshop.org')) {
      const el = document.querySelector('[itemprop="isbn"]');
      if (el && /^97[89]\d{10}$/.test(el.textContent.trim())) return el.textContent.trim();

      for (const meta of document.querySelectorAll('meta')) {
        const c = (meta.getAttribute('content') || '').trim();
        if (/^97[89]\d{10}$/.test(c)) return c;
      }

      const m = (document.body?.innerText || '').match(/\b(97[89]\d{10})\b/);
      return m ? m[1] : null;
    }

    return null;
  }

  function extractTitleAuthor() {
    const host = window.location.hostname;

    if (host.includes('bookshop.org')) {
      const title = (
        document.querySelector('[itemprop="name"]') ||
        document.querySelector('h1')
      )?.textContent?.trim();
      const author = (
        document.querySelector('[itemprop="author"]') ||
        document.querySelector('.book-author a') ||
        document.querySelector('.contributors a')
      )?.textContent?.trim();
      return { title, author };
    }

    if (host.includes('amazon.')) {
      const title = (
        document.querySelector('#productTitle') ||
        document.querySelector('.product-title-word-break')
      )?.textContent?.trim();
      const author = (
        document.querySelector('#bylineInfo .author a') ||
        document.querySelector('.contributorNameID')
      )?.textContent?.trim();
      return { title, author };
    }

    if (host.includes('waterstones.com')) {
      const title = (
        document.querySelector('[itemprop="name"]') ||
        document.querySelector('h1')
      )?.textContent?.trim();
      const author = (
        document.querySelector('[itemprop="author"]') ||
        document.querySelector('.author-name a') ||
        document.querySelector('.book-authors a')
      )?.textContent?.trim();
      return { title, author };
    }

    return { title: null, author: null };
  }

  function gmFetch(url) {
    return new Promise((resolve) => {
      GM_xmlhttpRequest({
        method: 'GET',
        url,
        timeout: 8000,
        onload: (r) => resolve({
          ok: r.status >= 200 && r.status < 400,
          text: r.responseText,
          finalUrl: r.finalUrl || url,
        }),
        onerror: () => resolve({ ok: false, text: '', finalUrl: url }),
        ontimeout: () => resolve({ ok: false, text: '', finalUrl: url }),
      });
    });
  }

  async function checkAnna(isbn, title, author) {
    const query = (title && author) ? `${title} ${author}` : isbn;
    const url = `https://annas-archive.gl/search?q=${encodeURIComponent(query)}`;
    const res = await gmFetch(url);
    if (!res.ok) return { found: null, url };

    const noResults = /no\s+results|0\s+results/i.test(res.text);
    if (noResults) return { found: false, url };

    // /md5/ followed by a 32-char hex hash = an actual file link, not site chrome
    const hasFiles = /\/md5\/[0-9a-f]{32}/i.test(res.text);
    if (hasFiles) return { found: true, url };

    return { found: null, url };
  }

  async function checkWaterstones(isbn) {
    const searchUrl = `https://www.waterstones.com/books/search/term/${isbn}`;
    const res = await gmFetch(searchUrl);
    if (!res.ok) return { found: null, url: searchUrl };

    // Redirect to a product page means direct hit
    if (res.finalUrl && /\/book\/[^/]+\/[^/]+\//.test(res.finalUrl)) {
      return { found: true, url: res.finalUrl };
    }

    const noResults = /no results|didn.t find|0 results found/i.test(res.text);
    if (noResults) return { found: false, url: searchUrl };

    const hasResults = /book-wrap|data-isbn|"@type"\s*:\s*"Book"|class="book/i.test(res.text);
    if (hasResults) return { found: true, url: searchUrl };

    // Search results are JS-rendered — can't determine, show link anyway
    return { found: null, url: searchUrl };
  }

  function renderRow(label, result) {
    if (result.found === true) {
      return `<div>✓ <a href="${result.url}" target="_blank" style="color:#7eb8f7;text-decoration:none">${label}</a></div>`;
    }
    if (result.found === false) {
      return `<div style="color:#666">✗ ${label} — not found</div>`;
    }
    // null = couldn't check, show link anyway
    return `<div>? <a href="${result.url}" target="_blank" style="color:#888;text-decoration:none">${label}</a> <span style="color:#555;font-size:11px">(couldn't verify)</span></div>`;
  }

  function buildWidget() {
    const div = document.createElement('div');
    div.id = '__book-links';
    div.style.cssText = `
      position: fixed;
      bottom: 20px;
      right: 20px;
      background: #16213e;
      color: #e0e0e0;
      border: 1px solid #0f3460;
      border-radius: 8px;
      padding: 12px 14px;
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
      font-size: 13px;
      line-height: 1.75;
      z-index: 2147483647;
      max-width: 270px;
      box-shadow: 0 4px 20px rgba(0,0,0,0.5);
    `;
    div.innerHTML = `
      <div style="display:flex;justify-content:space-between;align-items:center;margin-bottom:6px">
        <strong style="color:#a8d8ea">Book Links</strong>
        <span id="__bl-close" style="cursor:pointer;color:#555;font-size:18px;line-height:1;padding-left:10px">×</span>
      </div>
      <div id="__bl-isbn" style="color:#888;font-size:11px;margin-bottom:6px"></div>
      <div id="__bl-results"></div>
    `;
    document.body.appendChild(div);
    div.querySelector('#__bl-close').onclick = () => div.remove();
    return div;
  }

  async function run() {
    await new Promise(r => setTimeout(r, 800));

    const isbn = extractISBN();
    const { title, author } = extractTitleAuthor();
    const widget = buildWidget();

    if (!isbn && !title) {
      widget.querySelector('#__bl-results').innerHTML =
        '<div style="color:#e07b5a">Couldn\'t find book info on this page.</div>';
      return;
    }

    widget.querySelector('#__bl-isbn').textContent = isbn ? `ISBN ${isbn}` : (title || '');
    widget.querySelector('#__bl-results').textContent = 'Checking…';

    const isWaterstones = window.location.hostname.includes('waterstones.com');
    const checksToRun = [checkAnna(isbn, title, author)];
    if (!isWaterstones && isbn) checksToRun.push(checkWaterstones(isbn));

    const results = await Promise.all(checksToRun);
    const annaResult = results[0];
    const waterstonesResult = isWaterstones ? null : results[1];

    let html = '';
    if (!isWaterstones) html += renderRow('Waterstones', waterstonesResult);
    html += renderRow("Anna's Archive", annaResult);

    widget.querySelector('#__bl-results').innerHTML = html;
  }

  if (document.readyState === 'loading') {
    document.addEventListener('DOMContentLoaded', run);
  } else {
    run();
  }
})();