import { buildArweaveDataUrl, validateArweaveTxId, validateSha256Hex } from './arweave-file-service.js';

const ATTACH_PREFIX = '<SHiNE:attach;';
const ATTACH_BLOCK_RE = /^<SHiNE:attach;([^>]*)>\n?/u;
export const MAX_MESSAGE_ATTACHMENTS = 10;
const RECENT_UNAVAILABLE_MS = 20 * 60 * 1000;
const IMAGE_EXTENSIONS = new Set(['apng', 'avif', 'bmp', 'gif', 'jpeg', 'jpg', 'png', 'svg', 'webp']);
const VIDEO_EXTENSIONS = new Set(['avi', 'm4v', 'mkv', 'mov', 'mp4', 'mpeg', 'mpg', 'ogg', 'ogv', 'webm']);

export function escapeHtml(text) {
  return String(text || '')
    .replaceAll('&', '&amp;')
    .replaceAll('<', '&lt;')
    .replaceAll('>', '&gt;')
    .replaceAll('"', '&quot;')
    .replaceAll("'", '&#39;');
}

export function formatBytes(bytes) {
  const value = Number(bytes || 0);
  if (!Number.isFinite(value) || value <= 0) return '0 B';
  if (value < 1024) return `${value} B`;
  if (value < 1024 * 1024) return `${(value / 1024).toFixed(1)} KB`;
  return `${(value / (1024 * 1024)).toFixed(2)} MB`;
}

function normalizeName(name) {
  const clean = String(name || 'file')
    .replace(/[\u0000-\u001f\u007f]/g, '')
    .replace(/[\\/]/g, '_')
    .trim();
  return clean || 'file';
}

export function normalizeAttachment(input = {}) {
  const txId = String(input.ar || input.txId || '').trim();
  const sha256Hex = String(input.sha256 || input.sha256Hex || '').trim().toLowerCase();
  const size = Number(input.size || input.sizeBytes || 0);
  const name = normalizeName(input.name || input.fileName || 'file');
  if (!validateArweaveTxId(txId)) throw new Error('Некорректный Transaction ID Arweave.');
  if (!validateSha256Hex(sha256Hex)) throw new Error('Некорректный SHA-256 файла.');
  if (!Number.isInteger(size) || size <= 0) throw new Error('Некорректный размер файла.');
  return {
    v: 1,
    name,
    size,
    sha256: sha256Hex,
    ar: txId,
    uploadedAtMs: Number(input.uploadedAtMs || 0) || Date.now(),
  };
}

export function buildAttachmentBlock(attachment) {
  const item = normalizeAttachment(attachment);
  const encodedName = encodeURIComponent(item.name);
  return `<SHiNE:attach;v=1;name=${encodedName};size=${item.size};sha256=${item.sha256};ar=${item.ar}>`;
}

export function composeMessageWithAttachments(text, attachments = []) {
  const cleanText = String(text || '').trim();
  const rows = (Array.isArray(attachments) ? attachments : [])
    .slice(0, MAX_MESSAGE_ATTACHMENTS)
    .map(buildAttachmentBlock);
  if (!rows.length) return cleanText;
  return `${rows.join('\n')}${cleanText ? `\n${cleanText}` : ''}`;
}

function parseFields(rawFields) {
  const out = {};
  String(rawFields || '').split(';').forEach((part) => {
    const eq = part.indexOf('=');
    if (eq <= 0) return;
    const key = part.slice(0, eq).trim();
    const value = part.slice(eq + 1).trim();
    if (key) out[key] = value;
  });
  return out;
}

export function parseMessageAttachments(rawText) {
  let rest = String(rawText || '');
  const attachments = [];

  while (rest.startsWith(ATTACH_PREFIX)) {
    const match = rest.match(ATTACH_BLOCK_RE);
    if (!match) break;
    const fields = parseFields(match[1]);
    try {
      attachments.push(normalizeAttachment({
        name: decodeURIComponent(String(fields.name || 'file')),
        size: fields.size,
        sha256: fields.sha256,
        ar: fields.ar,
      }));
    } catch {
      // Битый attach-блок скрываем из UI, но не ломаем отображение текста.
    }
    rest = rest.slice(match[0].length);
  }

  return {
    attachments,
    text: rest.replace(/^\n+/u, ''),
  };
}

export function getAttachmentExtension(name) {
  const clean = String(name || '').trim().toLowerCase();
  const dot = clean.lastIndexOf('.');
  if (dot < 0 || dot === clean.length - 1) return '';
  return clean.slice(dot + 1).replace(/[^a-z0-9]/g, '');
}

export function getAttachmentKind(attachment = {}) {
  const ext = getAttachmentExtension(attachment.name);
  if (IMAGE_EXTENSIONS.has(ext)) return 'image';
  if (VIDEO_EXTENSIONS.has(ext)) return 'video';
  return 'file';
}

function isRecentMessage(messageTimestampMs) {
  const ts = Number(messageTimestampMs || 0);
  if (!Number.isFinite(ts) || ts <= 0) return false;
  return Date.now() - ts < RECENT_UNAVAILABLE_MS;
}

function createUnavailableBlock(messageTimestampMs) {
  const block = document.createElement('div');
  block.className = 'message-attachment-unavailable';
  block.textContent = isRecentMessage(messageTimestampMs)
    ? 'Скорее всего файл недоступен, потому что сообщение было создано недавно и файл ещё не распространился в Arweave. Попробуйте повторить через несколько минут.'
    : 'Файл недоступен.';
  return block;
}

function stopVideos(root) {
  root.querySelectorAll('video').forEach((video) => {
    try {
      video.pause();
      video.currentTime = 0;
    } catch {
      // Если браузер не даёт управлять видео, просто продолжаем перелистывание.
    }
  });
}

function createDownloadLink(url, label = 'Скачать') {
  const link = document.createElement('a');
  link.className = 'message-attachment-download';
  link.href = url;
  link.target = '_blank';
  link.rel = 'noopener';
  link.download = '';
  link.textContent = label;
  link.addEventListener('click', (event) => {
    event.stopPropagation();
  });
  return link;
}

function openAttachmentViewer({ item, url, kind }) {
  const root = document.getElementById('modal-root') || document.body;
  const overlay = document.createElement('div');
  overlay.className = 'modal attachment-viewer-modal';
  overlay.innerHTML = `
    <div class="attachment-viewer-card" role="dialog" aria-modal="true">
      <div class="attachment-viewer-head">
        <div class="attachment-viewer-title">${escapeHtml(item.name)}</div>
        <button class="icon-btn attachment-viewer-close" type="button" aria-label="Закрыть">×</button>
      </div>
      <div class="attachment-viewer-body"></div>
      <div class="attachment-viewer-actions"></div>
    </div>
  `;
  const close = () => {
    stopVideos(overlay);
    overlay.remove();
  };
  overlay.addEventListener('click', (event) => {
    if (event.target === overlay) close();
  });
  overlay.querySelector('.attachment-viewer-close')?.addEventListener('click', close);
  const body = overlay.querySelector('.attachment-viewer-body');
  if (kind === 'video') {
    const video = document.createElement('video');
    video.className = 'attachment-viewer-media';
    video.src = url;
    video.controls = true;
    video.autoplay = true;
    body.append(video);
  } else {
    const img = document.createElement('img');
    img.className = 'attachment-viewer-media';
    img.src = url;
    img.alt = item.name;
    body.append(img);
  }
  overlay.querySelector('.attachment-viewer-actions')?.append(createDownloadLink(url));
  root.append(overlay);
}

function replaceWithUnavailable(slide, messageTimestampMs) {
  if (!slide || slide.dataset.unavailable === '1') return;
  slide.dataset.unavailable = '1';
  slide.replaceChildren(createUnavailableBlock(messageTimestampMs));
}

function createFileCard({ item, url, messageTimestampMs, slide }) {
  const ext = getAttachmentExtension(item.name).toUpperCase() || 'FILE';
  const card = document.createElement('div');
  card.className = 'message-attachment-file-card';
  card.role = 'button';
  card.tabIndex = 0;
  card.title = 'Скачать файл';
  card.innerHTML = `
    <div class="message-attachment-file-ext">${escapeHtml(ext)}</div>
    <div class="message-attachment-file-main">
      <div class="message-attachment-name">${escapeHtml(item.name)}</div>
      <div class="message-attachment-meta">${escapeHtml(formatBytes(item.size))} · ${escapeHtml(item.ar)}</div>
    </div>
  `;
  const openFile = () => window.open(url, '_blank', 'noopener');
  card.addEventListener('click', (event) => {
    event.stopPropagation();
    openFile();
  });
  card.addEventListener('keydown', (event) => {
    if (event.key !== 'Enter' && event.key !== ' ') return;
    event.preventDefault();
    openFile();
  });
  card.append(createDownloadLink(url));
  void fetch(url, { method: 'HEAD', cache: 'no-store' })
    .then((response) => {
      if (!response.ok) replaceWithUnavailable(slide, messageTimestampMs);
    })
    .catch(() => replaceWithUnavailable(slide, messageTimestampMs));
  return card;
}

function createMediaSlide({ item, url, kind, messageTimestampMs, slide }) {
  const frame = document.createElement('div');
  frame.className = `message-attachment-media-frame message-attachment-media-frame--${kind}`;
  frame.role = 'button';
  frame.tabIndex = 0;
  frame.title = kind === 'video' ? 'Открыть видео' : 'Открыть изображение';
  frame.addEventListener('click', (event) => {
    event.stopPropagation();
    openAttachmentViewer({ item, url, kind });
  });
  frame.addEventListener('keydown', (event) => {
    if (event.key !== 'Enter' && event.key !== ' ') return;
    event.preventDefault();
    openAttachmentViewer({ item, url, kind });
  });

  if (kind === 'image') {
    const img = document.createElement('img');
    img.className = 'message-attachment-media';
    img.src = url;
    img.alt = item.name;
    img.loading = 'lazy';
    img.addEventListener('error', () => replaceWithUnavailable(slide, messageTimestampMs), { once: true });
    frame.append(img);
  } else {
    const video = document.createElement('video');
    video.className = 'message-attachment-media';
    video.src = url;
    video.preload = 'metadata';
    video.muted = true;
    video.playsInline = true;
    video.addEventListener('error', () => replaceWithUnavailable(slide, messageTimestampMs), { once: true });
    const play = document.createElement('span');
    play.className = 'message-attachment-play';
    play.textContent = '▶';
    frame.append(video, play);
  }

  frame.append(createDownloadLink(url));
  return frame;
}

export function createAttachmentCarouselElement(attachments = [], { gateway = '', messageTimestampMs = 0 } = {}) {
  const items = (Array.isArray(attachments) ? attachments : [])
    .slice(0, MAX_MESSAGE_ATTACHMENTS)
    .map((raw) => {
      try {
        return normalizeAttachment(raw);
      } catch {
        return null;
      }
    })
    .filter(Boolean);
  const wrap = document.createElement('div');
  wrap.className = 'message-attachments message-attachment-carousel';
  wrap.addEventListener('click', (event) => {
    event.stopPropagation();
  });
  if (!items.length) return wrap;

  let index = 0;
  let pointerStartX = 0;
  const viewport = document.createElement('div');
  viewport.className = 'message-attachment-carousel-viewport';
  const slide = document.createElement('div');
  slide.className = 'message-attachment-slide';
  const prev = document.createElement('button');
  prev.type = 'button';
  prev.className = 'message-attachment-arrow message-attachment-arrow--prev';
  prev.textContent = '‹';
  prev.setAttribute('aria-label', 'Предыдущее вложение');
  const next = document.createElement('button');
  next.type = 'button';
  next.className = 'message-attachment-arrow message-attachment-arrow--next';
  next.textContent = '›';
  next.setAttribute('aria-label', 'Следующее вложение');
  const counter = document.createElement('div');
  counter.className = 'message-attachment-counter';

  const render = () => {
    stopVideos(wrap);
    const item = items[index];
    const kind = getAttachmentKind(item);
    const url = buildArweaveDataUrl({ gateway, txId: item.ar });
    slide.dataset.unavailable = '0';
    slide.replaceChildren();
    slide.append(kind === 'file'
      ? createFileCard({ item, url, messageTimestampMs, slide })
      : createMediaSlide({ item, url, kind, messageTimestampMs, slide }));
    prev.disabled = index <= 0;
    next.disabled = index >= items.length - 1;
    counter.textContent = `${index + 1} из ${items.length}`;
  };

  const move = (delta) => {
    const nextIndex = Math.max(0, Math.min(items.length - 1, index + delta));
    if (nextIndex === index) return;
    index = nextIndex;
    render();
  };

  prev.addEventListener('click', (event) => {
    event.stopPropagation();
    move(-1);
  });
  next.addEventListener('click', (event) => {
    event.stopPropagation();
    move(1);
  });
  viewport.addEventListener('pointerdown', (event) => {
    pointerStartX = event.clientX;
  });
  viewport.addEventListener('pointerup', (event) => {
    const dx = event.clientX - pointerStartX;
    if (Math.abs(dx) < 40) return;
    move(dx < 0 ? 1 : -1);
  });

  viewport.append(slide, prev, next);
  wrap.append(viewport, counter);
  render();
  return wrap;
}

export function createAttachmentListElement(attachments = [], options = {}) {
  return createAttachmentCarouselElement(attachments, options);
}