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

const ATTACH_PREFIX = '<SHiNE:attach;';
const ATTACH_BLOCK_RE = /^<SHiNE:attach;([^>]*)>\n?/u;

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 : []).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 createAttachmentListElement(attachments = [], { gateway = '', compact = false } = {}) {
  const items = Array.isArray(attachments) ? attachments : [];
  const wrap = document.createElement('div');
  wrap.className = `message-attachments${compact ? ' message-attachments--compact' : ''}`;
  items.forEach((raw) => {
    let item;
    try {
      item = normalizeAttachment(raw);
    } catch {
      return;
    }
    const url = buildArweaveDataUrl({ gateway, txId: item.ar });
    const link = document.createElement('a');
    link.className = 'message-attachment-card';
    link.href = url;
    link.target = '_blank';
    link.rel = 'noopener';
    link.title = 'Открыть файл в Arweave';
    link.addEventListener('click', (event) => {
      event.stopPropagation();
    });
    link.innerHTML = `
      <span class="message-attachment-icon" aria-hidden="true">📎</span>
      <span class="message-attachment-main">
        <span class="message-attachment-name">${escapeHtml(item.name)}</span>
        <span class="message-attachment-meta">${escapeHtml(formatBytes(item.size))} · ${escapeHtml(item.ar)}</span>
      </span>
    `;
    wrap.append(link);
  });
  return wrap;
}