'use strict';
const CP1251 = (() => {
  let s = '';
  for (let i = 0; i < 0x80; i++) s += String.fromCharCode(i);
  s += 'ЂЃ‚ѓ„…†‡€‰Љ‹ЊЌЋЏђ‘’“”•–—\u0098™љ›њќћџ';
  s += '\u00A0ЎўЈ¤Ґ¦§Ё©Є«¬\u00AD®Ї';
  s += '°±Ііґµ¶·ё№є»јЅѕї';
  for (let i = 0x410; i <= 0x42F; i++) s += String.fromCharCode(i);
  for (let i = 0x430; i <= 0x44F; i++) s += String.fromCharCode(i);
  return s;
})();
const CP1251_INDEX = (() => {
  const m = new Map();
  for (let i = 0; i < CP1251.length; i++) { if (!m.has(CP1251[i])) m.set(CP1251[i], i); }
  return m;
})();
function toCp1251Bytes(str) {
  const bytes = [];
  for (const ch of str) {
    const b = CP1251_INDEX.get(ch);
    if (b === undefined) {
      const cp = ch.codePointAt(0).toString(16).toUpperCase().padStart(4, '0');
      throw new Error(`Символ ${JSON.stringify(ch)} (U+${cp}) не входит в Windows-1251`);
    }
    bytes.push(b);
  }
  return bytes;
}
function bytesToBits(bytes) { let out = ''; for (const b of bytes) out += b.toString(2).padStart(8, '0'); return out; }
let nodeCounter = 0;
class Node {
  constructor(freq, char = null, left = null, right = null) {
    this.freq = freq; this.char = char; this.left = left; this.right = right; this.order = nodeCounter++;
  }
}
function buildHuffman(freq) {
  let nodes = Object.entries(freq).map(([ch, f]) => new Node(f, ch))
    .sort((a, b) => a.freq - b.freq || a.order - b.order);
  while (nodes.length > 1) {
    const a = nodes.shift(); const b = nodes.shift();
    const merged = new Node(a.freq + b.freq, null, a, b);
    let i = 0;
    while (i < nodes.length && (nodes[i].freq < merged.freq || (nodes[i].freq === merged.freq && nodes[i].order < merged.order))) i++;
    nodes.splice(i, 0, merged);
  }
  return nodes[0] || null;
}
function buildCodes(root) {
  const codes = {};
  function walk(node, prefix) {
    if (!node) return;
    if (node.char !== null) { codes[node.char] = prefix || '0'; return; }
    walk(node.left, prefix + '0'); walk(node.right, prefix + '1');
  }
  walk(root, '');
  return codes;
}
function encode(text, codes) {
  const out = [];
  for (const ch of text) {
    if (!(ch in codes)) throw new Error(`Нет кода для символа ${JSON.stringify(ch)}`);
    out.push(codes[ch]);
  }
  return out.join('');
}
function countFreq(text) { const freq = {}; for (const ch of text) freq[ch] = (freq[ch] || 0) + 1; return freq; }
function bytesNeeded(bitCount) { return Math.ceil(bitCount / 8); }
function escapeHtml(s) { return s.replace(/[&<>"']/g, c => ({ '&': '&amp;', '<': '&lt;', '>': '&gt;', '"': '&quot;', "'": '&#39;' }[c])); }
function reprChar(ch) { return JSON.stringify(ch); }
function layoutTree(root) {
  const positions = new Map(); let counter = 0;
  function visit(node, depth) {
    if (!node) return;
    visit(node.left, depth + 1);
    positions.set(node, { x: counter++, y: depth });
    visit(node.right, depth + 1);
  }
  visit(root, 0);
  return positions;
}
function collectChars(node) {
  if (node.char !== null) return new Set([node.char]);
  const s = new Set();
  if (node.left) for (const c of collectChars(node.left)) s.add(c);
  if (node.right) for (const c of collectChars(node.right)) s.add(c);
  return s;
}
function innerLabel(node) {
  const chars = [...collectChars(node)].sort(); const s = chars.join('');
  if (s.length <= 6) return s;
  return s.slice(0, 3) + '…' + s.slice(-2);
}
const SVG_NS = 'http://www.w3.org/2000/svg';
function renderTree(root) {
  const container = document.getElementById('treeContainer');
  container.innerHTML = '';
  if (!root) return;
  const positions = layoutTree(root);
  const NODE_W = 68, NODE_H = 50, GAP_X = 22, GAP_Y = 64, PAD = 30;
  let maxX = 0, maxY = 0;
  for (const p of positions.values()) { if (p.x > maxX) maxX = p.x; if (p.y > maxY) maxY = p.y; }
  const width = PAD * 2 + (maxX + 1) * NODE_W + maxX * GAP_X;
  const height = PAD * 2 + (maxY + 1) * NODE_H + maxY * GAP_Y;
  const svg = document.createElementNS(SVG_NS, 'svg');
  svg.setAttribute('viewBox', `0 0 ${width} ${height}`);
  svg.setAttribute('width', width); svg.setAttribute('height', height);
  function pos(node) {
    const p = positions.get(node);
    return { x: PAD + p.x * (NODE_W + GAP_X) + NODE_W / 2, y: PAD + p.y * (NODE_H + GAP_Y) + NODE_H / 2 };
  }
  for (const [node] of positions) {
    const a = pos(node);
    for (const [child, label] of [[node.left, '0'], [node.right, '1']]) {
      if (!child) continue;
      const b = pos(child);
      const line = document.createElementNS(SVG_NS, 'line');
      line.setAttribute('x1', a.x); line.setAttribute('y1', a.y + NODE_H / 2);
      line.setAttribute('x2', b.x); line.setAttribute('y2', b.y - NODE_H / 2);
      line.setAttribute('stroke', '#3a4051'); line.setAttribute('stroke-width', '1.5');
      svg.appendChild(line);
      const t = document.createElementNS(SVG_NS, 'text');
      t.setAttribute('x', (a.x + b.x) / 2); t.setAttribute('y', (a.y + b.y) / 2);
      t.setAttribute('fill', '#6aa9ff'); t.setAttribute('font-size', '12');
      t.setAttribute('font-family', 'monospace'); t.setAttribute('text-anchor', 'middle');
      t.setAttribute('dominant-baseline', 'middle'); t.textContent = label;
      svg.appendChild(t);
    }
  }
  for (const [node] of positions) {
    const { x, y } = pos(node);
    const isLeaf = node.char !== null;
    const rect = document.createElementNS(SVG_NS, 'rect');
    rect.setAttribute('x', x - NODE_W / 2); rect.setAttribute('y', y - NODE_H / 2);
    rect.setAttribute('width', NODE_W); rect.setAttribute('height', NODE_H); rect.setAttribute('rx', 8);
    rect.setAttribute('fill', isLeaf ? '#3a3320' : '#1e2b3f');
    rect.setAttribute('stroke', isLeaf ? '#7a6a3a' : '#3a5a80');
    rect.setAttribute('stroke-width', '1'); svg.appendChild(rect);
    const t1 = document.createElementNS(SVG_NS, 'text');
    t1.setAttribute('x', x); t1.setAttribute('y', y - 6);
    t1.setAttribute('fill', isLeaf ? '#fde68a' : '#93c5fd');
    t1.setAttribute('font-size', '13'); t1.setAttribute('font-family', 'monospace');
    t1.setAttribute('text-anchor', 'middle'); t1.setAttribute('dominant-baseline', 'middle');
    t1.textContent = isLeaf ? node.char : innerLabel(node); svg.appendChild(t1);
    const t2 = document.createElementNS(SVG_NS, 'text');
    t2.setAttribute('x', x); t2.setAttribute('y', y + 12);
    t2.setAttribute('fill', '#8b93a7'); t2.setAttribute('font-size', '11');
    t2.setAttribute('font-family', 'monospace'); t2.setAttribute('text-anchor', 'middle');
    t2.setAttribute('dominant-baseline', 'middle'); t2.textContent = node.freq;
    svg.appendChild(t2);
  }
  container.appendChild(svg);
}
function initHaffman() {
  const LAWS = [
  'первый закон: Робот не может причинить вред человеку или своим бездействием допустить, чтобы человеку был причинён вред.',
  'второй закон: Робот должен повиноваться всем приказам, которые даёт человек, кроме тех случаев, когда эти приказы противоречат Первому закону.',
  'третий закон: Робот должен заботиться о своей безопасности в той мере, в которой это не противоречит Первому или Второму законам.'
];

document.getElementById('exampleBtn').addEventListener('click', () => {
  const randomLaw = LAWS[Math.floor(Math.random() * LAWS.length)];
  textInput.value = randomLaw;
  encodeAction();
});
  const textInput = document.getElementById('textInput');
  const encodeBtn = document.getElementById('encodeBtn');
  const clearBtn = document.getElementById('clearBtn');
  const errorBox = document.getElementById('error');
  const resultSec = document.getElementById('result');
  const treeSec = document.getElementById('treeSection');
  if (!textInput) return;
  function showError(msg) { errorBox.textContent = msg; errorBox.classList.remove('hidden'); }
  function hideError() { errorBox.classList.add('hidden'); }
  function resetOutput() {
    resultSec.classList.add('hidden'); treeSec.classList.add('hidden');
    document.getElementById('treeContainer').innerHTML = '';
  }
  function encodeAction() {
    hideError(); resetOutput();
    const text = textInput.value;
    if (!text) { showError('Введите текст.'); return; }
    let originalByteArr;
    try { originalByteArr = toCp1251Bytes(text); } catch (e) { showError(e.message); return; }
    const originalBits = bytesToBits(originalByteArr);
    const originalBytes = originalByteArr.length;
    const freq = countFreq(text);
    nodeCounter = 0;
    const root = buildHuffman(freq);
    const codes = buildCodes(root);
    let encodedBits;
    try { encodedBits = encode(text, codes); } catch (e) { showError(e.message); return; }
    const encodedBytes = bytesNeeded(encodedBits.length);
    document.getElementById('originalBits').textContent = originalBits;
    document.getElementById('encodedBits').textContent = encodedBits;
    document.getElementById('statOrigBits').textContent = originalBits.length;
    document.getElementById('statOrigBytes').textContent = `${originalBytes} байт (CP1251)`;
    document.getElementById('statEncBits').textContent = encodedBits.length;
    document.getElementById('statEncBytes').textContent = `${encodedBytes} байт (с округлением)`;
    const ratio = encodedBytes / originalBytes * 100;
    const saved = originalBytes - encodedBytes;
    const savedPct = saved / originalBytes * 100;
    document.getElementById('statRatio').textContent = ratio.toFixed(1) + '%';
    document.getElementById('statSaved').textContent =
      saved > 0 ? `экономия ${saved} байт (${savedPct.toFixed(1)}%)`
                : (saved === 0 ? 'без изменений' : `перерасход ${-saved} байт`);
    const tbody = document.querySelector('#freqTable tbody');
    tbody.innerHTML = '';
    const sorted = Object.entries(freq).sort((a, b) => { if (a[1] !== b[1]) return b[1] - a[1]; return a[0].localeCompare(b[0]); });
    for (const [ch, f] of sorted) {
      const tr = document.createElement('tr');
      tr.innerHTML = `<td class="ch">${escapeHtml(reprChar(ch))}</td><td class="num">${f}</td><td class="code">${codes[ch]}</td>`;
      tbody.appendChild(tr);
    }
    resultSec.classList.remove('hidden');
    renderTree(root);
    treeSec.classList.remove('hidden');
  }
  encodeBtn.addEventListener('click', encodeAction);
  clearBtn.addEventListener('click', () => { textInput.value = ''; hideError(); resetOutput(); });
  document.addEventListener('keydown', (e) => {
    if ((e.ctrlKey || e.metaKey) && e.key === 'Enter') { e.preventDefault(); encodeAction(); }
  });
  textInput.focus();
}
if (document.readyState === 'loading') { document.addEventListener('DOMContentLoaded', initHaffman); }
else { initHaffman(); }