/**
 * Backup & Diff viewer module for ObsiGate.
 *
 * Provides a modal UI to browse file backups, compare versions with
 * a unified diff view, and restore previous versions.
 *
 * Usage:
 *   import { openBackupViewer } from './backups.js';
 *   openBackupViewer(vaultName, filePath);
 */

import { api } from './auth.js';
import { showToast } from './ui.js';
import { refreshSidebarTreePreservingState } from './sidebar.js';
import { safeCreateIcons } from './utils.js';

// Global handler: same pattern as Graph View's initGraphView()
document.addEventListener('click', function(e) {
  const btn = e.target.closest('#backup-close');
  if (btn && state.overlay) close();
});

// ---------------------------------------------------------------------------
// State
// ---------------------------------------------------------------------------

const state = {
  vault: null,
  path: null,
  backups: [],
  overlay: null,
  leftVersion: null,
  rightVersion: null,
  diffText: '',
  diffLeft: '',
  diffRight: '',
  diffMode: 'unified',  // 'unified' or 'sidebyside'
};

// ---------------------------------------------------------------------------
// Public API
// ---------------------------------------------------------------------------

export async function openBackupViewer(vault, path) {
  state.vault = vault;
  state.path = path;
  state.backups = [];
  state.leftVersion = null;
  state.rightVersion = null;
  state.diffText = '';

  const overlay = createOverlay();
  document.body.appendChild(overlay);
  state.overlay = overlay;
  requestAnimationFrame(() => overlay.classList.add('active'));

  setBody(renderLoading());

  try {
    const data = await api(`/api/file/${encodeURIComponent(vault)}/backups?path=${encodeURIComponent(path)}`);
    state.backups = data.backups || [];
  } catch (err) {
    const msg = err?.detail || err?.message || 'Erreur inconnue';
    setBody(renderError(`Erreur API: ${msg}`));
    return;
  }

  if (state.backups.length === 0) {
    setBody(renderEmpty());
    return;
  }

  state.leftVersion = state.backups[0].timestamp;
  state.rightVersion = null;
  renderMainView();
  await loadDiff();
}

// ---------------------------------------------------------------------------
// DOM helpers
// ---------------------------------------------------------------------------

function createOverlay() {
  const overlay = document.createElement('div');
  overlay.className = 'obsigate-modal-overlay backup-viewer-overlay';
  overlay.addEventListener('click', (e) => {
    if (e.target === overlay) close();
  });

  const panel = document.createElement('div');
  panel.className = 'backup-viewer-panel';
  panel.id = 'backup-viewer-panel';
  overlay.appendChild(panel);

  // Close button OUTSIDE the panel — never touched by innerHTML, always present
  const closeBtn = document.createElement('button');
  closeBtn.className = 'editor-btn backup-close-btn';
  closeBtn.id = 'backup-close';
  closeBtn.title = 'Fermer';
  closeBtn.style.cssText = 'position:absolute;top:12px;right:12px;z-index:1002;flex-shrink:0';
  closeBtn.innerHTML = '<i data-lucide="x" style="width:15px;height:15px"></i>';
  closeBtn.addEventListener('click', (e) => {
    e.stopPropagation();
    close();
  });
  overlay.appendChild(closeBtn);

  // Keyboard: Escape closes the viewer
  _escHandler = (e) => {
    if (e.key === 'Escape' && state.overlay) close();
  };
  document.addEventListener('keydown', _escHandler);

  return overlay;
}

/** Replace panel content. Close button is static in the overlay, never replaced. */
function setBody(html) {
  const panel = document.getElementById('backup-viewer-panel');
  if (panel) panel.innerHTML = html;
}

let _escHandler = null;

function close() {
  if (!state.overlay) return;
  if (_escHandler) {
    document.removeEventListener('keydown', _escHandler);
    _escHandler = null;
  }
  state.overlay.classList.remove('active');
  setTimeout(() => {
    if (state.overlay) state.overlay.remove();
    state.overlay = null;
  }, 200);
}

// ---------------------------------------------------------------------------
// Rendering
// ---------------------------------------------------------------------------

function renderLoading() {
  return `
    <div class="backup-header">
      <h3>Backups</h3>
    </div>
    <div class="backup-body">
      <div class="tree-loading" style="padding:2rem;text-align:center">
        <div class="loading-spinner" style="width:24px;height:24px;border-width:3px;margin:0 auto"></div>
        <p style="margin-top:0.75rem;color:var(--text-muted);font-size:0.85rem">Chargement des backups...</p>
      </div>
    </div>`;
}

function renderError(msg) {
  return \`
    <div class="backup-header">
      <h3>Backups</h3>
    </div>
    <div class="backup-body" style="text-align:center;padding:2rem;color:var(--text-muted)">
      <p>${escapeHtml(msg)}</p>
    </div>`;
}

function renderEmpty() {
  return \`
    <div class="backup-header">
      <h3>Backups — \${escapeHtml(state.path)}</h3>
    </div>
    <div class="backup-body" style="text-align:center;padding:2rem;color:var(--text-muted)">
      <p>Aucun backup disponible pour ce fichier.</p>
      <p style="font-size:0.8rem;margin-top:0.5rem">Les backups sont créés automatiquement avant chaque modification.</p>
    </div>`;
}

function renderMainView() {
  const b = state.backups;
  const leftOpts = b.map(bk => {
    const sel = bk.timestamp === state.leftVersion ? 'selected' : '';
    return `<option value="${bk.timestamp}" ${sel}>${formatTimestamp(bk.timestamp)} (${formatSize(bk.size)})</option>`;
  }).join('');

  const rightOpts = [
    `<option value="current" ${state.rightVersion === null ? 'selected' : ''}>Version actuelle</option>`,
    ...b.map(bk => {
      const sel = bk.timestamp === state.rightVersion ? 'selected' : '';
      return `<option value="${bk.timestamp}" ${sel}>${formatTimestamp(bk.timestamp)} (${formatSize(bk.size)})</option>`;
    }),
  ].join('');

  const html = `
    <div class="backup-header">
      <div class="backup-header-left">
        <h3>Backups</h3>
        <span class="backup-file-path">${escapeHtml(state.path)}</span>
      </div>
      <div class="backup-header-right">
        <span class="backup-count">\${b.length} backup\${b.length > 1 ? 's' : ''}</span>
      </div>
    </div>

    <div class="backup-toolbar">
      <div class="backup-selector-group">
        <label>Comparer :</label>
        <select class="backup-select" id="backup-left-select">${leftOpts}</select>
      </div>
      <span class="backup-vs-label">vs</span>
      <div class="backup-selector-group">
        <select class="backup-select" id="backup-right-select">${rightOpts}</select>
      </div>
      <button class="backup-restore-btn" id="backup-restore-btn" title="Restaurer la version de gauche">
        <i data-lucide="rotate-ccw" class="icon-sm"></i> Restaurer
      </button>
      <button class="backup-diff-mode-btn" id="backup-diff-mode-btn" title="Vue cote a cote">
        <i data-lucide="columns-2" class="icon-sm"></i> Cote-a-cote
      </button>
    </div>

    <div class="backup-diff-container" id="backup-diff-container">
      <div class="backup-diff-loading">
        <div class="loading-spinner" style="width:24px;height:24px;border-width:3px;margin:0 auto"></div>
      </div>
    </div>

    <div class="backup-footer">
      <span class="backup-footer-hint">Backups créés lors de la sauvegarde manuelle (Ctrl+S)</span>
    </div>`;

  setBody(html);
  bindEvents();
}

// ---------------------------------------------------------------------------
// Event bindings
// ---------------------------------------------------------------------------

function bindEvents() {
  const leftSelect = document.getElementById('backup-left-select');
  leftSelect?.addEventListener('change', async () => {
    state.leftVersion = parseInt(leftSelect.value);
    await loadDiff();
  });

  const rightSelect = document.getElementById('backup-right-select');
  rightSelect?.addEventListener('change', async () => {
    const val = rightSelect.value;
    state.rightVersion = val === 'current' ? null : parseInt(val);
    await loadDiff();
  });

  const restoreBtn = document.getElementById('backup-restore-btn');
  restoreBtn?.addEventListener('click', async () => {
    await restoreBackup();
  });

  // Side-by-side toggle
  const modeBtn = document.getElementById('backup-diff-mode-btn');
  modeBtn?.addEventListener('click', () => {
    state.diffMode = state.diffMode === 'sidebyside' ? 'unified' : 'sidebyside';
    const container = document.getElementById('backup-diff-container');
    if (container) {
      container.innerHTML = state.diffMode === 'sidebyside'
        ? renderDiffSideBySide(state.diffLeft, state.diffRight)
        : renderDiff(state.diffText);
    }
    // Update icon and text
    const icon = modeBtn.querySelector('i');
    if (icon) icon.setAttribute('data-lucide', state.diffMode === 'sidebyside' ? 'columns-2' : 'align-justify');
    modeBtn.childNodes.forEach(n => { if (n.nodeType === 3) n.remove(); });
    modeBtn.appendChild(document.createTextNode(state.diffMode === 'sidebyside' ? ' Unifiee' : ' Cote-a-cote'));
    safeCreateIcons();
  });
}

// ---------------------------------------------------------------------------
// Data loading
// ---------------------------------------------------------------------------

async function loadDiff() {
  const container = document.getElementById('backup-diff-container');
  if (!container) return;

  container.innerHTML = `
    <div class="backup-diff-loading">
      <div class="loading-spinner" style="width:24px;height:24px;border-width:3px;margin:0 auto"></div>
    </div>`;

  let url = `/api/file/${encodeURIComponent(state.vault)}/diff?path=${encodeURIComponent(state.path)}&version=${state.leftVersion}`;
  if (state.rightVersion !== null) {
    url += `&compare_with=${state.rightVersion}`;
  }

  try {
    const data = await api(url);
    state.diffText = data.diff || '';
    state.diffLeft = data.left_content || '';
    state.diffRight = data.right_content || '';
    container.innerHTML = state.diffMode === 'sidebyside'
      ? renderDiffSideBySide(state.diffLeft, state.diffRight)
      : renderDiff(state.diffText);
  } catch (err) {
    container.innerHTML = `<div class="backup-diff-error">Erreur: ${escapeHtml(err?.detail || err?.message || 'Unknown')}</div>`;
  }
}

async function restoreBackup() {
  if (!state.leftVersion) return;

  const confirmed = confirm(
    `Restaurer "${state.path}" à la version du ${formatTimestamp(state.leftVersion)} ?\n\n` +
    `La version actuelle sera sauvegardée avant la restauration.`
  );
  if (!confirmed) return;

  const restoreBtn = document.getElementById('backup-restore-btn');
  if (restoreBtn) {
    restoreBtn.disabled = true;
    restoreBtn.textContent = 'Restauration...';
  }

  try {
    const resp = await api(
      `/api/file/${encodeURIComponent(state.vault)}/restore?path=${encodeURIComponent(state.path)}`,
      {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ version: state.leftVersion }),
      }
    );

    if (resp && resp.success) {
      showToast('Fichier restauré avec succès', 'success');
      await refreshSidebarTreePreservingState();
      close();
      if (typeof TabManager !== 'undefined' && TabManager.reloadCurrent) {
        TabManager.reloadCurrent();
      }
    } else {
      showToast('Échec de la restauration', 'error');
    }
  } catch (err) {
    showToast(`Erreur: ${err?.detail || err?.message || 'Unknown'}`, 'error');
  } finally {
    if (restoreBtn) {
      restoreBtn.disabled = false;
      restoreBtn.innerHTML = '<i data-lucide="rotate-ccw" class="icon-sm"></i> Restaurer';
      safeCreateIcons();
    }
  }
}

// ---------------------------------------------------------------------------
// Diff rendering
// ---------------------------------------------------------------------------

function renderDiff(diffText) {
  if (!diffText) {
    return '<div class="backup-diff-empty">Aucune différence — les versions sont identiques.</div>';
  }

  let html = '<div class="backup-diff-output"><table class="backup-diff-table">';
  const lines = diffText.split('\n');

  for (const line of lines) {
    let cssClass = 'diff-context';
    let prefix = ' ';
    if (line.startsWith('@@')) { cssClass = 'diff-hunk'; prefix = ''; }
    else if (line.startsWith('+')) { cssClass = 'diff-add'; prefix = '+'; }
    else if (line.startsWith('-')) { cssClass = 'diff-del'; prefix = '-'; }
    else if (line.startsWith('---') || line.startsWith('+++')) { cssClass = 'diff-header-line'; prefix = ''; }

    html += `<tr class="${cssClass}"><td class="diff-prefix">${prefix}</td><td class="diff-content"><pre>${escapeHtml(line)}</pre></td></tr>`;
  }

  html += '</table></div>';
  return html;
}

// ---------------------------------------------------------------------------
// Side-by-side diff rendering
// ---------------------------------------------------------------------------

function renderDiffSideBySide(leftText, rightText) {
  if (!leftText && !rightText) {
    return '<div class="backup-diff-empty">Aucune différence — les versions sont identiques.</div>';
  }

  const leftLines = (leftText || '').split('\n');
  const rightLines = (rightText || '').split('\n');

  // Compute matching opcodes using difflib-style SequenceMatcher
  // We build two arrays of line groups: equal, delete (left-only), insert (right-only), replace
  const sm = new difflibSeqMatcher(leftLines, rightLines);
  const ops = sm.getOpcodes();

  let html = '<div class="backup-diff-output backup-diff-sidebyside"><table class="backup-diff-table sidebyside"><colgroup><col style="width:50%"><col style="width:50%"></colgroup><tbody>';

  for (const [tag, i1, i2, j1, j2] of ops) {
    if (tag === 'equal') {
      for (let k = 0; k < (i2 - i1); k++) {
        html += `<tr class="diff-context"><td class="diff-content sidebyside-left"><pre>${escapeHtml(leftLines[i1 + k])}</pre></td><td class="diff-content sidebyside-right"><pre>${escapeHtml(rightLines[j1 + k])}</pre></td></tr>`;
      }
    } else if (tag === 'delete') {
      for (let k = i1; k < i2; k++) {
        html += `<tr class="diff-del"><td class="diff-content sidebyside-left"><pre>${escapeHtml(leftLines[k])}</pre></td><td class="diff-content sidebyside-right diff-empty-cell"></td></tr>`;
      }
    } else if (tag === 'insert') {
      for (let k = j1; k < j2; k++) {
        html += `<tr class="diff-add"><td class="diff-content sidebyside-left diff-empty-cell"></td><td class="diff-content sidebyside-right"><pre>${escapeHtml(rightLines[k])}</pre></td></tr>`;
      }
    } else if (tag === 'replace') {
      const maxLen = Math.max(i2 - i1, j2 - j1);
      for (let k = 0; k < maxLen; k++) {
        const leftLine = (i1 + k < i2) ? escapeHtml(leftLines[i1 + k]) : '';
        const rightLine = (j1 + k < j2) ? escapeHtml(rightLines[j1 + k]) : '';
        const leftClass = (i1 + k < i2) ? 'diff-del' : 'diff-empty-cell';
        const rightClass = (j1 + k < j2) ? 'diff-add' : 'diff-empty-cell';
        html += `<tr><td class="diff-content sidebyside-left ${leftClass}"><pre>${leftLine}</pre></td><td class="diff-content sidebyside-right ${rightClass}"><pre>${rightLine}</pre></td></tr>`;
      }
    }
  }

  html += '</tbody></table></div>';
  return html;
}

// Minimal SequenceMatcher for line-based diff (no external deps)
class difflibSeqMatcher {
  constructor(a, b) {
    this.a = a;
    this.b = b;
  }
  getOpcodes() {
    // Simple LCS-based diff using dynamic programming
    const m = this.a.length, n = this.b.length;
    const dp = Array.from({length: m + 1}, () => new Array(n + 1).fill(0));
    for (let i = 1; i <= m; i++) {
      for (let j = 1; j <= n; j++) {
        if (this.a[i - 1] === this.b[j - 1]) dp[i][j] = dp[i - 1][j - 1] + 1;
        else dp[i][j] = Math.max(dp[i - 1][j], dp[i][j - 1]);
      }
    }
    // Backtrack to build opcodes
    const ops = [];
    let i = m, j = n;
    const equalStart = (i2, j2) => {
      let ei = i2, ej = j2;
      while (ei > 0 && ej > 0 && this.a[ei - 1] === this.b[ej - 1]) { ei--; ej--; }
      return [ei, ej];
    };
    while (i > 0 || j > 0) {
      if (i > 0 && j > 0 && this.a[i - 1] === this.b[j - 1]) {
        const [ei, ej] = equalStart(i, j);
        if (ei < i) ops.unshift(['equal', ei, i, ej, j]);
        i = ei; j = ej;
      } else if (j > 0 && (i === 0 || dp[i][j - 1] >= dp[i - 1][j])) {
        ops.unshift(['insert', i, i, j - 1, j]);
        j--;
      } else if (i > 0 && (j === 0 || dp[i][j - 1] < dp[i - 1][j])) {
        ops.unshift(['delete', i - 1, i, j, j]);
        i--;
      }
    }
    // Merge adjacent delete+insert into replace
    const merged = [];
    for (let k = 0; k < ops.length; k++) {
      if (merged.length > 0 && merged[merged.length - 1][0] === 'delete' && ops[k][0] === 'insert' &&
          merged[merged.length - 1][4] === ops[k][3]) {
        const del = merged.pop();
        merged.push(['replace', del[1], del[2], ops[k][3], ops[k][4]]);
      } else {
        merged.push(ops[k]);
      }
    }
    return merged;
  }
}

// ---------------------------------------------------------------------------
// Utility
// ---------------------------------------------------------------------------

function formatTimestamp(ts) {
  const d = new Date(ts * 1000);
  const pad = (n) => String(n).padStart(2, '0');
  return `${d.getFullYear()}-${pad(d.getMonth() + 1)}-${pad(d.getDate())} ${pad(d.getHours())}:${pad(d.getMinutes())}`;
}

function formatSize(bytes) {
  if (bytes < 1024) return bytes + ' o';
  if (bytes < 1024 * 1024) return (bytes / 1024).toFixed(1) + ' Ko';
  return (bytes / (1024 * 1024)).toFixed(1) + ' Mo';
}

function escapeHtml(str) {
  const div = document.createElement('div');
  div.textContent = str;
  return div.innerHTML;
}