import { NextResponse } from 'next/server'
import { promises as fs } from 'fs'
import { auth } from '@/auth'
import { prisma } from '@/lib/prisma'
import JSZip from 'jszip'
import DOMPurify from 'isomorphic-dompurify'
import type { BrainstormIdea, Note } from '@prisma/client'

function htmlToMarkdown(html: string): string {
  if (!html) return ''
  let md = html
    .replace(/<h1>(.*?)<\/h1>/gi, '# $1\n\n')
    .replace(/<h2>(.*?)<\/h2>/gi, '## $1\n\n')
    .replace(/<h3>(.*?)<\/h3>/gi, '### $1\n\n')
    .replace(/<strong>(.*?)<\/strong>/gi, '**$1**')
    .replace(/<em>(.*?)<\/em>/gi, '*$1*')
    .replace(/<p>(.*?)<\/p>/gi, '$1\n\n')
    .replace(/<li>(.*?)<\/li>/gi, '- $1\n')
    .replace(/<ul>/gi, '')
    .replace(/<\/ul>/gi, '\n')
    .replace(/<ol>/gi, '')
    .replace(/<\/ol>/gi, '\n')
    .replace(/<br\s*\/?>/gi, '\n')
  md = md.replace(/<[^>]*>/g, '')
  return md.trim()
}

function sanitizeFilename(name: string): string {
  return name.replace(/[^a-zA-Z0-9_\-\s]/g, '').trim() || 'Untitled'
}

function uniqueBaseName(title: string, id: string): string {
  return `${sanitizeFilename(title)}--${id.slice(0, 8)}`
}

function serializeBrainstormIdeas(ideas: BrainstormIdea[]): string {
  const rendered = new Set<string>()
  const ideaIds = new Set(ideas.map((i) => i.id))

  const formatIdea = (idea: BrainstormIdea, depth: number): string => {
    if (rendered.has(idea.id)) return ''
    rendered.add(idea.id)
    const indent = '  '.repeat(depth)
    const pos =
      idea.positionX != null && idea.positionY != null
        ? ` (pos: ${idea.positionX}, ${idea.positionY})`
        : ''
    const conn = idea.connectionToSeed ? ` → seed: ${idea.connectionToSeed}` : ''
    const star = idea.isStarred ? ' ★' : ''
    const kind = idea.createdByType || 'idea'
    let block = `${indent}- **[${kind}]** ${idea.title}${star}${conn}${pos}\n`
    if (idea.description?.trim()) {
      block += `${indent}  ${idea.description.trim()}\n`
    }
    for (const child of ideas.filter((i) => i.parentIdeaId === idea.id)) {
      block += formatIdea(child, depth + 1)
    }
    return block
  }

  let md = ''
  const roots = ideas.filter(
    (i) => !i.parentIdeaId || !ideaIds.has(i.parentIdeaId)
  )
  for (const root of roots) {
    md += formatIdea(root, 0)
  }
  for (const idea of ideas) {
    if (!rendered.has(idea.id)) {
      md += formatIdea(idea, 0)
    }
  }
  return md || '_No ideas in this session._\n'
}

function resolveNoteFolder(
  zip: JSZip,
  note: Note,
  notebookName: string,
  activeNotebookFolders: Map<string, JSZip>
): JSZip {
  const notebookSegment = sanitizeFilename(notebookName)
  if (note.isArchived) {
    return zip.folder(`archive/${notebookSegment}`)!
  }
  if (note.trashedAt) {
    return zip.folder(`trash/${notebookSegment}`)!
  }
  let folder = activeNotebookFolders.get(notebookSegment)
  if (!folder) {
    folder = zip.folder(notebookSegment)!
    activeNotebookFolders.set(notebookSegment, folder)
  }
  return folder
}

export async function GET() {
  try {
    const session = await auth()
    if (!session?.user?.id) {
      return NextResponse.json({ success: false, error: 'Unauthorized' }, { status: 401 })
    }

    const userId = session.user.id
    const zip = new JSZip()

    const [allNotes, notebooks, labels, attachments, brainstorms] = await Promise.all([
      prisma.note.findMany({
        where: { userId },
        orderBy: { createdAt: 'desc' },
      }),
      prisma.notebook.findMany({
        where: { userId },
        orderBy: { name: 'asc' },
      }),
      prisma.label.findMany({
        where: { userId },
        include: { notes: { select: { id: true } } },
      }),
      prisma.noteAttachment.findMany({
        where: { note: { userId } },
      }),
      prisma.brainstormSession.findMany({
        where: { userId },
        include: { ideas: true },
        orderBy: { createdAt: 'desc' },
      }),
    ])

    const notebookMap = new Map(notebooks.map((nb) => [nb.id, nb.name]))

    const noteLabelMap = new Map<string, string[]>()
    for (const label of labels) {
      for (const note of label.notes) {
        const arr = noteLabelMap.get(note.id) || []
        arr.push(label.name)
        noteLabelMap.set(note.id, arr)
      }
    }

    const metadataJson = {
      version: '3.0.0',
      exportDate: new Date().toISOString(),
      user: {
        id: userId,
        email: session.user.email ?? '',
        name: session.user.name ?? '',
      },
      notebooks: notebooks.map((n) => ({ id: n.id, name: n.name, color: n.color })),
      labels: labels.map((l) => ({ id: l.id, name: l.name, color: l.color })),
      notes: allNotes.map((n) => ({
        id: n.id,
        title: n.title,
        isPinned: n.isPinned,
        isArchived: n.isArchived,
        trashedAt: n.trashedAt,
        createdAt: n.createdAt,
        updatedAt: n.updatedAt,
        notebookId: n.notebookId,
        labels: noteLabelMap.get(n.id) || [],
      })),
      brainstorms: brainstorms.map((b) => ({
        id: b.id,
        title: b.title,
        createdAt: b.createdAt,
        ideasCount: b.ideas.length,
      })),
    }
    zip.file('metadata.json', JSON.stringify(metadataJson, null, 2))

    const activeNotebookFolders = new Map<string, JSZip>()

    for (const note of allNotes) {
      const notebookName = note.notebookId
        ? notebookMap.get(note.notebookId) || 'Unsorted'
        : 'Unsorted'
      const folder = resolveNoteFolder(zip, note, notebookName, activeNotebookFolders)
      const noteTags = noteLabelMap.get(note.id) || []
      const fileBase = uniqueBaseName(note.title || 'Untitled Note', note.id)

      let mdContent = '---\n'
      mdContent += `title: "${note.title || 'Untitled'}"\n`
      mdContent += `id: "${note.id}"\n`
      mdContent += `createdAt: "${note.createdAt.toISOString()}"\n`
      mdContent += `updatedAt: "${note.updatedAt.toISOString()}"\n`
      mdContent += `tags: [${noteTags.map((t) => `"${t}"`).join(', ')}]\n`
      mdContent += `notebook: "${notebookName}"\n`
      mdContent += `pinned: ${note.isPinned}\n`
      mdContent += `archived: ${note.isArchived}\n`
      mdContent += '---\n\n'
      mdContent += htmlToMarkdown(note.content || '')

      folder.file(`${fileBase}.md`, mdContent)
      folder.file(`${fileBase}.json`, JSON.stringify(note, null, 2))
    }

    const canvasFolder = zip.folder('canvases')!
    for (const brainstorm of brainstorms) {
      const fileBase = uniqueBaseName(brainstorm.title || 'Untitled Brainstorm', brainstorm.id)

      let canvasMd = `# Brainstorm Canvas: ${brainstorm.title || 'Untitled'}\n\n`
      canvasMd += `- **Created At:** ${brainstorm.createdAt.toISOString()}\n`
      canvasMd += `- **Updated At:** ${brainstorm.updatedAt.toISOString()}\n`
      canvasMd += `- **Ideas Count:** ${brainstorm.ideas.length}\n\n`
      canvasMd += `## Ideas and Connections\n\n`
      canvasMd += serializeBrainstormIdeas(brainstorm.ideas)

      canvasFolder.file(`${fileBase}.md`, canvasMd)
      canvasFolder.file(`${fileBase}.json`, JSON.stringify(brainstorm, null, 2))
    }

    const attachmentsFolder = zip.folder('attachments')!
    for (const attachment of attachments) {
      try {
        const fileContent = await fs.readFile(attachment.filePath)
        const safeName = `${attachment.id.slice(0, 8)}-${sanitizeFilename(attachment.fileName)}`
        attachmentsFolder.file(safeName, fileContent)
      } catch (err) {
        console.error(`[Export] Failed to pack attachment file: ${attachment.filePath}`, err)
      }
    }

    const offlineNotes = allNotes.map((n) => ({
      title: n.title || 'Untitled Note',
      notebook: n.notebookId ? notebookMap.get(n.notebookId) || 'Unsorted' : 'Unsorted',
      tags: noteLabelMap.get(n.id) || [],
      content: DOMPurify.sanitize(n.content || ''),
      createdAt: n.createdAt.toISOString(),
      updatedAt: n.updatedAt.toISOString(),
      archived: n.isArchived,
      trashed: n.trashedAt !== null,
    }))

    const offlineCanvases = brainstorms.map((b) => ({
      title: b.title || 'Untitled Brainstorm',
      createdAt: b.createdAt.toISOString(),
      ideas: b.ideas.map((i) => ({
        title: i.title,
        description: i.description,
        kind: i.createdByType || 'idea',
        x: i.positionX,
        y: i.positionY,
        isStarred: i.isStarred,
        connectionToSeed: i.connectionToSeed,
        parentIdeaId: i.parentIdeaId,
      })),
    }))

    const indexHtml = `<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Memento Workspace Export Browser</title>
  <style>
    :root {
      --bg: #F8F9FA;
      --card-bg: #FFFFFF;
      --border: #E9ECEF;
      --text: #212529;
      --text-muted: #6C757D;
      --primary: #1C1C1C;
      --rose: #FFF5F5;
      --rose-border: #FFE3E3;
      --accent: #E9ECEF;
    }
    @media (prefers-color-scheme: dark) {
      :root {
        --bg: #121212;
        --card-bg: #1E1E1E;
        --border: #2D2D2D;
        --text: #F8F9FA;
        --text-muted: #ADB5BD;
        --primary: #FFFFFF;
        --rose: #2D1A1A;
        --rose-border: #4D2626;
        --accent: #2D2D2D;
      }
    }
    body {
      font-family: system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
      margin: 0;
      padding: 0;
      background-color: var(--bg);
      color: var(--text);
      display: flex;
      height: 100vh;
      overflow: hidden;
    }
    #sidebar {
      width: 320px;
      border-right: 1px solid var(--border);
      background-color: var(--card-bg);
      display: flex;
      flex-direction: column;
      height: 100%;
      flex-shrink: 0;
    }
    #sidebar-header { padding: 24px; border-bottom: 1px solid var(--border); }
    #sidebar-header h1 { font-size: 20px; margin: 0; font-weight: 700; }
    #sidebar-header p { font-size: 11px; color: var(--text-muted); margin: 4px 0 0 0; }
    #search-bar { margin: 16px 24px; }
    #search-input {
      width: 80%;
      padding: 10px 16px;
      border-radius: 12px;
      border: 1px solid var(--border);
      background-color: var(--bg);
      color: var(--text);
      font-size: 13px;
      outline: none;
    }
    #sidebar-list { flex-grow: 1; overflow-y: auto; padding: 0 16px 24px 16px; }
    .section-title {
      font-size: 10px;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.1em;
      color: var(--text-muted);
      margin: 20px 8px 8px 8px;
    }
    .item-card {
      padding: 12px 16px;
      border-radius: 12px;
      cursor: pointer;
      margin-bottom: 4px;
      border: 1px solid transparent;
    }
    .item-card:hover { background-color: var(--bg); }
    .item-card.active { background-color: var(--accent); border-color: var(--border); }
    .item-card h3 { font-size: 13px; font-weight: 600; margin: 0; }
    .item-card p {
      font-size: 11px;
      color: var(--text-muted);
      margin: 4px 0 0 0;
      display: flex;
      justify-content: space-between;
    }
    #content-area { flex-grow: 1; padding: 48px; overflow-y: auto; display: flex; flex-direction: column; }
    #welcome-screen { margin: auto; text-align: center; max-width: 400px; }
    #welcome-screen h2 { font-size: 28px; margin-bottom: 8px; }
    #welcome-screen p { color: var(--text-muted); font-size: 14px; line-height: 1.6; }
    #detail-container { display: none; max-width: 800px; width: 100%; margin: 0 auto; }
    .meta-badge {
      display: inline-block;
      padding: 4px 8px;
      border-radius: 6px;
      font-size: 10px;
      font-weight: 700;
      text-transform: uppercase;
      background-color: var(--border);
      color: var(--text-muted);
      margin-right: 8px;
    }
    #detail-header h2 { font-size: 36px; margin: 16px 0 8px 0; font-weight: 700; }
    #detail-header p {
      font-size: 12px;
      color: var(--text-muted);
      margin: 0 0 24px 0;
      border-bottom: 1px solid var(--border);
      padding-bottom: 16px;
    }
    #detail-body { font-size: 15px; line-height: 1.8; }
    .canvas-node {
      padding: 12px 16px;
      border-radius: 12px;
      border: 1px solid var(--border);
      margin-bottom: 8px;
      background-color: var(--card-bg);
      font-size: 13px;
    }
    .starred-node { background-color: var(--rose); border-color: var(--rose-border); }
  </style>
</head>
<body>
  <div id="sidebar">
    <div id="sidebar-header">
      <h1>Memento</h1>
      <p>Offline Workspace Export</p>
    </div>
    <div id="search-bar">
      <input type="text" id="search-input" placeholder="Search notes..." oninput="filterItems()">
    </div>
    <div id="sidebar-list">
      <div class="section-title">Notebooks & Notes</div>
      <div id="notes-list"></div>
      <div class="section-title">Canvases</div>
      <div id="canvases-list"></div>
    </div>
  </div>
  <div id="content-area">
    <div id="welcome-screen">
      <h2>Welcome Back</h2>
      <p>Explore your entire workspace offline. Use the sidebar to search and select your notes and canvases.</p>
    </div>
    <div id="detail-container">
      <div id="detail-header">
        <span id="notebook-badge" class="meta-badge">Notebook</span>
        <span id="date-badge" class="meta-badge">Date</span>
        <h2 id="note-title">Title</h2>
        <p id="note-meta">Meta description</p>
      </div>
      <div id="detail-body">Content</div>
    </div>
  </div>
  <script>
    const notes = ${JSON.stringify(offlineNotes)};
    const canvases = ${JSON.stringify(offlineCanvases)};
    const notesList = document.getElementById('notes-list');
    const canvasesList = document.getElementById('canvases-list');
    const welcomeScreen = document.getElementById('welcome-screen');
    const detailContainer = document.getElementById('detail-container');
    const noteTitle = document.getElementById('note-title');
    const dateBadge = document.getElementById('date-badge');
    const notebookBadge = document.getElementById('notebook-badge');
    const noteMeta = document.getElementById('note-meta');
    const detailBody = document.getElementById('detail-body');
    let activeIndex = -1;
    let activeType = '';

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

    function renderList() {
      notesList.innerHTML = notes.map((n, i) => \`
        <div class="item-card \${activeType === 'note' && activeIndex === i ? 'active' : ''}" data-type="note" data-index="\${i}" onclick="selectItem('note', \${i})">
          <h3>\${escapeHtml(n.title)}</h3>
          <p><span>\${escapeHtml(n.notebook)}</span> <span>\${new Date(n.updatedAt).toLocaleDateString()}</span></p>
        </div>
      \`).join('');
      canvasesList.innerHTML = canvases.map((c, i) => \`
        <div class="item-card \${activeType === 'canvas' && activeIndex === i ? 'active' : ''}" data-type="canvas" data-index="\${i}" onclick="selectItem('canvas', \${i})">
          <h3>\${escapeHtml(c.title)}</h3>
          <p><span>Canvas</span> <span>\${new Date(c.createdAt).toLocaleDateString()}</span></p>
        </div>
      \`).join('');
    }

    function selectItem(type, index) {
      activeIndex = index;
      activeType = type;
      renderList();
      welcomeScreen.style.display = 'none';
      detailContainer.style.display = 'block';
      if (type === 'note') {
        const note = notes[index];
        notebookBadge.innerText = note.notebook;
        dateBadge.innerText = new Date(note.updatedAt).toLocaleDateString();
        noteTitle.innerText = note.title;
        noteMeta.innerText = 'Created: ' + new Date(note.createdAt).toLocaleString() + ' | Tags: ' + (note.tags.join(', ') || 'None');
        detailBody.innerHTML = note.content;
      } else {
        const canvas = canvases[index];
        notebookBadge.innerText = 'Canvas';
        dateBadge.innerText = new Date(canvas.createdAt).toLocaleDateString();
        noteTitle.innerText = canvas.title;
        noteMeta.innerText = 'Total Ideas: ' + canvas.ideas.length;
        let nodesHtml = '<div style="margin-top: 24px;">';
        canvas.ideas.forEach(idea => {
          const pos = idea.x != null && idea.y != null ? ' (' + idea.x + ', ' + idea.y + ')' : '';
          const conn = idea.connectionToSeed ? ' | ' + escapeHtml(idea.connectionToSeed) : '';
          nodesHtml += '<div class="canvas-node' + (idea.isStarred ? ' starred-node' : '') + '">' +
            '<strong>[' + escapeHtml((idea.kind || 'idea').toUpperCase()) + ']</strong> ' + escapeHtml(idea.title) +
            (idea.description ? '<div style="margin-top:6px">' + escapeHtml(idea.description) + '</div>' : '') +
            '<div style="font-size: 10px; color: var(--text-muted); margin-top: 4px;">Position' + pos + conn + '</div></div>';
        });
        nodesHtml += '</div>';
        detailBody.innerHTML = nodesHtml;
      }
    }

    function filterItems() {
      const q = document.getElementById('search-input').value.toLowerCase();
      document.querySelectorAll('#notes-list .item-card').forEach((card) => {
        const i = Number(card.dataset.index);
        const n = notes[i];
        const match = n.title.toLowerCase().includes(q) || n.notebook.toLowerCase().includes(q) || n.content.toLowerCase().includes(q);
        card.style.display = match ? 'block' : 'none';
      });
      document.querySelectorAll('#canvases-list .item-card').forEach((card) => {
        const i = Number(card.dataset.index);
        const c = canvases[i];
        const hay = (c.title + ' ' + c.ideas.map(x => x.title + ' ' + (x.description || '')).join(' ')).toLowerCase();
        card.style.display = hay.includes(q) ? 'block' : 'none';
      });
    }

    renderList();
  </script>
</body>
</html>`

    zip.file('index.html', indexHtml)

    // v1: full buffer in memory (documented limit for very large workspaces)
    const zipBuffer = await zip.generateAsync({ type: 'nodebuffer' })

    const dateString = new Date().toISOString().split('T')[0]
    return new NextResponse(zipBuffer, {
      headers: {
        'Content-Type': 'application/zip',
        'Content-Disposition': `attachment; filename="memento-workspace-export-${dateString}.zip"`,
      },
    })
  } catch (error) {
    console.error('[GET /api/user/export] Export failed', error)
    return NextResponse.json({ success: false, error: 'Export failed' }, { status: 500 })
  }
}