const fs = require('fs');
const path = require('path');
const Database = require('better-sqlite3');

/**
 * Database Migration Script: Migrate existing sessions to projects
 *
 * This script:
 * 1. Scans existing session files from Claude Sessions directory
 * 2. Extracts unique project names from metadata.project field
 * 3. Creates projects with random icons and colors
 * 4. Updates sessions table with projectId references
 */

const VAULT_PATH = '/home/uroma/obsidian-vault';
const CLAUDE_SESSIONS_DIR = path.join(VAULT_PATH, 'Claude Sessions');
const DB_PATH = path.join(__dirname, '..', 'database.sqlite');

const ICONS = ['🚀', '📱', '🎨', '💻', '🔧', '📊', '🎯', '🔮', '⚡', '🌟'];
const COLORS = ['#4a9eff', '#ff6b6b', '#51cf66', '#ffd43b', '#cc5de8', '#ff922b', '#20c997', '#339af0'];

/**
 * Get random item from array
 */
function getRandomItem(array) {
  return array[Math.floor(Math.random() * array.length)];
}

/**
 * Parse frontmatter from markdown content
 */
function parseFrontmatter(content) {
  const frontmatterMatch = content.match(/^---\n([\s\S]*?)\n---/);
  if (!frontmatterMatch) {
    return null;
  }

  const frontmatter = {};
  frontmatterMatch[1].split('\n').forEach(line => {
    const [key, ...valueParts] = line.split(':');
    if (key && valueParts.length > 0) {
      frontmatter[key.trim()] = valueParts.join(':').trim();
    }
  });

  return frontmatter;
}

/**
 * Scan session files and extract project information
 */
function scanSessionFiles() {
  console.log('📂 Scanning session files...');
  console.log(`   Directory: ${CLAUDE_SESSIONS_DIR}`);

  if (!fs.existsSync(CLAUDE_SESSIONS_DIR)) {
    console.log('⚠️  Claude Sessions directory does not exist');
    return [];
  }

  const files = fs.readdirSync(CLAUDE_SESSIONS_DIR);
  const sessionFiles = files.filter(f => f.endsWith('.md') && f.includes('session-'));

  console.log(`   Found ${sessionFiles.length} session files`);

  const sessions = [];
  const projectMap = new Map(); // projectName -> { sessions: [], path: null }

  sessionFiles.forEach(file => {
    const filepath = path.join(CLAUDE_SESSIONS_DIR, file);
    const content = fs.readFileSync(filepath, 'utf-8');
    const frontmatter = parseFrontmatter(content);

    if (!frontmatter) {
      console.log(`   ⚠️  Skipping ${file}: No frontmatter found`);
      return;
    }

    const sessionId = frontmatter.session_id;
    const projectName = frontmatter.project;
    const workingDir = frontmatter.working_dir;
    const createdAt = frontmatter.created_at;

    if (!sessionId) {
      console.log(`   ⚠️  Skipping ${file}: No session_id in frontmatter`);
      return;
    }

    // Add session to list
    sessions.push({
      id: sessionId,
      projectName,
      workingDir,
      createdAt,
      file
    });

    // Group by project
    if (projectName) {
      if (!projectMap.has(projectName)) {
        projectMap.set(projectName, {
          sessions: [],
          path: workingDir,
          earliestDate: createdAt
        });
      }
      projectMap.get(projectName).sessions.push(sessionId);

      // Update earliest date if this session is older
      const currentDate = new Date(createdAt);
      const existingDate = new Date(projectMap.get(projectName).earliestDate);
      if (currentDate < existingDate) {
        projectMap.get(projectName).earliestDate = createdAt;
      }
    }
  });

  console.log(`   ✅ Processed ${sessions.length} sessions`);
  console.log(`   📊 Found ${projectMap.size} unique projects`);

  return { sessions, projectMap };
}

/**
 * Create projects in database
 */
function createProjects(db, projectMap) {
  console.log('\n🎨 Creating projects in database...');

  const insertProject = db.prepare(`
    INSERT INTO projects (name, description, icon, color, path, createdAt, lastActivity)
    VALUES (?, ?, ?, ?, ?, ?, ?)
  `);

  const projects = {};
  let createdCount = 0;

  for (const [projectName, data] of projectMap.entries()) {
    const icon = getRandomItem(ICONS);
    const color = getRandomItem(COLORS);
    const now = new Date().toISOString();

    try {
      const result = insertProject.run(
        projectName,
        `Sessions for ${projectName}`,
        icon,
        color,
        data.path || VAULT_PATH,
        data.earliestDate,
        now
      );

      projects[projectName] = {
        id: result.lastInsertRowid,
        name: projectName,
        icon,
        color,
        sessionCount: data.sessions.length
      };

      createdCount++;
      console.log(`   ✅ Created project: ${projectName} (${icon})`);
      console.log(`      - ID: ${result.lastInsertRowid}`);
      console.log(`      - Sessions: ${data.sessions.length}`);
      console.log(`      - Path: ${data.path || VAULT_PATH}`);
    } catch (error) {
      console.error(`   ❌ Error creating project ${projectName}:`, error.message);
    }
  }

  console.log(`\n   ✅ Created ${createdCount} projects`);

  return projects;
}

/**
 * Update sessions with projectId
 */
function updateSessions(db, sessions, projects) {
  console.log('\n🔗 Linking sessions to projects...');

  const insertSession = db.prepare(`
    INSERT OR REPLACE INTO sessions (id, projectId)
    VALUES (?, ?)
  `);

  let updatedCount = 0;
  let unlinkedCount = 0;

  sessions.forEach(session => {
    const projectName = session.projectName;

    if (projectName && projects[projectName]) {
      const projectId = projects[projectName].id;

      try {
        insertSession.run(session.id, projectId);
        updatedCount++;
        console.log(`   ✅ Linked ${session.id} -> ${projectName} (ID: ${projectId})`);
      } catch (error) {
        console.error(`   ❌ Error linking session ${session.id}:`, error.message);
      }
    } else {
      // Session without a project - add to sessions table without projectId
      try {
        insertSession.run(session.id, null);
        unlinkedCount++;
        console.log(`   ⚠️  Unlinked session: ${session.id} (no project)`);
      } catch (error) {
        console.error(`   ❌ Error adding session ${session.id}:`, error.message);
      }
    }
  });

  console.log(`\n   ✅ Linked ${updatedCount} sessions to projects`);
  console.log(`   ℹ️  ${unlinkedCount} sessions without projects`);

  return { updatedCount, unlinkedCount };
}

/**
 * Display migration summary
 */
function displaySummary(sessions, projects, stats) {
  console.log('\n' + '='.repeat(60));
  console.log('📊 MIGRATION SUMMARY');
  console.log('='.repeat(60));
  console.log(`\nSessions Processed: ${sessions.length}`);
  console.log(`Projects Created: ${Object.keys(projects).length}`);
  console.log(`Sessions Linked: ${stats.updatedCount}`);
  console.log(`Sessions Unlinked: ${stats.unlinkedCount}`);

  console.log('\n📁 Projects Created:');
  Object.values(projects).forEach(project => {
    console.log(`   ${project.icon} ${project.name} (${project.color})`);
    console.log(`      - ID: ${project.id}`);
    console.log(`      - Sessions: ${project.sessionCount}`);
  });

  console.log('\n' + '='.repeat(60));
  console.log('✅ Migration completed successfully!');
  console.log('='.repeat(60) + '\n');
}

/**
 * Main migration function
 */
function migrate() {
  console.log('🚀 Starting database migration for projects...\n');

  // Check if database exists
  if (!fs.existsSync(DB_PATH)) {
    console.error('❌ Database file not found:', DB_PATH);
    console.error('Please run the application first to initialize the database.');
    process.exit(1);
  }

  // Open database
  console.log('📦 Opening database...');
  const db = new Database(DB_PATH);
  db.pragma('journal_mode = WAL');

  try {
    // Step 1: Scan session files
    const { sessions, projectMap } = scanSessionFiles();

    if (sessions.length === 0) {
      console.log('\n⚠️  No sessions found to migrate');
      db.close();
      return;
    }

    // Step 2: Create projects
    const projects = createProjects(db, projectMap);

    if (Object.keys(projects).length === 0) {
      console.log('\n⚠️  No projects found to create');
      db.close();
      return;
    }

    // Step 3: Update sessions
    const stats = updateSessions(db, sessions, projects);

    // Step 4: Display summary
    displaySummary(sessions, projects, stats);

  } catch (error) {
    console.error('\n❌ Migration failed:', error);
    throw error;
  } finally {
    db.close();
    console.log('📦 Database connection closed\n');
  }
}

// Run migration if executed directly
if (require.main === module) {
  migrate();
}

module.exports = { migrate };