#!/usr/bin/env node

/**
 * Migration: Fix microchip UNIQUE constraint
 * 
 * Problem: The microchip field had a UNIQUE constraint which prevents multiple NULL values.
 * Solution: Remove the constraint and create a partial unique index that only applies to non-NULL values.
 * 
 * This script can be run safely multiple times.
 */

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

function migrateMicrochip() {
  const dbPath = process.env.DB_PATH || path.join(__dirname, '../../data/breedr.db');
  
  if (!fs.existsSync(dbPath)) {
    console.log('No database found at', dbPath);
    console.log('Skipping migration - database will be created with correct schema.');
    return;
  }

  console.log('Migrating database:', dbPath);
  const db = new Database(dbPath);
  db.pragma('foreign_keys = OFF'); // Temporarily disable for migration

  try {
    console.log('Starting microchip field migration...');

    // Check if the old unique constraint exists
    const tableInfo = db.pragma('table_info(dogs)');
    const microchipField = tableInfo.find(col => col.name === 'microchip');
    
    if (!microchipField) {
      console.log('Microchip field not found. Skipping migration.');
      return;
    }

    // SQLite doesn't support ALTER COLUMN, so we need to recreate the table
    console.log('Step 1: Creating new dogs table with correct schema...');
    
    db.exec(`
      -- Create new table with correct schema
      CREATE TABLE IF NOT EXISTS dogs_new (
        id INTEGER PRIMARY KEY AUTOINCREMENT,
        name TEXT NOT NULL,
        registration_number TEXT UNIQUE,
        breed TEXT NOT NULL,
        sex TEXT NOT NULL CHECK(sex IN ('male', 'female')),
        birth_date DATE,
        color TEXT,
        microchip TEXT,
        photo_urls TEXT,
        notes TEXT,
        is_active INTEGER DEFAULT 1,
        created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
        updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
      );
    `);

    console.log('Step 2: Copying data from old table...');
    
    // Copy all data from old table to new table
    db.exec(`
      INSERT INTO dogs_new 
      SELECT * FROM dogs;
    `);

    console.log('Step 3: Dropping old table and renaming new table...');
    
    // Drop old table and rename new table
    db.exec(`
      DROP TABLE dogs;
      ALTER TABLE dogs_new RENAME TO dogs;
    `);

    console.log('Step 4: Creating partial unique index for microchip...');
    
    // Create partial unique index (only applies to non-NULL values)
    db.exec(`
      CREATE UNIQUE INDEX IF NOT EXISTS idx_dogs_microchip 
      ON dogs(microchip) 
      WHERE microchip IS NOT NULL;
    `);

    console.log('Step 5: Recreating other indexes...');
    
    // Recreate other indexes
    db.exec(`
      CREATE INDEX IF NOT EXISTS idx_dogs_name ON dogs(name);
      CREATE INDEX IF NOT EXISTS idx_dogs_registration ON dogs(registration_number);
    `);

    console.log('Step 6: Recreating triggers...');
    
    // Recreate the updated_at trigger
    db.exec(`
      DROP TRIGGER IF EXISTS update_dogs_timestamp;
      CREATE TRIGGER update_dogs_timestamp 
      AFTER UPDATE ON dogs
      FOR EACH ROW
      BEGIN
        UPDATE dogs SET updated_at = CURRENT_TIMESTAMP WHERE id = NEW.id;
      END;
    `);

    console.log('✓ Migration completed successfully!');
    console.log('✓ Microchip field is now optional and can be left empty.');
    console.log('✓ Multiple dogs can have no microchip (NULL value).');
    console.log('✓ Unique constraint still prevents duplicate microchip numbers.');

  } catch (error) {
    console.error('Migration failed:', error.message);
    console.error('\nYou may need to restore from backup or manually fix the database.');
    throw error;
  } finally {
    db.pragma('foreign_keys = ON'); // Re-enable foreign keys
    db.close();
  }
}

if (require.main === module) {
  console.log('='.repeat(60));
  console.log('BREEDR Database Migration: Microchip Field Fix');
  console.log('='.repeat(60));
  console.log('');
  
  migrateMicrochip();
  
  console.log('');
  console.log('='.repeat(60));
  console.log('Migration Complete');
  console.log('='.repeat(60));
}

module.exports = { migrateMicrochip };