/**
 * SQLite Migration Utilities
 * 
 * This module handles the migration of data from Dexie to SQLite,
 * including data transformation, validation, and rollback capabilities.
 */

import { Database } from '@wa-sqlite/sql.js';
import { initDatabase, createSchema, createBackup } from './init';
import { 
  MigrationData, 
  MigrationResult,
  SQLiteAccount,
  SQLiteContact,
  SQLiteContactMethod,
  SQLiteSettings,
  SQLiteLog,
  SQLiteSecret,
  isSQLiteAccount,
  isSQLiteContact,
  isSQLiteSettings
} from './types';
import { logger } from '../../utils/logger';

// ============================================================================
// Migration Types
// ============================================================================

interface MigrationContext {
  db: Database;
  startTime: number;
  stats: MigrationResult['stats'];
  errors: Error[];
}

// ============================================================================
// Migration Functions
// ============================================================================

/**
 * Migrate data from Dexie to SQLite
 */
export async function migrateFromDexie(data: MigrationData): Promise<MigrationResult> {
  const startTime = Date.now();
  const context: MigrationContext = {
    db: (await initDatabase()).db,
    startTime,
    stats: {
      accounts: 0,
      contacts: 0,
      contactMethods: 0,
      settings: 0,
      logs: 0,
      secrets: 0
    },
    errors: []
  };

  try {
    // Create backup before migration
    const backup = await createBackup();

    // Create schema if needed
    await createSchema();

    // Perform migration in a transaction
    await context.db.transaction(async () => {
      // Migrate in order of dependencies
      await migrateAccounts(context, data.accounts);
      await migrateContacts(context, data.contacts);
      await migrateContactMethods(context, data.contactMethods);
      await migrateSettings(context, data.settings);
      await migrateLogs(context, data.logs);
      await migrateSecrets(context, data.secrets);
    });

    // Verify migration
    const verificationResult = await verifyMigration(context, data);
    if (!verificationResult.success) {
      throw new Error(`Migration verification failed: ${verificationResult.error}`);
    }

    return {
      success: true,
      stats: context.stats,
      duration: Date.now() - startTime
    };

  } catch (error) {
    logger.error('[SQLite] Migration failed:', error);
    
    // Attempt rollback
    try {
      await rollbackMigration(backup);
    } catch (rollbackError) {
      logger.error('[SQLite] Rollback failed:', rollbackError);
      context.errors.push(new Error('Migration and rollback failed'));
    }

    return {
      success: false,
      error: error instanceof Error ? error : new Error('Unknown migration error'),
      stats: context.stats,
      duration: Date.now() - startTime
    };
  }
}

// ============================================================================
// Migration Helpers
// ============================================================================

/**
 * Migrate accounts
 */
async function migrateAccounts(context: MigrationContext, accounts: SQLiteAccount[]): Promise<void> {
  for (const account of accounts) {
    try {
      if (!isSQLiteAccount(account)) {
        throw new Error(`Invalid account data: ${JSON.stringify(account)}`);
      }

      await context.db.exec(`
        INSERT INTO accounts (
          did, public_key_hex, created_at, updated_at,
          identity_json, mnemonic_encrypted, passkey_cred_id_hex, derivation_path
        ) VALUES (?, ?, ?, ?, ?, ?, ?, ?)
      `, [
        account.did,
        account.public_key_hex,
        account.created_at,
        account.updated_at,
        account.identity_json || null,
        account.mnemonic_encrypted || null,
        account.passkey_cred_id_hex || null,
        account.derivation_path || null
      ]);

      context.stats.accounts++;
    } catch (error) {
      context.errors.push(new Error(`Failed to migrate account ${account.did}: ${error}`));
      throw error; // Re-throw to trigger transaction rollback
    }
  }
}

/**
 * Migrate contacts
 */
async function migrateContacts(context: MigrationContext, contacts: SQLiteContact[]): Promise<void> {
  for (const contact of contacts) {
    try {
      if (!isSQLiteContact(contact)) {
        throw new Error(`Invalid contact data: ${JSON.stringify(contact)}`);
      }

      await context.db.exec(`
        INSERT INTO contacts (
          id, did, name, notes, profile_image_url,
          public_key_base64, next_pub_key_hash_b64,
          sees_me, registered, created_at, updated_at
        ) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
      `, [
        contact.id,
        contact.did,
        contact.name || null,
        contact.notes || null,
        contact.profile_image_url || null,
        contact.public_key_base64 || null,
        contact.next_pub_key_hash_b64 || null,
        contact.sees_me ? 1 : 0,
        contact.registered ? 1 : 0,
        contact.created_at,
        contact.updated_at
      ]);

      context.stats.contacts++;
    } catch (error) {
      context.errors.push(new Error(`Failed to migrate contact ${contact.id}: ${error}`));
      throw error;
    }
  }
}

/**
 * Migrate contact methods
 */
async function migrateContactMethods(
  context: MigrationContext, 
  methods: SQLiteContactMethod[]
): Promise<void> {
  for (const method of methods) {
    try {
      await context.db.exec(`
        INSERT INTO contact_methods (
          id, contact_id, label, type, value,
          created_at, updated_at
        ) VALUES (?, ?, ?, ?, ?, ?, ?)
      `, [
        method.id,
        method.contact_id,
        method.label,
        method.type,
        method.value,
        method.created_at,
        method.updated_at
      ]);

      context.stats.contactMethods++;
    } catch (error) {
      context.errors.push(new Error(`Failed to migrate contact method ${method.id}: ${error}`));
      throw error;
    }
  }
}

/**
 * Migrate settings
 */
async function migrateSettings(context: MigrationContext, settings: SQLiteSettings[]): Promise<void> {
  for (const setting of settings) {
    try {
      if (!isSQLiteSettings(setting)) {
        throw new Error(`Invalid settings data: ${JSON.stringify(setting)}`);
      }

      await context.db.exec(`
        INSERT INTO settings (
          key, account_did, value_json, created_at, updated_at
        ) VALUES (?, ?, ?, ?, ?)
      `, [
        setting.key,
        setting.account_did || null,
        setting.value_json,
        setting.created_at,
        setting.updated_at
      ]);

      context.stats.settings++;
    } catch (error) {
      context.errors.push(new Error(`Failed to migrate setting ${setting.key}: ${error}`));
      throw error;
    }
  }
}

/**
 * Migrate logs
 */
async function migrateLogs(context: MigrationContext, logs: SQLiteLog[]): Promise<void> {
  for (const log of logs) {
    try {
      await context.db.exec(`
        INSERT INTO logs (
          id, level, message, metadata_json, created_at
        ) VALUES (?, ?, ?, ?, ?)
      `, [
        log.id,
        log.level,
        log.message,
        log.metadata_json || null,
        log.created_at
      ]);

      context.stats.logs++;
    } catch (error) {
      context.errors.push(new Error(`Failed to migrate log ${log.id}: ${error}`));
      throw error;
    }
  }
}

/**
 * Migrate secrets
 */
async function migrateSecrets(context: MigrationContext, secrets: SQLiteSecret[]): Promise<void> {
  for (const secret of secrets) {
    try {
      await context.db.exec(`
        INSERT INTO secrets (
          key, value_encrypted, created_at, updated_at
        ) VALUES (?, ?, ?, ?)
      `, [
        secret.key,
        secret.value_encrypted,
        secret.created_at,
        secret.updated_at
      ]);

      context.stats.secrets++;
    } catch (error) {
      context.errors.push(new Error(`Failed to migrate secret ${secret.key}: ${error}`));
      throw error;
    }
  }
}

// ============================================================================
// Verification and Rollback
// ============================================================================

/**
 * Verify migration success
 */
async function verifyMigration(
  context: MigrationContext,
  data: MigrationData
): Promise<{ success: boolean; error?: string }> {
  try {
    // Verify counts
    const counts = await context.db.selectAll<{ table: string; count: number }>(`
      SELECT 'accounts' as table, COUNT(*) as count FROM accounts
      UNION ALL
      SELECT 'contacts', COUNT(*) FROM contacts
      UNION ALL
      SELECT 'contact_methods', COUNT(*) FROM contact_methods
      UNION ALL
      SELECT 'settings', COUNT(*) FROM settings
      UNION ALL
      SELECT 'logs', COUNT(*) FROM logs
      UNION ALL
      SELECT 'secrets', COUNT(*) FROM secrets
    `);

    const countMap = new Map(counts.map(c => [c.table, c.count]));

    if (countMap.get('accounts') !== data.accounts.length) {
      return { success: false, error: 'Account count mismatch' };
    }
    if (countMap.get('contacts') !== data.contacts.length) {
      return { success: false, error: 'Contact count mismatch' };
    }
    if (countMap.get('contact_methods') !== data.contactMethods.length) {
      return { success: false, error: 'Contact method count mismatch' };
    }
    if (countMap.get('settings') !== data.settings.length) {
      return { success: false, error: 'Settings count mismatch' };
    }
    if (countMap.get('logs') !== data.logs.length) {
      return { success: false, error: 'Log count mismatch' };
    }
    if (countMap.get('secrets') !== data.secrets.length) {
      return { success: false, error: 'Secret count mismatch' };
    }

    return { success: true };
  } catch (error) {
    return { 
      success: false, 
      error: error instanceof Error ? error.message : 'Unknown verification error'
    };
  }
}

/**
 * Rollback migration
 */
async function rollbackMigration(backup: Uint8Array): Promise<void> {
  const { db } = await initDatabase();
  
  try {
    // Close current connection
    await db.close();
    
    // Restore from backup
    const sqlite3 = await import('@wa-sqlite/sql.js');
    await sqlite3.open(backup);
    
    logger.info('[SQLite] Migration rollback successful');
  } catch (error) {
    logger.error('[SQLite] Migration rollback failed:', error);
    throw new Error('Failed to rollback migration');
  }
}