'use strict';

/**
 * Rollback Migration Script
 * 
 * This script reverts the last customer migration by reading the migration_history.json
 * and reversing all changes.
 * 
 * Rollback Operations:
 * - migrate_products/crops: Restores byPuid to original parent
 *   - If --reuse-existing-entities was used, also recreates deleted entities
 * - migrate_jobs: Restores byPuid to original parent
 * - migrate_invoices: Restores each invoice to its original byPuid
 * - update_parent_reference: Restores sub-account parent references
 * - convert_customer_to_admin: Restores kind and parent fields
 * - deactivate_source_customer: Restores customer to active state
 * 
 * Usage:
 *   node scripts/rollbackMigration.js
 *   node scripts/rollbackMigration.js --env ../environment_prod.env
 * 
 * Options:
 *   --env    Custom environment file path (default: ../environment.env)
 */

const path = require('path');
const args = process.argv.slice(2);
const envArgIndex = args.indexOf('--env');
const customEnvPath = envArgIndex !== -1 && args[envArgIndex + 1] ? args[envArgIndex + 1] : null;
const envPath = customEnvPath 
  ? (path.isAbsolute(customEnvPath) ? customEnvPath : path.join(process.cwd(), customEnvPath))
  : path.join(__dirname, '../environment.env');

console.log(`Loading environment from: ${envPath}`);
require('dotenv').config({ path: envPath });

const debug = require('debug')('agm:rollback-migration');
const mongoose = require('mongoose');
const { DBConnection } = require('../helpers/db/connect');
const mongoEnhanced = require('../helpers/mongo_enhanced');
const fs = require('fs').promises;

// Import models
const models = {
  User: require('../model/user'),
  Customer: require('../model/customer'),
  Job: require('../model/job'),
  Product: require('../model/product'),
  Crop: require('../model/crop'),
  CostingItem: require('../model/costing_items'),
  Invoice: require('../model/invoice')
};

const DEFAULT_HISTORY_FILE = path.join(__dirname, '../migration_history.json');

/**
 * Load the last migration from history file
 */
async function loadLastMigration(historyFile) {
  try {
    const content = await fs.readFile(historyFile, 'utf8');
    const migrations = JSON.parse(content);
    
    if (!Array.isArray(migrations) || migrations.length === 0) {
      throw new Error('No migrations found in history file');
    }
    
    // Get the last migration
    const lastMigration = migrations[migrations.length - 1];
    
    if (!lastMigration.completedAt) {
      throw new Error('Last migration has not been completed yet');
    }
    
    return lastMigration;
  } catch (error) {
    throw new Error(`Failed to read migration history: ${error.message}`);
  }
}

/**
 * Rollback the migration
 */
async function rollbackMigration(migrationRecord) {
  console.log('\n================================================================================');
  console.log('ROLLBACK MIGRATION');
  console.log('================================================================================\n');
  
  console.log(`Migration Date: ${migrationRecord.timestamp}`);
  console.log(`Completed At: ${migrationRecord.completedAt}`);
  console.log(`Source Customer IDs: ${migrationRecord.sourceCustomerIds.join(', ')}`);
  console.log(`Target Customer ID: ${migrationRecord.targetCustomerId}`);
  console.log('\nReverting changes...\n');

  await mongoEnhanced.enhancedRunInTransaction(async (session) => {
    debug('Starting rollback transaction...');

    const changes = migrationRecord.details.changes;
    let revertedCount = 0;

    // Process changes in reverse order
    for (let i = changes.length - 1; i >= 0; i--) {
      const change = changes[i];

      switch (change.action) {
        case 'deactivate_source_customer':
          console.log(`  → Reactivating source customer: ${change.customerId}`);
          await models.User.updateOne(
            { _id: change.customerId },
            {
              $set: {
                username: change.oldUsername,
                markedDelete: false,
                active: true
              }
            },
            { session }
          );
          revertedCount++;
          break;

        case 'delete_partner_system_users':
          console.log(`  → Restoring ${change.count} deleted partner system users`);
          if (change.deletedUsers && change.deletedUsers.length > 0) {
            for (const userData of change.deletedUsers) {
              // Check if user already exists before trying to restore
              const existingUser = await models.User.findById(userData._id).session(session);
              if (!existingUser) {
                // Remove version key and other mongoose internals
                const { __v, ...cleanData } = userData;
                await models.User.create([cleanData], { session });
              } else {
                console.log(`  → Partner system user ${userData.username || userData.partnerUsername} already exists, skipping restore`);
              }
            }
          }
          revertedCount++;
          break;

        case 'update_parent_reference':
          console.log(`  → Reverting parent reference for account: ${change.accountId}`);
          await models.User.updateOne(
            { _id: change.accountId },
            { $set: { parent: change.fromParent } },
            { session }
          );
          revertedCount++;
          break;

        case 'migrate_products':
          console.log(`  → Reverting ${change.count} products`);
          
          // Restore migrated products to original parent
          if (change.productIds && change.productIds.length > 0) {
            // Use specific product IDs to revert only the migrated products
            await models.Product.updateMany(
              { _id: { $in: change.productIds } },
              { $set: { byPuid: change.oldParent } },
              { session }
            );
          }
          
          // Restore deleted products (that were replaced by destination entities)
          if (change.deletedProducts && change.deletedProducts.length > 0) {
            console.log(`  → Restoring ${change.deletedProducts.length} deleted products`);
            for (const productData of change.deletedProducts) {
              // Check if product already exists before trying to restore
              const existingProduct = await models.Product.findById(productData._id).session(session);
              if (!existingProduct) {
                // Remove version key and other mongoose internals
                const { __v, ...cleanData } = productData;
                await models.Product.create([cleanData], { session });
              } else {
                console.log(`  → Product ${productData.name} already exists, skipping restore`);
              }
            }
          }
          
          revertedCount++;
          break;

        case 'migrate_crops':
          console.log(`  → Reverting ${change.count} crops`);
          
          // Restore migrated crops to original parent
          if (change.cropIds && change.cropIds.length > 0) {
            // Use specific crop IDs to revert only the migrated crops
            await models.Crop.updateMany(
              { _id: { $in: change.cropIds } },
              { $set: { byPuid: change.oldParent } },
              { session }
            );
          }
          
          // Restore deleted crops (that were replaced by destination entities)
          if (change.deletedCrops && change.deletedCrops.length > 0) {
            console.log(`  → Restoring ${change.deletedCrops.length} deleted crops`);
            for (const cropData of change.deletedCrops) {
              // Check if crop already exists before trying to restore
              const existingCrop = await models.Crop.findById(cropData._id).session(session);
              if (!existingCrop) {
                // Remove version key and other mongoose internals
                const { __v, ...cleanData } = cropData;
                await models.Crop.create([cleanData], { session });
              } else {
                console.log(`  → Crop ${cropData.name} already exists, skipping restore`);
              }
            }
          }
          
          revertedCount++;
          break;

        case 'migrate_costing_items':
          console.log(`  → Reverting ${change.count} costing items`);
          if (change.costingItemIds && change.costingItemIds.length > 0) {
            // Use specific item IDs to revert only the migrated items
            await models.CostingItem.updateMany(
              { _id: { $in: change.costingItemIds } },
              { $set: { byPuid: change.oldParent } },
              { session }
            );
          }
          revertedCount++;
          break;

        case 'migrate_jobs':
          console.log(`  → Reverting ${change.jobCount} jobs`);
          if (change.jobIds && change.jobIds.length > 0) {
            // Use specific job IDs to revert only the migrated jobs
            await models.Job.updateMany(
              { _id: { $in: change.jobIds } },
              { $set: { byPuid: change.oldParent } },
              { session }
            );
          }
          revertedCount++;
          break;

        case 'migrate_invoices':
          console.log(`  → Reverting ${change.count} invoices`);
          if (change.invoiceIds && change.invoiceIds.length > 0) {
            // Restore each invoice to its original customer (byPuid field)
            for (let i = 0; i < change.invoiceIds.length; i++) {
              const invoiceId = change.invoiceIds[i];
              const oldCustomerId = change.oldCustomerIds[i];
              
              if (oldCustomerId) {
                await models.Invoice.updateOne(
                  { _id: invoiceId },
                  { $set: { byPuid: oldCustomerId } },
                  { session }
                );
              }
            }
          }
          revertedCount++;
          break;

        case 'convert_customer_to_admin':
          console.log(`  → Reverting admin conversion for customer: ${change.customerId || change.sourceCustomerId}`);
          
          const customerId = change.customerId || change.sourceCustomerId;
          const originalKind = change.originalKind || '1'; // Default to APP (1) if not specified
          const originalParent = change.originalParent || null;
          
          // Handle old format where a new admin user was created
          if (change.newAdminId) {
            // Old format: delete the admin user that was created
            await models.User.deleteOne(
              { _id: change.newAdminId },
              { session }
            );
          }
          
          // Use direct MongoDB collection update to bypass Mongoose discriminator protection
          // This is necessary because 'kind' is a discriminator key and can't be changed via Mongoose
          const updateDoc = {
            $set: {
              kind: originalKind,
              parent: originalParent,
              active: true,
              markedDelete: false
            }
          };
          
          // Only add unset if there was a temp username
          if (change.oldUsername) {
            updateDoc.$unset = { username: 1 };
          }
          
          await models.Customer.collection.updateOne(
            { _id: mongoose.Types.ObjectId(customerId) },
            updateDoc,
            { session }
          );
          
          // If there was an old username (temp), restore the original
          if (change.oldUsername && change.username) {
            await models.Customer.collection.updateOne(
              { _id: mongoose.Types.ObjectId(customerId) },
              { $set: { username: change.username } },
              { session }
            );
          }
          
          revertedCount++;
          break;

        default:
          console.log(`  ⚠ Unknown action: ${change.action}`);
      }
    }

    console.log(`\n✅ Reverted ${revertedCount} changes successfully`);
    debug('Rollback transaction completed successfully');
  }, mongoEnhanced.DEFAULT_TRANSACTION_OPTIONS);
}

/**
 * Main execution
 */
async function main() {
  try {
    // Initialize database connection
    console.log('Connecting to database...');
    const dbConn = new DBConnection('Rollback Migration');
    await dbConn.connect();
    console.log('✓ Database connected\n');

    // Load the last migration
    console.log(`Loading migration history from: ${DEFAULT_HISTORY_FILE}`);
    const migrationRecord = await loadLastMigration(DEFAULT_HISTORY_FILE);

    if (migrationRecord.status !== 'completed') {
      throw new Error(`Last migration status is '${migrationRecord.status}', not 'completed'. Cannot rollback.`);
    }

    // Confirm with user
    console.log('\n⚠️  WARNING: This will revert all changes from the last migration!');
    console.log('Press Ctrl+C to cancel, or wait 3 seconds to continue...\n');
    
    await new Promise(resolve => setTimeout(resolve, 3000));

    // Execute rollback
    await rollbackMigration(migrationRecord);

    console.log('\n✅ Rollback completed successfully!\n');
    
    // Close database connection
    await mongoose.connection.close();
    process.exit(0);
  } catch (error) {
    console.error('\n❌ Rollback failed:', error.message);
    debug('Error:', error);
    if (mongoose.connection.readyState === 1) {
      await mongoose.connection.close();
    }
    process.exit(1);
  }
}

// Command-line execution
if (require.main === module) {
  main();
}

module.exports = { rollbackMigration, loadLastMigration };