#!/usr/bin/env node
'use strict';

/**
 * Migration Script: Migrate PartnerSystemUser 'customer' field to 'parent'
 * 
 * This script migrates existing PartnerSystemUser documents that have a 'customer' field
 * but no 'parent' field. It copies the customer value to parent and optionally removes
 * the customer field.
 * 
 * Usage:
 *   node scripts/migratePartnerSystemUserCustomerToParent.js [options]
 * 
 * Options:
 *   --preview       Show what will be migrated without making changes
 *   --remove-old    Remove the 'customer' field after migration (default: keep for safety)
 *   --env <path>    Path to environment file (default: ../environment.env)
 *   --help          Show this help message
 * 
 * Examples:
 *   # Preview migration (recommended first)
 *   node scripts/migratePartnerSystemUserCustomerToParent.js --preview
 * 
 *   # Execute migration (keep customer field for safety)
 *   node scripts/migratePartnerSystemUserCustomerToParent.js
 * 
 *   # Execute migration and remove customer field
 *   node scripts/migratePartnerSystemUserCustomerToParent.js --remove-old
 * 
 *   # Use production environment
 *   node scripts/migratePartnerSystemUserCustomerToParent.js --env ../environment_prod.env --preview
 */

const path = require('path');

// Parse command line arguments
const args = process.argv.slice(2);
const options = {
  preview: args.includes('--preview'),
  removeOld: args.includes('--remove-old'),
  envPath: '../environment.env',
  help: args.includes('--help') || args.includes('-h')
};

// Parse --env option
const envIndex = args.indexOf('--env');
if (envIndex !== -1 && args[envIndex + 1]) {
  options.envPath = args[envIndex + 1];
}

if (options.help) {
  console.log(`
Migration Script: Migrate PartnerSystemUser 'customer' field to 'parent'

Usage:
  node scripts/migratePartnerSystemUserCustomerToParent.js [options]

Options:
  --preview       Show what will be migrated without making changes
  --remove-old    Remove the 'customer' field after migration (default: keep for safety)
  --env <path>    Path to environment file (default: ../environment.env)
  --help          Show this help message

Examples:
  # Preview migration (recommended first)
  node scripts/migratePartnerSystemUserCustomerToParent.js --preview

  # Execute migration (keep customer field for safety)
  node scripts/migratePartnerSystemUserCustomerToParent.js

  # Execute migration and remove customer field
  node scripts/migratePartnerSystemUserCustomerToParent.js --remove-old
`);
  process.exit(0);
}

// Load environment
const envPath = path.isAbsolute(options.envPath) ? options.envPath : path.join(process.cwd(), options.envPath);
require('dotenv').config({ path: envPath });

const mongoose = require('mongoose');
const { DBConnection } = require('../helpers/db/connect');
const { UserTypes } = require('../helpers/constants');

// Create database connection instance
const dbConn = new DBConnection('Partner System User Migration');

// Get raw collection access (bypass mongoose schema)
async function getRawCollection() {
  return mongoose.connection.collection('users');
}

async function migratePartnerSystemUsers() {
  console.log('================================================================================');
  console.log('PARTNER SYSTEM USER MIGRATION: customer → parent');
  console.log('================================================================================');
  console.log(`Mode: ${options.preview ? 'PREVIEW (no changes)' : 'EXECUTE'}`);
  console.log(`Remove old customer field: ${options.removeOld ? 'YES' : 'NO'}`);
  console.log(`Environment: ${options.envPath}`);
  console.log('================================================================================\n');

  try {
    // Connect to database
    console.log('Connecting to database...');
    await dbConn.connect({ exitOnError: false });
    console.log('Connected successfully.\n');

    const usersCollection = await getRawCollection();

    // Find all PartnerSystemUser documents that need migration
    // Case 1: Has 'customer' but no 'parent'
    // Case 2: Has 'customer' and 'parent' but they differ (data inconsistency)
    const query = {
      kind: UserTypes.PARTNER_SYSTEM_USER,
      customer: { $exists: true }
    };

    const usersToMigrate = await usersCollection.find(query).toArray();
    
    console.log(`Found ${usersToMigrate.length} PartnerSystemUser document(s) with 'customer' field.\n`);

    if (usersToMigrate.length === 0) {
      console.log('✅ No migration needed - all documents are up to date.');
      return { migrated: 0, skipped: 0, errors: [] };
    }

    const stats = {
      migrated: 0,
      skipped: 0,
      alreadyCorrect: 0,
      errors: []
    };

    console.log('Processing documents:\n');

    for (const user of usersToMigrate) {
      const customerId = user.customer;
      const parentId = user.parent;
      const username = user.username || user.name || user._id;

      // Check if parent already matches customer
      if (parentId && parentId.toString() === customerId.toString()) {
        console.log(`  ⏭️  ${username}: parent already equals customer - ${options.removeOld ? 'will remove customer field' : 'skipping'}`);
        stats.alreadyCorrect++;
        
        if (!options.preview && options.removeOld) {
          // Remove the redundant customer field
          await usersCollection.updateOne(
            { _id: user._id },
            { $unset: { customer: '' } }
          );
          stats.migrated++;
        } else {
          stats.skipped++;
        }
        continue;
      }

      // Check for data inconsistency (parent exists but differs from customer)
      if (parentId && parentId.toString() !== customerId.toString()) {
        console.log(`  ⚠️  ${username}: INCONSISTENCY - parent (${parentId}) differs from customer (${customerId})`);
        console.log(`      → Will use customer value for parent`);
      }

      console.log(`  📝 ${username}:`);
      console.log(`      customer: ${customerId}`);
      console.log(`      parent:   ${parentId || '(not set)'} → ${customerId}`);

      if (!options.preview) {
        try {
          const updateOps = {
            $set: { parent: customerId }
          };

          if (options.removeOld) {
            updateOps.$unset = { customer: '' };
          }

          const result = await usersCollection.updateOne(
            { _id: user._id },
            updateOps
          );

          if (result.modifiedCount === 1) {
            console.log(`      ✅ Migrated successfully`);
            stats.migrated++;
          } else {
            console.log(`      ⚠️  No changes made (modifiedCount: ${result.modifiedCount})`);
            stats.skipped++;
          }
        } catch (error) {
          console.log(`      ❌ Error: ${error.message}`);
          stats.errors.push({ userId: user._id, username, error: error.message });
        }
      } else {
        stats.migrated++; // Count as would-be-migrated in preview
      }
    }

    console.log('\n================================================================================');
    console.log('MIGRATION SUMMARY');
    console.log('================================================================================');
    console.log(`Total documents found:    ${usersToMigrate.length}`);
    console.log(`Already correct:          ${stats.alreadyCorrect}`);
    if (options.preview) {
      console.log(`Would migrate:            ${stats.migrated}`);
      console.log(`Would skip:               ${stats.skipped}`);
    } else {
      console.log(`Successfully migrated:    ${stats.migrated}`);
      console.log(`Skipped:                  ${stats.skipped}`);
    }
    console.log(`Errors:                   ${stats.errors.length}`);

    if (stats.errors.length > 0) {
      console.log('\nErrors:');
      stats.errors.forEach(err => {
        console.log(`  - ${err.username} (${err.userId}): ${err.error}`);
      });
    }

    if (options.preview) {
      console.log('\n⚠️  PREVIEW MODE - No changes were made.');
      console.log('Run without --preview to execute the migration.');
    } else {
      console.log('\n✅ Migration completed.');
      if (!options.removeOld) {
        console.log('Note: The "customer" field was kept for safety.');
        console.log('Run with --remove-old to remove it in a future migration.');
      }
    }

    return stats;

  } catch (error) {
    console.error('\n❌ Migration failed:', error.message);
    throw error;
  }
}

// Verification function to check migration results
async function verifyMigration() {
  console.log('\n================================================================================');
  console.log('VERIFICATION');
  console.log('================================================================================\n');

  try {
    const usersCollection = await getRawCollection();

    // Check for documents with customer but no parent
    const missingParent = await usersCollection.countDocuments({
      kind: UserTypes.PARTNER_SYSTEM_USER,
      customer: { $exists: true },
      parent: { $exists: false }
    });

    // Check for documents with parent set
    const hasParent = await usersCollection.countDocuments({
      kind: UserTypes.PARTNER_SYSTEM_USER,
      parent: { $exists: true }
    });

    // Check for documents with both fields matching
    const pipeline = [
      {
        $match: {
          kind: UserTypes.PARTNER_SYSTEM_USER,
          parent: { $exists: true },
          customer: { $exists: true }
        }
      },
      {
        $project: {
          match: { $eq: ['$parent', '$customer'] }
        }
      },
      {
        $match: { match: true }
      },
      {
        $count: 'count'
      }
    ];

    const matchingResult = await usersCollection.aggregate(pipeline).toArray();
    const matchingCount = matchingResult[0]?.count || 0;

    console.log('Current state of PartnerSystemUser documents:');
    console.log(`  With parent field set:              ${hasParent}`);
    console.log(`  With customer but missing parent:   ${missingParent}`);
    console.log(`  With both fields matching:          ${matchingCount}`);

    if (missingParent === 0 && hasParent > 0) {
      console.log('\n✅ All PartnerSystemUser documents have parent field set.');
    } else if (missingParent > 0) {
      console.log(`\n⚠️  ${missingParent} document(s) still need migration.`);
    }

  } catch (error) {
    console.error('Verification failed:', error.message);
  }
}

// Main execution
async function main() {
  try {
    await migratePartnerSystemUsers();
    await verifyMigration();
  } catch (error) {
    console.error('Migration script failed:', error);
    process.exit(1);
  } finally {
    await mongoose.connection.close();
    console.log('\nDatabase connection closed.');
    process.exit(0);
  }
}

main();