#!/usr/bin/env node
/**
 * Referrals Partition Key Migration — Backfill Script
 *
 * Usage:
 *   npx tsx scripts/migrate-referrals.ts [options]
 *
 * Options:
 *   --productId <id>    Product ID to migrate (default: all products)
 *   --batchSize <n>     Batch size for backfill (default: 100)
 *   --verify            Run consistency verification after backfill
 *   --mode <mode>       Set migration mode (dual-write | new-only | old-only)
 *   --dryRun            Preview changes without writing
 *
 * Examples:
 *   npx tsx scripts/migrate-referrals.ts --productId lysnrai --verify
 *   npx tsx scripts/migrate-referrals.ts --batchSize 50 --dryRun
 *   npx tsx scripts/migrate-referrals.ts --mode new-only
 */

import { CosmosClient, type Container } from '@azure/cosmos';
import { config } from '../src/lib/config.js';
import type { ReferralDoc } from '../src/modules/referrals/types.js';

interface MigrationOptions {
  productId?: string;
  batchSize: number;
  verify: boolean;
  mode?: 'dual-write' | 'new-only' | 'old-only';
  dryRun: boolean;
}

function parseArgs(): MigrationOptions {
  const args = process.argv.slice(2);
  const options: MigrationOptions = {
    batchSize: 100,
    verify: false,
    dryRun: false,
  };

  for (let i = 0; i < args.length; i++) {
    const arg = args[i];
    switch (arg) {
      case '--productId':
        options.productId = args[++i];
        break;
      case '--batchSize':
        options.batchSize = parseInt(args[++i] || '100', 10);
        break;
      case '--verify':
        options.verify = true;
        break;
      case '--mode':
        options.mode = args[++i] as MigrationOptions['mode'];
        break;
      case '--dryRun':
        options.dryRun = true;
        break;
      case '--help':
        console.log(`
Referrals Partition Key Migration — Backfill Script

Usage: npx tsx scripts/migrate-referrals.ts [options]

Options:
  --productId <id>    Product ID to migrate (default: all)
  --batchSize <n>     Batch size for backfill (default: 100)
  --verify            Run consistency verification after backfill
  --mode <mode>       Set migration mode (dual-write|new-only|old-only)
  --dryRun            Preview changes without writing
  --help              Show this help

Examples:
  npx tsx scripts/migrate-referrals.ts --productId lysnrai --verify
  npx tsx scripts/migrate-referrals.ts --batchSize 50 --dryRun
  npx tsx scripts/migrate-referrals.ts --mode new-only
`);
        process.exit(0);
        break;
    }
  }

  return options;
}

async function getContainers(): Promise<{
  oldContainer: Container;
  newContainer: Container;
}> {
  const endpoint = config.COSMOS_ENDPOINT || process.env.COSMOS_ENDPOINT;
  const key = config.COSMOS_KEY || process.env.COSMOS_KEY;
  const database = config.COSMOS_DATABASE || process.env.COSMOS_DATABASE || 'lysnrai';

  if (!endpoint || !key) {
    throw new Error('COSMOS_ENDPOINT and COSMOS_KEY must be set');
  }

  const client = new CosmosClient({ endpoint, key });
  const db = client.database(database);

  return {
    oldContainer: db.container('referrals'),
    newContainer: db.container('referrals_v2'),
  };
}

async function getProductIds(oldContainer: Container): Promise<string[]> {
  const { resources } = await oldContainer.items
    .query<string>({
      query: 'SELECT DISTINCT VALUE c.productId FROM c WHERE IS_DEFINED(c.productId)',
    })
    .fetchAll();
  return resources;
}

async function backfillProduct(
  oldContainer: Container,
  newContainer: Container,
  productId: string,
  batchSize: number,
  dryRun: boolean
): Promise<{ migrated: number; skipped: number; errors: string[] }> {
  const result = { migrated: 0, skipped: 0, errors: [] as string[] };

  // Get all docs from old container for this product
  const { resources: oldDocs } = await oldContainer.items
    .query<ReferralDoc>({
      query: 'SELECT * FROM c WHERE c.productId = @productId',
      parameters: [{ name: '@productId', value: productId }],
    })
    .fetchAll();

  if (oldDocs.length === 0) {
    console.log(`[${productId}] No documents in old container`);
    return result;
  }

  console.log(`[${productId}] Found ${oldDocs.length} documents in old container`);

  if (dryRun) {
    console.log(`[${productId}] DRY RUN — would migrate ${oldDocs.length} documents`);
    return { migrated: oldDocs.length, skipped: 0, errors: [] };
  }

  // Get existing docs in new container
  const { resources: existingDocs } = await newContainer.items
    .query<ReferralDoc>({
      query: 'SELECT * FROM c WHERE c.productId = @productId',
      parameters: [{ name: '@productId', value: productId }],
    })
    .fetchAll();

  const existingIds = new Set(existingDocs.map((d) => d.id));
  console.log(`[${productId}] ${existingIds.size} documents already in new container`);

  // Filter docs needing migration
  const toMigrate = oldDocs.filter((d) => !existingIds.has(d.id));
  console.log(`[${productId}] ${toMigrate.length} documents need migration`);

  if (toMigrate.length === 0) {
    return result;
  }

  // Migrate in batches
  for (let i = 0; i < toMigrate.length; i += batchSize) {
    const batch = toMigrate.slice(i, i + batchSize);
    const batchNum = Math.floor(i / batchSize) + 1;
    const totalBatches = Math.ceil(toMigrate.length / batchSize);

    console.log(
      `[${productId}] Processing batch ${batchNum}/${totalBatches} (${batch.length} docs)`
    );

    await Promise.all(
      batch.map(async (doc) => {
        try {
          if (!doc.referrerId) {
            result.errors.push(`Doc ${doc.id}: missing referrerId (required for new PK)`);
            return;
          }

          await newContainer.items.create(doc);
          result.migrated++;
        } catch (err: any) {
          if (err.code === 409) {
            result.skipped++;
          } else {
            result.errors.push(`Doc ${doc.id}: ${err.message}`);
          }
        }
      })
    );
  }

  return result;
}

async function verifyConsistency(
  oldContainer: Container,
  newContainer: Container,
  productId: string
): Promise<{ inconsistencies: { id: string; issue: string }[]; totalChecked: number }> {
  const inconsistencies: { id: string; issue: string }[] = [];

  const [{ resources: oldDocs }, { resources: newDocs }] = await Promise.all([
    oldContainer.items
      .query<ReferralDoc>({
        query: 'SELECT * FROM c WHERE c.productId = @productId',
        parameters: [{ name: '@productId', value: productId }],
      })
      .fetchAll(),
    newContainer.items
      .query<ReferralDoc>({
        query: 'SELECT * FROM c WHERE c.productId = @productId',
        parameters: [{ name: '@productId', value: productId }],
      })
      .fetchAll(),
  ]);

  const oldMap = new Map(oldDocs.map((d) => [d.id, d]));
  const newMap = new Map(newDocs.map((d) => [d.id, d]));

  // Check docs in both containers for consistency
  for (const [id, newDoc] of newMap) {
    if (!oldMap.has(id)) continue;

    const oldDoc = oldMap.get(id)!;
    if (oldDoc.status !== newDoc.status) {
      inconsistencies.push({ id, issue: `status mismatch: ${oldDoc.status} vs ${newDoc.status}` });
    }
    if (oldDoc.referrerId !== newDoc.referrerId) {
      inconsistencies.push({ id, issue: 'referrerId mismatch' });
    }
  }

  // Check for docs only in old (pending backfill)
  for (const [id] of oldMap) {
    if (!newMap.has(id)) {
      inconsistencies.push({ id, issue: 'pending backfill (in old, missing in new)' });
    }
  }

  return { inconsistencies, totalChecked: oldDocs.length + newDocs.length };
}

async function setMigrationMode(mode: string): Promise<void> {
  // Validate mode
  const validModes = ['dual-write', 'new-only', 'old-only'];
  if (!validModes.includes(mode)) {
    throw new Error(`Invalid mode: ${mode}. Must be one of: ${validModes.join(', ')}`);
  }

  // Set environment variable for current process
  process.env.REFERRAL_MIGRATION_MODE = mode;
  console.log(`Migration mode set to: ${mode}`);
  console.log('Note: This is in-memory only. Update deployment config for persistence.');
}

async function main(): Promise<void> {
  const options = parseArgs();

  console.log('===============================================');
  console.log('Referrals Partition Key Migration — Backfill Script');
  console.log('===============================================');
  console.log(`Options: ${JSON.stringify(options, null, 2)}`);
  console.log('');

  // Handle mode-only operation
  if (options.mode) {
    await setMigrationMode(options.mode);
    return;
  }

  const { oldContainer, newContainer } = await getContainers();
  console.log('Connected to Cosmos DB');

  // Get product IDs to migrate
  const productIds = options.productId ? [options.productId] : await getProductIds(oldContainer);
  console.log(`Migrating for products: ${productIds.join(', ')}`);
  console.log('');

  let totalMigrated = 0;
  let totalSkipped = 0;
  let totalErrors = 0;

  // Backfill each product
  for (const productId of productIds) {
    console.log(`\n--- Processing ${productId} ---`);
    const result = await backfillProduct(
      oldContainer,
      newContainer,
      productId,
      options.batchSize,
      options.dryRun
    );

    console.log(`  Migrated: ${result.migrated}`);
    console.log(`  Skipped: ${result.skipped}`);
    if (result.errors.length > 0) {
      console.log(`  Errors: ${result.errors.length}`);
      result.errors.slice(0, 5).forEach((e) => console.log(`    - ${e}`));
      if (result.errors.length > 5) {
        console.log(`    ... and ${result.errors.length - 5} more`);
      }
    }

    totalMigrated += result.migrated;
    totalSkipped += result.skipped;
    totalErrors += result.errors.length;

    // Run verification if requested
    if (options.verify && !options.dryRun) {
      console.log(`\n  Verifying consistency...`);
      const verifyResult = await verifyConsistency(oldContainer, newContainer, productId);
      const realInconsistencies = verifyResult.inconsistencies.filter(
        (i) => !i.issue.includes('pending backfill')
      );

      if (realInconsistencies.length === 0) {
        console.log(`  Consistency check passed (pending: ${verifyResult.inconsistencies.filter(i => i.issue.includes('pending backfill')).length})`);
      } else {
        console.log(`  WARNING: ${realInconsistencies.length} inconsistencies found:`);
        realInconsistencies.slice(0, 5).forEach((i) => console.log(`    - ${i.id}: ${i.issue}`));
      }
    }
  }

  // Summary
  console.log('\n===============================================');
  console.log('Migration Summary');
  console.log('===============================================');
  console.log(`Total migrated: ${totalMigrated}`);
  console.log(`Total skipped: ${totalSkipped}`);
  console.log(`Total errors: ${totalErrors}`);

  if (totalErrors > 0) {
    process.exit(1);
  }

  console.log('\nMigration completed successfully!');
  console.log('');
  console.log('Next steps:');
  console.log('1. Run verification: npx tsx scripts/migrate-referrals.ts --verify');
  console.log('2. Switch to new-only mode: npx tsx scripts/migrate-referrals.ts --mode new-only');
  console.log('3. Monitor for issues, then delete old container when confident');
}

main().catch((err) => {
  console.error('Migration failed:', err);
  process.exit(1);
});