#!/usr/bin/env node

const { MongoClient, ObjectId } = require('mongodb');
const fs = require('fs');
const { createReadStream } = require('fs');
const { createInterface } = require('readline');
const path = require('path');

/**
 * Stream-based import of large JSON files
 * Optimized for 9GB+ files with minimal memory usage
 */
async function importLargeJsonFile(filePath, collectionName, batchSize = 1000) {
  console.log(`  📁 File: ${filePath}`);
  console.log(`  📦 Collection: ${collectionName}`);
  console.log(`  🔄 Batch Size: ${batchSize}`);

  const startTime = Date.now();
  let processed = 0;
  let skipped = 0;

  // Connect to MongoDB
  const client = new MongoClient(process.env.MONGO_URI || 'mongodb://root:password@localhost:27017/buildpath?authSource=admin');
  await client.connect();

  const db = client.db('matches');
  const collection = db.collection(collectionName);

  try {
    // Create indexes first for better performance
    await collection.createIndex({ "metadata.matchId": 1 }, { unique: true });
    await collection.createIndex({ "info.gameDuration": 1 });
    await collection.createIndex({ "info.participants.championId": 1 });
    await collection.createIndex({ "info.participants.win": 1 });

    // Check file size
    const fileStats = fs.statSync(filePath);
    const fileSize = (fileStats.size / (1024 * 1024 * 1024)).toFixed(2);
    console.log(`  📊 File size: ${fileSize} GB`);

    await processLineDelimitedFormat(filePath, collection, batchSize, startTime);

    const totalTime = ((Date.now() - startTime) / 1000).toFixed(1);
    console.log(`🎉 Import complete in ${totalTime} seconds`);
    console.log(`✅ Processed: ${processed.toLocaleString()} matches`);
    if (skipped > 0) {
      console.log(`⚠️  Skipped: ${skipped.toLocaleString()} invalid entries`);
    }
  } catch (error) {
    console.error('❌ Import failed:', error);
    process.exit(1);
  } finally {
    await client.close();
  }

  async function processLineDelimitedFormat(filePath, collection, batchSize, startTime) {
    const fileStream = createReadStream(filePath);
    const rl = createInterface({
      input: fileStream,
      crlfDelay: Infinity
    });

    let batch = [];
    let lineCount = 0;

    for await (const line of rl) {
      lineCount++;
      process.stdout.write(`\r  Processing line ${lineCount.toLocaleString()}...                `);

        try {
          if (line.trim() === '') continue;

          const match = JSON.parse(line);
          if (!match.metadata || !match.metadata.matchId) {
            skipped++;
            continue;
          }

          // Convert $oid fields to proper ObjectId format
          if (match._id && match._id.$oid) {
            match._id = new ObjectId(match._id.$oid);
          }

          batch.push(match);

        if (batch.length >= batchSize) {
          process.stdout.write(`\r  Inserting batch into MongoDB...    `);
          await insertBatch(batch, collection);
          batch = [];
        }
      } catch (error) {
        skipped++;
      }
    }

    // Insert remaining matches
    if (batch.length > 0) {
      await insertBatch(batch, collection);
    }
  }

  async function insertBatch(batch, collection) {
    if (batch.length === 0) return;

    try {
      const result = await collection.insertMany(batch, {
        ordered: false, // Continue on errors
        writeConcern: { w: 1 } // Acknowledge writes
      });

      return result;
    } catch (error) {
      if (error.code === 11000) {
        // Duplicate matches - skip
        return;
      }
      console.error(`❌ Batch insert error: ${error.message}`);
      throw error;
    }
  }
}

// Run the import if called directly
if (require.main === module) {
  const args = process.argv.slice(2);
  if (args.length < 2) {
    console.log('Usage: node process-matches.js <file-path> <collection-name> [batch-size]');
    console.log('Example: node process-matches.js ../data/16_1_1_matches.json 16.1.1 1000');
    process.exit(1);
  }

  const filePath = path.resolve(args[0]);
  const collectionName = args[1];
  const batchSize = args[2] ? parseInt(args[2]) : 1000;

  importLargeJsonFile(filePath, collectionName, batchSize)
    .then(() => process.exit(0))
    .catch((error) => {
      console.error('Import failed:', error);
      process.exit(1);
    });
}

module.exports = { importLargeJsonFile };