// Connect to the 'local' database where the oplog resides
//use local;
const { MongoClient } = require('mongodb')
//const client=new MongoClient('mongodb+srv://gayatriparekh:gayu%40211@cluster0.9fplife.mongodb.net/?retryWrites=true&w=majority&appName=Cluster0')
const client=new MongoClient('mongodb+srv://localhost:27017')
// Connect to database
client.connect()
    .then(() => console.log('Connected Successfully'))
    .catch(error => console.log('Failed to connect', error))
//-----
const session = client.startSession();
session.startTransaction();
try {
    const db = client.db('gkdbase');//const db = client.db('local');
    const collection = db.collection('log2');//const collection = db.collection('oplog.rs');
    //const abortTrans= await collection.find({sessionId}).toArray();
} catch (error) {
    //await session.abortTransaction();
    console.error(`Undo transaction ${sessionId} aborted: ${error}`);
} finally {
    session.endSession();
}
//-----
// Function to analyze the oplog and find potential aborted transactions
async function findAbortedTransactions() {
    print("Searching for potential aborted transactions in oplog...");

    // Fetch all oplog entries related to transactions
    const cursor = db.oplog.rs.find({
        "o.applyOps": { $exists: true },   // Look for entries with 'applyOps', indicating a multi-document transaction
    }).sort({ ts: -1 });  // Sort by timestamp, most recent first

    let abortedTransactions = [];

    // Iterate through the oplog entries
    cursor.forEach(oplogEntry => {
        const oplogTs = oplogEntry.ts;  // Oplog timestamp
        const transactionId = oplogEntry.txnNumber || "Unknown";  // Transaction ID if available
        const applyOps = oplogEntry.o.applyOps;  // Operations in the transaction

        // Analyze transaction details
        let hasAbortMarker = false;

        // Look for specific patterns indicating a transaction abort or rollback
        applyOps.forEach(op => {
            if (op.abort || op.rollback) {
                hasAbortMarker = true;
            }
        });

        // If no commit marker exists or if abort markers are found
        if (hasAbortMarker) {
            abortedTransactions.push({
                ts: oplogTs,
                txnNumber: transactionId,
                details: oplogEntry
            });
        }
    });

    // Print the results
    if (abortedTransactions.length > 0) {
        print("Found potential aborted transactions:");
        abortedTransactions.forEach(txn => {
            printjson({
                "Timestamp": txn.ts,
                "Transaction Number": txn.txnNumber,
                "Details": txn.details
            });
        });
    } else {
        print("No aborted transactions found in the oplog.");

        
        try {
            const db = client.db('gkdbase');
            //const collection = db.collection('testcol');
            const undoLog = db.collection('undo_log2');//const undoLog = db.collection('undo_log');
                   
            const undoOperations = await undoLog.find({ sessionId }).toArray();
            
            for (let op of undoOperations) {
                if (op.operation === 'delete') {
                    await collection.deleteOne({ _id: op.documentId }, { session });
                } else if (op.operation === 'insert') {
                    await collection.insertOne(op.document, { session });
                } else if (op.operation === 'update') {
                    await collection.updateOne({ _id: op.documentId }, { $set: op.originalDocument }, { session });
                }
            }
    
            await session.commitTransaction();
            console.log(`Undo transaction ${sessionId} committed successfully`);
        } catch (error) {
            await session.abortTransaction();
            console.error(`Undo transaction ${sessionId} aborted: ${error}`);
        } finally {
            session.endSession();
        }
        
    }
}

// Run the function
findAbortedTransactions();