//const client1 = require('./demo');

const { MongoClient } = require('mongodb');
const uri = ('mongodb+srv://gayatriparekh:gayu%40211@cluster0.9fplife.mongodb.net/?retryWrites=true&w=majority&appName=Cluster0');
const client = new MongoClient(uri);

async function connectToMongoDB() {
    await client.connect();
    console.log("Connected to MongoDB");
}
connectToMongoDB();
performTransaction()
async function performTransaction(){//(sessionId) {
    /* const session = client.startSession();
    session.startTransaction(); */
    const sessionId = client.startSession();
    sessionId.startTransaction();
    console.log("Transaction started...")
    try {
        const db = client.db('gkdbase');
        const collection = db.collection('testcol');
        const undoLog = db.collection('undo_log');

        const result1 = await collection.insertOne({ name: 'Ashish' }, { sessionId });
        await undoLog.insertOne({ sessionId, operation: 'delete', documentId: result1.insertedId }, { sessionId });

        const result2 = await collection.insertOne({ name: 'Rekha' }, { sessionId });
        await undoLog.insertOne({ sessionId, operation: 'delete', documentId: result2.insertedId }, { sessionId });

        //await session.commitTransaction();
        await sessionId.commitTransaction();
        console.log(`Transaction ${sessionId} committed successfully`);
    } catch (error) {
        //await session.abortTransaction();
        await sessionId.abortTransaction();
        console.error(`Transaction ${sessionId} aborted: ${error}`);
    } finally {
    //    session.endSession();
        sessionId.endSession();
    }
}

async function undoTransaction(sessionId) {
    const session = client.startSession();
    session.startTransaction();
    try {
        const db = client.db('gkdbase');
        const collection = db.collection('testcol');
        const undoLog = db.collection('undo_log');

        const dbLocal =client.db('local');
        const oploggk= dbLocal.collection('oplog.rs');
        const abortTrans= await oploggk.find({sessionId}).toArray();
        for (let gop of abortTrans) {
                if (gop.transactionState === 'abort') {

                } else {
                    await undoLog.updateOne({ _id: op.documentId }, { $set: op.originalDocument }, { session }); 
                }
            }
 

        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();
    }
}
module.exports = performTransaction;