/**
 * Tests that transactions larger than 16MB can only be created in FCV 4.2.
 *
 * @tags: [uses_transactions]
 */
(function() {
    "uses strict";
    load("jstests/libs/feature_compatibility_version.js");
    load("jstests/core/txns/libs/prepare_helpers.js");

    const dbName = "test";
    const collName = "large_transactions_require_fcv42";
    const testDB = db.getSiblingDB(dbName);
    const adminDB = db.getSiblingDB('admin');

    testDB[collName].drop({writeConcern: {w: "majority"}});
    assert.commandWorked(testDB.runCommand({create: collName, writeConcern: {w: "majority"}}));

    const sessionOptions = {causalConsistency: false};
    const session = testDB.getMongo().startSession(sessionOptions);
    const sessionDB = session.getDatabase(dbName);
    const sessionColl = sessionDB.getCollection(collName);

    // As we are not able to send a single request larger than 16MB, we insert two documents
    // of 10MB each to create a "large" transaction.
    const kSize10MB = 10 * 1024 * 1024;
    function createLargeDocument(id) {
        return {_id: id, longString: "a".repeat(kSize10MB)};
    }

    try {
        jsTestLog("Test that creating a transaction larger than 16MB succeeds in FCV 4.2.");
        let doc1 = createLargeDocument(1);
        let doc2 = createLargeDocument(2);

        checkFCV(adminDB, latestFCV);
        session.startTransaction();
        assert.commandWorked(sessionColl.insert(doc1));
        assert.commandWorked(sessionColl.insert(doc2));
        assert.commandWorked(session.commitTransaction_forTesting());

        jsTestLog("Downgrade the featureCompatibilityVersion.");
        assert.commandWorked(testDB.adminCommand({setFeatureCompatibilityVersion: lastStableFCV}));
        checkFCV(adminDB, lastStableFCV);

        jsTestLog("Test that trying to create a transaction larger than 16MB fails in FCV 4.0.");
        let doc3 = createLargeDocument(3);
        let doc4 = createLargeDocument(4);

        session.startTransaction();
        assert.commandWorked(sessionColl.insert(doc3));
        assert.commandFailedWithCode(sessionColl.insert(doc4), ErrorCodes.TransactionTooLarge);
        // We have to call 'abortTransaction' here to clear the transaction state in the shell.
        // Otherwise, the later call to 'startTransaction' will fail with 'Transaction already in
        // progress'.
        assert.commandFailedWithCode(session.abortTransaction_forTesting(),
                                     ErrorCodes.NoSuchTransaction);
    } finally {
        jsTestLog("Restore to FCV 4.2.");
        assert.commandWorked(testDB.adminCommand({setFeatureCompatibilityVersion: latestFCV}));
        checkFCV(adminDB, latestFCV);
    }

    jsTestLog(
        "Test that creating a transaction larger than 16MB succeeds after upgrading to FCV 4.2.");
    let doc5 = createLargeDocument(5);
    let doc6 = createLargeDocument(6);

    session.startTransaction();
    assert.commandWorked(sessionColl.insert(doc5));
    assert.commandWorked(sessionColl.insert(doc6));
    assert.commandWorked(session.commitTransaction_forTesting());

    session.endSession();
}());