// Tests for $merge with a non-existing target collection.
(function() {
    "use strict";

    load("jstests/aggregation/extras/merge_helpers.js");  // For withEachMergeMode.
    load("jstests/aggregation/extras/utils.js");          // For assertErrorCode.

    const st = new ShardingTest({shards: 2, rs: {nodes: 1}, config: 1});
    const sourceDB = st.s0.getDB("source_db");

    /**
     * Run an aggregation on 'sourceColl' that writes documents to 'targetColl' with $merge.
     */
    function testMerge(sourceColl, targetColl, shardedSource) {
        sourceColl.drop();

        if (shardedSource) {
            st.shardColl(sourceColl, {_id: 1}, {_id: 0}, {_id: 1}, sourceDB.getName());
        }

        for (let i = 0; i < 10; i++) {
            assert.commandWorked(sourceColl.insert({_id: i}));
        }

        // Test the behavior for each of the $merge modes. Since the target collection does not
        // exist, the behavior should be identical.
        withEachMergeMode(({whenMatchedMode, whenNotMatchedMode}) => {
            // Skip the combination of merge modes which will fail depending on the contents of the
            // source and target collection, as this will cause the assertion below to trip.
            if (whenMatchedMode == "fail" || whenNotMatchedMode == "fail")
                return;

            targetColl.drop();
            sourceColl.aggregate([{
                $merge: {
                    into: {db: targetColl.getDB().getName(), coll: targetColl.getName()},
                    whenMatched: whenMatchedMode,
                    whenNotMatched: whenNotMatchedMode,
                    on: "_id"
                }
            }]);
            assert.eq(whenNotMatchedMode == "discard" ? 0 : 10, targetColl.find().itcount());
        });

        // Test that $merge fails if the "on" field is anything but "_id" when the target collection
        // does not exist.
        withEachMergeMode(({whenMatchedMode, whenNotMatchedMode}) => {
            // Skip the combination of merge modes which will fail depending on the contents of the
            // source and target collection, as this will cause the assertion below to trip.
            if (whenMatchedMode == "fail" || whenNotMatchedMode == "fail")
                return;

            targetColl.drop();
            assertErrorCode(
                sourceColl,
                [{
                   $merge: {
                       into: {db: targetColl.getDB().getName(), coll: targetColl.getName()},
                       whenMatched: whenMatchedMode,
                       whenNotMatched: whenNotMatchedMode,
                       on: "not_allowed"
                   }
                }],
                51190);
        });

        // If 'targetColl' is in the same database as 'sourceColl', test that the legacy $out works
        // correctly.
        if (targetColl.getDB() == sourceColl.getDB()) {
            jsTestLog(
                `Testing $out from ${sourceColl.getFullName()} ` +
                `(${shardedSource ? "sharded" : "unsharded"}) to ${targetColl.getFullName()} ` +
                `with legacy syntax`);

            targetColl.drop();
            sourceColl.aggregate([{$out: targetColl.getName()}]);
            assert.eq(10, targetColl.find().itcount());
        }
    }

    const sourceColl = sourceDB["source_coll"];
    const outputCollSameDb = sourceDB["output_coll"];

    // Test $merge from an unsharded source collection to a non-existent output collection in the
    // same database.
    testMerge(sourceColl, outputCollSameDb, false);

    // Like the last test case, but perform a $merge from a sharded source collection to a
    // non-existent output collection in the same database.
    testMerge(sourceColl, outputCollSameDb, true);

    // Test that $merge in a sharded cluster fails when the output is sent to a different database
    // that doesn't exist.
    const foreignDb = st.s0.getDB("foreign_db");
    const outputCollDiffDb = foreignDb["output_coll"];
    foreignDb.dropDatabase();
    assert.throws(() => testMerge(sourceColl, outputCollDiffDb, false));
    assert.throws(() => testMerge(sourceColl, outputCollDiffDb, true));

    // Test $merge from an unsharded source collection to an output collection in a different
    // database where the database exists but the collection does not.
    assert.commandWorked(foreignDb["test"].insert({_id: "forcing database creation"}));
    testMerge(sourceColl, outputCollDiffDb, false);

    // Like the last test, but with a sharded source collection.
    testMerge(sourceColl, outputCollDiffDb, true);
    st.stop();
}());