// In SERVER-10689, the $switch expression was introduced. In this file, we test the functionality
// of the expression.

let coll = db.switch;
coll.drop();

// Insert an empty document so that something can flow through the pipeline.
coll.insert({});

// Ensure that a branch is correctly evaluated.
let pipeline = {
    "$project": {
        "_id": 0,
        "output": {
            "$switch": {
                "branches": [{"case": {"$eq": [1, 1]}, "then": "one is equal to one!"}],
            },
        },
    },
};
let res = coll.aggregate(pipeline).toArray();

assert.eq(res.length, 1);
assert.eq(res[0], {"output": "one is equal to one!"});

// Ensure that the first branch which matches is chosen.
pipeline = {
    "$project": {
        "_id": 0,
        "output": {
            "$switch": {
                "branches": [
                    {"case": {"$eq": [1, 1]}, "then": "one is equal to one!"},
                    {"case": {"$eq": [2, 2]}, "then": "two is equal to two!"},
                ],
            },
        },
    },
};
res = coll.aggregate(pipeline).toArray();

assert.eq(res.length, 1);
assert.eq(res[0], {"output": "one is equal to one!"});

// Ensure that the default is chosen if no case matches.
pipeline = {
    "$project": {
        "_id": 0,
        "output": {
            "$switch": {
                "branches": [{"case": {"$eq": [1, 2]}, "then": "one is equal to two!"}],
                "default": "no case matched.",
            },
        },
    },
};
res = coll.aggregate(pipeline).toArray();

assert.eq(res.length, 1);
assert.eq(res[0], {"output": "no case matched."});

// Ensure that nullish values are treated as false when they are a "case", and are null
// otherwise.
pipeline = {
    "$project": {
        "_id": 0,
        "output": {
            "$switch": {
                "branches": [{"case": null, "then": "Null was true!"}],
                "default": "No case matched.",
            },
        },
    },
};
res = coll.aggregate(pipeline).toArray();

assert.eq(res.length, 1);
assert.eq(res[0], {"output": "No case matched."});

pipeline = {
    "$project": {
        "_id": 0,
        "output": {
            "$switch": {
                "branches": [{"case": "$missingField", "then": "Null was true!"}],
                "default": "No case matched.",
            },
        },
    },
};
res = coll.aggregate(pipeline).toArray();

assert.eq(res.length, 1);
assert.eq(res[0], {"output": "No case matched."});

pipeline = {
    "$project": {
        "_id": 0,
        "output": {"$switch": {"branches": [{"case": true, "then": null}], "default": false}},
    },
};
res = coll.aggregate(pipeline).toArray();

assert.eq(res.length, 1);
assert.eq(res[0], {"output": null});

pipeline = {
    "$project": {
        "_id": 0,
        "output": {"$switch": {"branches": [{"case": true, "then": "$missingField"}], "default": false}},
    },
};
res = coll.aggregate(pipeline).toArray();

assert.eq(res.length, 1);
assert.eq(res[0], {});

pipeline = {
    "$project": {
        "_id": 0,
        "output": {"$switch": {"branches": [{"case": null, "then": false}], "default": null}},
    },
};
res = coll.aggregate(pipeline).toArray();

assert.eq(res.length, 1);
assert.eq(res[0], {"output": null});

pipeline = {
    "$project": {
        "_id": 0,
        "output": {"$switch": {"branches": [{"case": null, "then": false}], "default": "$missingField"}},
    },
};
res = coll.aggregate(pipeline).toArray();

assert.eq(res.length, 1);
assert.eq(res[0], {});