// Test that count within a $collStats stage returns the correct number of documents.
// @tags: [assumes_no_implicit_collection_creation_after_drop]
(function() {
"use strict";

load("jstests/aggregation/extras/utils.js");  // For "assertErrorCode".
load("jstests/libs/fixture_helpers.js");      // For "FixtureHelpers".

let testDB = db.getSiblingDB("aggregation_count_db");
let coll = testDB.aggregation_count;
coll.drop();

let nDocs = 1000;
for (var i = 0; i < nDocs; i++) {
    assert.commandWorked(coll.insert({a: i}));
}

// Test that $collStats must be first stage.
let pipeline = [{$match: {}}, {$collStats: {}}];
assertErrorCode(coll, pipeline, 40602);

// Test that an error is returned if count is not an object.
pipeline = [{$collStats: {count: 1}}];
assertErrorCode(coll, pipeline, ErrorCodes.TypeMismatch, "count spec must be an object");
pipeline = [{$collStats: {count: "1"}}];
assertErrorCode(coll, pipeline, ErrorCodes.TypeMismatch, "count spec must be an object");

// Test that an error is returned if count is not an empty object.
pipeline = [{$collStats: {count: {unrecognized: 1}}}];
assertErrorCode(coll, pipeline, 31170, "count spec must be an empty object");

// Test the accuracy of the record count as a standalone option.
pipeline = [{$collStats: {count: {}}}];
let result = coll.aggregate(pipeline).next();
assert.eq(nDocs, result.count);

// Test the record count alongside latencyStats and storageStats.
pipeline = [{$collStats: {count: {}, latencyStats: {}}}];
result = coll.aggregate(pipeline).next();
assert.eq(nDocs, result.count);
assert(result.hasOwnProperty("latencyStats"));
assert(result.latencyStats.hasOwnProperty("reads"));
assert(result.latencyStats.hasOwnProperty("writes"));
assert(result.latencyStats.hasOwnProperty("commands"));

pipeline = [{$collStats: {count: {}, latencyStats: {}, storageStats: {}}}];
result = coll.aggregate(pipeline).next();
assert.eq(nDocs, result.count);
assert(result.hasOwnProperty("latencyStats"));
assert(result.latencyStats.hasOwnProperty("reads"));
assert(result.latencyStats.hasOwnProperty("writes"));
assert(result.latencyStats.hasOwnProperty("commands"));
assert(result.hasOwnProperty("storageStats"));
assert.eq(nDocs, result.storageStats.count);

// Test the record count against an empty collection.
assert.commandWorked(coll.remove({}));
pipeline = [{$collStats: {count: {}}}];
result = coll.aggregate(pipeline).next();
assert.eq(0, result.count);

// Test that we error when the collection does not exist.
coll.drop();
assertErrorCode(coll, pipeline, ErrorCodes.NamespaceNotFound);

// Test that we error when the database does not exist.
assert.commandWorked(testDB.dropDatabase());
assertErrorCode(coll, pipeline, ErrorCodes.NamespaceNotFound);
}());