// SERVER-17943: Add $filter aggregation expression.

// For assertErrorCode.
load('jstests/aggregation/extras/utils.js');

(function() {
    'use strict';

    var coll = db.agg_filter_expr;
    coll.drop();

    assert.writeOK(coll.insert({_id: 0, a: [1,2,3,4,5]}));
    assert.writeOK(coll.insert({_id: 1, a: [2,4]}));
    assert.writeOK(coll.insert({_id: 2, a: []}));
    assert.writeOK(coll.insert({_id: 3, a: [1]}));
    assert.writeOK(coll.insert({_id: 4, a: null}));
    assert.writeOK(coll.insert({_id: 5, a: undefined}));
    assert.writeOK(coll.insert({_id: 6}));

    // Create filter to only accept odd numbers.
    filterDoc = {input: '$a', as: 'x', cond: {$eq: [1, {$mod: ['$$x', 2]}]}};
    var expectedResults = [
        {_id: 0, b: [1,3,5]},
        {_id: 1, b: []},
        {_id: 2, b: []},
        {_id: 3, b: [1]},
        {_id: 4, b: null},
        {_id: 5, b: null},
        {_id: 6, b: null},
    ];
    var results = coll.aggregate([{$project: {b: {$filter: filterDoc}}}]).toArray();
    assert.eq(results, expectedResults);

    // Invalid filter expressions.

    // Insert a document so that the initial cursor doesn't immediately return EOF.
    coll.insert({_id: 0, a: [1, 2]});

    // '$filter' is not a document.
    var filterDoc = 'string';
    assertErrorCode(coll, [{$project: {b: {$filter: filterDoc}}}], 28646);

    // Extra field(s).
    filterDoc = {input: '$a', as: 'x', cond: true, extra: 1};
    assertErrorCode(coll, [{$project: {b: {$filter: filterDoc}}}], 28647);

    // Missing 'input'.
    filterDoc = {as: 'x', cond: true};
    assertErrorCode(coll, [{$project: {b: {$filter: filterDoc}}}], 28648);

    // Missing 'as'.
    filterDoc = {input: '$a', cond: true};
    assertErrorCode(coll, [{$project: {b: {$filter: filterDoc}}}], 28649);

    // Missing 'cond'.
    filterDoc = {input: '$a', as: 'x'};
    assertErrorCode(coll, [{$project: {b: {$filter: filterDoc}}}], 28650);

    // 'as' is not a valid variable name.
    filterDoc = {input: '$a', as: '$x', cond: true};
    assertErrorCode(coll, [{$project: {b: {$filter: filterDoc}}}], 16867);

    // 'input' is not an array.
    filterDoc = {input: 'string', as: 'x', cond: true};
    assertErrorCode(coll, [{$project: {b: {$filter: filterDoc}}}], 28651);

    coll.drop();
    assert.writeOK(coll.insert({a: 'string'}));
    filterDoc = {input: '$a', as: 'x', cond: true};
    assertErrorCode(coll, [{$project: {b: {$filter: filterDoc}}}], 28651);
}());