From 9e71c66e2d5149bfb8c0daedf035414a70f9d2f4 Mon Sep 17 00:00:00 2001
From: Suyash Kumar <suyashk@google.com>
Date: Wed, 10 Jul 2024 19:55:15 -0700
Subject: [PATCH] Add support for now() FHIR Path version of Now().

This addresses part of https://github.com/google/cql/issues/39.

PiperOrigin-RevId: 651237467
---
 parser/operators.go                         | 11 +++++++++++
 parser/operators_test.go                    | 10 ++++++++++
 tests/enginetests/operator_datetime_test.go | 12 ++++++++++++
 3 files changed, 33 insertions(+)

diff --git a/parser/operators.go b/parser/operators.go
index d61236f..02e45fe 100644
--- a/parser/operators.go
+++ b/parser/operators.go
@@ -1042,6 +1042,17 @@ func (p *Parser) loadSystemOperators() error {
 				}
 			},
 		},
+		{
+			name:     "now",
+			operands: [][]types.IType{{}},
+			model: func() model.IExpression {
+				return &model.Now{
+					NaryExpression: &model.NaryExpression{
+						Expression: model.ResultType(types.DateTime),
+					},
+				}
+			},
+		},
 		{
 			name:     "TimeOfDay",
 			operands: [][]types.IType{{}},
diff --git a/parser/operators_test.go b/parser/operators_test.go
index 8d3525f..11daf1a 100644
--- a/parser/operators_test.go
+++ b/parser/operators_test.go
@@ -812,6 +812,16 @@ func TestBuiltInFunctions(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "now()",
+			cql:  "now()",
+			want: &model.Now{
+				NaryExpression: &model.NaryExpression{
+					Operands:   []model.IExpression{},
+					Expression: model.ResultType(types.DateTime),
+				},
+			},
+		},
 		{
 			name: "TimeOfDay()",
 			cql:  "TimeOfDay()",
diff --git a/tests/enginetests/operator_datetime_test.go b/tests/enginetests/operator_datetime_test.go
index 4568a5f..9470413 100644
--- a/tests/enginetests/operator_datetime_test.go
+++ b/tests/enginetests/operator_datetime_test.go
@@ -726,6 +726,18 @@ func TestEvaluationTimestamp(t *testing.T) {
 			},
 			wantResult: newOrFatal(t, result.DateTime{Date: time.Date(2024, time.January, 1, 0, 0, 0, 1, time.UTC), Precision: model.MILLISECOND}),
 		},
+		{
+			name:                "now() returns passed evaluation timestamp",
+			cql:                 "define TESTRESULT: now()",
+			evaluationTimestamp: time.Date(2024, time.January, 1, 0, 0, 0, 1, time.UTC),
+			wantModel: &model.Now{
+				NaryExpression: &model.NaryExpression{
+					Operands:   []model.IExpression{},
+					Expression: model.ResultType(types.DateTime),
+				},
+			},
+			wantResult: newOrFatal(t, result.DateTime{Date: time.Date(2024, time.January, 1, 0, 0, 0, 1, time.UTC), Precision: model.MILLISECOND}),
+		},
 		{
 			name:                "Time returns passed evaluation timestamp time components",
 			cql:                 "define TESTRESULT: TimeOfDay()",