From bba4c0a63006e936644301483d6f7a0d29283f37 Mon Sep 17 00:00:00 2001
From: Asdine El Hrychy <asdine.elhrychy@gmail.com>
Date: Sun, 25 Jul 2021 22:35:18 -0400
Subject: [PATCH] Add typeof function

---
 internal/expr/functions/builtins.go           | 41 +++++++++++++++++++
 internal/expr/functions/builtins_test.go      |  5 +++
 .../functions/testdata/builtin_functions.sql  | 36 ++++++++++++++++
 3 files changed, 82 insertions(+)
 create mode 100644 internal/expr/functions/testdata/builtin_functions.sql

diff --git a/internal/expr/functions/builtins.go b/internal/expr/functions/builtins.go
index 785e2a3e2..15bdb559d 100644
--- a/internal/expr/functions/builtins.go
+++ b/internal/expr/functions/builtins.go
@@ -11,6 +11,13 @@ import (
 )
 
 var builtinFunctions = Definitions{
+	"typeof": &definition{
+		name:  "typeof",
+		arity: 1,
+		constructorFn: func(args ...expr.Expr) (expr.Function, error) {
+			return &TypeOf{Expr: args[0]}, nil
+		},
+	},
 	"pk": &definition{
 		name:  "pk",
 		arity: 0,
@@ -60,6 +67,40 @@ func BuiltinDefinitions() Definitions {
 	return builtinFunctions
 }
 
+type TypeOf struct {
+	Expr expr.Expr
+}
+
+func (t *TypeOf) Eval(env *environment.Environment) (types.Value, error) {
+	v, err := t.Expr.Eval(env)
+	if err != nil {
+		return nil, err
+	}
+
+	return types.NewTextValue(v.Type().String()), nil
+}
+
+// IsEqual compares this expression with the other expression and returns
+// true if they are equal.
+func (t *TypeOf) IsEqual(other expr.Expr) bool {
+	if other == nil {
+		return false
+	}
+
+	o, ok := other.(*TypeOf)
+	if !ok {
+		return false
+	}
+
+	return expr.Equal(t.Expr, o.Expr)
+}
+
+func (t *TypeOf) Params() []expr.Expr { return []expr.Expr{t.Expr} }
+
+func (t *TypeOf) String() string {
+	return stringutil.Sprintf("typeof(%v)", t.Expr)
+}
+
 // PK represents the pk() function.
 // It returns the primary key of the current document.
 type PK struct{}
diff --git a/internal/expr/functions/builtins_test.go b/internal/expr/functions/builtins_test.go
index c98723605..7ba5e6e43 100644
--- a/internal/expr/functions/builtins_test.go
+++ b/internal/expr/functions/builtins_test.go
@@ -2,6 +2,7 @@ package functions_test
 
 import (
 	"bytes"
+	"path/filepath"
 	"testing"
 
 	"github.com/genjidb/genji/document"
@@ -56,3 +57,7 @@ func TestPk(t *testing.T) {
 		})
 	}
 }
+
+func TestBuiltinFunctions(t *testing.T) {
+	testutil.ExprRunner(t, filepath.Join("testdata", "builtin_functions.sql"))
+}
diff --git a/internal/expr/functions/testdata/builtin_functions.sql b/internal/expr/functions/testdata/builtin_functions.sql
new file mode 100644
index 000000000..191c1ca3f
--- /dev/null
+++ b/internal/expr/functions/testdata/builtin_functions.sql
@@ -0,0 +1,36 @@
+-- test: typeof
+! typeof()
+
+! typeof(a)
+'field not found'
+
+> typeof(1)
+'integer'
+
+> typeof(1 + 1)
+'integer'
+
+> typeof(2.0)
+'double'
+
+> typeof(2.0)
+'double'
+
+> typeof(true)
+'bool'
+
+> typeof('hello')
+'text'
+
+> typeof('\xAA')
+'blob'
+
+> typeof([])
+'array'
+
+> typeof({})
+'document'
+
+> typeof(NULL)
+'null'
+