fn: add objects.fields

internal/expr/functions/object.go

@@ -0,0 +1,73 @@
+package functions
+
+import (
+	"fmt"
+
+	"github.com/chaisql/chai/internal/environment"
+	"github.com/chaisql/chai/internal/expr"
+	"github.com/chaisql/chai/internal/object"
+	"github.com/chaisql/chai/internal/types"
+)
+
+var objectsFunctions = Definitions{
+	"fields": &definition{
+		name:  "fields",
+		arity: 1,
+		constructorFn: func(args ...expr.Expr) (expr.Function, error) {
+			return &ObjectFields{Expr: args[0]}, nil
+		},
+	},
+}
+
+func ObjectsDefinitions() Definitions {
+	return objectsFunctions
+}
+
+// ObjectFields implements the objects.fields function
+// which returns the list of top-level fields of an object.
+// If the argument is not an object, it returns null.
+type ObjectFields struct {
+	Expr expr.Expr
+}
+
+func (s *ObjectFields) Eval(env *environment.Environment) (types.Value, error) {
+	val, err := s.Expr.Eval(env)
+	if err != nil {
+		return nil, err
+	}
+
+	if val.Type() != types.ObjectValue {
+		return types.NewNullValue(), nil
+	}
+
+	obj := types.As[types.Object](val)
+	var fields []string
+	err = obj.Iterate(func(k string, _ types.Value) error {
+		fields = append(fields, k)
+		return nil
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	return types.NewArrayValue(object.NewArrayFromSlice(fields)), nil
+}
+
+func (s *ObjectFields) IsEqual(other expr.Expr) bool {
+	if other == nil {
+		return false
+	}
+
+	o, ok := other.(*ObjectFields)
+	if !ok {
+		return false
+	}
+
+	return expr.Equal(s.Expr, o.Expr)
+}
+
+func (s *ObjectFields) Params() []expr.Expr { return []expr.Expr{s.Expr} }
+
+func (s *ObjectFields) String() string {
+	return fmt.Sprintf("objects.fields(%v)", s.Expr)
+}