feat: support now() time functions

plugin/filter/expr.go

@@ -2,6 +2,7 @@ package filter
 
 import (
 	"errors"
+	"time"
 
 	exprv1 "google.golang.org/genproto/googleapis/api/expr/v1alpha1"
 )
@@ -37,3 +38,90 @@ func GetIdentExprName(expr *exprv1.Expr) (string, error) {
 	}
 	return expr.GetIdentExpr().GetName(), nil
 }
+
+// GetFunctionValue evaluates CEL function calls and returns their value.
+// This is specifically for time functions like now().
+func GetFunctionValue(expr *exprv1.Expr) (any, error) {
+	callExpr, ok := expr.ExprKind.(*exprv1.Expr_CallExpr)
+	if !ok {
+		return nil, errors.New("invalid function call expression")
+	}
+
+	switch callExpr.CallExpr.Function {
+	case "now":
+		if len(callExpr.CallExpr.Args) != 0 {
+			return nil, errors.New("now() function takes no arguments")
+		}
+		return time.Now().Unix(), nil
+	case "_-_":
+		// Handle subtraction for expressions like "now() - 60 * 60 * 24"
+		if len(callExpr.CallExpr.Args) != 2 {
+			return nil, errors.New("subtraction requires exactly two arguments")
+		}
+		left, err := GetExprValue(callExpr.CallExpr.Args[0])
+		if err != nil {
+			return nil, err
+		}
+		right, err := GetExprValue(callExpr.CallExpr.Args[1])
+		if err != nil {
+			return nil, err
+		}
+		leftInt, ok1 := left.(int64)
+		rightInt, ok2 := right.(int64)
+		if !ok1 || !ok2 {
+			return nil, errors.New("subtraction operands must be integers")
+		}
+		return leftInt - rightInt, nil
+	case "_*_":
+		// Handle multiplication for expressions like "60 * 60 * 24"
+		if len(callExpr.CallExpr.Args) != 2 {
+			return nil, errors.New("multiplication requires exactly two arguments")
+		}
+		left, err := GetExprValue(callExpr.CallExpr.Args[0])
+		if err != nil {
+			return nil, err
+		}
+		right, err := GetExprValue(callExpr.CallExpr.Args[1])
+		if err != nil {
+			return nil, err
+		}
+		leftInt, ok1 := left.(int64)
+		rightInt, ok2 := right.(int64)
+		if !ok1 || !ok2 {
+			return nil, errors.New("multiplication operands must be integers")
+		}
+		return leftInt * rightInt, nil
+	case "_+_":
+		// Handle addition
+		if len(callExpr.CallExpr.Args) != 2 {
+			return nil, errors.New("addition requires exactly two arguments")
+		}
+		left, err := GetExprValue(callExpr.CallExpr.Args[0])
+		if err != nil {
+			return nil, err
+		}
+		right, err := GetExprValue(callExpr.CallExpr.Args[1])
+		if err != nil {
+			return nil, err
+		}
+		leftInt, ok1 := left.(int64)
+		rightInt, ok2 := right.(int64)
+		if !ok1 || !ok2 {
+			return nil, errors.New("addition operands must be integers")
+		}
+		return leftInt + rightInt, nil
+	default:
+		return nil, errors.New("unsupported function: " + callExpr.CallExpr.Function)
+	}
+}
+
+// GetExprValue attempts to get a value from an expression, trying constants first, then functions.
+func GetExprValue(expr *exprv1.Expr) (any, error) {
+	// Try to get constant value first
+	if constValue, err := GetConstValue(expr); err == nil {
+		return constValue, nil
+	}
+
+	// If not a constant, try to evaluate as a function
+	return GetFunctionValue(expr)
+}