Implemented expression patcher

pkg/toolkit/expr.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 
 	"github.com/expr-lang/expr"
+	"github.com/expr-lang/expr/ast"
 	"github.com/expr-lang/expr/vm"
 )
 
@@ -38,7 +39,7 @@ func (wc *WhenCond) Evaluate(r *Record) (bool, error) {
 	}
 	wc.rc.SetRecord(r)
 
-	output, err := expr.Run(wc.whenCond, nil)
+	output, err := expr.Run(wc.whenCond, map[string]any{"null": NullValue})
 	if err != nil {
 		return false, fmt.Errorf("unable to evaluate when condition: %w", err)
 	}
@@ -57,9 +58,10 @@ func compileCond(whenCond string, driver *Driver) (*vm.Program, *RecordContext,
 	if whenCond == "" {
 		return nil, nil, nil
 	}
-	rc, funcs := newRecordContext(driver)
+	rc, ops := newRecordContext(driver)
+	ops = append(ops, expr.Patch(exprPatcher{}))
 
-	cond, err := expr.Compile(whenCond, funcs...)
+	cond, err := expr.Compile(whenCond, ops...)
 	if err != nil {
 		return nil, nil, ValidationWarnings{
 			NewValidationWarning().
@@ -87,6 +89,78 @@ func newRecordContext(driver *Driver) (*RecordContext, []expr.Option) {
 		)
 		funcs = append(funcs, f)
 	}
-
 	return rctx, funcs
 }
+
+func valIsNotNull(params ...any) (any, error) {
+	return !valueIsNull(params[0]), nil
+}
+
+func valIsNull(params ...any) (any, error) {
+	vv, ok := params[0].(NullType)
+	if !ok {
+		return false, nil
+	}
+	return vv == NullValue, nil
+}
+
+// exprPatcher - patcher for the expression compiler. It patches the expression tree by some identifiers to
+// function calls. For instance is null, is not null, records address
+type exprPatcher struct{}
+
+func (exprPatcher) Visit(node *ast.Node) {
+	switch {
+	case isNullOp(node):
+	case isNotNullOp(node):
+	case isRecordOp(node):
+		patchRecordOp(node)
+	}
+}
+
+func isNullOp(node *ast.Node) bool {
+	_, ok := (*node).(*ast.IdentifierNode)
+	if !ok {
+		return false
+	}
+	return false
+}
+
+func isNotNullOp(node *ast.Node) bool {
+	_, ok := (*node).(*ast.IdentifierNode)
+	if !ok {
+		return false
+	}
+	return false
+}
+
+func isRecordOp(node *ast.Node) bool {
+	mn, ok := (*node).(*ast.MemberNode)
+	if !ok {
+		return false
+	}
+	owner, ok := (mn.Node).(*ast.IdentifierNode)
+	if !ok {
+		return false
+	}
+	_, ok = (mn.Property).(*ast.StringNode)
+	if !ok {
+		return false
+	}
+	return owner.Value == "record"
+}
+
+func patchRecordOp(node *ast.Node) {
+	mn, ok := (*node).(*ast.MemberNode)
+	if !ok {
+		return
+	}
+	attr, ok := (mn.Property).(*ast.StringNode)
+	if !ok {
+		return
+	}
+	ast.Patch(node, &ast.CallNode{
+		Callee: &ast.IdentifierNode{
+			Value: fmt.Sprintf("__%s", attr.Value),
+		},
+	})
+}