func EvaluateUnaryExpr(expr *ast.UnaryExpr, context *Context) ast.Value {
var val ast.Value = nil
switch t := expr.Expr.(type) {
case *ast.BinaryExpr:
val = EvaluateBinaryExpr(t, context)
case *ast.UnaryExpr:
val = EvaluateUnaryExpr(t, context)
case *ast.Variable:
if varVal, ok := context.GetVariable(t.Name); ok {
val = varVal.(ast.Expr)
}
default:
val = ast.Value(t)
}
switch expr.Op.Type {
case ast.T_NOP:
// do nothing
case ast.T_LOGICAL_NOT:
if bVal, ok := val.(ast.BooleanValue); ok {
val = ast.NewBoolean(bVal.Boolean())
}
case ast.T_MINUS:
switch n := val.(type) {
case *ast.Number:
n.Value = -n.Value
}
}
return val
}
/*
EvaluateBinaryExpr recursively.
*/
func EvaluateBinaryExpr(expr *ast.BinaryExpr, context *Context) ast.Value {
var lval ast.Value = nil
var rval ast.Value = nil
switch expr := expr.Left.(type) {
case *ast.BinaryExpr:
lval = EvaluateBinaryExpr(expr, context)
case *ast.UnaryExpr:
lval = EvaluateUnaryExpr(expr, context)
case *ast.Variable:
if varVal, ok := context.GetVariable(expr.Name); ok {
lval = varVal.(ast.Expr)
}
default:
lval = ast.Value(expr)
}
switch expr := expr.Right.(type) {
case *ast.UnaryExpr:
rval = EvaluateUnaryExpr(expr, context)
case *ast.BinaryExpr:
rval = EvaluateBinaryExpr(expr, context)
case *ast.Variable:
if varVal, ok := context.GetVariable(expr.Name); ok {
rval = varVal.(ast.Expr)
}
default:
rval = ast.Value(expr)
}
if lval != nil && rval != nil {
return Compute(expr.Op, lval, rval)
}
return nil
}
/*
EvaluateExpr calls EvaluateBinaryExpr. except EvaluateExpr
prevents calculate css slash as division. otherwise it's the same as
EvaluateBinaryExpr.
*/
func EvaluateExpr(expr ast.Expr, context *Context) ast.Value {
switch t := expr.(type) {
case *ast.BinaryExpr:
// For binary expression that is a CSS slash, we evaluate the expression as a literal string (unquoted)
if t.IsCssSlash() {
// return string object without quote
return ast.NewString(0, t.Left.(*ast.Number).String()+"/"+t.Right.(*ast.Number).String(), nil)
}
return EvaluateBinaryExpr(t, context)
case *ast.UnaryExpr:
return EvaluateUnaryExpr(t, context)
default:
return ast.Value(expr)
}
}
func EvaluateUnaryExprInBooleanContext(expr *ast.UnaryExpr, context *Context) ast.Value {
var val ast.Value = nil
switch t := expr.Expr.(type) {
case *ast.BinaryExpr:
val = EvaluateBinaryExpr(t, context)
case *ast.UnaryExpr:
val = EvaluateUnaryExpr(t, context)
default:
val = ast.Value(t)
}
switch expr.Op.Type {
case ast.T_LOGICAL_NOT:
if bval, ok := val.(ast.BooleanValue); ok {
return ast.NewBoolean(bval.Boolean())
} else {
panic(fmt.Errorf("BooleanValue interface is not support for %+v", val))
}
}
return val
}