package filtering

import (
	"fmt"
	"os"

	"github.com/araddon/qlbridge/datasource"
	"github.com/araddon/qlbridge/expr"
	"github.com/araddon/qlbridge/value"
	"github.com/araddon/qlbridge/vm"
)

type ExprValue struct {
	Node       expr.Node
	Expression string
}

func (e *ExprValue) String() string {
	if e.Node != nil {
		return e.Node.String()
	} else {
		return "<Empty Expression>"
	}
}
func (e *ExprValue) Set(value string) error {
	if value == "" {
		e.Node = nil
		e.Expression = value
		return nil
	}
	ast, err := expr.ParseExpression(value)
	if err != nil {
		return err
	}
	e.Node = ast
	e.Expression = value
	return nil
}

func (e *ExprValue) Validate(line map[string]interface{}) bool {
	if e.Node == nil {
		return true
	}
	context := datasource.NewContextSimpleNative(line)
	val, ok := vm.Eval(context, e.Node)
	if !ok || val == nil { // errors when evaluating
		return false
	}
	if val.Type() != value.BoolType {
		fmt.Fprintln(os.Stderr, "WARNING: The 'where' expression doesn't return a boolean")
		return false
	}
	if val.Value().(bool) != true {
		return false
	}
	return true
}