package matchers

import (
	"fmt"
	"reflect"

	"github.com/onsi/gomega/format"
)

type BeClosedMatcher struct {
}

func (matcher *BeClosedMatcher) Match(actual interface{}) (success bool, err error) {
	if !isChan(actual) {
		return false, fmt.Errorf("BeClosed matcher expects a channel.  Got:\n%s", format.Object(actual, 1))
	}

	channelType := reflect.TypeOf(actual)
	channelValue := reflect.ValueOf(actual)

	if channelType.ChanDir() == reflect.SendDir {
		return false, fmt.Errorf("BeClosed matcher cannot determine if a send-only channel is closed or open.  Got:\n%s", format.Object(actual, 1))
	}

	winnerIndex, _, open := reflect.Select([]reflect.SelectCase{
		{Dir: reflect.SelectRecv, Chan: channelValue},
		{Dir: reflect.SelectDefault},
	})

	var closed bool
	if winnerIndex == 0 {
		closed = !open
	} else if winnerIndex == 1 {
		closed = false
	}

	return closed, nil
}

func (matcher *BeClosedMatcher) FailureMessage(actual interface{}) (message string) {
	return format.Message(actual, "to be closed")
}

func (matcher *BeClosedMatcher) NegatedFailureMessage(actual interface{}) (message string) {
	return format.Message(actual, "to be open")
}