1package matchers
 2
 3import (
 4	"fmt"
 5	"reflect"
 6
 7	"github.com/onsi/gomega/format"
 8)
 9
10type SatisfyMatcher struct {
11	Predicate interface{}
12
13	// cached type
14	predicateArgType reflect.Type
15}
16
17func NewSatisfyMatcher(predicate interface{}) *SatisfyMatcher {
18	if predicate == nil {
19		panic("predicate cannot be nil")
20	}
21	predicateType := reflect.TypeOf(predicate)
22	if predicateType.Kind() != reflect.Func {
23		panic("predicate must be a function")
24	}
25	if predicateType.NumIn() != 1 {
26		panic("predicate must have 1 argument")
27	}
28	if predicateType.NumOut() != 1 || predicateType.Out(0).Kind() != reflect.Bool {
29		panic("predicate must return bool")
30	}
31
32	return &SatisfyMatcher{
33		Predicate:        predicate,
34		predicateArgType: predicateType.In(0),
35	}
36}
37
38func (m *SatisfyMatcher) Match(actual interface{}) (success bool, err error) {
39	// prepare a parameter to pass to the predicate
40	var param reflect.Value
41	if actual != nil && reflect.TypeOf(actual).AssignableTo(m.predicateArgType) {
42		// The dynamic type of actual is compatible with the predicate argument.
43		param = reflect.ValueOf(actual)
44
45	} else if actual == nil && m.predicateArgType.Kind() == reflect.Interface {
46		// The dynamic type of actual is unknown, so there's no way to make its
47		// reflect.Value. Create a nil of the predicate argument, which is known.
48		param = reflect.Zero(m.predicateArgType)
49
50	} else {
51		return false, fmt.Errorf("predicate expects '%s' but we have '%T'", m.predicateArgType, actual)
52	}
53
54	// call the predicate with `actual`
55	fn := reflect.ValueOf(m.Predicate)
56	result := fn.Call([]reflect.Value{param})
57	return result[0].Bool(), nil
58}
59
60func (m *SatisfyMatcher) FailureMessage(actual interface{}) (message string) {
61	return format.Message(actual, "to satisfy predicate", m.Predicate)
62}
63
64func (m *SatisfyMatcher) NegatedFailureMessage(actual interface{}) (message string) {
65	return format.Message(actual, "to not satisfy predicate", m.Predicate)
66}