// Copyright 2010 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package gomock

import (
	"fmt"
	"reflect"
	"strings"
)

// A Matcher is a representation of a class of values.
// It is used to represent the valid or expected arguments to a mocked method.
type Matcher interface {
	// Matches returns whether x is a match.
	Matches(x interface{}) bool

	// String describes what the matcher matches.
	String() string
}

// WantFormatter modifies the given Matcher's String() method to the given
// Stringer. This allows for control on how the "Want" is formatted when
// printing .
func WantFormatter(s fmt.Stringer, m Matcher) Matcher {
	type matcher interface {
		Matches(x interface{}) bool
	}

	return struct {
		matcher
		fmt.Stringer
	}{
		matcher:  m,
		Stringer: s,
	}
}

// StringerFunc type is an adapter to allow the use of ordinary functions as
// a Stringer. If f is a function with the appropriate signature,
// StringerFunc(f) is a Stringer that calls f.
type StringerFunc func() string

// String implements fmt.Stringer.
func (f StringerFunc) String() string {
	return f()
}

// GotFormatter is used to better print failure messages. If a matcher
// implements GotFormatter, it will use the result from Got when printing
// the failure message.
type GotFormatter interface {
	// Got is invoked with the received value. The result is used when
	// printing the failure message.
	Got(got interface{}) string
}

// GotFormatterFunc type is an adapter to allow the use of ordinary
// functions as a GotFormatter. If f is a function with the appropriate
// signature, GotFormatterFunc(f) is a GotFormatter that calls f.
type GotFormatterFunc func(got interface{}) string

// Got implements GotFormatter.
func (f GotFormatterFunc) Got(got interface{}) string {
	return f(got)
}

// GotFormatterAdapter attaches a GotFormatter to a Matcher.
func GotFormatterAdapter(s GotFormatter, m Matcher) Matcher {
	return struct {
		GotFormatter
		Matcher
	}{
		GotFormatter: s,
		Matcher:      m,
	}
}

type anyMatcher struct{}

func (anyMatcher) Matches(interface{}) bool {
	return true
}

func (anyMatcher) String() string {
	return "is anything"
}

type eqMatcher struct {
	x interface{}
}

func (e eqMatcher) Matches(x interface{}) bool {
	return reflect.DeepEqual(e.x, x)
}

func (e eqMatcher) String() string {
	return fmt.Sprintf("is equal to %v", e.x)
}

type nilMatcher struct{}

func (nilMatcher) Matches(x interface{}) bool {
	if x == nil {
		return true
	}

	v := reflect.ValueOf(x)
	switch v.Kind() {
	case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map,
		reflect.Ptr, reflect.Slice:
		return v.IsNil()
	}

	return false
}

func (nilMatcher) String() string {
	return "is nil"
}

type notMatcher struct {
	m Matcher
}

func (n notMatcher) Matches(x interface{}) bool {
	return !n.m.Matches(x)
}

func (n notMatcher) String() string {
	// TODO: Improve this if we add a NotString method to the Matcher interface.
	return "not(" + n.m.String() + ")"
}

type assignableToTypeOfMatcher struct {
	targetType reflect.Type
}

func (m assignableToTypeOfMatcher) Matches(x interface{}) bool {
	return reflect.TypeOf(x).AssignableTo(m.targetType)
}

func (m assignableToTypeOfMatcher) String() string {
	return "is assignable to " + m.targetType.Name()
}

type allMatcher struct {
	matchers []Matcher
}

func (am allMatcher) Matches(x interface{}) bool {
	for _, m := range am.matchers {
		if !m.Matches(x) {
			return false
		}
	}
	return true
}

func (am allMatcher) String() string {
	ss := make([]string, 0, len(am.matchers))
	for _, matcher := range am.matchers {
		ss = append(ss, matcher.String())
	}
	return strings.Join(ss, "; ")
}

type lenMatcher struct {
	i int
}

func (m lenMatcher) Matches(x interface{}) bool {
	v := reflect.ValueOf(x)
	switch v.Kind() {
	case reflect.Array, reflect.Chan, reflect.Map, reflect.Slice, reflect.String:
		return v.Len() == m.i
	default:
		return false
	}
}

func (m lenMatcher) String() string {
	return fmt.Sprintf("has length %d", m.i)
}

// Constructors

// All returns a composite Matcher that returns true if and only all of the
// matchers return true.
func All(ms ...Matcher) Matcher { return allMatcher{ms} }

// Any returns a matcher that always matches.
func Any() Matcher { return anyMatcher{} }

// Eq returns a matcher that matches on equality.
//
// Example usage:
//   Eq(5).Matches(5) // returns true
//   Eq(5).Matches(4) // returns false
func Eq(x interface{}) Matcher { return eqMatcher{x} }

// Len returns a matcher that matches on length. This matcher returns false if
// is compared to a type that is not an array, chan, map, slice, or string.
func Len(i int) Matcher {
	return lenMatcher{i}
}

// Nil returns a matcher that matches if the received value is nil.
//
// Example usage:
//   var x *bytes.Buffer
//   Nil().Matches(x) // returns true
//   x = &bytes.Buffer{}
//   Nil().Matches(x) // returns false
func Nil() Matcher { return nilMatcher{} }

// Not reverses the results of its given child matcher.
//
// Example usage:
//   Not(Eq(5)).Matches(4) // returns true
//   Not(Eq(5)).Matches(5) // returns false
func Not(x interface{}) Matcher {
	if m, ok := x.(Matcher); ok {
		return notMatcher{m}
	}
	return notMatcher{Eq(x)}
}

// AssignableToTypeOf is a Matcher that matches if the parameter to the mock
// function is assignable to the type of the parameter to this function.
//
// Example usage:
//   var s fmt.Stringer = &bytes.Buffer{}
//   AssignableToTypeOf(s).Matches(time.Second) // returns true
//   AssignableToTypeOf(s).Matches(99) // returns false
//
//   var ctx = reflect.TypeOf((*context.Context)).Elem()
//   AssignableToTypeOf(ctx).Matches(context.Background()) // returns true
func AssignableToTypeOf(x interface{}) Matcher {
	if xt, ok := x.(reflect.Type); ok {
		return assignableToTypeOfMatcher{xt}
	}
	return assignableToTypeOfMatcher{reflect.TypeOf(x)}
}
