package list

import (
	"github.com/stretchr/testify/assert"
	"pgregory.net/rapid"
	"testing"
)

func TestListLen(t *testing.T) {
	assert.Equal(t, 0, Empty().Len(), "should insert at head")
	assert.Equal(t, 1, Empty().Conj(1).Len(), "should insert at head")
	assert.Equal(t, 2, Empty().Conj(1).Conj(2).Len(), "should insert at head")
}

func TestListString(t *testing.T) {
	assert.Equal(t, "()", Empty().String(), "should insert at head")
}

func TestListConj(t *testing.T) {
	var l IList
	assert.Equal(t, "()", Empty().String(), "should insert at head")
	l = New(5)
	assert.Equal(t, "(5)", l.String(), "should insert at head")
	l = Empty().Conj(4)
	assert.Equal(t, "(4)", l.String(), "should insert at head")
}

func TestListFirst(t *testing.T) {
	l := Empty().Conj(5).Conj(6).Conj(7)
	assert.Equal(t, 7, l.First(), "should return first element")
	assert.Equal(t, nil, Empty().First(), "should return nil")
}

func TestListRest(t *testing.T) {
	l := Empty().Conj(5).Conj(6).Conj(7)
	assert.Equal(t, "(6 5)", l.Rest().String(), "should return rest sublist")
	assert.Equal(t, "(5)", l.Rest().Rest().String(), "should return rest sublist")
	assert.Equal(t, "()", l.Rest().Rest().Rest().String(), "should return rest sublist")
	assert.Equal(t, Empty(), Empty().Rest(), "should return rest sublist")
	assert.Equal(t, Empty(), Rest(Empty().Rest()), "should return rest sublist")
}

// generative tests
func ListLengthProperty(t *testing.T) {
	myList := Empty()
	expectedSized := 0
	rapid.Check(t, func(t *rapid.T) {
		t.Repeat(map[string]func(*rapid.T){
			"conj": func(t *rapid.T) {
				expectedSized += 1
				myList = myList.Conj(rapid.Int().Draw(t, "el"))
			},
			"rest": func(t *rapid.T) {
				if !myList.IsEmpty() {
					expectedSized -= 1
				}
				myList = myList.Rest()
			},
			"": func(t *rapid.T) {
				assert.Equal(t, myList.Len(), expectedSized, "must be equal")
			},
		})
	})
}