package list

import (
	"regexp"
	"strings"
	"testing"

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

// intListGen returns a generator for either empty list or random ints
func intListGen() *rapid.Generator[IList] {
	return rapid.OneOf(rapid.Custom(func(t *rapid.T) IList {
		myList := Empty()
		t.Repeat(map[string]func(*rapid.T){
			"conj": func(t *rapid.T) {
				myList = myList.Conj(rapid.Int().Draw(t, "el"))
			},
		})
		return myList
	}), rapid.Just(Empty()))
}

// descSortedIntListGen returns a generator for list of at least several descending ints
func descSortedIntListGen() *rapid.Generator[IList] {
	return rapid.Custom(func(t *rapid.T) IList {
		myList := New(0)
		i := 1
		t.Repeat(map[string]func(*rapid.T){
			"conj": func(t *rapid.T) {
				myList = myList.Conj(i)
				i += 1
			},
		})
		return myList
	}).Filter(func(l IList) bool {
		return l.Len() > 1
	})
}

func TestFirstIsNilOnlyWhenEmpty(t *testing.T) {
	assert.Equal(t, 1, New(3).Conj(2).Conj(1).First())

	rapid.Check(t, func(t *rapid.T) {
		myList := intListGen().Draw(t, "myList")
		assert.Equal(t, myList.IsEmpty(), myList.First() == nil, "first is nil only when list is empty")
	})
}

func TestConj(t *testing.T) {
	rapid.Check(t, func(t *rapid.T) {
		myList := intListGen().Draw(t, "myList")
		newElem := rapid.Int().Draw(t, "newElem")
		myList2 := myList.Conj(newElem)
		assert.Equal(t, myList.Len()+1, myList2.Len(), "conj increases length")
		assert.Equal(t, newElem, myList2.First(), "first after conj returns inserted number")
	})
}

func TestRest(t *testing.T) {
	rapid.Check(t, func(t *rapid.T) {
		myList := intListGen().Draw(t, "myList")
		if myList.IsEmpty() {
			assert.Equal(t, myList.Len(), myList.Rest().Len(), "rest does not change length for empty list")
		} else {
			assert.Equal(t, myList.Len()-1, myList.Rest().Len(), "rest decreases length of non-empty list")
		}
	})

	rapid.Check(t, func(t *rapid.T) {
		myList := descSortedIntListGen().Draw(t, "myList")
		assert.Greater(t, myList.First(), myList.Rest().First(), "rest decreases value in list head")
	})
}

func TestStringifyIntList(t *testing.T) {
	assert.Equal(t, "(1 2 3)", New(3).Conj(2).Conj(1).String())

	rapid.Check(t, func(t *rapid.T) {
		myList := intListGen().Draw(t, "myList")
		s := myList.String()
		r := regexp.MustCompile(`^\([\d\s-]*\)$`)
		assert.True(t, r.Match([]byte(s)), s+" looks like a stringified list")
		if !myList.IsEmpty() {
			assert.Equal(t, myList.Len(), strings.Count(s, " ")+1, "number of spaces in string should match count of elements")
		} else {
			assert.Equal(t, 0, strings.Count(s, " "), "no spaces in string for empty list")
		}
	})
}