// Copyright 2025 PingCAP, 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,
// See the License for the specific language governing permissions and
// limitations under the License.

package ringbuffer

import (
	"testing"

	"github.com/stretchr/testify/assert"
)

func TestRingBuffer(t *testing.T) {
	rb := NewRingBuffer[int](3)

	rb.PushBack(1)
	rb.PushBack(2)
	rb.PushBack(3)

	{
		item, ok := rb.Front()
		assert.Equal(t, true, ok)
		assert.Equal(t, 1, item)
	}

	rb.PushBack(4)

	{
		item, ok := rb.Front()
		assert.Equal(t, true, ok)
		assert.Equal(t, 2, item)
	}

	{
		item, ok := rb.Back()
		assert.Equal(t, true, ok)
		assert.Equal(t, 4, item)
	}

	rb.PushBack(5)
	rb.PushBack(6)
	rb.PushBack(7)
	rb.PushBack(8)

	assert.Equal(t, true, rb.IsFull())
	{
		item, ok := rb.Front()
		assert.Equal(t, true, ok)
		assert.Equal(t, 6, item)
	}

	{
		item, ok := rb.Back()
		assert.Equal(t, true, ok)
		assert.Equal(t, 8, item)
	}

	{
		item, ok := rb.PopFront()
		assert.Equal(t, true, ok)
		assert.Equal(t, 6, item)
	}
	{
		item, ok := rb.PopFront()
		assert.Equal(t, true, ok)
		assert.Equal(t, 7, item)
	}
	{
		item, ok := rb.PopFront()
		assert.Equal(t, true, ok)
		assert.Equal(t, 8, item)
	}
	{
		item, ok := rb.PopFront()
		assert.Equal(t, false, ok)
		assert.Equal(t, 0, item)
	}
	assert.Equal(t, true, rb.IsEmpty())

	rb.PushBack(1)
	rb.PushBack(2)
	assert.Equal(t, 2, rb.Length())

	rb.PushBack(3)

	assert.Equal(t, 3, rb.Length())

	{
		item, ok := rb.Front()
		assert.Equal(t, true, ok)
		assert.Equal(t, 1, item)
	}

	rb.PushBack(4)

	{
		item, ok := rb.Front()
		assert.Equal(t, true, ok)
		assert.Equal(t, 2, item)
	}

	{
		item, ok := rb.Back()
		assert.Equal(t, true, ok)
		assert.Equal(t, 4, item)
	}

	{
		itr := rb.ForwardIterator()
		items := make([]int, 0)
		for item, ok := itr.Next(); ok; item, ok = itr.Next() {
			items = append(items, item)
		}
		assert.Equal(t, []int{2, 3, 4}, items)
	}

	{
		itr := rb.BackwardIterator()
		items := make([]int, 0)
		for item, ok := itr.Next(); ok; item, ok = itr.Next() {
			items = append(items, item)
		}
		assert.Equal(t, []int{4, 3, 2}, items)
	}

	{
		item, ok := rb.PopBack()
		assert.Equal(t, true, ok)
		assert.Equal(t, 4, item)
		item, ok = rb.PopBack()
		assert.Equal(t, true, ok)
		assert.Equal(t, 3, item)
		item, ok = rb.PopBack()
		assert.Equal(t, true, ok)
		assert.Equal(t, 2, item)
		_, ok = rb.PopBack()
		assert.Equal(t, false, ok)
	}

	{
		rb.PushBack(1)
		rb.PushBack(2)

		rb.PushBack(3)
		rb.PushBack(4)
		rb.PushBack(5)

		item, ok := rb.PopBack()
		assert.Equal(t, true, ok)
		assert.Equal(t, 5, item)
		item, ok = rb.PopBack()
		assert.Equal(t, true, ok)
		assert.Equal(t, 4, item)
		item, ok = rb.PopBack()
		assert.Equal(t, true, ok)
		assert.Equal(t, 3, item)
		_, ok = rb.PopBack()
		assert.Equal(t, false, ok)
	}

	{
		rb.PushBack(1)
		rb.PushBack(2)

		rb.PushBack(3)
		rb.PushBack(4)
		rb.PushBack(5)

		rb.PushFront(6)
		rb.PushFront(7)
	}

	{
		itr := rb.ForwardIterator()
		items := make([]int, 0)
		for item, ok := itr.Next(); ok; item, ok = itr.Next() {
			items = append(items, item)
		}
		assert.Equal(t, []int{7, 6, 3}, items)
	}

	{
		itr := rb.BackwardIterator()
		items := make([]int, 0)
		for item, ok := itr.Next(); ok; item, ok = itr.Next() {
			items = append(items, item)
		}
		assert.Equal(t, []int{3, 6, 7}, items)
	}
}

func TestRingBufferReverse(t *testing.T) {
	rb := NewRingBuffer[int](3)

	rb.PushFront(1)
	rb.PushFront(2)
	rb.PushFront(3)

	{
		item, ok := rb.Back()
		assert.Equal(t, true, ok)
		assert.Equal(t, 1, item)
	}

	rb.PushFront(4)

	{
		item, ok := rb.Back()
		assert.Equal(t, true, ok)
		assert.Equal(t, 2, item)
	}

	{
		item, ok := rb.Front()
		assert.Equal(t, true, ok)
		assert.Equal(t, 4, item)
	}

	rb.PushFront(5)
	rb.PushFront(6)
	rb.PushFront(7)
	rb.PushFront(8)

	assert.Equal(t, true, rb.IsFull())
	{
		item, ok := rb.Back()
		assert.Equal(t, true, ok)
		assert.Equal(t, 6, item)
	}

	{
		item, ok := rb.Front()
		assert.Equal(t, true, ok)
		assert.Equal(t, 8, item)
	}

	{
		item, ok := rb.PopBack()
		assert.Equal(t, true, ok)
		assert.Equal(t, 6, item)
	}
	{
		item, ok := rb.PopBack()
		assert.Equal(t, true, ok)
		assert.Equal(t, 7, item)
	}
	{
		item, ok := rb.PopBack()
		assert.Equal(t, true, ok)
		assert.Equal(t, 8, item)
	}
	{
		item, ok := rb.PopBack()
		assert.Equal(t, false, ok)
		assert.Equal(t, 0, item)
	}
	assert.Equal(t, true, rb.IsEmpty())

	rb.PushFront(1)
	rb.PushFront(2)
	assert.Equal(t, 2, rb.Length())

	rb.PushFront(3)

	assert.Equal(t, 3, rb.Length())

	{
		item, ok := rb.Back()
		assert.Equal(t, true, ok)
		assert.Equal(t, 1, item)
	}

	rb.PushFront(4)

	{
		item, ok := rb.Back()
		assert.Equal(t, true, ok)
		assert.Equal(t, 2, item)
	}

	{
		item, ok := rb.Front()
		assert.Equal(t, true, ok)
		assert.Equal(t, 4, item)
	}

	{
		itr := rb.BackwardIterator()
		items := make([]int, 0)
		for item, ok := itr.Next(); ok; item, ok = itr.Next() {
			items = append(items, item)
		}
		assert.Equal(t, []int{2, 3, 4}, items)
	}

	{
		itr := rb.ForwardIterator()
		items := make([]int, 0)
		for item, ok := itr.Next(); ok; item, ok = itr.Next() {
			items = append(items, item)
		}
		assert.Equal(t, []int{4, 3, 2}, items)
	}

	{
		item, ok := rb.PopFront()
		assert.Equal(t, true, ok)
		assert.Equal(t, 4, item)
		item, ok = rb.PopFront()
		assert.Equal(t, true, ok)
		assert.Equal(t, 3, item)
		item, ok = rb.PopFront()
		assert.Equal(t, true, ok)
		assert.Equal(t, 2, item)
		_, ok = rb.PopFront()
		assert.Equal(t, false, ok)
	}

	{
		rb.PushFront(1)
		rb.PushFront(2)

		rb.PushFront(3)
		rb.PushFront(4)
		rb.PushFront(5)

		item, ok := rb.PopFront()
		assert.Equal(t, true, ok)
		assert.Equal(t, 5, item)
		item, ok = rb.PopFront()
		assert.Equal(t, true, ok)
		assert.Equal(t, 4, item)
		item, ok = rb.PopFront()
		assert.Equal(t, true, ok)
		assert.Equal(t, 3, item)
		_, ok = rb.PopFront()
		assert.Equal(t, false, ok)
	}

	{
		rb.PushFront(1)
		rb.PushFront(2)

		rb.PushFront(3)
		rb.PushFront(4)
		rb.PushFront(5)

		rb.PushBack(6)
		rb.PushBack(7)
	}

	{
		itr := rb.BackwardIterator()
		items := make([]int, 0)
		for item, ok := itr.Next(); ok; item, ok = itr.Next() {
			items = append(items, item)
		}
		assert.Equal(t, []int{7, 6, 3}, items)
	}

	{
		itr := rb.ForwardIterator()
		items := make([]int, 0)
		for item, ok := itr.Next(); ok; item, ok = itr.Next() {
			items = append(items, item)
		}
		assert.Equal(t, []int{3, 6, 7}, items)
	}
}