// Copyright 2024 The Ebitengine Authors
//
// 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 convert_test

import (
	"bytes"
	"io"
	"math/rand/v2"
	"testing"
	"unsafe"

	"github.com/hajimehoshi/ebiten/v2/audio/internal/convert"
)

func randInt16s(n int) []int16 {
	r := make([]int16, n)
	for i := range r {
		r[i] = int16(rand.IntN(1<<16) - (1 << 15))
	}
	return r
}

func TestFloat32(t *testing.T) {
	type testCase struct {
		Name string
		In   []int16
	}
	cases := []testCase{
		{
			Name: "empty",
			In:   nil,
		},
		{
			Name: "-1, 0, 1",
			In:   []int16{-32768, 0, 32767},
		},
		{
			Name: "8 0s",
			In:   []int16{0, 0, 0, 0, 0, 0, 0, 0},
		},
		{
			Name: "random 256 values",
			In:   randInt16s(256),
		},
		{
			Name: "random 65536 values",
			In:   randInt16s(65536),
		},
	}
	for _, c := range cases {
		c := c
		t.Run(c.Name, func(t *testing.T) {
			for _, seek := range []bool{false, true} {
				seek := seek
				name := "nonseek"
				if seek {
					name = "seek"
				}
				t.Run(name, func(t *testing.T) {
					var in, out []byte
					if len(c.In) > 0 {
						outF32 := make([]float32, len(c.In))
						for i := range c.In {
							outF32[i] = float32(c.In[i]) / (1 << 15)
						}
						in = unsafe.Slice((*byte)(unsafe.Pointer(unsafe.SliceData(c.In))), len(c.In)*2)
						out = unsafe.Slice((*byte)(unsafe.Pointer(unsafe.SliceData(outF32))), len(outF32)*4)
					}
					r := convert.NewFloat32BytesReaderFromInt16BytesReader(bytes.NewReader(in)).(io.ReadSeeker)
					var got []byte
					for {
						var buf [97]byte
						n, err := r.Read(buf[:])
						got = append(got, buf[:n]...)
						if err != nil {
							if err != io.EOF {
								t.Fatal(err)
							}
							break
						}
						if seek {
							// Shifting by incomplete bytes should not affect the result.
							for i := 0; i < 4; i++ {
								if _, err := r.Seek(int64(i), io.SeekCurrent); err != nil {
									if err != io.EOF {
										t.Fatal(err)
									}
									break
								}
							}
						}
					}
					want := out
					if !bytes.Equal(got, want) {
						t.Errorf("got: %v, want: %v", got, want)
					}
				})
			}
		})
	}
}