// Copyright 2018 The Ebiten 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 audio_test

import (
	"bytes"
	"io"
	"math"
	"testing"

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

func TestInfiniteLoop(t *testing.T) {
	indexToByte := func(index int) byte {
		return byte(math.Sin(float64(index)) * 256)
	}

	src := make([]byte, 256)
	for i := range src {
		src[i] = indexToByte(i)
	}
	l := audio.NewInfiniteLoop(bytes.NewReader(src), int64(len(src)))

	buf := make([]byte, len(src)*4)
	if _, err := io.ReadFull(l, buf); err != nil {
		t.Error(err)
	}
	for i, b := range buf {
		got := b
		want := indexToByte(i % len(src))
		if got != want {
			t.Errorf("index: %d, got: %v, want: %v", i, got, want)
		}
	}

	n, err := l.Seek(int64(len(src))*5+128, io.SeekStart)
	if err != nil {
		t.Error(err)
	}
	if want := int64(128); n != want {
		t.Errorf("got: %v, want: %v", n, want)
	}

	n2, err := l.Seek(int64(len(src))*6+64, io.SeekCurrent)
	if err != nil {
		t.Error(err)
	}
	if want := int64(192); n2 != want {
		t.Errorf("got: %v, want: %v", n, want)
	}

	buf2 := make([]byte, len(src)*7)
	if _, err := io.ReadFull(l, buf2); err != nil {
		t.Error(err)
	}
	for i, b := range buf2 {
		got := b
		want := indexToByte((i + 192) % len(src))
		if got != want {
			t.Errorf("index: %d, got: %v, want: %v", i, got, want)
		}
	}

	// Seek to negative position is an error.
	if _, err := l.Seek(-1, io.SeekStart); err == nil {
		t.Errorf("got: %v, want: %v", err, nil)
	}
}

func TestInfiniteLoopWithIntro(t *testing.T) {
	const (
		srcLength   = 17 * 4
		introLength = 19 * 4
		loopLength  = 23 * 4
	)

	indexToByte := func(index int) byte {
		return byte(math.Sin(float64(index)) * 256)
	}
	src := make([]byte, srcLength)
	for i := range src {
		src[i] = indexToByte(i)
	}
	srcInf := audio.NewInfiniteLoop(bytes.NewReader(src), srcLength)
	srcInf.SetNoBlendForTesting(true)
	l := audio.NewInfiniteLoopWithIntro(srcInf, introLength, loopLength)
	l.SetNoBlendForTesting(true)

	buf := make([]byte, srcLength*4)
	if _, err := io.ReadFull(l, buf); err != nil {
		t.Error(err)
	}
	for i, b := range buf {
		got := b
		want := byte(0)
		if i < introLength {
			want = indexToByte(i % srcLength)
		} else {
			want = indexToByte(((i-introLength)%loopLength + introLength) % srcLength)
		}
		if got != want {
			t.Errorf("index: %d, got: %v, want: %v", i, got, want)
		}
	}

	n, err := l.Seek(srcLength*5+128, io.SeekStart)
	if err != nil {
		t.Error(err)
	}
	if want := int64((srcLength*5+128-introLength)%loopLength + introLength); n != want {
		t.Errorf("got: %v, want: %v", n, want)
	}

	n2, err := l.Seek(srcLength*6+64, io.SeekCurrent)
	if err != nil {
		t.Error(err)
	}
	if want := int64(((srcLength*11+192)-introLength)%loopLength + introLength); n2 != want {
		t.Errorf("got: %v, want: %v", n, want)
	}

	buf2 := make([]byte, srcLength*7)
	if _, err := io.ReadFull(l, buf2); err != nil {
		t.Error(err)
	}
	for i, b := range buf2 {
		got := b
		idx := ((int(n2+int64(i))-introLength)%loopLength + introLength) % srcLength
		want := indexToByte(idx)
		if got != want {
			t.Errorf("index: %d, got: %v, want: %v", i, got, want)
		}
	}

	// Seek to negative position is an error.
	if _, err := l.Seek(-1, io.SeekStart); err == nil {
		t.Errorf("got: %v, want: %v", err, nil)
	}
}

func TestInfiniteLoopWithIncompleteSize(t *testing.T) {
	// s1 should work as if 4092 is given.
	s1 := audio.NewInfiniteLoop(bytes.NewReader(make([]byte, 4096)), 4095)
	n1, err := s1.Seek(4093, io.SeekStart)
	if err != nil {
		t.Error(err)
	}
	if got, want := n1, int64(4093-4092); got != want {
		t.Errorf("got: %d, want: %d", got, want)
	}

	// s2 should work as if 2044 and 2044 are given.
	s2 := audio.NewInfiniteLoopWithIntro(bytes.NewReader(make([]byte, 4096)), 2047, 2046)
	n2, err := s2.Seek(4093, io.SeekStart)
	if err != nil {
		t.Error(err)
	}
	if got, want := n2, int64(2044+(4093-(2044+2044))); got != want {
		t.Errorf("got: %d, want: %d", got, want)
	}
}

type slowReader struct {
	src io.ReadSeeker
	eof bool
}

func (s *slowReader) Read(buf []byte) (int, error) {
	if len(buf) == 0 {
		if s.eof {
			return 0, io.EOF
		}
		return 0, nil
	}

	n, err := s.src.Read(buf[:1])
	if err == io.EOF {
		s.eof = true
	}
	return n, err
}

func (s *slowReader) Seek(offset int64, whence int) (int64, error) {
	s.eof = false
	return s.src.Seek(offset, whence)
}

func TestInfiniteLoopWithSlowSource(t *testing.T) {
	src := make([]byte, 4096)
	for i := range src {
		src[i] = byte(i)
	}
	r := &slowReader{
		src: bytes.NewReader(src),
	}
	loop := audio.NewInfiniteLoop(r, 4096)

	buf := make([]byte, 4096)

	// With a slow source, whose Read always reads at most one byte,
	// an infinite loop should adjust the reading size along with bitDepthInBytes (= 2).

	n0, err := loop.Read(buf)
	if err != nil {
		t.Error(err)
	}
	if got, want := n0, 0; got != want {
		t.Errorf("got: %d, want: %d", got, want)
	}

	n1, err := loop.Read(buf)
	if err != nil {
		t.Error(err)
	}
	if got, want := n1, 2; got != want {
		t.Errorf("got: %d, want: %d", got, want)
	}
	if got, want := buf[0], byte(0); got != want {
		t.Errorf("got: %d, want: %d", got, want)
	}
	if got, want := buf[1], byte(1); got != want {
		t.Errorf("got: %d, want: %d", got, want)
	}

	n2, err := loop.Read(buf)
	if err != nil {
		t.Error(err)
	}
	if got, want := n2, 0; got != want {
		t.Errorf("got: %d, want: %d", got, want)
	}

	n3, err := loop.Read(buf)
	if err != nil {
		t.Error(err)
	}
	if got, want := n3, 2; got != want {
		t.Errorf("got: %d, want: %d", got, want)
	}
	if got, want := buf[0], byte(2); got != want {
		t.Errorf("got: %d, want: %d", got, want)
	}
	if got, want := buf[1], byte(3); got != want {
		t.Errorf("got: %d, want: %d", got, want)
	}
}