audio: reduce dependency on the package oto

Updates #1900

audio/oto.go

@@ -0,0 +1,43 @@
+// Copyright 2021 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
+
+import (
+	"io"
+
+	"github.com/hajimehoshi/oto/v2"
+)
+
+// otoContext is an interface for *oto.Context.
+type otoContext interface {
+	NewPlayer(io.Reader) oto.Player
+	Suspend() error
+	Resume() error
+	Err() error
+}
+
+// contextProxy is a proxy between otoContext and context.
+type contextProxy struct {
+	otoContext
+}
+
+// contextProxy implements context.
+func (c *contextProxy) NewPlayer(r io.Reader) otoPlayer {
+	return c.otoContext.NewPlayer(r)
+}
+
+func otoContextToContext(ctx otoContext) context {
+	return &contextProxy{ctx}
+}

audio/player.go

@@ -19,12 +19,24 @@ import (
 	"runtime"
 	"sync"
 	"time"
-
-	"github.com/hajimehoshi/oto/v2"
 )
 
+// otoPlayer is exactly same as the interface oto.Player.
+// This is defined in order to remove the dependency on Oto from this file.
+type otoPlayer interface {
+	Pause()
+	Play()
+	IsPlaying() bool
+	Reset()
+	Volume() float64
+	SetVolume(volume float64)
+	UnplayedBufferSize() int
+	Err() error
+	io.Closer
+}
+
 type context interface {
-	NewPlayer(io.Reader) oto.Player
+	NewPlayer(io.Reader) otoPlayer
 	Suspend() error
 	Resume() error
 	Err() error
@@ -52,7 +64,7 @@ func newPlayerFactory(sampleRate int) *playerFactory {
 
 type player struct {
 	context *Context
-	player  oto.Player
+	player  otoPlayer
 	src     io.Reader
 	stream  *timeStream
 	factory *playerFactory

audio/player_js.go

@@ -26,8 +26,9 @@ func newContext(sampleRate, channelNum, bitDepthInBytes int) (context, chan stru
 	if js.Global().Get("go2cpp").Truthy() {
 		ready := make(chan struct{})
 		close(ready)
-		return go2cpp.NewContext(sampleRate, channelNum, bitDepthInBytes), ready, nil
+		return otoContextToContext(go2cpp.NewContext(sampleRate, channelNum, bitDepthInBytes)), ready, nil
 	}
 
-	return oto.NewContext(sampleRate, channelNum, bitDepthInBytes)
+	ctx, ready, err := oto.NewContext(sampleRate, channelNum, bitDepthInBytes)
+	return otoContextToContext(ctx), ready, err
 }

audio/player_notjs.go

@@ -22,5 +22,6 @@ import (
 )
 
 func newContext(sampleRate, channelNum, bitDepthInBytes int) (context, chan struct{}, error) {
-	return oto.NewContext(sampleRate, channelNum, bitDepthInBytes)
+	ctx, ready, err := oto.NewContext(sampleRate, channelNum, bitDepthInBytes)
+	return otoContextToContext(ctx), ready, err
 }