move all resources to a single file (#3)

Also add some missing doc comments.

Author: quasilyte

audio.go

@@ -0,0 +1,119 @@
+package resource
+
+import (
+	"github.com/hajimehoshi/ebiten/v2"
+	"github.com/hajimehoshi/ebiten/v2/audio"
+	"golang.org/x/image/font"
+)
+
+// AudioID is a typed key for Audio resources.
+// See also: AudioInfo.
+type AudioID int
+
+type AudioInfo struct {
+	// A path that will be used to read the resource data.
+	Path string
+
+	// Group is a sound group ID.
+	// Groups are used to apply group-wide operations like
+	// volume adjustments.
+	// Conventionally, group 0 is "sound effect", 1 is "music", 2 is "voice".
+	Group uint
+
+	// Volume adjust how loud this sound will be.
+	// The default value of 0 means "unadjusted".
+	// Value greated than 0 increases the volume, negative values decrease it.
+	// This setting accepts values in [-1, 1] range, where -1 mutes the sound
+	// while 1 makes it as loud as possible.
+	Volume float64
+}
+
+type Audio struct {
+	// An ID that was associated with this resource.
+	ID AudioID
+
+	// An initialized audio player that can be used to play the audio.
+	// Note that you may need to rewind it before playing the sound.
+	// The player wraps an original stream, so you can't access it directly.
+	Player *audio.Player
+
+	Group  uint
+	Volume float64
+}
+
+// FontID is a typed key for Font resources.
+// See also: FontInfo.
+type FontID int
+
+type FontInfo struct {
+	// A path that will be used to read the resource data.
+	Path string
+
+	Size int
+
+	LineSpacing float64
+}
+
+type Font struct {
+	// An ID that was associated with this resource.
+	ID FontID
+
+	Face font.Face
+}
+
+// ImageID is a typed key for Image resources.
+// See also: ImageInfo.
+type ImageID int
+
+type ImageInfo struct {
+	// A path that will be used to read the resource data.
+	Path string
+
+	FrameWidth  float64
+	FrameHeight float64
+}
+
+type Image struct {
+	// An ID that was associated with this resource.
+	ID ImageID
+
+	// An ebiten Image object initialized from the resource bytes.
+	Data *ebiten.Image
+
+	DefaultFrameWidth  float64
+	DefaultFrameHeight float64
+}
+
+// RawID is a typed key for Raw resources.
+// See also: RawInfo.
+type RawID int
+
+type RawInfo struct {
+	// A path that will be used to read the resource data.
+	Path string
+}
+
+type Raw struct {
+	// An ID that was associated with this resource.
+	ID RawID
+
+	// Data is an uninterpreted resource contents.
+	Data []byte
+}
+
+// ShaderID is a typed key for Shader resources.
+// See also: ShaderInfo.
+type ShaderID int
+
+type ShaderInfo struct {
+	// A path that will be used to read the resource data.
+	Path string
+}
+
+type Shader struct {
+	// An ID that was associated with this resource.
+	ID ShaderID
+
+	// A compiled shader.
+	Data *ebiten.Shader
+}