Add audio device switching UI

internal/mixer/device.go

@@ -0,0 +1,108 @@
+package mixer
+
+import (
+	"strings"
+
+	"github.com/veandco/go-sdl2/sdl"
+)
+
+// Device describes an audio output device as seen through SDL's core
+// enumeration APIs. Name is the raw SDL device string used to open the device
+// and to persist the selection; Label is the humanized name shown to the user.
+type Device struct {
+	Name  string
+	Label string
+}
+
+// humanizeRules maps raw SDL device names to human-readable labels. Rules are
+// evaluated in order; the first rule whose keyword is a case-insensitive
+// substring of the raw name wins.
+var humanizeRules = []struct {
+	keywords []string
+	label    string
+}{
+	{[]string{"hdmi", "monitor", "tv"}, "HDMI | Monitor | TV"},
+	{[]string{"headset", "headphone"}, "Headset"},
+	{[]string{"usb"}, "USB"},
+	{[]string{"analog", "built-in", "builtin", "internal", "speaker"}, "Internal Speakers"},
+}
+
+// HumanizeDeviceName maps a raw SDL audio device name to a human-readable
+// label. Raw names come from SDL_GetAudioDeviceName, e.g. PipeWire sink
+// descriptions ("Built-in Audio Analog Stereo", "Built-in Audio Digital
+// Stereo (HDMI)") or PulseAudio sink names ("alsa_output.pci-0000_00_1f.3.
+// analog-stereo"). If no rule matches, the raw name is returned unchanged.
+func HumanizeDeviceName(raw string) string {
+	lower := strings.ToLower(raw)
+	for _, rule := range humanizeRules {
+		for _, kw := range rule.keywords {
+			if strings.Contains(lower, kw) {
+				return rule.label
+			}
+		}
+	}
+	return raw
+}
+
+// enumeratePlaybackDevices returns the available playback devices from SDL's
+// core audio enumeration, each with a humanized label. It is the single place
+// that touches SDL2's device enumeration APIs; a future SDL3 migration only
+// needs to change this function and the mixer.OpenAudioDevice boundary.
+func enumeratePlaybackDevices() []Device {
+	n := sdl.GetNumAudioDevices(false)
+	if n <= 0 {
+		return nil
+	}
+	out := make([]Device, 0, n)
+	for i := 0; i < n; i++ {
+		if name := sdl.GetAudioDeviceName(i, false); name != "" {
+			out = append(out, Device{Name: name, Label: HumanizeDeviceName(name)})
+		}
+	}
+	return out
+}
+
+// ListDevices returns the list of available output devices (from core SDL).
+// Name holds the raw device string (use it with SwitchDevice/CurrentDevice);
+// Label holds the humanized display name.
+func ListDevices() []Device {
+	mu.Lock()
+	defer mu.Unlock()
+	return enumeratePlaybackDevices()
+}
+
+// matchDevice resolves a stored/preferred device name against enumerated
+// device names. An exact match wins; otherwise the first device whose name
+// contains the preferred string (case-insensitive) is returned, tolerating
+// PipeWire/PulseAudio node-name suffixes. Returns false when the preferred
+// name is empty or no device matches.
+func matchDevice(names []string, preferred string) (string, bool) {
+	if preferred == "" {
+		return "", false
+	}
+	for _, name := range names {
+		if name == preferred {
+			return name, true
+		}
+	}
+	lowerPref := strings.ToLower(preferred)
+	for _, name := range names {
+		if strings.Contains(strings.ToLower(name), lowerPref) {
+			return name, true
+		}
+	}
+	return "", false
+}
+
+// resolvePreferredDevice finds the enumeration name to open for a persisted
+// device selection. Returns false when the preferred name is empty or no
+// enumerated device matches, in which case the caller should fall back to the
+// system default.
+func resolvePreferredDevice(preferred string) (string, bool) {
+	devs := enumeratePlaybackDevices()
+	names := make([]string, 0, len(devs))
+	for _, d := range devs {
+		names = append(names, d.Name)
+	}
+	return matchDevice(names, preferred)
+}