// Fenrir console screen reader.
// Copyright (c) 2026 Storm Dragon
// SPDX-License-Identifier: GPL-3.0-or-later

package sound

/*
#cgo pkg-config: alsa
#include <alsa/asoundlib.h>
#include <stdlib.h>

static int fenrir_pcm_open(snd_pcm_t **pcm, const char *device) {
    int result = snd_pcm_open(pcm, device, SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK);
    if (result < 0) return result;
    result = snd_pcm_set_params(*pcm, SND_PCM_FORMAT_FLOAT,
        SND_PCM_ACCESS_RW_INTERLEAVED, 2, 48000, 1, 20000);
    if (result < 0) {
        snd_pcm_close(*pcm);
        *pcm = NULL;
    }
    return result;
}
*/
import "C"

import (
	"fmt"
	"syscall"
	"unsafe"
)

type alsaPCM struct{ handle *C.snd_pcm_t }

func open_alsa(s *Service, device string) error {
	name := C.CString(device)
	defer C.free(unsafe.Pointer(name))
	pcm := &alsaPCM{}
	if result := C.fenrir_pcm_open(&pcm.handle, name); result < 0 {
		return fmt.Errorf("open ALSA PCM %q: %s", device, C.GoString(C.snd_strerror(result)))
	}
	s.start_pcm(pcm)
	return nil
}

// ALSA receives interleaved native-endian stereo float samples. All PCM calls
// after setup belong to the playback worker; Close runs after that worker exits.
func (p *alsaPCM) write(samples []float32) (int, error) {
	result := C.snd_pcm_writei(p.handle, unsafe.Pointer(&samples[0]), C.snd_pcm_uframes_t(len(samples)/2))
	if result < 0 {
		return 0, syscall.Errno(-result)
	}
	return int(result) * 2, nil
}
func (p *alsaPCM) prepare() error { return pcm_error(C.snd_pcm_prepare(p.handle)) }
func (p *alsaPCM) drain() error   { return pcm_error(C.snd_pcm_drain(p.handle)) }
func (p *alsaPCM) close()         { C.snd_pcm_drop(p.handle); C.snd_pcm_close(p.handle) }
func pcm_error(result C.int) error {
	if result < 0 {
		return syscall.Errno(-result)
	}
	return nil
}