package audio

// Playing a message through the RADIO instead of a sound card.
//
// A SunSDR takes its transmit audio over TCI, on the same socket as the
// commands, so the voice keyer can hand it the message directly: no virtual
// cable, no second sound card, no Windows mixer between the recording and the
// air. To everything above, that radio is simply another output device.
//
// The device it presents itself as is a name rather than a WASAPI endpoint id,
// which is why Play checks for it before opening anything: there is no endpoint
// to open, and asking Windows for one produces a confusing error about a device
// that does not exist rather than the truth, which is that nothing is connected
// to the radio.

import (
	"errors"
	"sync"
)

// NetworkDeviceID is the id the radio-over-network output carries in the
// settings and in the device lists. A fixed string, not a Windows endpoint id:
// it is chosen by us and must survive a radio being switched off and on.
const NetworkDeviceID = "net:radio"

// NetworkPlayer sends already-decoded PCM to the radio, returning when the
// message has been played or when stop is closed.
//
// It carries the same arguments as the sound-card path so that Play can hand
// over whatever it read, and the radio can decide what converting it needs —
// the sample rate a WAV was recorded at is not the radio's business until the
// moment it has to be resampled.
type NetworkPlayer func(pcm []byte, rate, ch, bits int, stop <-chan struct{}) error

var (
	netMu     sync.RWMutex
	netPlayer NetworkPlayer
)

// SetNetworkPlayer installs (or clears, with nil) the radio's transmit path.
//
// Package-level rather than per-Manager: there is one radio, the CAT backend
// owns it, and a Manager that happened to be built before the radio connected
// would otherwise be permanently unable to reach it.
func SetNetworkPlayer(fn NetworkPlayer) {
	netMu.Lock()
	netPlayer = fn
	netMu.Unlock()
}

// networkPlayer returns the installed player, or nil.
func networkPlayer() NetworkPlayer {
	netMu.RLock()
	defer netMu.RUnlock()
	return netPlayer
}

// NetworkPlayerReady says whether a radio is currently able to take transmit
// audio, so the settings panel can offer the option honestly rather than
// listing a device that would fail when used.
func NetworkPlayerReady() bool { return networkPlayer() != nil }

// errNoNetworkRadio is what a message played to a radio that is not there
// comes back with. Named, because "the device could not be opened" would send
// an operator hunting through Windows sound settings for a device that never
// existed.
var errNoNetworkRadio = errors.New("no radio is connected to take the audio — check the CAT link (the radio output only works with a TCI radio)")