package audio

import (
	"context"
	"fmt"
	"io"
)

// Sink names (part of the public contract; spec: audio.sink = "oto"|"null").
const (
	NameOto  = "oto"
	NameNull = "null"
)

// Sink plays audio bytes. The bytes come from Provider.Synthesize; oto
// understands RIFF/WAVE (PCM, the delivery format of osbuiltin) and MP3
// (the delivery format of the cloud providers ElevenLabs/OpenAI/Edge).
type Sink interface {
	// Play plays the data and blocks until the end or until ctx is
	// cancelled.
	Play(ctx context.Context, data []byte) error

	// Name returns the sink name (audio.sink configuration).
	Name() string
}

// NewSink returns the sink for the configured name ("oto" or "null"). log
// is an optional log output: the CLI passes its stderr so the null sink can
// write its discard line (nil = discard silently); the oto sink needs no
// log. Unknown names are a clear error.
func NewSink(name string, log io.Writer) (Sink, error) {
	switch name {
	case NameOto:
		return OtoSink{}, nil
	case NameNull:
		return NullSink{W: log}, nil
	default:
		return nil, fmt.Errorf("unknown audio sink %q (allowed: %q, %q)", name, NameOto, NameNull)
	}
}

// NullSink discards every announcement without sound; for CI, servers and
// tests. If W is set (NewSink passes the CLI's log output), Play logs one
// line about it so "runs through silently" stays visible.
type NullSink struct {
	W io.Writer // optional log output; nil = discard silently
}

// Name implements Sink.
func (NullSink) Name() string { return NameNull }

// Play implements Sink: discards the data.
func (n NullSink) Play(ctx context.Context, data []byte) error {
	if n.W != nil {
		fmt.Fprintf(n.W, "audio: %d bytes discarded (null sink)\n", len(data))
	}
	return nil
}