// Package audio unifies TTS, STT, Music, and SFX generation under a single
// Manager. Replaces internal/tts (surface preserved via internal/tts/alias.go
// backward-compat layer).
//
// Phase 1 delivers TTS parity; STT/Music/SFX interfaces ship as stubs —
// implementations land in Phase 3 (Music/SFX) and Phase 4 (STT).
package audio

import (
	"context"
	"errors"
	"io"
)

// ErrStreamingNotSupported is returned when a caller requests streaming TTS
// on a provider that does not implement StreamingTTSProvider.
var ErrStreamingNotSupported = errors.New("streaming not supported")

// ---- TTS (implemented Phase 1) ----

// TTSProvider synthesizes text into audio bytes.
type TTSProvider interface {
	Name() string
	Synthesize(ctx context.Context, text string, opts TTSOptions) (*SynthResult, error)
}

// StreamingTTSProvider is the optional streaming extension of TTSProvider.
// Providers that support HTTP chunked streaming implement this to return
// bytes as they arrive, reducing time-to-first-byte for long texts.
type StreamingTTSProvider interface {
	TTSProvider
	SynthesizeStream(ctx context.Context, text string, opts TTSOptions) (*StreamResult, error)
}

// StreamResult is the output of a streaming TTS synthesis call. Callers MUST
// Close the Audio reader when finished to release the underlying HTTP body.
type StreamResult struct {
	Audio     io.ReadCloser // chunked audio stream — caller must Close
	Extension string        // file extension without dot: "mp3", "opus", "ogg"
	MimeType  string        // e.g. "audio/mpeg", "audio/ogg"
}

// TTSOptions carries per-request synthesis parameters.
//
// Params is a read-only map view owned by the caller.
// Implementations MUST NOT mutate it. If a provider needs to merge
// defaults with caller values, it MUST copy before writing.
// READ-ONLY constraint is documented here and enforced by convention.
type TTSOptions struct {
	Voice    string         // provider-specific voice ID
	Model    string         // provider-specific model ID
	Format   string         // output format: "mp3", "opus", etc.
	Speakers []SpeakerVoice // multi-speaker TTS (Gemini); len>0 switches to multi mode
	// Params is a READ-ONLY map owned by the caller. Provider implementations
	// MUST NOT mutate it; copy before merging with defaults.
	Params map[string]any // provider-specific knobs (nested keys like "voice_settings.stability" allowed)
}

// SpeakerVoice binds a speaker label to a voice ID for multi-speaker TTS.
// JSON tags match the frontend MultiSpeakerEditor shape so the persisted
// tts.gemini.speakers blob round-trips without transformation.
type SpeakerVoice struct {
	Speaker string `json:"speaker"` // e.g. "host", "guest"
	VoiceID string `json:"voiceId"` // provider-specific voice ID
}

// SynthResult is the output of a TTS synthesis call.
type SynthResult struct {
	Audio     []byte // raw audio bytes
	Extension string // file extension without dot: "mp3", "opus", "ogg"
	MimeType  string // e.g. "audio/mpeg", "audio/ogg"
}

// AutoMode controls when TTS is automatically applied to replies.
type AutoMode string

const (
	AutoOff     AutoMode = "off"     // Disabled
	AutoAlways  AutoMode = "always"  // Apply to all eligible replies
	AutoInbound AutoMode = "inbound" // Only if user sent audio/voice
	AutoTagged  AutoMode = "tagged"  // Only if reply contains [[tts]] directive
)

// Mode controls which reply kinds get TTS.
type Mode string

const (
	ModeFinal Mode = "final" // Only final replies (default)
	ModeAll   Mode = "all"   // All replies including tool/block
)

// VoiceListProvider is implemented by TTS providers that support dynamic
// voice listing. The HTTP voices handler uses this interface so it is not
// coupled to a specific provider implementation.
type VoiceListProvider interface {
	// ListVoices returns the provider's available voices.
	// Implementations may cache results internally.
	ListVoices(ctx context.Context) ([]Voice, error)
}

// ---- STT (Phase 4) ----

// STTProvider transcribes audio bytes to text.
type STTProvider interface {
	Name() string
	Transcribe(ctx context.Context, in STTInput, opts STTOptions) (*TranscriptResult, error)
}

// STTInput is the audio to transcribe. Bytes or FilePath may be set; FilePath
// preferred for large files to avoid memory pressure.
type STTInput struct {
	Bytes    []byte // raw audio bytes (in-memory)
	FilePath string // path on disk (preferred for >1MB files)
	MimeType string // e.g. "audio/ogg"
	Filename string // original filename (used for multipart form)
}

// STTOptions tunes transcription.
type STTOptions struct {
	Language  string // BCP-47/ISO-639-1 hint, empty = auto-detect
	ModelID   string // provider-specific model ID (default "scribe_v1")
	Diarize   bool   // enable speaker diarization
	TimeoutMs int    // per-call timeout override; 0 = provider default
}

// TranscriptResult is the output of transcription.
type TranscriptResult struct {
	Text     string  // transcribed text
	Language string  // detected or hinted language
	Duration float64 // audio duration in seconds (if returned by provider)
	Provider string  // provider name that produced the transcript
}

// ---- Music (stubs — implementations land in Phase 3) ----

// MusicProvider generates music from prompt + optional lyrics.
type MusicProvider interface {
	Name() string
	GenerateMusic(ctx context.Context, opts MusicOptions) (*AudioResult, error)
}

// MusicOptions controls music generation.
type MusicOptions struct {
	Prompt       string
	Lyrics       string
	Instrumental bool
	Duration     int    // seconds (ElevenLabs: converts to music_length_ms)
	Model        string // provider-specific model override
	TimeoutSec   int    // 0 = provider default
}

// ---- SFX (implementations land in Phase 3) ----

// SFXProvider generates short sound effects from a prompt.
type SFXProvider interface {
	Name() string
	GenerateSFX(ctx context.Context, opts SFXOptions) (*AudioResult, error)
}

// SFXOptions controls SFX generation.
type SFXOptions struct {
	Prompt   string
	Duration int // seconds (provider may cap)
}

// AudioResult is the shared output of music/SFX generation.
type AudioResult struct {
	Audio     []byte
	Extension string
	MimeType  string
	Model     string // actual model used (optional, for observability)
	Provider  string // provider name that produced the audio (optional, for observability)
}