majordomo/provider/llamaswap/sfx.go

// sfx.go implements a second musicgen.Model factory against a Stable Audio
// Open shim (sfxgen) reached through llama-swap's /upstream passthrough
// (ADR-0024):
//
//	POST /upstream/<id>/v1/sfx   JSON {prompt, seconds?, steps?, cfg_scale?, seed?}
//
// Unlike the ACE-Step music path (music.go), /v1/sfx is SYNCHRONOUS: the
// response body is the finished WAV clip — no job queue, no polling. The
// surface reuses the musicgen types (a sound effect is a short audio clip
// from a text prompt); only the provider method differs.
package llamaswap

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"strings"

	"gitea.stevedudenhoeffer.com/steve/majordomo/llm"
	"gitea.stevedudenhoeffer.com/steve/majordomo/musicgen"
)

// SFXModel returns a musicgen.Model bound to a sync sound-effect backend.
// The id selects which upstream llama-swap loads.
func (p *Provider) SFXModel(id string, opts ...musicgen.ModelOption) (musicgen.Model, error) {
	if err := p.requireBaseURL(); err != nil {
		return nil, err
	}
	_ = musicgen.ApplyModelOptions(opts)
	return &sfxModel{p: p, id: id}, nil
}

type sfxModel struct {
	p  *Provider
	id string
}

// sfxRequest is the sfxgen shim's /v1/sfx shape. Optional fields stay off
// the wire so the model's own defaults apply.
type sfxRequest struct {
	Prompt   string   `json:"prompt"`
	Seconds  int      `json:"seconds,omitempty"`
	Steps    *int     `json:"steps,omitempty"`
	CFGScale *float64 `json:"cfg_scale,omitempty"`
	Seed     *int64   `json:"seed,omitempty"`
}

// Generate implements musicgen.Model. The clip-length ceiling (~11s for
// Stable Audio Open Small) is the backend's to enforce, not this client's.
func (m *sfxModel) Generate(ctx context.Context, req musicgen.Request, opts ...musicgen.Option) (*musicgen.Result, error) {
	req = req.Apply(opts...)
	if strings.TrimSpace(req.Prompt) == "" {
		return nil, fmt.Errorf("%w: sfx generation requires a prompt", llm.ErrUnsupported)
	}
	if req.Lyrics != "" {
		return nil, fmt.Errorf("%w: sfx generation does not support lyrics", llm.ErrUnsupported)
	}
	if req.DurationSeconds < 0 {
		return nil, fmt.Errorf("%w: duration must be >= 0, got %d", llm.ErrUnsupported, req.DurationSeconds)
	}
	if req.Steps != nil && *req.Steps <= 0 {
		return nil, fmt.Errorf("%w: inference steps must be > 0, got %d", llm.ErrUnsupported, *req.Steps)
	}
	// The endpoint emits WAV only; a caller asking for another container
	// would silently get mislabelled bytes — reject instead.
	if f := strings.ToLower(strings.TrimSpace(req.Format)); f != "" && f != "wav" {
		return nil, fmt.Errorf("%w: sfx output is wav only, got format %q", llm.ErrUnsupported, req.Format)
	}

	path, err := upstreamPath(m.id, "/v1/sfx")
	if err != nil {
		return nil, err
	}
	wire := sfxRequest{
		Prompt:   req.Prompt,
		Seconds:  req.DurationSeconds,
		Steps:    req.Steps,
		CFGScale: req.CFGScale,
		Seed:     req.Seed,
	}
	encoded, err := json.Marshal(wire)
	if err != nil {
		return nil, fmt.Errorf("llama-swap: encode sfx request: %w", err)
	}
	raw, contentType, err := m.p.doRaw(ctx, http.MethodPost, path, m.id, "application/json", bytes.NewReader(encoded), maxResponseBytes)
	if err != nil {
		return nil, err
	}
	if len(raw) == 0 {
		return nil, &llm.APIError{Provider: m.p.name, Model: m.id, Message: "sfx response contained no audio"}
	}
	mimeType := audioResultMIME(contentType, raw)
	if mimeType == "" {
		return nil, &llm.APIError{Provider: m.p.name, Model: m.id,
			Message: fmt.Sprintf("sfx response is not audio (Content-Type %q): %s", contentType, truncateForError(raw))}
	}
	return &musicgen.Result{Audio: musicgen.Audio{Data: raw, MIME: mimeType}}, nil
}

// audioResultMIME resolves an audio body's MIME type: the response
// Content-Type when it is a concrete audio type, else content sniffing
// (RIFF/WAVE and friends), else "" — the caller treats undetectable as an
// upstream error, mirroring videoMIME. Sniffed "audio/wave" is normalized
// to the conventional "audio/wav".
func audioResultMIME(contentType string, data []byte) string {
	if mt := mimeFromContentType(contentType, "audio/"); mt != "" {
		return mt
	}
	if mt := http.DetectContentType(data); strings.HasPrefix(mt, "audio/") {
		if mt == "audio/wave" {
			return "audio/wav"
		}
		return mt
	}
	return ""
}