frontend/src/api/facezoomClient.ts

/**
 * facezoomClient.ts — API client for the Face Zoom feature.
 *
 * Completely independent of client.ts, upscaleClient.ts, bgremoveClient.ts,
 * facerestoreClient.ts, and objectRemovalClient.ts.
 * Do not import from or share state with any other feature's client.
 *
 * Endpoints
 * ---------
 * POST /facezoom/upload          — submit image, get job_id back immediately
 * GET  /facezoom/result/{job_id} — poll status; completed response carries
 *                                  per-face results (face_index, image URL,
 *                                  codeformer_applied, similarity)
 * POST /facezoom/download        — JSON body {job_id, face_indices} → ZIP blob
 *
 * ZIP download pattern
 * --------------------
 * Unlike all other features (single image via GET), Face Zoom downloads a ZIP
 * via POST with a JSON body (because the caller selects which face indices to
 * include).  The response is a binary blob (application/zip) — we convert it
 * to an object URL and trigger a temporary <a> click.  A plain <a href download>
 * is NOT used because cross-origin binary POSTs require a fetch first.
 */

export const FACEZOOM_API_BASE = import.meta.env.VITE_API_BASE ?? "http://localhost:8000";

// ---------------------------------------------------------------------------
// Types
// ---------------------------------------------------------------------------

export interface FaceZoomFaceResult {
  face_index:         number;
  result_image_url:   string;   // full http://localhost:8000/storage/… URL
  codeformer_applied: boolean;  // true = CodeFormer accepted; false = ESRGAN-only
  similarity:         number;   // ArcFace cosine sim (0.0–1.0)
}

export interface FaceZoomResult {
  job_id:        string;
  status:        "pending" | "processing" | "completed" | "failed";
  error_message: string | null;
  faces:         FaceZoomFaceResult[];  // empty until completed
}

// ---------------------------------------------------------------------------
// Upload
// ---------------------------------------------------------------------------

/**
 * POST /facezoom/upload — submit an image for face detection + zoom restoration.
 *
 * Backend detects all faces, crops each with 40% margin, upscales 4× via
 * RealESRGAN, then runs CodeFormer with ArcFace identity check per face.
 * Returns job_id immediately; poll getFaceZoomResult() for per-face results.
 */
export async function uploadForFaceZoom(file: File): Promise<{ job_id: string }> {
  const formData = new FormData();
  formData.append("file", file);
  // Send "preserve" (w=0.95) — Face Zoom targets small crops (60-80 px) where
  // higher fidelity avoids uncanny eye sharpening that "balanced" (w=0.85) can
  // introduce.  No per-preset picker is exposed in the UI.
  formData.append("fidelity_preset", "preserve");

  const response = await fetch(`${FACEZOOM_API_BASE}/facezoom/upload`, {
    method: "POST",
    body:   formData,
  });

  if (!response.ok) {
    let detail = `HTTP ${response.status}`;
    try {
      const json = await response.json();
      if (json?.detail) detail = json.detail;
    } catch { /* ignore */ }
    throw new Error(detail);
  }

  return response.json() as Promise<{ job_id: string }>;
}

// ---------------------------------------------------------------------------
// Result polling
// ---------------------------------------------------------------------------

/**
 * GET /facezoom/result/{job_id} — poll the current status of a face zoom job.
 *
 * When status === "completed", the faces array contains one entry per detected
 * face with its result image URL, whether CodeFormer was applied, and the
 * ArcFace cosine similarity score.  The array is empty while the job is still
 * pending or processing.
 */
export async function getFaceZoomResult(jobId: string): Promise<FaceZoomResult> {
  const response = await fetch(`${FACEZOOM_API_BASE}/facezoom/result/${jobId}`);
  if (!response.ok) throw new Error(`HTTP ${response.status}`);
  return response.json() as Promise<FaceZoomResult>;
}

// ---------------------------------------------------------------------------
// ZIP download
// ---------------------------------------------------------------------------

/**
 * POST /facezoom/download — download a ZIP of selected face crops.
 *
 * Sends {job_id, face_indices} as JSON, expects a binary ZIP response.
 * Converts the blob to an object URL and triggers a synthetic <a> click so
 * the browser saves it as "face_zoom_results.zip".
 *
 * @param jobId       The completed job's ID.
 * @param faceIndices Which face indices to include (subset or all).
 */
export async function downloadFaceZoomZip(
  jobId: string,
  faceIndices: number[],
): Promise<void> {
  const response = await fetch(`${FACEZOOM_API_BASE}/facezoom/download`, {
    method:  "POST",
    headers: { "Content-Type": "application/json" },
    body:    JSON.stringify({ job_id: jobId, face_indices: faceIndices }),
  });

  if (!response.ok) {
    let detail = `HTTP ${response.status}`;
    try {
      const json = await response.json();
      if (json?.detail) detail = json.detail;
    } catch { /* ignore */ }
    throw new Error(detail);
  }

  const blob = await response.blob();
  const url  = URL.createObjectURL(blob);
  const a    = document.createElement("a");
  a.href     = url;
  a.download = "face_zoom_results.zip";
  document.body.appendChild(a);
  a.click();
  document.body.removeChild(a);
  URL.revokeObjectURL(url);
}