// P4 Files (AK-P4a) §6 — web-side presigned download URL builder for the
// auth-proxy media route. Bucket stays private (AD-23); the proxy redirects an
// authorized request to a short-lived signed URL. Reuses the shared SigV4
// signer from @toolctrl/storage (no @aws-sdk/s3-request-presigner dependency).

import { loadRequiredWebConfig } from "@toolctrl/config";
import { createS3SignedUrlAdapter, createSigV4DownloadSigner, StorageAdapterError } from "@toolctrl/storage";
import { resolveStorageBucket } from "./storageService";

export const MEDIA_SIGNED_URL_TTL_SECONDS = 300;

function sanitizeFilename(filename: string): string {
  // Strip quotes/control chars so the value is safe inside a Content-Disposition header.
  return filename.replace(/["\\\r\n]/g, "").slice(0, 200);
}

/**
 * Create a short-lived (default 300s) presigned GET URL for an object in the
 * private files bucket. `filename` (optional) sets an inline Content-Disposition
 * so the browser shows a sensible name on download.
 */
export async function createMediaDownloadUrl({
  key,
  filename,
  ttlSeconds = MEDIA_SIGNED_URL_TTL_SECONDS,
}: {
  key: string;
  filename?: string;
  ttlSeconds?: number;
}): Promise<string> {
  const { storage } = loadRequiredWebConfig();
  const bucket = resolveStorageBucket();
  const adapter = createS3SignedUrlAdapter({
    bucket,
    downloadSigner: createSigV4DownloadSigner({
      endpoint: storage.endpoint ?? "",
      region: storage.region ?? "",
      bucket,
      accessKeyId: storage.accessKeyId ?? "",
      secretAccessKey: storage.secretAccessKey ?? "",
      sessionToken: storage.sessionToken,
      forcePathStyle: storage.forcePathStyle === undefined ? undefined : storage.forcePathStyle.toLowerCase() === "true",
    }),
    uploadSigner: () => {
      throw new StorageAdapterError("signed_upload_failed", "Signed upload URLs are not supported by the media proxy.", {
        operation: "createSignedUploadUrl",
        bucket,
      });
    },
  });
  const result = await adapter.createSignedDownloadUrl({
    key,
    expiresInSeconds: ttlSeconds,
    ...(filename ? { responseContentDisposition: `inline; filename="${sanitizeFilename(filename)}"` } : {}),
  });
  return result.url;
}