const RECOVERABLE_KINDS = new Set(["CHUNK_LOAD_FAILURE", "DEPLOY_MISMATCH"]);

/**
 * @param {{
 *   failureKind: string,
 *   manifestLoaded: boolean,
 *   currentBuildId: string,
 *   activeReleaseId: string,
 *   storage: import("../ports/storage-port.js").StoragePort
 * }} input
 */
export function decideChunkRecovery(input) {
  if (!RECOVERABLE_KINDS.has(input.failureKind)) {
    return { action: "support", reason: "not-recoverable" };
  }
  if (!input.manifestLoaded) {
    return { action: "support", reason: "manifest-unavailable" };
  }
  if (input.activeReleaseId === input.currentBuildId) {
    return { action: "support", reason: "same-release" };
  }

  const releasePair = `${input.currentBuildId}->${input.activeReleaseId}`;
  const guard = input.storage.read("CHUNK_RELOAD_GUARD");
  if (!guard.ok || guard.value === releasePair) {
    return { action: "support", reason: "reload-already-attempted" };
  }

  const recorded = input.storage.write("CHUNK_RELOAD_GUARD", releasePair);
  if (!recorded.ok) {
    return { action: "support", reason: "guard-write-failed" };
  }
  return { action: "reload-once", releasePair };
}