/**
 * Live G13 scheduling and how a GitHub event is split into change sets.
 *
 * Isolation is a per-change rule. pull_request and local runs classify the
 * merge-base...HEAD range (one PR). merge_group classifies each first-parent
 * commit vs its parent (one queued PR per squash or merge-commit). The group
 * union is not a change set: a Terraform-only PR stacked with an app-only PR
 * must still pass. push is not classified; landing already happened.
 */

export function shouldRunLiveIsolation(eventName) {
  return !eventName || eventName === "pull_request" || eventName === "merge_group";
}

export function usesPerCommitIsolation(eventName) {
  return eventName === "merge_group";
}

/**
 * File lists to run through check_app_terraform_isolation.py.
 * `commitDiffs` is first-parent order (oldest first); ignored except on
 * merge_group.
 */
export function liveIsolationFileSets(eventName, rangeFiles, commitDiffs) {
  if (usesPerCommitIsolation(eventName)) {
    return commitDiffs.map((commit) => commit.files);
  }
  return [rangeFiles];
}