import type { PullRequestCheckoutRef } from "../services/forge-service.js";

// upstream for clones where origin is your fork
export function buildPullHeadCheckoutRefs(number: number): PullRequestCheckoutRef[] {
  return [
    { remoteName: "origin", remoteRef: `refs/pull/${number}/head` },
    { remoteName: "upstream", remoteRef: `refs/pull/${number}/head` },
  ];
}

// forgejo username pattern, covers github logins too
export function normalizeForgeOwnerForBranch(owner: string | null): string | null {
  const normalized = owner?.trim().toLowerCase() ?? "";
  if (!/^[a-z0-9][a-z0-9_.-]*$/.test(normalized)) {
    return null;
  }
  // git refuses .. and .lock, trailing dot too
  if (normalized.includes("..") || normalized.endsWith(".") || normalized.endsWith(".lock")) {
    return null;
  }
  return normalized;
}

export interface ForkLocalBranchNameInput {
  headRef: string;
  number: number;
  isCrossRepository: boolean;
  headOwnerLogin: string | null;
  /** "pull-ref" when headRef is a synthetic pull ref, not a real branch name (agit PRs, deleted branches); undefined means "branch" */
  headRefKind?: "branch" | "pull-ref";
}

export function buildForkLocalBranchName(params: ForkLocalBranchNameInput): string {
  const pullRefFallback = `pr-${params.number}`;
  // headRef is the literal pull ref (e.g. refs/pull/42/head) when there is no
  // real branch to name after, so use the pr number instead
  const headSegment = params.headRefKind === "pull-ref" ? pullRefFallback : params.headRef;
  if (!params.isCrossRepository) {
    return headSegment;
  }
  const owner = normalizeForgeOwnerForBranch(params.headOwnerLogin);
  if (!owner) {
    // don't double up pr-<n>/pr-<n> when the owner is also unknown
    return headSegment === pullRefFallback ? headSegment : `${pullRefFallback}/${headSegment}`;
  }
  return `${owner}/${headSegment}`;
}