/**
 * Route templates for metrics: a path reduced to its shape (`/:owner/:repo/issues/:n`), never carrying account,
 * repository, branch or file names. Only words from a fixed list of route segments survive; anything else
 * becomes a parameter, so a template is safe to send to analytics whatever the path held.
 */

/** First path segments that are app pages, not account names. */
export const APP_ROOTS = new Set([
  "",
  "abuse",
  "admin",
  "explore",
  "ingest",
  "features",
  "forgot-password",
  "login",
  "new",
  "notifications",
  "orgs",
  "pricing",
  "projects",
  "reset-password",
  "search",
  "self-host",
  "settings",
  "signup",
  "verify-email",
  "api",
  "auth",
]);

const STATIC_SEGMENTS = new Set(
  `abuse accept acceptable-use access actions admin advisories agents ai ai-fix alerts api apply approve artifacts
  attempts audit auto_merge billing blame blob branch-protections branches bypass caches cancel check
  code-owner-review code-scanning codeowners collaborators comments commit commits compare conflicts containers
  contents cookies credential decline deliveries dependencies deploy-tokens deployments discussions dismissals
  dispatches dmca domain drafts edit editor-sessions environments explore features files find forgot-password forks
  hooks import insights integrations invitations issues labels lfs lfs-quota lfs-usage linked-issues login
  mcp-usage members merge merge_queue milestones new notification-settings notifications org
  organization_invitations orgs permissions pings planning policy privacy projects protections pull pull-template
  pulls push-blocks push-protection registration-token releases replies repos requested_reviewers
  requested-reviewers rerequest rerun reset-password review reviews rollback runners runs scratch search
  secret-scanning secrets security security-advisories self-host settings signatures signing-keys signup site
  site-usage sites state status statuses suggestions support tags terms threads tokens transfer tree two-factor
  unblock update-branch usage user v1 variables verify-email webhooks workflows info refs git-upload-pack
  git-receive-pack objects batch locks raw archive download attachments og camo avatars mcp ingest jobs runner
  sse ws listen oauth authorize token register revoke callback github _serverFn graph day years diff patch`
    .split(/\s+/)
    .filter(Boolean),
);

function segmentTemplate(segment: string): string {
  if (segment === "") return "";
  if (STATIC_SEGMENTS.has(segment)) return segment;
  if (/^\d+$/.test(segment)) return ":n";
  if (/\.(diff|patch)$/.test(segment)) return `:range.${segment.split(".").pop()}`;
  return ":param";
}

export function routeTemplate(pathname: string): string {
  const parts = pathname.split("/").slice(1);
  if (parts.length === 0) return "/";
  const [first = "", second, ...rest] = parts;
  // Server function ids are code identifiers (vite.config.ts serverFnId), never user data.
  if (first === "_serverFn") return `/_serverFn/${second && /^[A-Za-z0-9._]{1,120}$/.test(second) ? second : ":fn"}`;
  if (APP_ROOTS.has(first.toLowerCase())) {
    const tail = second === undefined ? [] : [second, ...rest];
    return `/${[first, ...tail.map(segmentTemplate)].join("/")}`;
  }
  if (second === undefined) return "/:owner";
  const repo = second.endsWith(".git") ? ":repo.git" : ":repo";
  return `/${[":owner", repo, ...rest.map(segmentTemplate)].join("/")}`;
}

const PLACEHOLDER = /^:(owner|repo|repo\.git|n|param|fn|range\.(diff|patch))$/;
const SERVER_FN = /^[A-Za-z0-9._]{1,120}$/;

/** Whether `value` is already a template this module produced (only route words and placeholders). */
export function isRouteTemplate(value: string): boolean {
  if (value === "/") return true;
  if (!value.startsWith("/")) return false;
  const parts = value.slice(1).split("/");
  if (parts[0] === "_serverFn") return parts.length === 2 && (parts[1] === ":fn" || SERVER_FN.test(parts[1] ?? ""));
  return parts.every(
    (part, index) => PLACEHOLDER.test(part) || STATIC_SEGMENTS.has(part) || (index === 0 && APP_ROOTS.has(part)),
  );
}