// Hydra admin-API client (todo §6): typed `fetch` wrappers over Ory Hydra's OAuth2 admin
// endpoints (internal admin port) — the login/consent challenge handshake other apps log in
// *through* us with. Built-in `fetch` only, no SDK dep (AGENTS.md); `fetchImpl`-injectable
// like the kratos/keto clients. We authenticate the user (login) and grant scopes (consent);
// Hydra mints the tokens.

export interface OAuth2Client {
  client_id?: string;
  client_name?: string;
  client_secret?: string; // write-only: Hydra returns it once, on create, for a confidential client
  grant_types?: string[];
  metadata?: Record<string, unknown>; // arbitrary client metadata; `first_party: true` ⇒ auto-consent (§6)
  redirect_uris?: string[];
  response_types?: string[];
  scope?: string; // space-separated
  token_endpoint_auth_method?: string; // "client_secret_basic" (confidential) | "none" (public/PKCE)
}

export interface ClientList {
  clients: OAuth2Client[];
  nextPageToken: string | null; // cursor for the next page; null on the last
}

// A login request Hydra hands us at /oauth2/login. `skip` ⇒ Hydra already authenticated this
// subject (honour it, don't re-prompt); otherwise we authenticate via the Kratos session.
export interface LoginRequest {
  challenge: string;
  client?: OAuth2Client;
  request_url?: string;
  requested_scope?: string[];
  skip: boolean;
  subject: string;
}

export interface AcceptLogin {
  acr?: string;
  remember?: boolean;
  remember_for?: number; // seconds; 0 ⇒ for the browser-session lifetime
  subject: string;
}

// A consent request Hydra hands us at /oauth2/consent. `skip` ⇒ already consented (or a
// skip-consent client); else we show the scope screen (or auto-accept a first-party client).
export interface ConsentRequest {
  challenge: string;
  client?: OAuth2Client;
  request_url?: string;
  requested_access_token_audience?: string[];
  requested_scope?: string[];
  skip: boolean;
  subject: string;
}

// OIDC claims surfaced to the client: id_token (always) / access_token (introspection only).
export interface ConsentSession {
  access_token?: Record<string, unknown>;
  id_token?: Record<string, unknown>;
}

export interface AcceptConsent {
  grant_access_token_audience?: string[];
  grant_scope?: string[];
  remember?: boolean;
  remember_for?: number; // seconds; 0 ⇒ for the browser-session lifetime
  session?: ConsentSession;
}

export interface RejectRequest {
  error?: string;
  error_description?: string;
}

// Hydra's answer to an accept/reject: the URL to send the browser to, to resume the flow.
export interface Completed {
  redirect: string;
}

// Carries the HTTP status so a caller can branch (parallels KratosError/KetoError).
export class HydraError extends Error {
  body: string;
  status: number;
  constructor(message: string, status: number, body: string) {
    super(message);
    this.body = body;
    this.name = "HydraError";
    this.status = status;
  }
}

export interface HydraAdmin {
  acceptConsentRequest(challenge: string, body: AcceptConsent): Promise<Completed>;
  acceptLoginRequest(challenge: string, body: AcceptLogin): Promise<Completed>;
  acceptLogoutRequest(challenge: string): Promise<Completed>; // RP-initiated logout (§6): confirm + resume
  createClient(client: OAuth2Client): Promise<OAuth2Client>;
  deleteClient(id: string): Promise<void>;
  getClient(id: string): Promise<OAuth2Client | null>;
  getConsentRequest(challenge: string): Promise<ConsentRequest>;
  getLoginRequest(challenge: string): Promise<LoginRequest>;
  listClients(opts?: { pageSize?: number; pageToken?: string }): Promise<ClientList>;
  rejectConsentRequest(challenge: string, body: RejectRequest): Promise<Completed>;
  rejectLoginRequest(challenge: string, body: RejectRequest): Promise<Completed>;
}

// Hydra paginates with a Link header; pull the page_token of rel="next" (the href is relative, so
// resolve against a throwaway base to read the query param). Mirrors kratos-admin's helper.
function nextPageToken(link: string | null): string | null {
  const href = link?.match(/<([^>]+)>\s*;\s*rel="next"/)?.[1];
  return href ? new URL(href, "http://hydra").searchParams.get("page_token") : null;
}

export function createHydraAdmin(config: { baseUrl: string; fetchImpl?: typeof fetch }): HydraAdmin {
  const base = config.baseUrl.replace(/\/+$/, "");
  const http = config.fetchImpl ?? fetch;
  const json = { "content-type": "application/json" };
  // Hydra keys each handshake off a ?<kind>_challenge= query (login/consent/logout).
  const reqUrl = (kind: "consent" | "login" | "logout", challenge: string, action = "") =>
    `${base}/admin/oauth2/auth/requests/${kind}${action}?${kind}_challenge=${encodeURIComponent(challenge)}`;
  const clientsUrl = `${base}/admin/clients`;
  const clientUrl = (id: string) => `${clientsUrl}/${encodeURIComponent(id)}`;

  async function fail(action: string, res: Response): Promise<never> {
    throw new HydraError(`Hydra admin ${action} failed (${res.status})`, res.status, await res.text());
  }
  async function complete(action: string, res: Response): Promise<Completed> {
    if (res.status !== 200) return fail(action, res);
    return { redirect: ((await res.json()) as { redirect_to: string }).redirect_to };
  }

  const put = (action: string, url: string, body: unknown) =>
    http(url, { body: JSON.stringify(body), headers: json, method: "PUT" }).then((r) => complete(action, r));

  return {
    async acceptConsentRequest(challenge, body) {
      return put("accept consent", reqUrl("consent", challenge, "/accept"), body);
    },

    async acceptLoginRequest(challenge, body) {
      return put("accept login", reqUrl("login", challenge, "/accept"), body);
    },

    // RP-initiated logout: Hydra hands the browser to /oauth2/logout?logout_challenge=…; accept to
    // end its OAuth2 session and get the post-logout redirect (no body / no first-party teardown —
    // /logout owns the Kratos session). A stale/consumed challenge → HydraError 4xx (app degrades).
    async acceptLogoutRequest(challenge) {
      return put("accept logout", reqUrl("logout", challenge, "/accept"), {});
    },

    // OAuth2 client registration (§6, admin screen). Hydra generates the client_id/secret when
    // omitted; the secret rides the 201 body and is never retrievable afterwards.
    async createClient(client) {
      const res = await http(clientsUrl, { body: JSON.stringify(client), headers: json, method: "POST" });
      if (res.status !== 201) return fail("create client", res);
      return (await res.json()) as OAuth2Client;
    },

    async deleteClient(id) {
      const res = await http(clientUrl(id), { method: "DELETE" });
      if (res.status !== 204) await fail("delete client", res);
    },

    async getClient(id) {
      const res = await http(clientUrl(id));
      if (res.status === 404) return null;
      if (res.status !== 200) return fail("get client", res);
      return (await res.json()) as OAuth2Client;
    },

    async getConsentRequest(challenge) {
      const res = await http(reqUrl("consent", challenge));
      if (res.status !== 200) return fail("get consent request", res);
      return (await res.json()) as ConsentRequest;
    },

    async getLoginRequest(challenge) {
      const res = await http(reqUrl("login", challenge));
      if (res.status !== 200) return fail("get login request", res);
      return (await res.json()) as LoginRequest;
    },

    async listClients(opts = {}) {
      const url = new URL(clientsUrl);
      if (opts.pageSize !== undefined) url.searchParams.set("page_size", String(opts.pageSize));
      if (opts.pageToken) url.searchParams.set("page_token", opts.pageToken);
      const res = await http(url);
      if (res.status !== 200) return fail("list clients", res);
      return { clients: (await res.json()) as OAuth2Client[], nextPageToken: nextPageToken(res.headers.get("link")) };
    },

    async rejectConsentRequest(challenge, body) {
      return put("reject consent", reqUrl("consent", challenge, "/reject"), body);
    },

    async rejectLoginRequest(challenge, body) {
      return put("reject login", reqUrl("login", challenge, "/reject"), body);
    },
  };
}