import type {
  OAuthClientInformation,
  OAuthTokens,
  OAuthMetadata,
} from "@modelcontextprotocol/sdk/shared/auth.js";
import {
  OAuthClientInformationSchema,
  OAuthTokensSchema,
} from "@modelcontextprotocol/sdk/shared/auth.js";
import type { OAuthStorage } from "./storage.js";
import { type createOAuthStore, type ServerOAuthState } from "./store.js";
import type {
  IdpSessionState,
  OAuthClientRegistrationKind,
  SaveClientInformationOptions,
  SaveTokensOptions,
} from "./storage.js";

/**
 * Concrete OAuthStorage implementation parameterized on a Zustand store.
 * The store carries the storage adapter (sessionStorage, file, remote HTTP, …),
 * so the same body works for browser, Node, and remote environments.
 *
 * With an async storage adapter (file, remote HTTP) the store is empty until
 * hydration completes. Every read used on the post-OAuth-redirect callback path
 * (`getCodeVerifier`, `getServerMetadata`, `getClientInformation`, `getTokens`)
 * — and every save — therefore awaits {@link ready} first; saves wait so a
 * late hydration merge cannot clobber a value written before it landed. The
 * underlying store is created with `skipHydration: true`
 * ({@link createOAuthStore}), so the constructor's `rehydrate()` is the single
 * hydration and there is no auto-hydration to race it. With a synchronous
 * adapter (sessionStorage) hydration resolves on the next microtask and the
 * behaviour is effectively unchanged.
 */
export class OAuthStorageBase implements OAuthStorage {
  private readonly store: ReturnType<typeof createOAuthStore>;
  private readonly hydrated: Promise<void>;
  private hydrationError?: Error;

  constructor(store: ReturnType<typeof createOAuthStore>) {
    this.store = store;
    // The store is created with `skipHydration: true` so this is the SOLE
    // hydration. Driving it explicitly (rather than relying on persist's
    // auto-hydration + onFinishHydration) lets us catch a rejecting adapter —
    // onFinishHydration only fires on success, so a throwing getItem would
    // otherwise leave `hydrated` pending forever and hang every getter.
    // A failed hydration resolves to "empty store", which is the correct
    // fallback (reads return undefined; writes proceed) — but the failure is
    // recorded so callers can distinguish "no token stored" from "could not
    // read the store" (e.g. corrupt file, EACCES, backend 500).
    const recordFailure = (err: unknown) => {
      this.hydrationError =
        err instanceof Error
          ? err
          : new Error(
              typeof err === "string"
                ? err
                : "OAuth storage hydration failed (adapter getItem threw or returned invalid data)",
            );
      console.warn(
        "[OAuthStorage] hydration failed; continuing with empty state:",
        this.hydrationError,
      );
    };
    this.hydrated = this.store.persist.hasHydrated()
      ? Promise.resolve()
      : Promise.resolve(this.store.persist.rehydrate()).then(
          () => {
            // Zustand swallows getItem errors internally (routing them to
            // onRehydrateStorage) and resolves rehydrate() regardless;
            // hasHydrated() only flips true on success, so use it to detect a
            // silently-failed hydration. The underlying error is lost in this
            // path — record a generic one so getHydrationError() is non-null.
            if (!this.store.persist.hasHydrated()) recordFailure(undefined);
          },
          (err: unknown) => recordFailure(err),
        );
  }

  /**
   * If hydration failed (adapter threw, file unreadable/corrupt, backend
   * non-2xx), the captured error. Undefined when hydration succeeded or has
   * not yet completed — call after `await ready()`. Lets callers report
   * "oauth.json is unreadable" instead of a misleading "no token stored".
   */
  getHydrationError(): Error | undefined {
    return this.hydrationError;
  }

  /**
   * Resolves once the underlying persist adapter has hydrated the store.
   * Callers that need to read state outside the typed getters can await this
   * directly (e.g. before reading the store via `getState()` for diagnostics).
   */
  ready(): Promise<void> {
    return this.hydrated;
  }

  /**
   * Run a `clear*` mutation against a hydrated store: synchronously if
   * hydration has already landed, otherwise deferred until it does.
   *
   * `clear*` are declared synchronous in {@link OAuthStorage} (some feed sync
   * SDK getters), so unlike the `save*` family they cannot `await this.hydrated`
   * up front. But a clear applied to the still-empty pre-hydration store is
   * doubly wrong: (a) the pending `rehydrate()` would merge the persisted
   * (un-cleared) blob back over it, resurrecting the credential; and worse,
   * (b) applying it triggers a persist write of the near-empty store, which for
   * a whole-blob adapter (file / remote HTTP) can clobber the on-disk blob —
   * every other server's tokens included — before hydration ever reads it.
   * Deferring the mutation until after hydration avoids both: it merges onto
   * the real persisted state. The common case (hydration already settled) stays
   * synchronous and immediately observable. A failed hydration still resolves
   * {@link hydrated} (see constructor), so a deferred clear runs harmlessly
   * against the empty store. The effect of a pre-hydration clear is therefore
   * asynchronous, which is safe: the only callers are fire-and-forget
   * invalidations that never synchronously read the value straight back.
   */
  private clearAfterHydration(mutate: () => void): void {
    if (this.store.persist.hasHydrated()) {
      mutate();
    } else {
      void this.hydrated.then(mutate);
    }
  }

  async getClientInformation(
    serverUrl: string,
    isPreregistered?: boolean,
  ): Promise<OAuthClientInformation | undefined> {
    await this.hydrated;
    const state = this.store.getState().getServerState(serverUrl);
    const clientInfo = isPreregistered
      ? state.preregisteredClientInformation
      : state.clientInformation;

    if (!clientInfo) {
      return undefined;
    }

    return await OAuthClientInformationSchema.parseAsync(clientInfo);
  }

  /**
   * Intentionally synchronous — same invariant as {@link getScope}: safe
   * without awaiting hydration only because a preceding awaited read has
   * already flushed it. Its sole caller, `buildOAuthConnectionState`
   * (`connection-state.ts`), reads this right after awaiting
   * `getClientInformation`/`getServerMetadata`, so on the post-redirect
   * callback path (where the in-memory store is reset) hydration has landed
   * by the time this runs. A future refactor reading it without a preceding
   * awaited storage read would get a pre-hydration `undefined`.
   */
  getClientRegistrationKind(
    serverUrl: string,
  ): OAuthClientRegistrationKind | undefined {
    return this.store.getState().getServerState(serverUrl)
      .clientRegistrationKind;
  }

  async saveClientInformation(
    serverUrl: string,
    clientInformation: OAuthClientInformation,
    options: SaveClientInformationOptions,
  ): Promise<void> {
    await this.hydrated;
    this.store.getState().setServerState(serverUrl, {
      clientInformation,
      clientRegistrationKind: options.registrationKind,
    });
  }

  async savePreregisteredClientInformation(
    serverUrl: string,
    clientInformation: OAuthClientInformation,
  ): Promise<void> {
    await this.hydrated;
    this.store.getState().setServerState(serverUrl, {
      preregisteredClientInformation: clientInformation,
      clientRegistrationKind: "static",
    });
  }

  clearClientInformation(serverUrl: string, isPreregistered?: boolean): void {
    this.clearAfterHydration(() => {
      const updates: Partial<ServerOAuthState> = {};
      if (isPreregistered) {
        updates.preregisteredClientInformation = undefined;
      } else {
        updates.clientInformation = undefined;
        updates.clientRegistrationKind = undefined;
      }
      this.store.getState().setServerState(serverUrl, updates);
    });
  }

  async getTokens(serverUrl: string): Promise<OAuthTokens | undefined> {
    await this.hydrated;
    const state = this.store.getState().getServerState(serverUrl);
    if (!state.tokens) {
      return undefined;
    }

    return await OAuthTokensSchema.parseAsync(state.tokens);
  }

  async saveTokens(
    serverUrl: string,
    tokens: OAuthTokens,
    options?: SaveTokensOptions,
  ): Promise<void> {
    await this.hydrated;
    this.store.getState().setServerState(serverUrl, {
      tokens,
      ...(options?.enterpriseManaged === true && { enterpriseManaged: true }),
    });
  }

  clearTokens(serverUrl: string): void {
    this.clearAfterHydration(() =>
      this.store.getState().setServerState(serverUrl, { tokens: undefined }),
    );
  }

  async getCodeVerifier(serverUrl: string): Promise<string | undefined> {
    await this.hydrated;
    const state = this.store.getState().getServerState(serverUrl);
    return state.codeVerifier;
  }

  async saveCodeVerifier(
    serverUrl: string,
    codeVerifier: string,
  ): Promise<void> {
    await this.hydrated;
    this.store.getState().setServerState(serverUrl, { codeVerifier });
  }

  clearCodeVerifier(serverUrl: string): void {
    this.clearAfterHydration(() =>
      this.store
        .getState()
        .setServerState(serverUrl, { codeVerifier: undefined }),
    );
  }

  /**
   * Intentionally synchronous. The only caller is
   * {@link BaseOAuthClientProvider.scope}, a sync getter the SDK requires
   * (it feeds the sync `clientMetadata` getter). It is safe without awaiting
   * hydration because of an ordering invariant the callers uphold: some
   * awaited read always precedes it, flushing hydration first.
   *   - Pre-redirect half of the flow: `saveScope` (which awaits hydration)
   *     writes the value in the same session, so the in-memory store has it.
   *   - Post-redirect callback path: the in-memory store is reset, so the
   *     value comes from hydration — but `buildOAuthConnectionState`
   *     (`connection-state.ts`) awaits `getClientInformation`/
   *     `getServerMetadata` (both of which await hydration) before it reads
   *     `getScope`, so hydration has already landed by then.
   * A future refactor that reads `getScope` without a preceding awaited
   * storage read would break this invariant.
   */
  getScope(serverUrl: string): string | undefined {
    const state = this.store.getState().getServerState(serverUrl);
    return state.scope;
  }

  async saveScope(serverUrl: string, scope: string | undefined): Promise<void> {
    await this.hydrated;
    this.store.getState().setServerState(serverUrl, { scope });
  }

  clearScope(serverUrl: string): void {
    this.clearAfterHydration(() =>
      this.store.getState().setServerState(serverUrl, { scope: undefined }),
    );
  }

  async getServerMetadata(serverUrl: string): Promise<OAuthMetadata | null> {
    await this.hydrated;
    const state = this.store.getState().getServerState(serverUrl);
    return state.serverMetadata || null;
  }

  async saveServerMetadata(
    serverUrl: string,
    metadata: OAuthMetadata,
  ): Promise<void> {
    await this.hydrated;
    this.store
      .getState()
      .setServerState(serverUrl, { serverMetadata: metadata });
  }

  clearServerMetadata(serverUrl: string): void {
    this.clearAfterHydration(() =>
      this.store
        .getState()
        .setServerState(serverUrl, { serverMetadata: undefined }),
    );
  }

  clear(serverUrl: string): void {
    this.clearAfterHydration(() =>
      this.store.getState().clearServerState(serverUrl),
    );
  }

  async getIdpSession(issuer: string): Promise<IdpSessionState | undefined> {
    await this.hydrated;
    const session = this.store.getState().getIdpSession(issuer);
    if (
      !session.idToken &&
      !session.refreshToken &&
      session.idTokenExpiresAt === undefined
    ) {
      return undefined;
    }
    return session;
  }

  async saveIdpSession(
    issuer: string,
    session: Partial<IdpSessionState>,
  ): Promise<void> {
    await this.hydrated;
    this.store.getState().setIdpSession(issuer, session);
  }

  clearIdpSession(issuer: string): void {
    this.clearAfterHydration(() =>
      this.store.getState().clearIdpSession(issuer),
    );
  }

  clearEnterpriseManagedResourceServers(): void {
    this.clearAfterHydration(() =>
      this.store.getState().clearEnterpriseManagedResourceServers(),
    );
  }
}