import type { OAuthSession } from "@atproto/oauth-client-node";
import type { AppContext } from "./app-context.js";
import type { CookieSession } from "./cookie-session-store.js";

/**
 * Result of restoring an OAuth session from a cookie token.
 */
export interface RestoredSession {
  oauthSession: OAuthSession;
  cookieSession: CookieSession;
}

/**
 * Restore an OAuth session from a cookie token.
 *
 * Looks up the cookie token in the CookieSessionStore, then restores
 * the OAuth session from the library's session store (with automatic
 * token refresh).
 *
 * Returns both the OAuth session and cookie session if successful,
 * allowing callers to access handle and other cookie metadata without
 * redundant store queries.
 *
 * Returns null if the cookie session doesn't exist, is expired,
 * or the OAuth session is not found (expected cases).
 * Throws on unexpected errors (network failures, etc.) that should bubble up.
 */
export async function restoreOAuthSession(
  ctx: AppContext,
  cookieToken: string
): Promise<RestoredSession | null> {
  const cookieSession = ctx.cookieSessionStore.get(cookieToken);
  if (!cookieSession) {
    return null;
  }

  try {
    // Restore OAuth session from library's session store
    // This will automatically refresh tokens if needed
    const oauthSession = await ctx.oauthClient.restore(cookieSession.did);
    if (!oauthSession) {
      return null;
    }
    return { oauthSession, cookieSession };
  } catch (error) {
    // Check if this is an expected "session not found" error
    if (error instanceof Error && error.message.includes("not found")) {
      return null;
    }

    // Unexpected error - log and re-throw
    ctx.logger.error("Unexpected error restoring OAuth session", {
      operation: "restoreOAuthSession",
      did: cookieSession.did,
      error: error instanceof Error ? error.message : String(error),
    });
    throw error;
  }
}