import { createContext, useCallback, useContext, useMemo, useState, type ReactNode } from "react";

import type { AuthResult } from "../api/types";
import { sessionStore, type Session } from "./store";

interface SessionApi {
  session: Session | null;
  signIn: (auth: AuthResult) => void;
  /** Leaves the account. Anonymous history is always wiped: it cannot be restored anyway. */
  signOut: (opts?: { wipe?: boolean }) => void;
}

const Ctx = createContext<SessionApi | null>(null);

export function SessionProvider({ children }: { children: ReactNode }) {
  // The old shared demo account ("tok-andrey") is retired: every visitor now gets a private copy.
  const [session, setSession] = useState<Session | null>(() => {
    const s = sessionStore.load();
    return s && s.token === "tok-andrey" ? null : s;
  });

  const signIn = useCallback((auth: AuthResult) => {
    const next: Session = { token: auth.token, mode: auth.mode, displayName: auth.display_name };
    sessionStore.save(next);
    setSession(next);
  }, []);

  const signOut = useCallback((opts?: { wipe?: boolean }) => {
    setSession((current) => {
      sessionStore.clear(current, opts?.wipe ?? current?.mode === "anonymous");
      return null;
    });
  }, []);

  const value = useMemo(() => ({ session, signIn, signOut }), [session, signIn, signOut]);
  return <Ctx.Provider value={value}>{children}</Ctx.Provider>;
}

export function useSession(): SessionApi {
  const value = useContext(Ctx);
  if (!value) throw new Error("useSession outside SessionProvider");
  return value;
}