import { HttpErrorResponse } from '@angular/common/http';
import { computed, inject } from '@angular/core';
import { Router } from '@angular/router';
import { mapResponse } from '@ngrx/operators';
import {
  signalStore,
  withComputed,
  withHooks,
  withMethods,
  withState,
} from '@ngrx/signals';
import {
  Dispatcher,
  Events,
  on,
  withEventHandlers,
  withReducer,
} from '@ngrx/signals/events';
import {
  AuthConfig,
  AuthGateway,
  AuthorizationFlow,
  CurrentUser,
  isExpired,
  ProfileGateway,
  Session,
  SessionStorage,
} from '@task-stream/web/identity/domain';
import { exhaustMap, firstValueFrom, from, map, switchMap, tap } from 'rxjs';
import { authApiEvents, authPageEvents, sessionEvents } from './auth.events';

export type AuthStatus =
  | 'restoring'
  | 'anonymous'
  | 'signing-in'
  | 'authenticated';

interface AuthState {
  status: AuthStatus;
  session: Session | null;
  user: CurrentUser | null;
  /** undefined = not loaded yet, null = only personal access tokens. */
  config: AuthConfig | null | undefined;
  error: string | null;
}

const initialState: AuthState = {
  status: 'restoring',
  session: null,
  user: null,
  config: undefined,
  error: null,
};

function describe(error: unknown): string {
  if (error instanceof HttpErrorResponse) {
    return (
      (error.error as { message?: string } | null)?.message ?? error.message
    );
  }
  return error instanceof Error ? error.message : String(error);
}

export const AuthStore = signalStore(
  { providedIn: 'root' },
  withState(initialState),
  withComputed(({ status, user }) => ({
    isAuthenticated: computed(() => status() === 'authenticated'),
    initials: computed(() =>
      (user()?.name ?? '')
        .split(/\s+/)
        .map((part) => part[0])
        .join('')
        .slice(0, 2)
        .toUpperCase(),
    ),
  })),
  withReducer(
    on(authApiEvents.configLoaded, ({ payload }) => ({ config: payload })),
    on(
      authPageEvents.signInWithPassword,
      authPageEvents.signInWithPireon,
      authPageEvents.callbackReceived,
      () => ({ status: 'signing-in' as const, error: null }),
    ),
    on(
      authApiEvents.signedIn,
      authApiEvents.sessionRestored,
      ({ payload }) => ({
        status: 'authenticated' as const,
        session: payload.session,
        user: payload.user,
        error: null,
      }),
    ),
    on(authApiEvents.sessionRefreshed, ({ payload }) => ({ session: payload })),
    on(authApiEvents.signInFailed, ({ payload }) => ({
      status: 'anonymous' as const,
      session: null,
      user: null,
      error: payload,
    })),
    on(authApiEvents.signedOut, authApiEvents.anonymous, () => ({
      status: 'anonymous' as const,
      session: null,
      user: null,
    })),
  ),
  withEventHandlers(
    (
      store,
      events = inject(Events),
      auth = inject(AuthGateway),
      profile = inject(ProfileGateway),
      flow = inject(AuthorizationFlow),
      storage = inject(SessionStorage),
      router = inject(Router),
    ) => {
      /** Token → who is it → signed in. */
      const signIn = (
        session$: ReturnType<AuthGateway['password']>,
        returnUrl: string,
      ) =>
        session$.pipe(
          switchMap((session) =>
            profile
              .me(session.accessToken)
              .pipe(map((user) => ({ session, user }))),
          ),
          mapResponse({
            next: ({ session, user }) =>
              authApiEvents.signedIn({ session, user, returnUrl }),
            error: (error) => authApiEvents.signInFailed(describe(error)),
          }),
        );

      return {
        loadConfig$: events.on(authPageEvents.opened).pipe(
          exhaustMap(() =>
            auth.config().pipe(
              mapResponse({
                next: (config) => authApiEvents.configLoaded(config),
                error: () => authApiEvents.configLoaded(null),
              }),
            ),
          ),
        ),
        redirectToPireon$: events.on(authPageEvents.signInWithPireon).pipe(
          exhaustMap(({ payload }) => {
            const config = store.config();
            if (!config?.clientId)
              return [
                authApiEvents.signInFailed(
                  'Pireon sign-in is not configured on the API',
                ),
              ];
            return from(flow.start(config, payload.returnUrl)).pipe(
              map(() => null),
            );
          }),
        ),
        password$: events
          .on(authPageEvents.signInWithPassword)
          .pipe(
            exhaustMap(({ payload }) =>
              signIn(
                auth.password(payload.username, payload.password),
                payload.returnUrl,
              ),
            ),
          ),
        callback$: events.on(authPageEvents.callbackReceived).pipe(
          exhaustMap(({ payload }) => {
            try {
              const response = flow.complete(
                new URLSearchParams(payload.query),
              );
              return signIn(
                auth.exchangeCode(
                  response.code,
                  response.codeVerifier,
                  response.redirectUri,
                ),
                response.returnUrl,
              );
            } catch (error) {
              return [authApiEvents.signInFailed(describe(error))];
            }
          }),
        ),
        persist$: events
          .on(authApiEvents.signedIn, authApiEvents.sessionRefreshed)
          .pipe(
            tap(() => {
              const session = store.session();
              if (session) storage.save(session);
            }),
          ),
        navigateIn$: events
          .on(authApiEvents.signedIn)
          .pipe(
            tap(
              ({ payload }) =>
                void router.navigateByUrl(payload.returnUrl || '/'),
            ),
          ),
        signOut$: events
          .on(sessionEvents.signOutRequested, sessionEvents.expired)
          .pipe(
            tap(() => storage.clear()),
            map(() => authApiEvents.signedOut()),
          ),
        navigateOut$: events
          .on(authApiEvents.signedOut)
          .pipe(tap(() => void router.navigateByUrl('/login'))),
      };
    },
  ),
  withMethods(
    (store, auth = inject(AuthGateway), dispatcher = inject(Dispatcher)) => {
      let refreshing: Promise<string | null> | null = null;

      return {
        /**
         * A valid access token for API calls: refreshed when about to expire
         * (once, even if many requests ask at the same time).
         */
        async validAccessToken(): Promise<string | null> {
          const session = store.session();
          if (!session) return null;
          if (!isExpired(session)) return session.accessToken;
          if (!session.refreshToken) {
            dispatcher.dispatch(sessionEvents.expired());
            return null;
          }
          refreshing ??= firstValueFrom(auth.refresh(session.refreshToken))
            .then((fresh) => {
              dispatcher.dispatch(authApiEvents.sessionRefreshed(fresh));
              return fresh.accessToken;
            })
            .catch(() => {
              dispatcher.dispatch(sessionEvents.expired());
              return null;
            })
            .finally(() => (refreshing = null));
          return refreshing;
        },
        expire(): void {
          if (store.status() === 'authenticated')
            dispatcher.dispatch(sessionEvents.expired());
        },
      };
    },
  ),
  withHooks({
    /** Restores the stored session (and checks it is still accepted). */
    onInit(store) {
      const storage = inject(SessionStorage);
      const profile = inject(ProfileGateway);
      const dispatcher = inject(Dispatcher);
      const stored = storage.load();
      if (!stored) {
        dispatcher.dispatch(authApiEvents.anonymous());
        return;
      }
      // Seed the token so validAccessToken() can refresh it if needed.
      dispatcher.dispatch(authApiEvents.sessionRefreshed(stored));
      void store.validAccessToken().then((token) => {
        if (!token) {
          dispatcher.dispatch(authApiEvents.anonymous());
          return;
        }
        profile.me(token).subscribe({
          next: (user) =>
            dispatcher.dispatch(
              authApiEvents.sessionRestored({
                session: store.session() ?? stored,
                user,
              }),
            ),
          error: () => {
            storage.clear();
            dispatcher.dispatch(authApiEvents.anonymous());
          },
        });
      });
    },
  }),
);