/**
 * @file authAutomat.js
 * @description Central authentication and multi-tenant session manager.
 * Tracks current user, Google OAuth client ID, and active company selection.
 *
 * Upstream Triggers:
 * - `AuthBootstrap.jsx`: Calls `bootstrapSession(session)` on initial app load.
 * - `LoginPage.jsx`: Calls `loginWithGoogle(credential)` or `loginWithCredentials(body)`.
 * - `UserMenu.jsx`: Calls `switchCompany(companyId)` or `logout()`.
 *
 * Downstream Triggers:
 * Subscribed to by almost all company-scoped automats, orchestrating their loading
 * when authenticated (`authed` + `selectedCompanyId`) and reset on logout (`anon`):
 * - `companyAutomat`, `categoryAutomat`, `brandAutomat`, `unitAutomat`, `posterminalAutomat`
 * - `attributeAutomat`, `propertyAutomat`, `supplierAutomat`, `warehouseAutomat`
 * - `sseAutomat`: Disconnects/reconnects SSE stream to `/api/events` per company
 * - `chatAutomat`: Reconnects AI chat SSE stream and reloads conversations
 * - `articleIndexAutomat`: Resets the derived index on logout; loads it lazily from
 *   the category views once the session is established
 * - `createListAutomat` instances (`deliveryAutomat`, `quoteAutomat`,
 *   `orderAutomat`, `entityAutomat`, `customergroupAutomat`, `numberAutomat`)
 * - Grid history automats (`articleHistoryGridAutomat`, `globalHistoryGridAutomat`)
 * - `artikelAutomat`: Clears cached articles on logout
 */

import { Automat } from 'react-automat';
import { auth, company } from '../api';

/**
 * @typedef {Object} AuthUser
 * @property {string|number|null} [selectedCompanyId] Currently selected company.
 * @property {*} [key] Additional user properties returned by the API.
 */

/**
 * @typedef {Object} AuthState
 * @property {AuthUser|null} user Authenticated user, or `null` for anonymous sessions.
 * @property {string|null} googleClientId Google Identity Services client ID.
 * @property {'loading'|'anon'|'authed'} status Current authentication lifecycle state.
 */

/** Emitted after an authenticated session has been established. */
export const AUTH_SESSION_ESTABLISHED = 'auth/sessionEstablished';
/** Emitted after the active company has changed. */
export const AUTH_COMPANY_CHANGED = 'auth/companyChanged';
/** Emitted after the current user has logged out. */
export const AUTH_LOGGED_OUT = 'auth/loggedOut';

/** @type {AuthState} */
const initialState = {
    user: null,
    googleClientId: null,
    status: 'loading',
};

let emit = () => { };

/**
 * Registers the application-level dispatcher used for authentication events.
 *
 * @param {(event: {type: string}) => void} dispatch Event dispatcher.
 * @returns {void}
 */
export function setAuthEventDispatcher(dispatch) {
    emit = dispatch;
}

function normalizePicture(picture) {
    if (!picture || typeof picture !== 'string') return null;
    if (picture.startsWith('http://') || picture.startsWith('https://') || picture.startsWith('data:')) {
        return picture;
    }
    const mime = picture.startsWith('/9j/') ? 'image/jpeg' : 'image/png';
    return `data:${mime};base64,${picture}`;
}

/**
 * Merges API user data while retaining the current company selection when the
 * response does not contain one.
 *
 * @param {AuthUser|null} current Current user.
 * @param {AuthUser|null|undefined} incoming User data returned by the API.
 * @returns {AuthUser|null} Merged user.
 */
function mergeUser(current, incoming) {
    if (!incoming) return current;
    const selectedCompanyId =
        incoming.selectedCompanyId ?? current?.selectedCompanyId ?? null;
    const merged = { ...current, ...incoming, selectedCompanyId };
    if (merged.picture) {
        merged.picture = normalizePicture(merged.picture);
    }
    return merged;
}

let authAutomat;

const actions = {
    /**
     * Restores an existing session or requests it from the authentication API.
     *
     * @param {{user?: AuthUser|null, googleClientId?: string|null}|null} [session]
     *   Optional preloaded session.
     * @returns {Promise<Object>} Resolved session response.
     */
    async bootstrapSession(session) {
        try {
            const nextSession = session ?? await auth.me();
            const googleClientId =
                nextSession.googleClientId ?? authAutomat.state.googleClientId;

            if (!nextSession.user) {
                if (authAutomat.state.status !== 'authed') {
                    authAutomat.setState({ user: null, googleClientId, status: 'anon' });
                } else {
                    authAutomat.setState({ googleClientId });
                }
                return nextSession;
            }

            const user = mergeUser(authAutomat.state.user, nextSession.user);
            authAutomat.setState({ user, googleClientId, status: 'authed' });
            emit({ type: AUTH_SESSION_ESTABLISHED });
            return nextSession;
        } catch (error) {
            if (authAutomat.state.status === 'loading') {
                authAutomat.setState({ user: null, status: 'anon' });
            }
            throw error;
        }
    },

    /**
     * Exchanges a Google credential for an authenticated application session.
     *
     * @param {string} credential Google Identity Services credential.
     * @returns {Promise<Object>} Authenticated session.
     */
    async loginWithGoogle(credential) {
        try {
            const { session } = await auth.loginWithGoogle(credential);
            if (!session?.user) {
                throw new Error('Login ok but session cookie not accepted (/api/auth/me still unauthorized)');
            }
            const user = mergeUser(authAutomat.state.user, session.user);
            authAutomat.setState({
                user,
                googleClientId: session.googleClientId ?? authAutomat.state.googleClientId,
                status: 'authed',
            });
            emit({ type: AUTH_SESSION_ESTABLISHED });
            return session;
        } catch (error) {
            authAutomat.setState({ user: null, status: 'anon' });
            throw error;
        }
    },

    /**
     * Selects the company used by the current session.
     *
     * @param {string|number} companyId Company identifier.
     * @returns {Promise<AuthUser>} Updated user.
     */
    async selectCompany(companyId) {
        const data = await company.select(companyId);
        const user = mergeUser(
            authAutomat.state.user,
            data.user ?? { selectedCompanyId: companyId },
        );
        authAutomat.setState({ user, status: 'authed' });
        emit({ type: AUTH_COMPANY_CHANGED });
        return user;
    },

    /**
     * Creates a company and selects it for the current user.
     *
     * @param {Object} payload Company creation payload.
     * @returns {Promise<AuthUser>} Updated user.
     */
    async createCompany(payload) {
        const data = await company.create(payload);
        let incoming = data.user;
        if (!incoming && data.company?.id) {
            const selected = await company.select(data.company.id);
            incoming = selected.user ?? { selectedCompanyId: data.company.id };
        }
        if (!incoming) {
            throw new Error('Unternehmen angelegt, aber keine Benutzerdaten erhalten.');
        }

        const user = mergeUser(authAutomat.state.user, incoming);
        authAutomat.setState({ user, status: 'authed' });
        emit({ type: AUTH_COMPANY_CHANGED });
        return user;
    },

    /**
     * Ends the server session, clears the current user, and returns to `/`.
     *
     * @returns {Promise<void>}
     */
    async logout() {
        await auth.logout();
        window.history.replaceState(null, '', '/');
        authAutomat.setState({ user: null, status: 'anon' });
        emit({ type: AUTH_LOGGED_OUT });
    },
};

/**
 * Global authentication state container.
 *
 * @type {Automat<AuthState>}
 */
authAutomat = new Automat(initialState, actions, { name: 'auth' });

/**
 * Re-reads `GET /api/auth/me` from the server.
 *
 * Called after login, logout, and company switches so the automat reflects
 * the current server session rather than an optimistic guess.
 *
 * @returns {Promise<{user: AuthUser|null, googleClientId: string|null}>} Session.
 */
export function bootstrapAuthMe() {
    return auth.me();
}

export default authAutomat;