// @flow

import React from 'react';
import SplashScreen from 'react-native-splash-screen';

import { setColorScheme } from '../../base/color-scheme';
import { DialogContainer } from '../../base/dialog';
import { updateFlags } from '../../base/flags/actions';
import { CALL_INTEGRATION_ENABLED, SERVER_URL_CHANGE_ENABLED } from '../../base/flags/constants';
import { getFeatureFlag } from '../../base/flags/functions';
import { Platform } from '../../base/react';
import { DimensionsDetector, clientResized } from '../../base/responsive-ui';
import { updateSettings } from '../../base/settings';
import logger from '../logger';

import { AbstractApp } from './AbstractApp';
import type { Props as AbstractAppProps } from './AbstractApp';

// Register middlewares and reducers.
import '../middlewares';
import '../reducers';

declare var __DEV__;

/**
 * The type of React {@code Component} props of {@link App}.
 */
type Props = AbstractAppProps & {

    /**
     * An object of colors that override the default colors of the app/sdk.
     */
    colorScheme: ?Object,

    /**
     * Identifier for this app on the native side.
     */
    externalAPIScope: string,

    /**
     * An object with the feature flags.
     */
    flags: Object,

    /**
     * An object with user information (display name, email, avatar URL).
     */
    userInfo: ?Object
};

/**
 * Root app {@code Component} on mobile/React Native.
 *
 * @extends AbstractApp
 */
export class App extends AbstractApp {
    _init: Promise<*>;

    /**
     * Initializes a new {@code App} instance.
     *
     * @param {Props} props - The read-only React {@code Component} props with
     * which the new instance is to be initialized.
     */
    constructor(props: Props) {
        super(props);

        // In the Release configuration, React Native will (intentionally) throw
        // an unhandled JavascriptException for an unhandled JavaScript error.
        // This will effectively kill the app. In accord with the Web, do not
        // kill the app.
        this._maybeDisableExceptionsManager();

        // Bind event handler so it is only bound once per instance.
        this._onDimensionsChanged = this._onDimensionsChanged.bind(this);
    }

    /**
     * Initializes the color scheme.
     *
     * @inheritdoc
     *
     * @returns {void}
     */
    componentDidMount() {
        super.componentDidMount();

        SplashScreen.hide();

        this._init.then(() => {
            const { dispatch, getState } = this.state.store;

            // We set these early enough so then we avoid any unnecessary re-renders.
            dispatch(setColorScheme(this.props.colorScheme));
            dispatch(updateFlags(this.props.flags));

            // Check if serverURL is configured externally and not allowed to change.
            const serverURLChangeEnabled = getFeatureFlag(getState(), SERVER_URL_CHANGE_ENABLED, true);

            if (!serverURLChangeEnabled) {
                // As serverURL is provided externally, so we push it to settings.
                if (typeof this.props.url !== 'undefined') {
                    const { serverURL } = this.props.url;

                    if (typeof serverURL !== 'undefined') {
                        dispatch(updateSettings({ serverURL }));
                    }
                }
            }

            dispatch(updateSettings(this.props.userInfo || {}));

            // Update settings with feature-flag.
            const callIntegrationEnabled = this.props.flags[CALL_INTEGRATION_ENABLED];

            if (typeof callIntegrationEnabled !== 'undefined') {
                dispatch(updateSettings({ disableCallIntegration: !callIntegrationEnabled }));
            }
        });
    }

    /**
     * Overrides the parent method to inject {@link DimensionsDetector} as
     * the top most component.
     *
     * @override
     */
    _createMainElement(component, props) {
        return (
            <DimensionsDetector
                onDimensionsChanged = { this._onDimensionsChanged }>
                { super._createMainElement(component, props) }
            </DimensionsDetector>
        );
    }

    /**
     * Attempts to disable the use of React Native
     * {@link ExceptionsManager#handleException} on platforms and in
     * configurations on/in which the use of the method in questions has been
     * determined to be undesirable. For example, React Native will
     * (intentionally) throw an unhandled {@code JavascriptException} for an
     * unhandled JavaScript error in the Release configuration. This will
     * effectively kill the app. In accord with the Web, do not kill the app.
     *
     * @private
     * @returns {void}
     */
    _maybeDisableExceptionsManager() {
        if (__DEV__) {
            // As mentioned above, only the Release configuration was observed
            // to suffer.
            return;
        }
        if (Platform.OS !== 'android') {
            // A solution based on RTCSetFatalHandler was implemented on iOS and
            // it is preferred because it is at a later step of the
            // error/exception handling and it is specific to fatal
            // errors/exceptions which were observed to kill the app. The
            // solution implemented bellow was tested on Android only so it is
            // considered safest to use it there only.
            return;
        }

        const oldHandler = global.ErrorUtils.getGlobalHandler();
        const newHandler = _handleException;

        if (!oldHandler || oldHandler !== newHandler) {
            newHandler.next = oldHandler;
            global.ErrorUtils.setGlobalHandler(newHandler);
        }
    }

    _onDimensionsChanged: (width: number, height: number) => void;

    /**
     * Updates the known available size for the app to occupy.
     *
     * @param {number} width - The component's current width.
     * @param {number} height - The component's current height.
     * @private
     * @returns {void}
     */
    _onDimensionsChanged(width: number, height: number) {
        const { dispatch } = this.state.store;

        dispatch(clientResized(width, height));
    }

    /**
     * Renders the platform specific dialog container.
     *
     * @returns {React$Element}
     */
    _renderDialogContainer() {
        return (
            <DialogContainer />
        );
    }
}

/**
 * Handles a (possibly unhandled) JavaScript error by preventing React Native
 * from converting a fatal error into an unhandled native exception which will
 * kill the app.
 *
 * @param {Error} error - The (possibly unhandled) JavaScript error to handle.
 * @param {boolean} fatal - If the specified error is fatal, {@code true};
 * otherwise, {@code false}.
 * @private
 * @returns {void}
 */
function _handleException(error, fatal) {
    if (fatal) {
        // In the Release configuration, React Native will (intentionally) throw
        // an unhandled JavascriptException for an unhandled JavaScript error.
        // This will effectively kill the app. In accord with the Web, do not
        // kill the app.
        logger.error(error);
    } else {
        // Forward to the next globalHandler of ErrorUtils.
        const { next } = _handleException;

        typeof next === 'function' && next(error, fatal);
    }
}