/*
 * Copyright (C) 2020-2022  Yomichan Authors
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

class Environment {
    constructor() {
        this._cachedEnvironmentInfo = null;
    }

    async prepare() {
        this._cachedEnvironmentInfo = await this._loadEnvironmentInfo();
    }

    getInfo() {
        if (this._cachedEnvironmentInfo === null) { throw new Error('Not prepared'); }
        return this._cachedEnvironmentInfo;
    }

    async _loadEnvironmentInfo() {
        const browser = await this._getBrowser();
        const os = await this._getOperatingSystem();
        return {
            browser,
            platform: {os}
        };
    }

    async _getOperatingSystem() {
        try {
            const {os} = await this._getPlatformInfo();
            if (typeof os === 'string') {
                return os;
            }
        } catch (e) {
            // NOP
        }
        return 'unknown';
    }

    _getPlatformInfo() {
        return new Promise((resolve, reject) => {
            chrome.runtime.getPlatformInfo((result) => {
                const error = chrome.runtime.lastError;
                if (error) {
                    reject(error);
                } else {
                    resolve(result);
                }
            });
        });
    }

    async _getBrowser() {
        try {
            if (chrome.runtime.getURL('/').startsWith('ms-browser-extension://')) {
                return 'edge-legacy';
            }
            if (/\bEdge?\//.test(navigator.userAgent)) {
                return 'edge';
            }
        } catch (e) {
            // NOP
        }
        if (typeof browser !== 'undefined') {
            try {
                const info = await browser.runtime.getBrowserInfo();
                if (info.name === 'Fennec') {
                    return 'firefox-mobile';
                }
            } catch (e) {
                // NOP
            }
            if (this._isSafari()) {
                return 'safari';
            }
            return 'firefox';
        } else {
            return 'chrome';
        }
    }

    _isSafari() {
        const {vendor, userAgent} = navigator;
        return (
            typeof vendor === 'string' &&
            typeof userAgent === 'string' &&
            vendor.includes('Apple') &&
            !userAgent.includes('CriOS') &&
            !userAgent.includes('FxiOS')
        );
    }
}