// *****************************************************************************
// Copyright (C) 2017 TypeFox and others.
//
// This program and the accompanying materials are made available under the
// terms of the Eclipse Public License v. 2.0 which is available at
// http://www.eclipse.org/legal/epl-2.0.
//
// This Source Code may also be made available under the following Secondary
// Licenses when the conditions for such availability set forth in the Eclipse
// Public License v. 2.0 are satisfied: GNU General Public License, version 2
// with the GNU Classpath Exception which is available at
// https://www.gnu.org/software/classpath/license.html.
//
// SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0
// *****************************************************************************

function is(userAgent: string, platform: string): boolean {
    if (typeof navigator !== 'undefined') {
        if (navigator.userAgent && navigator.userAgent.indexOf(userAgent) >= 0) {
            return true;
        }
    }
    if (typeof process !== 'undefined') {
        return (process.platform === platform);
    }
    return false;
}

export const isWindows = is('Windows', 'win32');
export const isOSX = is('Mac', 'darwin');

export const EOL = isWindows ? '\r\n' : '\n';

export type CMD = [string, string[]];
export function cmd(command: string, ...args: string[]): CMD {
    return [
        isWindows ? 'cmd' : command,
        isWindows ? ['/c', command, ...args] : args
    ];
}

export namespace OS {

    /**
     * Enumeration of the supported operating systems.
     */
    export enum Type {
        Windows = 'Windows',
        Linux = 'Linux',
        OSX = 'OSX'
    }

    /**
     * Returns with the type of the operating system. If it is neither [Windows](isWindows) nor [OS X](isOSX), then
     * it always return with the `Linux` OS type.
     */
    export function type(): OS.Type {
        if (isWindows) {
            return Type.Windows;
        }
        if (isOSX) {
            return Type.OSX;
        }
        return Type.Linux;
    }

    export const backend = {
        type,
        isWindows,
        isOSX,
        EOL
    };

}

export const OSBackendProviderPath = '/os';

export const OSBackendProvider = Symbol('OSBackendProvider');

export interface OSBackendProvider {
    getBackendOS(): Promise<OS.Type>;
}