source: node_modules/supports-color/index.js

'use strict';
const os = require('os');
const hasFlag = require('has-flag');

const env = process.env;

let forceColor;
if (hasFlag('no-color') ||
        hasFlag('no-colors') ||
        hasFlag('color=false')) {
        forceColor = false;
} else if (hasFlag('color') ||
        hasFlag('colors') ||
        hasFlag('color=true') ||
        hasFlag('color=always')) {
        forceColor = true;
}
if ('FORCE_COLOR' in env) {
        forceColor = env.FORCE_COLOR.length === 0 || parseInt(env.FORCE_COLOR, 10) !== 0;
}

function translateLevel(level) {
        if (level === 0) {
                return false;
        }

        return {
                level,
                hasBasic: true,
                has256: level >= 2,
                has16m: level >= 3
        };
}

function supportsColor(stream) {
        if (forceColor === false) {
                return 0;
        }

        if (hasFlag('color=16m') ||
                hasFlag('color=full') ||
                hasFlag('color=truecolor')) {
                return 3;
        }

        if (hasFlag('color=256')) {
                return 2;
        }

        if (stream && !stream.isTTY && forceColor !== true) {
                return 0;
        }

        const min = forceColor ? 1 : 0;

        if (process.platform === 'win32') {
                // Node.js 7.5.0 is the first version of Node.js to include a patch to
                // libuv that enables 256 color output on Windows. Anything earlier and it
                // won't work. However, here we target Node.js 8 at minimum as it is an LTS
                // release, and Node.js 7 is not. Windows 10 build 10586 is the first Windows
                // release that supports 256 colors. Windows 10 build 14931 is the first release
                // that supports 16m/TrueColor.
                const osRelease = os.release().split('.');
                if (
                        Number(process.versions.node.split('.')[0]) >= 8 &&
                        Number(osRelease[0]) >= 10 &&
                        Number(osRelease[2]) >= 10586
                ) {
                        return Number(osRelease[2]) >= 14931 ? 3 : 2;
                }

                return 1;
        }

        if ('CI' in env) {
                if (['TRAVIS', 'CIRCLECI', 'APPVEYOR', 'GITLAB_CI'].some(sign => sign in env) || env.CI_NAME === 'codeship') {
                        return 1;
                }

                return min;
        }

        if ('TEAMCITY_VERSION' in env) {
                return /^(9\.(0*[1-9]\d*)\.|\d{2,}\.)/.test(env.TEAMCITY_VERSION) ? 1 : 0;
        }

        if (env.COLORTERM === 'truecolor') {
                return 3;
        }

        if ('TERM_PROGRAM' in env) {
                const version = parseInt((env.TERM_PROGRAM_VERSION || '').split('.')[0], 10);

                switch (env.TERM_PROGRAM) {
                        case 'iTerm.app':
                                return version >= 3 ? 3 : 2;
                        case 'Apple_Terminal':
                                return 2;
                        // No default
                }
        }

        if (/-256(color)?$/i.test(env.TERM)) {
                return 2;
        }

        if (/^screen|^xterm|^vt100|^vt220|^rxvt|color|ansi|cygwin|linux/i.test(env.TERM)) {
                return 1;
        }

        if ('COLORTERM' in env) {
                return 1;
        }

        if (env.TERM === 'dumb') {
                return min;
        }

        return min;
}

function getSupportLevel(stream) {
        const level = supportsColor(stream);
        return translateLevel(level);
}

module.exports = {
        supportsColor: getSupportLevel,
        stdout: getSupportLevel(process.stdout),
        stderr: getSupportLevel(process.stderr)
};