catdad/grandma

var isStream = require('is-stream');

function assertType(type) {
    if (type !== 'readable' && type !== 'writable') {
        throw new Error(type + ' is not a known stream type');
    }
}

function assertObjectMode(stream, state, errStr) {
    if (!stream[state] || !stream[state].objectMode) {
        throw new TypeError(errStr);
    }
}

isStream.stdio = function isStdio(stream) {
    return stream === process.stdin ||
           stream === process.stdout ||
           stream === process.stderr;
};

isStream.assertStream = function assertStream(stream, type, errStr) {
    assertType(type);

    // When redirecting to a file, for some reason, this is not
    // detected as a writable stream, even though it is.
    //
    //   `grandma run testname -d 2ms -c 1 > file.log`
    //
    // So we are just going to manually make this pass...
    //
    // https://github.com/nodejs/node/issues/8828
    //
    // womp womp
    if (type === 'writable' && stream === process.stdout) {
        return true;
    }

    if (!isStream[type](stream)) {
        throw new TypeError(errStr);
    }
};

isStream.assertObjectStream = function assertObjectStream(stream, type, errStr) {
    isStream.assertStream(stream, type, errStr);

    if (type === 'readable') {
        assertObjectMode(stream, '_readableState', errStr);
    } else if (type === 'writable') {
        assertObjectMode(stream, '_writableState', errStr);
    }
};

module.exports = isStream;