function noop(value) {
    return value;
}

function generateMultiplier(multiplier) {
    if (multiplier.min === 0 && multiplier.max === 0) {
        return '*';
    }

    if (multiplier.min === 0 && multiplier.max === 1) {
        return '?';
    }

    if (multiplier.min === 1 && multiplier.max === 0) {
        return multiplier.comma ? '#' : '+';
    }

    if (multiplier.min === 1 && multiplier.max === 1) {
        return '';
    }

    return (
        (multiplier.comma ? '#' : '') +
        (multiplier.min === multiplier.max
            ? '{' + multiplier.min + '}'
            : '{' + multiplier.min + ',' + (multiplier.max !== 0 ? multiplier.max : '') + '}'
        )
    );
}

function generateTypeOpts(node) {
    switch (node.type) {
        case 'Range':
            return (
                ' [' +
                (node.min === null ? '-∞' : node.min) +
                ',' +
                (node.max === null ? '∞' : node.max) +
                ']'
            );

        default:
            throw new Error('Unknown node type `' + node.type + '`');
    }
}

function generateSequence(node, forceBraces, decorate) {
    var result = node.terms.map(function(term) {
        return generate(term, forceBraces, decorate);
    }).join(node.combinator === ' ' ? ' ' : ' ' + node.combinator + ' ');

    if (node.explicit || forceBraces) {
        result = (result[0] !== ',' ? '[ ' : '[') + result + ' ]';
    }

    return result;
}

function generate(node, forceBraces, decorate) {
    var result;

    switch (node.type) {
        case 'Group':
            result =
                generateSequence(node, forceBraces, decorate) +
                (node.disallowEmpty ? '!' : '');
            break;

        case 'Multiplier':
            // return since node is a composition
            return (
                generate(node.term, forceBraces, decorate) +
                decorate(generateMultiplier(node), node)
            );

        case 'Type':
            result = '<' + node.name + (node.opts ? decorate(generateTypeOpts(node.opts), node.opts) : '') + '>';
            break;

        case 'Property':
            result = '<\'' + node.name + '\'>';
            break;

        case 'Keyword':
            result = node.name;
            break;

        case 'AtKeyword':
            result = '@' + node.name;
            break;

        case 'Function':
            result = node.name + '(';
            break;

        case 'String':
        case 'Token':
            result = node.value;
            break;

        case 'Comma':
            result = ',';
            break;

        default:
            throw new Error('Unknown node type `' + node.type + '`');
    }

    return decorate(result, node);
}

module.exports = function(node, options) {
    var decorate = noop;
    var forceBraces = false;

    if (typeof options === 'function') {
        decorate = options;
    } else if (options) {
        forceBraces = Boolean(options.forceBraces);
        if (typeof options.decorate === 'function') {
            decorate = options.decorate;
        }
    }

    return generate(node, forceBraces, decorate);
};