aymericbeaumet/metalsmith-redirect

const path = require('path');

function isDirectory(url) {
    return path.extname(url) === '';
}

function isHTML(url, options) {
    const htmlExtensions = options.htmlExtensions || ['.html'];

    return htmlExtensions.includes(path.extname(url));
}

function isAbsolute(url) {
    return /^(?:\/|\\|(?:https?|ftp):\/\/)/.test(url);
}

module.exports = wrappedPath => {
    return {
        get() {
            // Handle Windows style path
            wrappedPath = wrappedPath.replace(/\\/g, '/');

            return wrappedPath;
        },

        appendHTMLIndexIfNeeded() {
            if (isDirectory(wrappedPath)) {
                // Save the prefix (http:/, ftp:/, ...) in order to avoid issues with
                // path.join()
                let prefix = '';
                const idx = wrappedPath.indexOf('/');
                if (idx > 0) {
                    prefix = wrappedPath.slice(0, idx + 1);
                    wrappedPath = wrappedPath.slice(idx + 1);
                }

                wrappedPath = prefix + path.join(wrappedPath, 'index.html');
            }

            return this;
        },

        ensureHTML(options) {
            if (!isHTML(wrappedPath, options || {})) {
                throw new Error(`"${wrappedPath}" is not a valid HTML path`);
            }

            return this;
        },

        relativeTo(filepath) {
            if (isAbsolute(wrappedPath)) {
                return this;
            }

            const dir =
        path.extname(filepath) === '' ? filepath : path.dirname(filepath);
            wrappedPath = path.join(dir, wrappedPath);

            return this;
        }
    };
};