var url = require("url");
var path = require("path");

// Is the link an external link
var isExternal = function(href) {
    try {
        return Boolean(url.parse(href).protocol);
    } catch(err) { }

    return false;
};

// Return true if the link is relative
var isRelative = function(href) {
    try {
        var parsed = url.parse(href);

        return !!(!parsed.protocol && parsed.path);
    } catch(err) {}

    return true;
};

// Return true if the link is an achor
var isAnchor = function(href) {
    try {
        var parsed = url.parse(href);
        return !!(!parsed.protocol && !parsed.path && parsed.hash);
    } catch(err) {}

    return false;
};

// Normalize a path to be a link
var normalizeLink = function(s) {
    return s.replace(/\\/g, "/");
};

// Relative to absolute path
// dir: directory parent of the file currently in rendering process
// outdir: directory parent from the html output

var toAbsolute = function(_href, dir, outdir) {
    if (isExternal(_href)) return _href;

    // Path "_href" inside the base folder
    var hrefInRoot = path.normalize(path.join(dir, _href));
    if (_href[0] == "/") hrefInRoot = path.normalize(_href.slice(1));

    // Make it relative to output
    _href = path.relative(outdir, hrefInRoot);

    // Normalize windows paths
    _href = normalizeLink(_href);

    return _href;
};

// Join links
var join = function() {
    var _href = path.join.apply(path, arguments);

    return normalizeLink(_href);
};

// Change extension
var changeExtension = function(filename, newext) {
    return path.join(
        path.dirname(filename),
        path.basename(filename, path.extname(filename))+newext
    );
};

module.exports = {
    isAnchor: isAnchor,
    isRelative: isRelative,
    isExternal: isExternal,
    toAbsolute: toAbsolute,
    join: join,
    changeExtension: changeExtension,
    normalize: normalizeLink
};