const htmlspecialchars_table = {
    nbsp: "\xA0",
    quot: '"',
    apos: "'",
    lt: "<",
    gt: ">",
    amp: "&"
};

function htmlspecialchars_decode(s)
{
    // Only a limited set of named entries is supported by design,
    // because supporting all of them would require a large translation table
    if (s == null)
    {
        // or undefined, because null == undefined
        return "";
    }
    return s.replace(
        /&(nbsp|quot|apos|lt|gt|amp|#x[0-9a-f]+|#[0-9]+);/gi,
        (m, m1) =>
        {
            if (m1[0] == "#")
            {
                return String.fromCharCode(
                    m1[1] == "x"
                        ? parseInt(m1.substr(2), 16)
                        : parseInt(m1.substr(1), 10)
                );
            }
            return htmlspecialchars_table[m1];
        }
    );
}

function parse(content, components, createElement)
{
    content = content.replace(/>\s+</g, "><");
    const tag_re = /<(\/?)([a-z0-9\-]+)(([^>'"]+|"[^"]*"|'[^']*')*)>/i;
    const attr_re = /^\s*([^\s="']+)(?:=([^"'\s]+|"[^"]*"|'[^']*'))?/i;
    let m;
    let r = [];
    let stack = [r];
    while ((m = tag_re.exec(content)))
    {
        let text = content.substr(0, m.index);
        let close = m[1];
        let tag = m[2];
        let attrs = m[3];
        content = content.substr(m.index + m[0].length);
        text = text.replace(/^\s+/, "").replace(/\s+$/, "");
        if (text !== "")
        {
            r.push(htmlspecialchars_decode(text));
        }
        if (close && stack.length > 1)
        {
            stack.pop();
            r = stack[stack.length - 1];
        }
        else
        {
            attrs = attrs.replace(/\s+$/, "");
            if (attrs[attrs.length - 1] == "/")
            {
                close = true;
                attrs = attrs.substr(0, attrs.length - 1).replace(/\s+$/, "");
            }
            let attrhash = {};
            while ((m = attr_re.exec(attrs)))
            {
                let key = m[1].toLowerCase();
                let value = m[2];
                if (value != null)
                {
                    // remember that null == undefined, so this checks for undefined too
                    if (value[0] == '"' || value[0] == "'")
                    {
                        value = value.substr(1, value.length - 2);
                    }
                    value = htmlspecialchars_decode(value);
                }
                else
                {
                    value = "true";
                }
                if (key === "href")
                {
                    // 0x0A-0B-0C are ignored in schema value in IE
                    value = value.replace(/[\x0a\x0b\x0c]+/g, "");
                }
                if (key.substr(0, 2) !== "on" &&
                    (key !== "href" || !/^javascript:/.exec(value)))
                {
                    if (key === "class")
                    {
                        // Convert to className for React
                        key = "className";
                    }
                    else if (key === "style")
                    {
                        // Convert to an object for React
                        let obj = {};
                        value = value.replace(/^\s+/, "").replace(/\s+$/, "");
                        for (let part of value.split(/\s*;\s*/))
                        {
                            let pos = part.indexOf(":");
                            if (pos >= 0)
                            {
                                let part_key = part
                                    .substr(0, pos)
                                    .replace(/\s+$/, "")
                                    .replace(/-([a-z])/g, (m, m1) =>
                                        m1.toUpperCase()
                                    );
                                let part_value = part
                                    .substr(pos + 1)
                                    .replace(/^\s+/, "");
                                obj[part_key] = part_value;
                            }
                        }
                        value = obj;
                    }
                    attrhash[key] = value;
                }
                attrs = attrs.substr(m[0].length);
            }
            if (!close)
            {
                attrhash["children"] = [];
            }
            attrhash["key"] = r.length;
            r.push(createElement(components[tag] || tag, attrhash));
            if (!close)
            {
                stack.push(attrhash["children"]);
                r = attrhash["children"];
            }
        }
    }
    content = content.replace(/^\s+/, "").replace(/\s+$/, "");
    if (content !== "")
    {
        r.push(htmlspecialchars_decode(content));
    }
    return stack[0];
}

module.exports = { htmlspecialchars_decode, parse };