interface ITagKeyValue {
    key: string,
    value?: string
}

enum EncodeTarget {
    Html = 0,
    Url = 1
}

function makeStartTag(tag:any, attrs: ITagKeyValue | ITagKeyValue[] | undefined = undefined ) {
    if (!tag) {return ''; }
    

    var attrsStr = '';
    if (attrs) {
        var arrAttrs = ([] as ITagKeyValue[]).concat(attrs);
        attrsStr = arrAttrs.map(function(attr:any){
            return attr.key + (attr.value ? '="' + attr.value + '"' : '');
        }).join(' ');
    }

    var closing = '>';
    if (tag === 'img' || tag === 'br') {
        closing = '/>';
    }
    return attrsStr ? `<${tag} ${attrsStr}${closing}` : `<${tag}${closing}`;
}

function makeEndTag(tag: any = '') {
    return tag && `</${tag}>` || '';
}

function decodeHtml(str: string) {
    return encodeMappings(EncodeTarget.Html).reduce(decodeMapping, str);
}

function encodeHtml(str: string, preventDoubleEncoding = true) {
    if (preventDoubleEncoding) {
        str = decodeHtml(str);
    }
    return encodeMappings(EncodeTarget.Html).reduce(encodeMapping, str);
}

function encodeLink(str: string) {
    let linkMaps = encodeMappings(EncodeTarget.Url);
    let decoded = linkMaps.reduce(decodeMapping, str);
    return linkMaps.reduce(encodeMapping, decoded);
}

function encodeMappings(mtype: EncodeTarget) {
    let maps = [
        ['&', '&amp;'], 
        ['<', '&lt;'],
        ['>', '&gt;'],
        ['"', '&quot;'],
        ["'", "&#x27;"],
        ['\\/', '&#x2F;'],
        ['\\(', '&#40;'],
        ['\\)', '&#41;']
    ];
    if (mtype === EncodeTarget.Html) {
        return maps.filter(([v,_]) => 
            v.indexOf('(') === -1 || v.indexOf(')') === -1
        );
    } else { // for url
        return maps.filter(([v,_]) => v.indexOf('/') === -1);
    }
}
function encodeMapping(str: string, mapping: string[]) {
    return str.replace(new RegExp(mapping[0], 'g'), mapping[1]);
}
function decodeMapping(str: string, mapping: string[]) {
    return str.replace(
        new RegExp(mapping[1], 'g'), mapping[0].replace('\\','')
    );
}
export {
    makeStartTag,
    makeEndTag,
    encodeHtml,
    decodeHtml,
    encodeLink,
    ITagKeyValue
};