var entityMap = require("../maps/entities.json"),
    legacyMap = require("../maps/legacy.json"),
    xmlMap = require("../maps/xml.json"),
    decodeCodePoint = require("./decode_codepoint.js");

var decodeXMLStrict = getStrictDecoder(xmlMap),
    decodeHTMLStrict = getStrictDecoder(entityMap);

function getStrictDecoder(map) {
    var keys = Object.keys(map).join("|"),
        replace = getReplacer(map);

    keys += "|#[xX][\\da-fA-F]+|#\\d+";

    var re = new RegExp("&(?:" + keys + ");", "g");

    return function(str) {
        return String(str).replace(re, replace);
    };
}

var decodeHTML = (function() {
    var legacy = Object.keys(legacyMap).sort(sorter);

    var keys = Object.keys(entityMap).sort(sorter);

    for (var i = 0, j = 0; i < keys.length; i++) {
        if (legacy[j] === keys[i]) {
            keys[i] += ";?";
            j++;
        } else {
            keys[i] += ";";
        }
    }

    var re = new RegExp("&(?:" + keys.join("|") + "|#[xX][\\da-fA-F]+;?|#\\d+;?)", "g"),
        replace = getReplacer(entityMap);

    function replacer(str) {
        if (str.substr(-1) !== ";") str += ";";
        return replace(str);
    }

    //TODO consider creating a merged map
    return function(str) {
        return String(str).replace(re, replacer);
    };
})();

function sorter(a, b) {
    return a < b ? 1 : -1;
}

function getReplacer(map) {
    return function replace(str) {
        if (str.charAt(1) === "#") {
            if (str.charAt(2) === "X" || str.charAt(2) === "x") {
                return decodeCodePoint(parseInt(str.substr(3), 16));
            }
            return decodeCodePoint(parseInt(str.substr(2), 10));
        }
        return map[str.slice(1, -1)];
    };
}

module.exports = {
    XML: decodeXMLStrict,
    HTML: decodeHTML,
    HTMLStrict: decodeHTMLStrict
};