/**
 * utf8 utf16转码，解决中文问题
 */

'use strict';

module.exports = (function() {
    var _e = {};

    _e.utf16to8 = function(str) {
        var out, i, len, c;
        out = '';
        len = str.length;
        for (i = 0; i < len; i++) {
            c = str.charCodeAt(i);
            if ((c >= 0x0001) && (c <= 0x007F)) {
                out += str.charAt(i);
            } else if (c > 0x07FF) {
                out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F));
                out += String.fromCharCode(0x80 | ((c >> 6) & 0x3F));
                out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
            } else {
                out += String.fromCharCode(0xC0 | ((c >> 6) & 0x1F));
                out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F));
            }
        }
        return out;
    };

    _e.utf8to16 = function(str) {
        var out, i, len, c;
        var char2, char3;
        out = '';
        len = str.length;
        i = 0;
        while (i < len) {
            c = str.charCodeAt(i++);
            switch (c >> 4) {

            case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
                // 0xxxxxxx
                out += str.charAt(i - 1);
                break;
            case 12: case 13:
                // 110x xxxx   10xx xxxx
                char2 = str.charCodeAt(i++);
                out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F));
                break;
            case 14:
                // 1110 xxxx  10xx xxxx  10xx xxxx
                char2 = str.charCodeAt(i++);
                char3 = str.charCodeAt(i++);
                out += String.fromCharCode(((c & 0x0F) << 12) |
                ((char2 & 0x3F) << 6) |
                ((char3 & 0x3F) << 0));
                break;
            }
        }
        return out;
    };

    return _e;
})();