/**
 * @author bmwhitn [brian.m.whitney@outlook.com]
 * @copyright Crown Copyright 2017
 * @license Apache-2.0
 */

import Operation from "../Operation.mjs";

/**
 * Microsoft Script Decoder operation
 */
class MicrosoftScriptDecoder extends Operation {

    /**
     * MicrosoftScriptDecoder constructor
     */
    constructor() {
        super();

        this.name = "Microsoft Script Decoder";
        this.module = "Default";
        this.description = "Decodes Microsoft Encoded Script files that have been encoded with Microsoft's custom encoding. These are often VBS (Visual Basic Script) files that are encoded and renamed with a '.vbe' extention or JS (JScript) files renamed with a '.jse' extention.<br><br><b>Sample</b><br><br>Encoded:<br><code>#@~^RQAAAA==-mD~sX|:/TP{~J:+dYbxL~@!F@*@!+@*@!&amp;@*eEI@#@&amp;@#@&amp;.jm.raY 214Wv:zms/obI0xEAAA==^#~@</code><br><br>Decoded:<br><code>var my_msg = &#34;Testing <1><2><3>!&#34;;\n\nVScript.Echo(my_msg);</code>";
        this.infoURL = "https://wikipedia.org/wiki/JScript.Encode";
        this.inputType = "string";
        this.outputType = "string";
        this.args = [];
    }

    /**
     * @param {string} input
     * @param {Object[]} args
     * @returns {string}
     */
    run(input, args) {
        const matcher = /#@~\^.{6}==(.+).{6}==\^#~@/;
        const encodedData = matcher.exec(input);
        if (encodedData) {
            return MicrosoftScriptDecoder._decode(encodedData[1]);
        } else {
            return "";
        }
    }

    /**
     * Decodes Microsoft Encoded Script files that can be read and executed by cscript.exe/wscript.exe.
     * This is a conversion of a Python script that was originally created by Didier Stevens
     * (https://DidierStevens.com).
     *
     * @private
     * @param {string} data
     * @returns {string}
     */
    static _decode(data) {
        const result = [];
        let index = -1;
        data = data.replace(/@&/g, String.fromCharCode(10))
            .replace(/@#/g, String.fromCharCode(13))
            .replace(/@\*/g, ">")
            .replace(/@!/g, "<")
            .replace(/@\$/g, "@");

        for (let i = 0; i < data.length; i++) {
            const byte = data.charCodeAt(i);
            let char = data.charAt(i);
            if (byte < 128) {
                index++;
            }

            if ((byte === 9 || byte > 31 && byte < 128) &&
                byte !== 60 &&
                byte !== 62 &&
                byte !== 64) {
                char = D_DECODE[byte].charAt(D_COMBINATION[index % 64]);
            }
            result.push(char);
        }
        return result.join("");
    }

}

const D_DECODE = [
    "",
    "",
    "",
    "",
    "",
    "",
    "",
    "",
    "",
    "\x57\x6E\x7B",
    "\x4A\x4C\x41",
    "\x0B\x0B\x0B",
    "\x0C\x0C\x0C",
    "\x4A\x4C\x41",
    "\x0E\x0E\x0E",
    "\x0F\x0F\x0F",
    "\x10\x10\x10",
    "\x11\x11\x11",
    "\x12\x12\x12",
    "\x13\x13\x13",
    "\x14\x14\x14",
    "\x15\x15\x15",
    "\x16\x16\x16",
    "\x17\x17\x17",
    "\x18\x18\x18",
    "\x19\x19\x19",
    "\x1A\x1A\x1A",
    "\x1B\x1B\x1B",
    "\x1C\x1C\x1C",
    "\x1D\x1D\x1D",
    "\x1E\x1E\x1E",
    "\x1F\x1F\x1F",
    "\x2E\x2D\x32",
    "\x47\x75\x30",
    "\x7A\x52\x21",
    "\x56\x60\x29",
    "\x42\x71\x5B",
    "\x6A\x5E\x38",
    "\x2F\x49\x33",
    "\x26\x5C\x3D",
    "\x49\x62\x58",
    "\x41\x7D\x3A",
    "\x34\x29\x35",
    "\x32\x36\x65",
    "\x5B\x20\x39",
    "\x76\x7C\x5C",
    "\x72\x7A\x56",
    "\x43\x7F\x73",
    "\x38\x6B\x66",
    "\x39\x63\x4E",
    "\x70\x33\x45",
    "\x45\x2B\x6B",
    "\x68\x68\x62",
    "\x71\x51\x59",
    "\x4F\x66\x78",
    "\x09\x76\x5E",
    "\x62\x31\x7D",
    "\x44\x64\x4A",
    "\x23\x54\x6D",
    "\x75\x43\x71",
    "\x4A\x4C\x41",
    "\x7E\x3A\x60",
    "\x4A\x4C\x41",
    "\x5E\x7E\x53",
    "\x40\x4C\x40",
    "\x77\x45\x42",
    "\x4A\x2C\x27",
    "\x61\x2A\x48",
    "\x5D\x74\x72",
    "\x22\x27\x75",
    "\x4B\x37\x31",
    "\x6F\x44\x37",
    "\x4E\x79\x4D",
    "\x3B\x59\x52",
    "\x4C\x2F\x22",
    "\x50\x6F\x54",
    "\x67\x26\x6A",
    "\x2A\x72\x47",
    "\x7D\x6A\x64",
    "\x74\x39\x2D",
    "\x54\x7B\x20",
    "\x2B\x3F\x7F",
    "\x2D\x38\x2E",
    "\x2C\x77\x4C",
    "\x30\x67\x5D",
    "\x6E\x53\x7E",
    "\x6B\x47\x6C",
    "\x66\x34\x6F",
    "\x35\x78\x79",
    "\x25\x5D\x74",
    "\x21\x30\x43",
    "\x64\x23\x26",
    "\x4D\x5A\x76",
    "\x52\x5B\x25",
    "\x63\x6C\x24",
    "\x3F\x48\x2B",
    "\x7B\x55\x28",
    "\x78\x70\x23",
    "\x29\x69\x41",
    "\x28\x2E\x34",
    "\x73\x4C\x09",
    "\x59\x21\x2A",
    "\x33\x24\x44",
    "\x7F\x4E\x3F",
    "\x6D\x50\x77",
    "\x55\x09\x3B",
    "\x53\x56\x55",
    "\x7C\x73\x69",
    "\x3A\x35\x61",
    "\x5F\x61\x63",
    "\x65\x4B\x50",
    "\x46\x58\x67",
    "\x58\x3B\x51",
    "\x31\x57\x49",
    "\x69\x22\x4F",
    "\x6C\x6D\x46",
    "\x5A\x4D\x68",
    "\x48\x25\x7C",
    "\x27\x28\x36",
    "\x5C\x46\x70",
    "\x3D\x4A\x6E",
    "\x24\x32\x7A",
    "\x79\x41\x2F",
    "\x37\x3D\x5F",
    "\x60\x5F\x4B",
    "\x51\x4F\x5A",
    "\x20\x42\x2C",
    "\x36\x65\x57"
];

const D_COMBINATION = [
    0, 1, 2, 0, 1, 2, 1, 2, 2, 1, 2, 1, 0, 2, 1, 2, 0, 2, 1, 2, 0, 0, 1, 2, 2, 1, 0, 2, 1, 2, 2, 1,
    0, 0, 2, 1, 2, 1, 2, 0, 2, 0, 0, 1, 2, 0, 2, 1, 0, 2, 1, 2, 0, 0, 1, 2, 2, 0, 0, 1, 2, 0, 2, 1
];

export default MicrosoftScriptDecoder;