'use strict';

const renderBytes = require("../../render/bytes");

let sequenceMap = {
    "ucs2-level1": Buffer.from([0x25, 0x2F, 0x40]),
    "ucs2-level2": Buffer.from([0x25, 0x2F, 0x43]),
    "ucs2-level3": Buffer.from([0x25, 0x2F, 0x45])
}

module.exports = function parseEscapeSequences(escapeSequences) {
    let pos = 0;
    let finished = false;
    let encodings = [];

    while (finished === false) {
        if (escapeSequences.readUInt8(pos) === 0) {
            /* We've run out of escape sequences to parse */
            break;
        }

        /* We only check for 3-byte-long escape sequences, for now... */
        let slice3 = escapeSequences.slice(pos, pos + 3);

        let encoding = Object.keys(sequenceMap).find((encoding) => sequenceMap[encoding].equals(slice3));

        if (encoding == null) {
            throw new Error(`Encountered unrecognized escape sequence; remaining bytes to parse: ${renderBytes(escapeSequences.slice(pos))}`);
        } else {
            pos += sequenceMap[encoding].length;
            encodings.push(encoding);
        }
    }


    if (encodings.length === 0) {
        return ["ascii"];
    } else {
        return encodings;
    }
};