/** Convert a telnet IAC sequence from raw bytes to a human readable format that
 *  can be output for debugging purposes.
 * @example
 * var IAC = "\xFF", DO = "\xFD", TTYPE = "\x18";
 * DecafMUD.debugIAC(IAC + DO + TTYPE);
 * // Returns: "IAC DO TERMINAL-TYPE"
 * @param {String} seq The sequence to convert.
 * @returns {String} The human readable description of the IAC sequence. */
DecafMUD.debugIAC = function(seq) {
    var out = '', t = DecafMUD.TN, state = 0, st = false, l = seq.length,
        i2w = iacToWord;

    for( var i = 0; i < l; i++ ) {
        var c = seq.charAt(i),
            cc = c.charCodeAt(0);

        // TTYPE Sequence
        if ( state === 2 ) {
            if ( c === t.ECHO ) { out += 'SEND '; }
            else if ( c === t.IS ) { out += 'IS '; }
            else if ( c === t.IAC ) {
                if ( st ) { st = false; out += '" IAC '; }
                else { out += 'IAC '; }
                state = 0;
            } else {
                if ( !st ) { st = true; out += '"'; }
                out += c;
            }
            continue;
        }

        // MSSP / MSDP Sequence
        else if ( state === 3 || state === 4 ) {
            if ( c === t.IAC || (cc >= 1 && cc <= 4) ) {
                if ( st ) { st = false; out += '" '; }
                if ( c === t.IAC ) {
                    out += 'IAC ';
                    state = 0; }
                else if ( cc === 3 ) { out += 'MSDP_OPEN '; }
                else if ( cc === 4 ) { out += 'MSDP_CLOSE '; }
                else {
                    if ( state === 3 ) { out += 'MSSP_'; }
                    else { out += 'MSDP_'; }
                    if ( cc === 1 ) { out += 'VAR '; }
                    else { out += 'VAL '; }
                }
            } else {
                if ( !st ) { st = true; out += '"'; }
                out += c;
            }
            continue;
        }

        // NAWS Sequence
        else if ( state === 5 ) {
            if ( c === t.IAC ) {
                st = false; out += 'IAC ';
                state = 0;
            } else {
                if ( st === false ) { st = cc * 255; }
                else {
                    out += (cc + st).toString() + ' ';
                    st = false;
                }
            }
            continue;
        }

        // CHARSET Sequence
        else if ( state === 6 ) {
            if ( c === t.IAC || (cc > 0 && cc < 8) ) {
                if ( st ) { st = false; out += '" '; }
                if ( c === t.IAC ) {
                    out += 'IAC ';
                    state = 0; }
                else if ( cc === 1 ) { out += 'REQUEST '; }
                else if ( cc === 2 ) { out += 'ACCEPTED '; }
                else if ( cc === 3 ) { out += 'REJECTED '; }
                else if ( cc === 4 ) { out += 'TTABLE-IS '; }
                else if ( cc === 5 ) { out += 'TTABLE-REJECTED '; }
                else if ( cc === 6 ) { out += 'TTABLE-ACK '; }
                else if ( cc === 7 ) { out += 'TTABLE-NAK '; }
            } else {
                if ( !st ) { st = true; out += '"'; }
                out += c;
            }
        }

        // ZMP Sequence
        else if ( state === 7 ) {
            if ( c === t.IAC || cc === 0 ) {
                if ( st ) { st = false; out += '" '; }
                if ( c === t.IAC ) {
                    out += 'IAC ';
                    state = 0; }
                else if ( cc === 0 ) { out += 'NUL '; }
            } else {
                if ( !st ) { st = true; out += '"'; }
                out += c;
            }
        }

        // Normal Sequence
        else if ( state < 2 ) {
            out += i2w(c) + ' '; }

        if ( state === 0 ) {
            if ( c === t.SB ) { state = 1; }
        } else if ( state === 1 ) {
            if ( c === t.TTYPE || c === t.TSPEED ) { state = 2; }
            else if ( c === t.MSSP ) { state = 3; }
            else if ( c === t.MSDP ) { state = 4; }
            else if ( c === t.NAWS ) { state = 5; }
            else if ( c === t.CHARSET ) { state = 6; }
            else if ( c === t.SENDLOC ) { state = 6; }
            else if ( c === t.GMCP ) { state = 6; }
            else if ( c === t.ZMP ) { state = 7; }
            else { state = 0; }
        }
    }

    return out.substr(0, out.length-1);
}