// Boot script
var _TVDOS = {};
_TVDOS.DRIVES = {}; // Object where key-value pair is <drive-letter> : [serial-port, drive-number]
// actually figure out the drive letter association
// Drive A is always the device we're currently on
_TVDOS.DRIVES["A"] = _BIOS.FIRST_BOOTABLE_PORT;



Object.freeze(_TVDOS);

///////////////////////////////////////////////////////////////////////////////

var filesystem = {};
filesystem._toPorts = function(driveLetter) {
    let port = _TVDOS.DRIVES[driveLetter.toUpperCase()];
    if (port === undefined) {
        throw Error("Drive letter '" + driveLetter.toUpperCase() + "' does not exist");
    }
    return port
};
filesystem._close = function(portNo) {
    com.sendMessage(portNo, "CLOSE");
};
filesystem._flush = function(portNo) {
    com.sendMessage(portNo, "FLUSH");
};
// @return true if operation committed successfully, false otherwise; throws error
//         if unknown mode or invalid drive letter was given
filesystem.open = function(driveLetter, path, operationMode) {
    let port = filesystem._toPorts(driveLetter);

    filesystem._flush(port[0]); filesystem._close(port[0]);

    let mode = operationMode.toUpperCase();
    if (mode != "R" && mode != "W" && mode != "A") {
        throw Error("Unknown file opening mode: " + mode);
    }

    com.sendMessage(port[0], "OPEN"+mode+'"'+path+'",'+port[1]);
    let response = com.getStatusCode();
    return (response == 0);
};
// @return the entire contents of the file in String
filesystem.readAll = function() {
    let port = filesystem._toPorts(driveLetter);
    com.sendMessage(port[0], "READ");
    let response = com.getStatusCode();
    if (response < 0 || response >= 128) {
        let status = com.getDeviceStatus(port[0]);
        throw Error("Reading a file failed with "+status.code+": "+status.message);
    }
    return com.pullMessage(port[0]);
};
Object.freeze(filesystem);