function get_name()
    return "DISK DRIVE CONTROLLER"
end

NUM_TRACKS = 8
NUM_SECTORS = 8

function get_description()
    return {
        "*input* is a non-blocking XBus input connected to a computer.",
        "*output* is an XBus output connected to the same computer.",
        "*motor* is a simple output connected to a stepper motor.",
        "*read* is a simple input connected to the read head.",
        "<PAGE>",
        "The purpose of this device is to read data from a rotating data disk.",
        "The disk is divided into " .. NUM_TRACKS .. " tracks and " .. NUM_SECTORS .. " sectors.",
        "(For a visual representation, refer to the 'Disk sector' article on Wikipedia.)",
        "The outermost track is track zero, then numbering increases inwards.",
        "The read head of the drive can be moved between tracks via *motor*. 50 makes the head stay still, 0 moves it one track outwards, 100 moves it one track inwards. The head will complete the requested movement by the start of the *next* time unit.",
        "The disk is rotating at the fixed speed of one sector per time unit.",
        "<PAGE>",
        "Input consists of disk coordinates <track>,<sector>.",
        "Move the head to the specified track via *motor*, wait until the correct sector gets rotated below the head, then send the value of *read* to *output*",
        "The head starts at track zero. Rotation starts at sector zero."
    }
end

function get_board()
    return [[
        #.##############.#
        ##################
        0################2
        ##################
        1################3
        ##################
        #.##############.#
    ]]
end

function get_data()
    math.random()   -- this is just to force nicer values for test case #1
    local disk_contents = {}
    for i=0,NUM_TRACKS-1 do
        disk_contents[i] = {}
        for j=0,NUM_SECTORS-1 do
            disk_contents[i][j] = math.random(1, 100)
        end
    end

    local current_track = 0
    local next_input_time = math.random(1, 2)
    local target_track = 0
    local target_sector = -1
    local input = {}
    local output = {}
    local motor = {}
    local read_arr = {}
    for time = 1,60 do
        local current_sector = (time-1)%NUM_SECTORS
        read_arr[time] = disk_contents[current_track][current_sector]
        if time == next_input_time then
            target_track = math.random(0, NUM_TRACKS-1)
            target_sector = math.random(0, NUM_SECTORS-1)
            input[time] = {target_track, target_sector}
        end
        if current_track < target_track then
            motor[time] = 100
        elseif current_track > target_track then
            motor[time] = 0
        else
            motor[time] = 50
        end
        if current_track == target_track and current_sector == target_sector then
            output[time] = {read_arr[time]}
            target_sector = -1
            next_input_time = math.max(time + math.random(1, 2), next_input_time+2)
        end
        if motor[time] == 100 then
            current_track = current_track + 1
        elseif motor[time] == 0 then
            current_track = current_track - 1
        end
    end

    create_terminal('input', '0', TYPE_XBUS_NONBLOCKING, DIR_INPUT, input)
    create_terminal('output', '1', TYPE_XBUS, DIR_OUTPUT, output)
    create_terminal('motor', '2', TYPE_SIMPLE, DIR_OUTPUT, motor)
    create_terminal('read', '3', TYPE_SIMPLE, DIR_INPUT, read_arr)
end