-- Master Startup Script for a Distributed Lua Shell Cluster
-- (Clients only execute the commands. The master waits for the first valid result.)

-- Function to open all attached modems
local function openAllModems()
  local sides = {"left", "right", "top", "bottom", "front", "back"}
  local opened = {}
  for _, side in ipairs(sides) do
    if peripheral.getType(side) == "modem" then
      rednet.open(side)
      table.insert(opened, side)
      print("Opened rednet on modem at side: " .. side)
    end
  end
  if #opened == 0 then
    error("No modems found! Please attach at least one modem.")
  end
end

openAllModems()

print("Supercomputer Lua Shell (Clients Only) - Only valid Lua commands are supported.")
print("Master Computer ID is: " .. os.getComputerID())
print("Listening on protocol 'supercomp' for client registrations...")

local clients = {}  -- table to hold registered client IDs

-- Registration listener runs continuously to register clients
local function registrationListener()
  while true do
    local senderID, message, protocol = rednet.receive("supercomp")
    if protocol == "supercomp" then
      if message == "register" then
        clients[senderID] = true
        rednet.send(senderID, "registered", "supercomp")
        print("Client " .. senderID .. " registered. Total clients: " .. tostring((function(t) local c=0; for _ in pairs(t) do c=c+1 end; return c end)(clients)))
      end
    end
  end
end

-- Main command loop (master does not execute commands locally)
local function commandInputLoop()
  while true do
    print("\nEnter Lua command (clients will execute this):")
    local cmd = read()
    if cmd and cmd ~= "" then
      -- Send the command to all registered clients.
      for cid, _ in pairs(clients) do
        rednet.send(cid, cmd, "supercomp")
      end

      -- Wait for the first valid response from any client.
      local startTime = os.clock()
      local responder, result, proto = nil, nil, nil
      repeat
        local remaining = 10 - (os.clock() - startTime)
        if remaining <= 0 then break end
        responder, result, proto = rednet.receive("supercomp", remaining)
        -- Ignore registration and cancel messages.
        if result == "registered" or result == "cancel" then
          responder, result, proto = nil, nil, nil
        end
      until responder ~= nil

      if responder and result then
        print("Result: " .. tostring(result))
        -- Send cancel signal to all other clients.
        for cid, _ in pairs(clients) do
          if cid ~= responder then
            rednet.send(cid, "cancel", "supercomp")
          end
        end
      else
        print("No response received within the timeout period.")
      end
    end
  end
end

-- Run both tasks concurrently.
parallel.waitForAll(registrationListener, commandInputLoop)