CC-SSH Agent

-- ============================================================
--  cct_agent.lua  -  Network agent for CC:T Remote
--
--  Run this on every computer EXCEPT the gateway.
--  The gateway (running cct_remote daemon) will discover
--  this computer via rednet and proxy commands to it.
--
--  Requirements: a modem on any side (wired or wireless)
--  Usage:  cct_agent          (or put in startup file)
-- ============================================================

local REDNET_PROTOCOL = "cct_remote"

-- ── Colour helpers ──────────────────────────────────────────

local function colour(c)
  if not term.isColour() then return end
  term.setTextColour(c)
end
local function reset() colour(colours.white) end
local function printC(c, ...)
  colour(c) ; print(...) ; reset()
end

-- ── Output capture ──────────────────────────────────────────

local function captureOutput(fn)
  local lines   = {}
  local curLine = ""

  local fakeTerm = {}
  for k, v in pairs(term.current()) do fakeTerm[k] = v end

  fakeTerm.write = function(text)
    curLine = curLine .. tostring(text)
  end

  fakeTerm.blit = function(text)
    curLine = curLine .. tostring(text)
  end

  fakeTerm.setCursorPos = function(x, y)
    if curLine ~= "" then
      lines[#lines + 1] = curLine
      curLine = ""
    end
  end

  fakeTerm.scroll = function()
    if curLine ~= "" then
      lines[#lines + 1] = curLine
      curLine = ""
    end
  end

  fakeTerm.clear        = function() end
  fakeTerm.clearLine    = function() end
  fakeTerm.setTextColour       = function() end
  fakeTerm.setTextColor        = function() end
  fakeTerm.setBackgroundColour = function() end
  fakeTerm.setBackgroundColor  = function() end

  local prev = term.redirect(fakeTerm)
  local ok, err = pcall(fn)
  term.redirect(prev)

  if curLine ~= "" then lines[#lines + 1] = curLine end

  return ok, table.concat(lines, "\n"), tostring(err)
end

-- ── Modem open ──────────────────────────────────────────────

local function openModem()
  local sides = { "top","bottom","left","right","front","back" }
  for _, side in ipairs(sides) do
    if peripheral.getType(side) == "modem" then
      rednet.open(side)
      return side
    end
  end
  for _, name in ipairs(peripheral.getNames()) do
    if peripheral.getType(name) == "modem" then
      rednet.open(name)
      return name
    end
  end
  return nil
end

-- ── Run a command, return ok + output ───────────────────────

local function runCommand(code)
  local fn = load(code, "remote", "t", _ENV)
  if fn then
    local ok, out, err = captureOutput(fn)
    return ok, ok and (out ~= "" and out or "OK") or err
  else
    local ok, out, err = captureOutput(function()
      if not shell.run(code) then error("shell.run failed") end
    end)
    return ok, ok and (out ~= "" and out or "OK") or err
  end
end

-- ── Main ────────────────────────────────────────────────────

local modemSide = openModem()
if not modemSide then
  printError("No modem found. Attach a modem and restart.")
  return
end

local myId    = os.getComputerID()
local myLabel = os.getComputerLabel() or ("Agent " .. myId)

printC(colours.yellow, "=== CC:T Agent ===")
printC(colours.lime,   "ID:    " .. myId)
printC(colours.lime,   "Label: " .. myLabel)
printC(colours.lime,   "Modem: " .. modemSide)
printC(colours.yellow, "Waiting for gateway...  (Ctrl+T to stop)")

-- Announce ourselves so gateways already running pick us up
rednet.broadcast({ type = "hello", label = myLabel }, REDNET_PROTOCOL)

while true do
  local senderId, msg, protocol = rednet.receive(REDNET_PROTOCOL)

  if type(msg) ~= "table" then goto continue end

  -- Gateway is pinging to discover agents
  if msg.type == "ping" then
    rednet.send(senderId, { type = "pong", label = myLabel }, REDNET_PROTOCOL)
    printC(colours.cyan, "Ping from gateway " .. senderId)

  -- Gateway is sending a command to run
  elseif msg.type == "run" and msg.code then
    printC(colours.yellow, "CMD from " .. senderId .. ": " .. msg.code)
    local ok, data = runCommand(msg.code)

    rednet.send(senderId, {
      type  = "response",
      msgId = msg.msgId or "",
      ok    = ok,
      data  = data,
    }, REDNET_PROTOCOL)

    printC(ok and colours.lime or colours.red,
      (ok and "[ok] " or "[err] ") .. data)
  end

  ::continue::
end