--[[
  remote.lua - Bidirectional remote command execution
  Usage: remote [channel]
  Both computers must run this on the same channel.
]]

local channel = tonumber(arg[1]) or 12345
local modem = peripheral.find("modem")
if not modem then
    print("ERROR: No wireless modem attached.")
    return
end
modem.open(channel)

local myID = os.getComputerID()
local inputBuffer = ""

print("=== Remote Control ===")
print("My ID: " .. myID)
print("Channel: " .. channel)
print("Type a command and press Enter to send it to other computer(s).")
print("Type 'exit' to quit.")
print("-----------------------")

local function printPrompt()
    term.write("[" .. myID .. "]> ", false)
end

-- Execute a command and capture stdout+stderr
local function executeCommand(cmd)
    local outFile = "/tmp/out_" .. myID .. ".txt"
    local errFile = "/tmp/err_" .. myID .. ".txt"
    shell.run(cmd .. " > " .. outFile .. " 2> " .. errFile)
    local output = ""
    if fs.exists(outFile) then
        local f = fs.open(outFile, "r")
        output = f.readAll() or ""
        f.close()
        fs.delete(outFile)
    end
    if fs.exists(errFile) then
        local f = fs.open(errFile, "r")
        local err = f.readAll() or ""
        f.close()
        fs.delete(errFile)
        if err ~= "" then
            if output ~= "" then output = output .. "\n" end
            output = output .. err
        end
    end
    if output == "" then output = "(no output)" end
    return output
end

-- Main event loop
while true do
    printPrompt()
    term.write(inputBuffer)
    term.setCursorBlink(true)

    local event, p1, p2, p3 = os.pullEvent()

    if event == "char" then
        local char = p1
        inputBuffer = inputBuffer .. char
        -- redraw the line
        local x, y = term.getCursorPos()
        term.setCursorPos(1, y)
        term.clearLine()
        printPrompt()
        term.write(inputBuffer)

    elseif event == "key" then
        if p2 == false then  -- key release
            local key = p1
            if key == keys.enter then
                local cmd = inputBuffer
                inputBuffer = ""
                if cmd == "exit" then
                    print("\nExiting.")
                    break
                end
                print("\nSending command: " .. cmd)
                modem.transmit(channel, channel, {
                    type = "exec",
                    cmd = cmd,
                    sender = myID
                })
                -- prompt will be redrawn in next loop iteration
            elseif key == keys.backspace then
                if #inputBuffer > 0 then
                    inputBuffer = inputBuffer:sub(1, -2)
                    local x, y = term.getCursorPos()
                    term.setCursorPos(1, y)
                    term.clearLine()
                    printPrompt()
                    term.write(inputBuffer)
                end
            -- ignore arrow keys etc. for simplicity
            end
        end

    elseif event == "modem_message" then
        local senderID = p1
        local replyChannel = p2
        local msg = p3

        if msg.target and msg.target == myID then
            -- This is a reply to a command I sent
            print("\n[Reply from " .. senderID .. "]")
            print(msg.data)

        elseif msg.type == "exec" and msg.sender ~= myID then
            -- Received a command to execute
            print("\n[Executing command from " .. msg.sender .. "]")
            print("Command: " .. msg.cmd)
            local output = executeCommand(msg.cmd)
            -- Send the result back to the sender
            modem.transmit(channel, channel, {
                type = "result",
                data = output,
                target = msg.sender
            })
            print("Reply sent.")
        end

    elseif event == "terminate" then
        print("\nTerminated.")
        break
    end
end