--[[
  Wireless Keyboard - Receiver
  Usage: wrecv <channel>
  Default channel: 12345
]]

local args = {...}
local channel = tonumber(args[1]) or 12345

local modem = peripheral.find("modem") or peripheral.find("wireless_modem")
if not modem then
    print("ERROR: Wireless modem not found. Please attach one.")
    return
end

modem.open(channel)

term.clear()
term.setCursorPos(1, 1)
print("=== Wireless Keyboard - Receiver ===")
print("Channel: " .. channel)
print("Status: Listening")
print("-----------------------------------")
print("Output:")
print("-----------------------------------")
print("[Ctrl+T to quit]")
print("")
print("> ", false)

local outputLineY = 8 -- line where "Output:" is, actual output starts at line 9
local cursorX = 3     -- after "> "
local cursorY = 8     -- but we write "> " at line 8? Actually after printing "> ", cursor moves.
-- Let's just manage cursor position manually.

-- We will simply use term.write() and let cursor move naturally, but we need to handle backspace.
-- To simplify, we can keep track of current row and column.
-- But simpler: just write to screen and let cursor be where it is.
-- However, backspace requires special handling.

-- We'll use a buffer to store all output text, but that could get large.
-- Alternative: just write characters and handle backspace by moving cursor back.

-- For this simple version, we'll just write directly and handle backspace by moving cursor.
-- We'll keep it simple: when backspace arrives, move cursor back one char and overwrite with space.

-- We'll also keep an output string for reference (optional).

local outputBuffer = ""

-- Function to print received char
local function printChar(char)
    term.write(char)
    outputBuffer = outputBuffer .. char
end

-- Function to handle backspace
local function handleBackspace()
    local x, y = term.getCursorPos()
    if x > 3 and y == outputLineY + 1 then -- we are on the first output line after "> "
        -- move back, write space, move back
        term.setCursorPos(x - 1, y)
        term.write(" ")
        term.setCursorPos(x - 1, y)
        outputBuffer = outputBuffer:sub(1, -2)
    elseif y > outputLineY + 1 then
        -- go to end of previous line (simplified: assume 50 chars per line)
        term.setCursorPos(50, y - 1)
        -- not handling fully, just move to previous line end
        outputBuffer = outputBuffer:sub(1, -2)
    end
end

-- Function to handle enter
local function handleEnter()
    term.write("\n> ", false)
    outputBuffer = outputBuffer .. "\n"
end

-- Start printing at the "> " position
term.setCursorPos(3, outputLineY + 1) -- assuming outputLineY is the line with "Output:", next line is output
-- Actually we already printed "> " at line 8? Let's recalc.
-- After printing the header, we printed blank line then "> " at line 8? Let's just set cursor manually after header.

-- Simpler: At start, clear, print header, then print "> " and set cursor to after it.
term.clear()
term.setCursorPos(1,1)
print("=== Wireless Keyboard - Receiver ===")
print("Channel: " .. channel)
print("Status: Listening")
print("-----------------------------------")
print("Output:")
print("-----------------------------------")
print("[Ctrl+T to quit]")
print("") -- blank line
term.write("> ", false) -- write prompt, cursor stays after it
-- Now cursor is at column 3, row 9 (if we count rows). We'll store that.
local baseRow = 9
local baseCol = 3
-- We'll use term.getCursorPos() to get current position.

while true do
    local event, p1, p2, p3 = os.pullEvent()
    
    if event == "modem_message" then
        local senderId = p1
        local replyChannel = p2
        local message = p3
        
        if message.type == "char" then
            local char = message.data
            term.write(char)
            
        elseif message.type == "control" then
            local control = message.data
            if control == "backspace" then
                local x, y = term.getCursorPos()
                if x > baseCol and y == baseRow then
                    term.setCursorPos(x - 1, y)
                    term.write(" ")
                    term.setCursorPos(x - 1, y)
                elseif y > baseRow then
                    -- go to end of previous line (assume line width 50)
                    term.setCursorPos(50, y - 1)
                end
            elseif control == "enter" then
                term.write("\n> ", false)
                -- update baseRow? Actually cursor moves to new line, but we can keep baseRow fixed for backspace handling.
                -- We'll just set baseRow to current row after writing new prompt.
                local x, y = term.getCursorPos()
                baseRow = y
                baseCol = x
            elseif control == "delete" then
                local x, y = term.getCursorPos()
                if x < 50 and y == baseRow then
                    term.write(" ")
                    term.setCursorPos(x, y)
                end
            end
            
        elseif message.type == "line" then
            local line = message.data
            term.write(line)
            -- optionally execute command: shell.run(line)
        end
        
    elseif event == "terminate" then
        print("\n\nReceiver stopped.")
        break
    end
end