ComputerCraft Email Client - ENET

local logged_in = false;
local width, height = term.getSize();
local center = width/2;
local user = {
  Name = "";
};
local server = {
  IP = -1;
}
local goldUser = term.isColor();

--term functions & locally assigning them prevents us from having to search them in term and
--is more efficient
  local twrite = term.write;
  local tcolor = term.setTextColor;
  local isColor = term.isColor;
  local hasModem = false;
  local scp = term.setCursorPos;
  local clear = function() term.clear(); if(user.Name~="")then scp(width-#user.Name,height); tcolor(8); twrite(user.Name); end scp(1,1); end
  local gcp = term.getCursorPos;
  local tick = os.clock;

--graphic interface functions
  function ui_list(items)
    local interaction=true;
    local change = true;
    local selected=1;
    local item;
    while(interaction==true)do
        if(change)then
          clear();
          for i=1,#items do
            item = items[i];
            if(selected == i)then
              item = "< "..item.." >"
            end
            scp(width/2-#item/2,i+2);
            write(item,8);
          end
          change = false;
        end
        local eventData = {os.pullEvent()};
        local event = eventData[1];
        if(event == 'key')then
          local key = eventData[2];
          if(key == 200)then --up key
            if(selected~=1)then
              selected = selected - 1;
              change = true;
            end
          elseif(key == 208)then --down key
            if(selected~=#items)then
              selected = selected + 1;
              change = true;
            end
          elseif(key == 28)then --enter key
            return items[selected]
          end
        elseif(event == 'mouse_click')then
          local y = eventData[4]-2;
          if(y>=1 and y<=#items)then
            if(y==selected)then
              return items[selected];
            else
              selected = y;
              change = true;
            end
          end
        end
    end
  end

--define functions

  function waitForInput()
    local event;
    repeat
      event = os.pullEvent();
    until event == 'mouse_click' or event=='char' or event=='key'
  end

  function write(text, color, ignore)
    if(isColor)then
      tcolor(color or 16);
    end
    twrite(text);
    if(not ignore)then
      scp(1,({gcp()})[2]+1);
    end
  end

  function getModem()
    local sides = {"left","right","front","back","bottom","top"};
    for i=1,#sides do
      hasModem = (peripheral.isPresent(sides[i]) and peripheral.getType(sides[i])=='modem') or false;
      if(hasModem)then
        hasModem = sides[i];
        return hasModem;
      end
    end
  end

  function writeCentered(text, color, ignore)
    text = tostring(text);
    if(isColor)then
      tcolor(color or 16);
    end
    scp(center-#text/2,({gcp()})[2]);
    twrite(text);
    if(not ignore)then
      scp(1,({gcp()})[2]+1);
    end
  end

  function setY(y,inc)
    if(inc)then
      y = ({gcp()})[2]+y;
    end
    scp(1,y);
  end

  function connect()
    getModem();
    if(not hasModem)then
      clear();
      write("ERROR: No Modem is connected!", 16384); --red
      return false;
    end
    rednet.open(hasModem);
    local id;
    clear();
    repeat
      write("Enter the server computer's id!", 8);
      write("ID: ", 8, true); --light blue
      tcolor(16); --gold text
      id=tonumber(io.read());
      if(id==nil)then
        clear();
        write("ERROR: ID must be a number!", 16384); --red
      end
    until id~=nil
  --send a message saying you want to connect
    rednet.send(id, "connect");
    local key, sender, response, distance;
  --wait for the server to respond to you
    local start = tick();
    local timePassed=0;
    local loading = {"0oo", "o0o", "oo0"};
    local tp = -1;
    local track = 0;
    repeat
      sender, response, distance = rednet.receive(.5);
      timePassed = tick()-start;
      if(timePassed-tp > 0.5)then
        tp=timePassed;
        track = track+1;
        clear();
        writeCentered("Loading "..loading[track%3+1],8);
      end
    until sender==id or timePassed >= 10

    if(sender~=id)then
      clear();
      write("ERROR: Failed to get a response!", 16384); --red
      return false;
    else
      if(response:lower() == "handshake")then
        clear();
        rednet.send(id, "connected");
        write("Connected to server: "..id, 8); --light blue
        server.IP = id;
        return true;
      end
    end
  end

while(true)do
  local list = {"Info","Connect"};
  if(server.IP~=-1)then
    list[2] = "Disconnect";
    if(user.Name == "")then
      list[3] = "Create an Account";
      list[4] = "Login";
    else
      list[3] = "Log Out";
      list[4] = "My Account";
    end
  end
  local clicked = ui_list(list);
  if(clicked=='Connect')then
    if(not connect())then
      if(hasModem)then
        rednet.close(hasModem);
      end
    end
    waitForInput();
  elseif(clicked=='Disconnect')then
    rednet.send(server.IP, "disconnect");
    server.IP = -1;
  elseif(clicked=='Create an Account')then
    local username, password;
    clear();
    writeCentered("Account Creation",8);
    write("Username: ",8,true);
    username = io.read();
    write("Password: ",8,true);
    password = io.read();
    local data = "*newaccount".."\28"..username.."\28"..password.."\28";
    rednet.send(server.IP, data);
    local sender,response = rednet.receive(10); clear();
    if(response == 'success')then
      writeCentered("Account Created!", 8);
      user.Name = username;
    else
      writeCentered(response, 16384);
    end
    waitForInput();
  elseif(clicked=='Log Out')then
    user.Name = "";
    rednet.send(server.IP, "logout");
  elseif(clicked=='Login')then
    local username, password;
    clear();
    writeCentered("Account Login",8);
    write("Username: ",8,true);
    username = io.read();
    write("Password: ",8,true);
    password = io.read();
    local data = "*loginaccount".."\28"..username.."\28"..password.."\28";
    rednet.send(server.IP, data);
    local sender, response = rednet.receive(10); clear();
    if(response == 'success')then
      writeCentered("Logged In!", 8);
      user.Name = username;
    else
      writeCentered(response, 16384);
    end
    waitForInput();
  elseif(clicked=='Info')then
    clear();
    writeCentered("Info",8);
    setY(2,true);
    write("Author: ENET",8);
    write("Published: 11/12/12",8);
    write("Usage: Free",8);
    waitForInput();
  end
end