local args={...}

for k,v in pairs(rs.getSides()) do
  if peripheral.getType(v) == "modem" then
    rednetSide = v
    break
  end
end

if not rednetSide then print("Rednet is needed!") return end

rednet.open(rednetSide)

local clients = {}

function getDir(file)
  return string.gsub(file,fs.getName(file).."%/","")
end

function fix(file)
  if file:sub(1,1) == "/" then
    file = file:sub(2)
  end
  return file
end

function getPerms(file)
  if perms[fix(getDir(file))] then
    if perms[fix(file)] then
      return perms[fix(file)]
    else
      return perms[fix(getDir(file))]
    end
  else
    return {write="all",read="all"}
  end
end

function hasRead(file, user)
  local perms = getPerms(file).read
  if perms == "anon" then
    return true
  elseif perms == "logged_in" then
    return user~=nil
  elseif type(perms) == "table" then
    for k,v in pairs(perms) do
      if user == v then return true end
    end
    return false
  end
end

function hasWrite(file, user)
  local perms = getPerms(file).write
  if perms == "all" then
    return true
  elseif perms == "logged_in" then
    return user~=nil
  elseif type(perms) == "table" then
    for k,v in pairs(perms) do
      if user == v then return true end
    end
    return false
  end
end

function put(id,data)
  local filename ,contents = string.gmatch(data,"^(.-):(.+)$")()

  local user
  if clients[id] then
    user=clients[id].user
  end
  if not hasWrite(filename,user) then
    if not user then
	  user = "an anonymous user"
	end
    print("User " .. user .. " tried to write forbidden file " ..filename)
    return false
  else
    local f = fs.open(filename,"w")
    f.write(contents)
    f.close()
    return true
  end
end

function get(id,data)
  local filename = data

  local user
  if clients[id] then
    user=clients[id].user
  end

  if not hasRead(filename,user) then
    if not user then
	  user = "an anonymous user"
	end
    print("User " .. user .. " tried to read forbidden file ".. filename)
  else
    local f = fs.open(filename,"r")
    rednet.send(id,"DATA " .. f.readAll())
    f.close()
  end
end

function auth(id,data)
  local u , pass = string.gmatch(data,"^(.-):(.+)$")()

  if pass == users[u] then
    print(u .. " connected with id ".. id)
    clients[id] = {user=u}
    return true
  else
    print("Attempt to log into " .. u .. " failed!")
    return false
  end
end

function host()
  while true do
    local clientID,msg = rednet.receive()
    print(clientID," ",msg)
    if msg:sub(1,7) == "CONNECT" then
      if auth(clientID,msg:sub(9)) then
        rednet.send(clientID,"ACCEPT")
      else
        rednet.send(clientID,"DENY")
      end
    elseif msg:sub(1,3) == "GET" then
      get(clientID,msg:sub(5))
    elseif msg:sub(1,3) == "PUT" then
      put(clientID,msg:sub(5))
    elseif msg:sub(1,4) == "QUIT" then
      clients[clientID] = nil
    end
  end
end

function client()
  while true do
    local serverID,msg = rednet.receive()

    if msg == "ACCEPT" then
      print("Connection accepted.")
    elseif msg == "DENY" then
      print("Permission denied.")
    elseif msg:sub(1,4) == "DATA" then
      print(msg:sub(5))
    end
  end
end

function readFile(name)
  local f = fs.open(name,"r")
  local r = f.readAll()
  f.close()
  return r
end

function toCmd(line)
  if string.lower(line:sub(1,3)) == "get" then
    return "GET " .. line:sub(5)
  elseif string.lower(line:sub(1,3)) == "put" then
    return "PUT " .. line:sub(5) .. readFile(line:sub(5))
  end
end

function input()
  while true do
    local line = io.read()
    rednet.send(server,toCmd(line))
  end
end


if #args >= 1 then

  if args[1] == "host" then
    local f= fs.open("users","r")
    users = textutils.unserialize(f.readAll())
    f.close()

    f = fs.open("perms","r")
    perms = textutils.unserialize(f.readAll())
    f.close()
    host()
  else
    local id = tonumber(args[1])

    io.write("Username: ")
    local user = read()
    io.write("Password: ")
    local pass = read("*")
    rednet.send(id,"CONNECT "..user..":"..pass)
    parallel.waitForAny(client,input)
  end
else
  print("Usage: ftp host|<id>")
end

rednet.close(rednetSide)