startup

term.clear()
term.setCursorPos(1, 1)


function receive()
    rednet.open("left")
    while true do
        local senderId, message = rednet.receive()
        print("Received message from ID: " .. senderId .. ", length: " .. #message)

        local cmd = message:match("%S+")
        message = message:gsub(cmd.." ", "")
        if cmd == "LOGIN" then
            local data = message:match("%S+:%S+")
            local f, t = message:find(":")
            if f ~= nil and t ~= nil then
                local username = data:sub(0, t-1)
                local password = data:sub(t+1)

                if fs.exists("users/" .. username) then
                    local file = fs.open("users/"..username, "r")
                    local pw = file.readLine()
                    if password == pw then
                        rednet.send(senderId, "RIGHT_PASSWORD")
                        print("User "..username.." successfully logged in!")
                    else
                        rednet.send(senderId, "WRONG_PASSWORD")
                        print("User "..username.." failed to log in!")
                    end
                    file.close()
                else
                    rednet.send(senderId, "USER_NOT_EXISTS")
                    print("User "..username.." doesn't exists!")
                end
            else
                rednet.send(senderId, "WRONG_FORMAT")
                print("WRONG_FORMAT")
            end
        elseif cmd == "SEND" then
            local data = message:match("%S+:%S+")
            local f, t = message:find(":")
            if f ~= nil and t ~= nil then
                local username = data:sub(0, t-1)
                local password = data:sub(t+1)
                message = message:gsub(data.." ", "")

                if fs.exists("users/" .. username) then
                    local file = fs.open("users/"..username, "r")
                    local pw = file.readLine()
                    file.close()
                    if password == pw then
                        local to = message:match("%S+")
                        message = message:gsub(to.." ", "")

                        if fs.exists("users/" .. to) then
                            local count = #fs.list("mails/" .. to)
                            if not fs.exists("mails/"..to) then
                                fs.makeDir("mails/"..to)
                            end
                            local file = fs.open("mails/" .. to .. "/"  .. count+1, "w")
                            file.writeLine(username)
                            file.writeLine(message)
                            file.close()

                            rednet.send(senderId, "SUCCESSFUL_SENT")
                            print("E-Mail sent from "..username.." to "..to..", length: "..#message)
                        else
                            rednet.send(senderId, "TARGET_NOT_EXISTS")
                        end
                    else
                        rednet.send(senderId, "FAILED_SENT")
                    end
                else
                    rednet.send(senderId, "FAILED_SENT")
                end
            end
        elseif cmd == "CHECK" then
            local data = message:match("%S+:%S+")
            local f, t = message:find(":")
            if f ~= nil and t ~= nil then
                local username = data:sub(0, t-1)
                local password = data:sub(t+1)

                if fs.exists("users/" .. username) then
                    local file = fs.open("users/"..username, "r")
                    local pw = file.readLine()
                    file.close()
                    if password == pw then
                        for i, file in ipairs(fs.list("mails/"..username)) do

                        end


                        rednet.send(senderId, "lag")
                    end
                end
            end
        else
            print("Unknown command: "..cmd)
        end
    end
end

receive()