Email client (for dexter9)

local configFile = ".emailClientConfig"
local config = {
    modem = "top",
    server = 0
}

local function waitForSpace()
    local key = false
    while not key do
        local event, _key = os.pullEvent("key")
        key = (_key == 57)
    end
end

local function saveConfig()
    local handle = fs.open(configFile, "w")
    handle.write(textutils.serialize(config))
    handle.close()
end

local function loadConfig()
    local handle = fs.open(configFile, "r")
    if not handle then
        saveConfig() -- saves default config
        handle = fs.open(configFile, "r")
    end
    config = textutils.unserialize(handle.readAll())
    handle.close()
end

local function isValidSide(_side)
    local rsSides = rs.getSides()
    local valid = false
    for key, value in pairs(rsSides) do valid = (value == _side) or valid end
    return valid
end

local function configureModem()
    term.clear()
    term.setCursorPos(1, 1)
    print("Error: No modem on side '" .. config.modem .. "'")
    local side = false
    while not side do
        print("Enter modem side:")
        local _side = read()
        if isValidSide(_side) then
            if peripheral.getType(_side) == "modem" then
                print("Configuration updated")
                side = _side
                print("Press Space to continue...")
                waitForSpace()
            else
                print("There is no modem on side '" .. _side .. "'")
            end
        else
            print("Invalid side")
        end
    end
    config.modem = side
    saveConfig()
end

local function configureServer()
    term.clear()
    term.setCursorPos(1, 1)
    print("Current server ID: " .. config.server)
    local server = false
    while not server do
        print("Enter server ID:")
        local _server = read()
        if tostring(tonumber(_server)) == _server then
            print("Configuration updated")
            server = _server
            print("Press Space to continue...")
            waitForSpace()
        else
            print("'" .. _server .. "' is not a valid ID")
        end
    end
    config.server = tonumber(server)
    saveConfig()
end

loadConfig()
local termw, termh = term.getSize()
local modemAlreadyOpened
if isValidSide(config.modem) then
    if peripheral.getType(config.modem) == "modem" then
        modemAlreadyOpened = rednet.isOpen(config.modem)
        rednet.open(config.modem)
    else
        configureModem()
        modemAlreadyOpened = rednet.isOpen(config.modem)
        rednet.open(config.modem)
    end
else
    configureModem()
    modemAlreadyOpened = rednet.isOpen(config.modem)
    rednet.open(config.modem)
end

local function receive()
    local email = false
    local from, message
    while not email do
        event, sender, rmessage = os.pullEvent("rednet_message")
        if sender == config.server then
            local fullMessage = textutils.unserialize(rmessage)
            from = fullMessage.from
            message = fullMessage.message
            email = true
        end
    end
    return from, message
end

local running = true
while running do
    term.clear()
    term.setCursorPos(1, 1)
    print("Type 'e' to send an email")
    print("Type 'r' to receive an email")
    print("Type 's' to select server")
    print("Type 'c' to create an account")
    print("Type 'x' to exit")
    local userInput = read()
    if string.find(string.lower(userInput), "r") then
        print("Waiting for incoming email...")
        param1, param2 = receive()
        term.clear()
        term.setCursorPos(1, 1)
        print("    You have just received an email!")
        print("       From: " .. param1)
        print("    Message: " .. param2)
        term.setCursorPos(1, termh)
        term.write("Press Space to go back")
        waitForSpace()
    elseif string.find(string.lower(userInput), "e") then
        term.clear()
        term.setCursorPos(1, 1)
        local fullMessage = {}
        write("To which user would you like this message to be forwarded to?\n> ")
        fullMessage.user = read()
        write("And what is the message you want to forward?\n> ")
        fullMessage.message = read()
        fullMessage.ecommand = "send"
        rednet.send(config.server, textutils.serialize(fullMessage))
        print("Waiting for response...")
        local response = false
        while not response do
            local sender, message = rednet.receive(5)
            if not sender then
                response = true
                print("Failure! (Server didn't respond)")
                print("Press Space to go back")
                waitForSpace()
            elseif sender == config.server then
                local status = textutils.unserialize(message).status
                if status == "ok" then
                    print("Sent!")
                    print("Press Space to go back")
                    waitForSpace()
                else
                    print("Failure! (Status: '" .. status .. "')")
                end
            end
        end
    elseif string.find(string.lower(userInput), "c") then
        term.clear()
        term.setCursorPos(1, 1)
        local fullMessage = {}
        write("Type in your username:\n> ")
        fullMessage.username = read()
        fullMessage.ecommand = "create"
        rednet.send(config.server, textutils.serialize(fullMessage))
        print("Waiting for response...")
        local response = false
        while not response do
            local sender, message = rednet.receive(5)
            if not sender then
                response = true
                print("Failure! (Server didn't respond)")
                print("Press Space to go back")
                waitForSpace()
            elseif sender == config.server then
                local status = textutils.unserialize(message).status
                if status == "ok" then
                    print("Account created successfully!")
                    print("Press Space to go back")
                    waitForSpace()
                else
                    print("Failure! (Status: '" .. status .. "')")
                end
            end
        end
    elseif string.find(string.lower(userInput), "s") then
        configureServer()
    elseif string.find(string.lower(userInput), "x") then
        running = false
    end
end

if not modemAlreadyOpened then rednet.close(config.modem) end
term.clear()
term.setCursorPos(1, 1)