data = {
    users = {
        ["admin"] = {
            password = "admin"
        }
    }
}

function save_data()
    db = fs.open("auth.db", "w")
    db.write(textutils.serialize(data))
    db.close()
end

function load_data()
    if fs.exists("auth.db") then
        db = fs.open("auth.db", "r")
        db_contents = db.readAll()
        db.close()

        data = textutils.unserialize(db_contents)
    end
end

function generate_token(user)
    local token = hash(user .. os.time() .. math.random())
    data.users[user].token = token

    return token
end

function convert_password(password)
    return hash(password .. "3m&LmNm7")
end

-- Does a complex hash of a string to make it harder to guess
function hash(str)
    local hash = 0
    local len = string.len(str)
    local byte = 0

    for i = 1, len do
        byte = string.byte(str, i)
        hash = bit32.band(hash * 31 + byte, 0xFFFFFFFF)
    end

    return hash
end

function log(str)
    io.write("[" .. os.time() .. "] " .. str .. "\n")
end

load_data()
math.randomseed(os.time())

while true do
    client_id, msg = rednet.receive("auth")
    request = msg

    if request.action == nil then
        rednet.send(client_id, "invalid request", "auth")
    end

    if request.action == "register" then
        if request.username == nil or request.password == nil then
            rednet.send(client_id, "invalid request", "auth")
        end

        if data.users[request.username] ~= nil then
            rednet.send(client_id, "user already exists", "auth")
        end

        data.users[request.username] = {
            password = convert_password(request.password)
        }

        save_data()

        rednet.send(client_id, "ok", "auth")
        log(request.username .. " registered")
    end

    if request.action == "login" then
        if request.username == nil or request.password == nil then
            rednet.send(client_id, "invalid request", "auth")
            
        elseif data.users[request.username] == nil then
            rednet.send(client_id, "user not found", "auth")

            log(request.username .. " failed log in attempt")
        elseif convert_password(request.password) == data.users[request.username].password then
            local token = generate_token(request.username)

            rednet.send(client_id, token, "auth")

            log(request.username .. " logged in")
        else
            rednet.send(client_id, "invalid password", "auth")
        end

    end

    if request.action == "token" then
        if request.token == nil or request.token == "" or request.token == -1 then
            rednet.send(client_id, "invalid request", "auth")
        else

            for user, userdata in pairs(data.users) do
                if userdata.token == request.token then
                    rednet.send(client_id, user, "auth")
                end
            end

            rednet.send(client_id, "invalid token", "auth")
        end
    end

    if request.action == "profile" then
        if request.username == nil then
            rednet.send(client_id, "invalid request", "auth")
        end

        local profile = {}

        if data.users[request.username].profile_data ~= nil then
            profile = data.users[request.username].profile_data
        else
            profile.display_name = request.username
        end

        profile.username = request.username

        rednet.send(client_id, data.users[request.username], "auth")
    end

    if request.action == "update_profile" then
        if request.username == nil or request.token == nil then
            rednet.send(client_id, "invalid request", "auth")
        end

        if data.users[request.username].token == request.token then
            if request.profile_data ~= nil then
                data.users[request.username].profile_data = request.profile_data
            end

            save_data()

            rednet.send(client_id, "ok")
            log(request.username .. " updated their profile", "auth")
        else
            rednet.send(client_id, "invalid token", "auth")
        end
    end
end