Meigs2 Posts - Answer Overflow

Meigs2

•Created by Meigs2 on 3/19/2023 in #help

❔ Secure, Efficient Data Access in Hybrid Desktop/Web App

Hey yall! I'm currently working on a hybrid web/desktop application. Is there any sort of .net mechanism/design pattern/authorization schema where an action to request data can be "approved" by the application server and allow a client to directly receive something like a result from a database query? Idea being, I'd like to improve query times on desktop clients by skipping the server-side steps of loading the query result into memory and then re-serializing over the network again. Security is a pretty big concern, and given code is running on a computer accessible by staff who could have potential malicious intentions or who leave their pc exposed to external access, having application code or even having direct DB access is a no-go. Some more details: The business domain requires a high degree of secure and auditing, so all the business logic and execution will be running through the application server, which will handle authentication, running queries, etc. Because this system might have relatively high data-throughput (reporting and audit logging is critically important), I'm slightly worried that if the desktop app just queried data entirely through the server, having to serialize and de-serialize data constantly over the local network might introduce significant slowdowns. I know it's premature at this point, but I'd like to have this in the back of my head while designing so I can accommodate when necessary. My initial thought/solution would be to have those specific queries execute using a sql data reader and "stream" the result of the query to the client, skipping serialization using something like SingnalR or a similar network stream. If you've ran into a similar situation before, or there exisits a pattern/feature in ASP.NET already for this scenario, please let me know. Thanks!

2 replies

CC#

•Created by Meigs2 on 9/18/2022 in #help

Composing a validation function using functional concepts

Hey yall, I've been trying to get into using and applying functional concepts in some of my projects and I'm having some conceptual issues with composing monads. Problem: I'm creating a structure to represent a "Version" for a project of mine for structured versioning of databases. A Version is comprised of a Major, Minor, and Patch version numbers, represented by integers. All Versions require a Major number, but do not require a Minor or Patch version. If a Patch version is present, a minor version is required. i.e.

Valid: (0, 0, 0)
Valid: (1, 45, 0)
Valid: (5, 3)

INVALID: (1, {}, 3)
INVALID: ()
INVALID: ({}, 3)

Valid: (0, 0, 0)
Valid: (1, 45, 0)
Valid: (5, 3)

INVALID: (1, {}, 3)
INVALID: ()
INVALID: ({}, 3)

What I need help with I could write the validation function very easily in regular old C#, however I think this problem can better be solved in a more "functional" manner, but I believe I'm missing a fundamental concept in functional programming. When implementing Validate, I don't quite understand how I can functionally compose a chain of validation results when the rules for the validation logic comprise of smaller functions whos validation inputs and outputs use more specific values than the containing structure. i.e.

Validate:
Version version -> Validation<Version>

Rule 1:
int Major -> Validation<int>

Rule 2:
int Minor -> Validation<int>
... etc

Validate:
Version version -> Validation<Version>

Rule 1:
int Major -> Validation<int>

Rule 2:
int Minor -> Validation<int>
... etc

I dont understand how to compose Validate when the individual rules use ints. I can call Rule1(version.Major), which returns a Validation<int>, but that means when calling Bind on the result, the value I get into the next function is an int, not the original Version that I need to continue with. The library I'm using is half home-rolled, using LaYumba.Functional as a base. I'm not looking for an exact solution here, just the right functional concept for "passing down" the original value in a series of Either-like monads. Details: My record is defined as such:

public record Version
{
    public int Major { get; init; }
    public Option<int> Minor { get; init; }
    public Option<int> Patch { get; init; }
    
    public override string ToString() => $"{Major}{"." + Minor}.{"." + Patch}";

    private Version(int major, Option<int> minor, Option<int> patch)
    {
        Major = major;
        Minor = minor;
        Patch = patch;
    }
}

public record Version
{
    public int Major { get; init; }
    public Option<int> Minor { get; init; }
    public Option<int> Patch { get; init; }
    
    public override string ToString() => $"{Major}{"." + Minor}.{"." + Patch}";

    private Version(int major, Option<int> minor, Option<int> patch)
    {
        Major = major;
        Minor = minor;
        Patch = patch;
    }
}

Where Option is a monad with the usual Bind, Map, etc defined. I have a validation function, and some other validation rules defined as follows:

    public static Validation<Version> Validate(Version version)
    {
        // TODO: implement
    }
    
    private static Validation<int> IsValidMajorVersion(int major) => 
        major < 0 ? Invalid("Major version must be greater than or equal to 0") : Valid(major);
    
    private static Validation<int> IsValidMinorVersion(int minor) =>
        minor < 0 ? Invalid("Minor version must be greater than or equal to 0") : Valid(minor);
    
    private static Validation<int> IsValidPatchVersion(int patch) =>
        patch < 0 ? Invalid("Patch version must be greater than or equal to 0") : Valid(patch);

    public static Validation<Version> Validate(Version version)
    {
        // TODO: implement
    }
    
    private static Validation<int> IsValidMajorVersion(int major) => 
        major < 0 ? Invalid("Major version must be greater than or equal to 0") : Valid(major);
    
    private static Validation<int> IsValidMinorVersion(int minor) =>
        minor < 0 ? Invalid("Minor version must be greater than or equal to 0") : Valid(minor);
    
    private static Validation<int> IsValidPatchVersion(int patch) =>
        patch < 0 ? Invalid("Patch version must be greater than or equal to 0") : Valid(patch);

Where Validation<T> is a success/fail style Either monad where Left is an enumerable of errors, and Right is the value of the successful validation. I could make all the "lower" validation rules take in a version and my issues would be solved but... that seems not quite correct, and I feel like there's a functional solution to compose them properly. I have to somehow lift version into a monad and do a Match on success or fail? I can lift the version into an Option and match on Some/None, but I still have to pass the version around? I think I'm missing something critical conceptually. Thanks!

7 replies

Gaming

Programming