sa/Stars Assistant/Services/PlanetManager.cs

using System;
using System.ComponentModel;
using System.Reactive.Linq;
using DynamicData;
using DynamicData.Binding;
using Splat;
using StarsAssistant.Model;
using StarsAssistant.ViewModels;

namespace StarsAssistant.Services;

public class PlanetManager
{
    protected Services.Game Game = Locator.Current.GetService<Services.Game>()!;

    /// <summary>
    /// SourceCache for DynamicData views
    /// </summary> 
    private SourceCache<Planet, string> _planets = new(p => p.Name);

    /// <summary>
    /// Observable changeset showing all player planets converted to view models.
    /// </summary>
    public IObservable<IChangeSet<PlayerPlanetViewModel, string>> PlayerPlanetsSource
        =>  _planets
                .Connect()
                .Filter(planet => planet.OwnerId == Game.Player.Name)
                .Transform(planet => new PlayerPlanetViewModel(planet));

    public PlanetManager() {}

    /// <summary>
    /// Load the planet records from the database and push them into our source cache.
    /// </summary>
    public void InitFromDatabase() 
    {
        using var db = Locator.Current.GetService<StarsDatabase>()!;
        var allPlanets = db.Planet.ToList();
        var cacheKeys = _planets.Keys.ToList();
        var planetNames = from p in allPlanets select p.Name;
        var planetsToDelete = cacheKeys.Except(planetNames);
        _planets.Edit(innerCache => 
            {
                foreach (var name in planetsToDelete)
                    innerCache.RemoveKey(name);
                innerCache.AddOrUpdate(allPlanets);
            }
        );
    }
}