Gremlin/Gremlin_BlazorServer/Services/GenericController.cs

using System.Diagnostics;
using Gremlin_BlazorServer.Data.DBClasses;
using Gremlin_BlazorServer.Data.EntityClasses;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.ChangeTracking;
using Microsoft.EntityFrameworkCore.Metadata;

namespace Gremlin_BlazorServer.Services;

public class GenericController {
    private static readonly GremlinDb gremlinDb = new();

    public static IList<TResult>? GetAll<TResult>(string include) where TResult : class, IMetadata {
        try {
            return gremlinDb.Set<TResult>().Include(include).ToList();
        }
        catch (Exception exception) {
            Console.WriteLine(exception.InnerException);
            return null;
        }
    }

    public static IList<TResult>? GetAll<TResult>(Predicate<TResult> search) where TResult : class, IMetadata {
        ArgumentNullException.ThrowIfNull(search);
        try {
            return gremlinDb.Set<TResult>().AsEnumerable().Where(t => search(t)).ToList();
        }
        catch (Exception exception) {
            Console.WriteLine(exception.InnerException);
            return null;
        }
    }

    public static async Task<IList<TResult>?> GetAllAsync<TResult>() where TResult : class, IMetadata {
        try {
            return await gremlinDb.Set<TResult>().ToListAsync();
        }
        catch (Exception exception) {
            Console.WriteLine(exception.InnerException);
            return null;
        }
    }

    public async Task<IList<TResult>?> GetAllAsync<TResult>(string include) where TResult : class, IMetadata {
        try {
            return await gremlinDb.Set<TResult>().Include(include).ToListAsync();
        }
        catch (Exception exception) {
            Console.WriteLine(exception.InnerException);
            return null;
        }
    }

    public async Task<IList<TResult>?> GetAllAsync<TResult>(string include1, string include2) where TResult : class, IMetadata {
        try {
            return await gremlinDb.Set<TResult>().Include(include1).Include(include2).ToListAsync();
        }
        catch (Exception exception) {
            Console.WriteLine(exception.InnerException);
            return null;
        }
    }

    public static async Task<IList<TResult>?> GetAllAsync<TResult>(Predicate<TResult> search) where TResult : class, IMetadata {
        ArgumentNullException.ThrowIfNull(search);
        try {
            return await Task.Run(() => gremlinDb.Set<TResult>().AsEnumerable().Where(t => search(t)).ToList());
        }
        catch (Exception exception) {
            Console.WriteLine(exception.InnerException);
            return null;
        }
    }

    public async Task<IList<TResult>?> GetAllAsync<TResult>(Predicate<TResult> search, string include) where TResult : class, IMetadata {
        ArgumentNullException.ThrowIfNull(search);
        try {
            return await Task.Run(() => gremlinDb.Set<TResult>().Include(include).AsEnumerable().Where(t => search(t)).ToList());
        }
        catch (Exception exception) {
            Console.WriteLine(exception.InnerException);
            return null;
        }
    }

    public static TResult? Get<TResult>(Predicate<TResult> search) where TResult : class, IMetadata, new() {
        try {
            return gremlinDb.Set<TResult>().AsEnumerable().FirstOrDefault(t => search(t));
        }
        catch (Exception e) {
            Console.WriteLine(e.InnerException);
            return null;
        }
    }

    public static async Task<TResult> Get<TResult>(Predicate<TResult> search, string include1) where TResult : class, IMetadata, new() {
        ArgumentNullException.ThrowIfNull(search);
        try {
            return await Task.Run(() => gremlinDb.Set<TResult>().Include(include1).AsEnumerable().First(t => search(t)));
        }
        catch (Exception exception) {
            Console.WriteLine(exception.InnerException);
            return new();
        }
    }

    public static async Task<TResult> Get<TResult>(Predicate<TResult> search, string include1, string include2) where TResult : class, IMetadata, new() {
        ArgumentNullException.ThrowIfNull(search);
        try {
            return await Task.Run(() => gremlinDb.Set<TResult>().Include(include1).Include(include2).AsEnumerable().First(t => search(t)));
        }
        catch (Exception exception) {
            Console.WriteLine(exception.InnerException);
            return new();
        }
    }

    public static async Task<TResult> GetLastAsync<TResult>() where TResult : class, IMetadata, new() {
        try {
            return await Task.Run(() => gremlinDb.Set<TResult>().AsEnumerable().Last());
        }
        catch (Exception exception) {
            Console.WriteLine(exception.InnerException);
            return new();
        }
    }

    public static int Insert<T>(T entity) where T : class, IMetadata {
        try {
            gremlinDb.Set<T>().Add(entity);
            return gremlinDb.SaveChanges();
        }
        catch (DbUpdateException ex) {
            Console.WriteLine($"{ex.InnerException}");
            HandleConcurrencyExceptions(ex);
            return -1;
        }
        catch (Exception exception) {
            Console.WriteLine(exception.InnerException);
            return 0;
        }
    }

    public static int Insert<T>(IEnumerable<T> entities) where T : class, IMetadata {
        // gremlinDb.Set<T>().ToList(); //Get newest versions fresh from db
        try {
            gremlinDb.Set<T>().AddRange(entities);
            return gremlinDb.SaveChanges();
        }
        catch (DbUpdateException ex) {
            HandleConcurrencyExceptions(ex);
            return -1;
        }
        catch (Exception exception) {
            Console.WriteLine(exception.InnerException);
            return 0;
        }
    }

    public static async Task<bool> IsExistingAsync<T>(Predicate<T> search) where T : class, IMetadata {
        try {
            return await Task.Run(() => gremlinDb.Set<T>().AsEnumerable().Any(t => search(t)));
        }
        catch (Exception exception) {
            Console.WriteLine(exception.InnerException);
            return false;
        }
    }

    public static int Update<T>(T entity) where T : class, IMetadata {
        try {
            gremlinDb.Set<T>().Update(entity);
            return gremlinDb.SaveChanges(false);
        }
        catch (DbUpdateException ex) {
            HandleConcurrencyExceptions(ex);
            return -1;
        }
        catch (Exception exception) {
            Console.WriteLine(exception.InnerException);
            return 0;
        }
    }

    public static int Update<T>(IEnumerable<T> entities) where T : class, IMetadata {
        try {
            gremlinDb.Set<T>().UpdateRange(entities);
            return gremlinDb.SaveChanges();
        }
        catch (DbUpdateException ex) {
            HandleConcurrencyExceptions(ex);
            return -1;
        }
        catch (Exception exception) {
            Console.WriteLine(exception.InnerException);
            return 0;
        }
    }

    public static async Task<int> RemoveAsync<T>(T entity) where T : class, IMetadata {
        try {
            await Task.Run(() => gremlinDb.Set<T>().Remove(entity));
            return await gremlinDb.SaveChangesAsync();
        }
        catch (Exception exception) {
            Console.WriteLine(exception.InnerException);
            return 0;
        }
    }

    private static void HandleConcurrencyExceptions(DbUpdateException ex) {
        Console.WriteLine($"!!! HandleConcurrencyException: {ex.Message}");
        foreach (EntityEntry entry in ex.Entries)
            switch (entry.Entity) {
                case Quote or CustomDescription or Account or Contact or Product: {
                    PropertyValues proposedValues = entry.CurrentValues;
                    PropertyValues? databaseValues = entry.GetDatabaseValues();

                    foreach (IProperty property in proposedValues.Properties) {
                        object? proposedValue = proposedValues[property];
                        object? databaseValue = databaseValues[property];
                        // TODO: decide which value should be written to database
                        // proposedValues[property] = <>;
                    }

                    // Refresh original values to bypass next concurrency check
                    entry.OriginalValues.SetValues(proposedValues);
                    break;
                }
                default:
                    throw new NotSupportedException("Don't know how to handle concurrency conflicts for " + entry.Metadata.Name);
            }
    }


    public static async Task<int> RemoveDublicatesAsync<T>() where T : class, IMetadata {
        try {
            List<T> entities = gremlinDb.Set<T>().AsEnumerable().GroupBy(e => new { e.HashCode}).SelectMany(grp => grp.Skip(1)).ToList();
            gremlinDb.Set<T>().RemoveRange(entities);    
            return await gremlinDb.SaveChangesAsync();    
        }
        catch (Exception exception) {
            Console.WriteLine(exception.InnerException);
            return 0;
        }
    }
}