Connected.Framework/Connected.Entities/EntitiesExtensions.cs

using System.Collections.Immutable;
using System.Linq.Expressions;
using System.Reflection;
using Connected.Data;
using Connected.Entities.Annotations;
using Connected.Entities.Query;
using Connected.Interop;
using Connected.Notifications;
using Connected.ServiceModel;

namespace Connected.Entities;

public static class EntitiesExtensions
{
	/// <summary>
	/// Converts the <see cref="IDto"/> object into entity and overwrites the provided properties.
	/// </summary>
	/// <remarks>
	/// All provided arguments are used when overwriting properties in the order they  are specified. This means
	/// the value from the last defined property is used when setting the entity's value.
	/// </remarks>
	/// <typeparam name="TEntity">The type of the entity to create.</typeparam>
	/// <param name="args">The arguments containing base property set.</param>
	/// <param name="state">The state modifier to which entity is set.</param>
	/// <param name="sources">An array of additional modifier objects providing modified values.</param>
	/// <returns>A new instance of the entity with modified values.</returns>
	public static TEntity AsEntity<TEntity>(this IDto args, State state, params object[] sources)
		where TEntity : IEntity
	{
		if (typeof(TEntity).CreateInstance<TEntity>() is not TEntity instance)
			throw new NullReferenceException(typeof(TEntity).Name);

		return Merge(instance, args, state, sources);
	}

	public static TArgs AsArguments<TArgs>(this IEntity entity) where TArgs : IDto
	{
		var instance = typeof(TArgs).CreateInstance<TArgs>();

		return Serializer.Merge(instance, entity);
	}

	public static TArgs AsArguments<TArgs, TPrimaryKey>(this IPrimaryKey<TPrimaryKey> entity)
		where TArgs : IDto
		where TPrimaryKey : notnull
	{
		var instance = typeof(TArgs).CreateInstance<TArgs>();

		return Serializer.Merge(instance, entity);
	}

	public static TArgs Patch<TArgs, TEntity>(this IDto args, TEntity? entity, params object[] sources)
		where TArgs : IDto
		where TEntity : IEntity
	{
		if (entity is null)
		{
			var e = args.AsEntity<TEntity>(State.Default);

			return e.AsArguments<TArgs>(args);
		}

		return Merge(entity, args, State.Default, sources).AsArguments<TArgs>();
	}

	public static TArgs AsArguments<TArgs>(this IEntity entity, params object[] sources) where TArgs : IDto
	{
		var instance = typeof(TArgs).CreateInstance<TArgs>();

		return Serializer.Merge(instance, entity, sources);
	}

	public static TArgs AsEventArguments<TArgs>(this IEntity entity) where TArgs : IEventArgs
	{
		var instance = typeof(TArgs).CreateInstance<TArgs>();

		return Serializer.Merge(instance, entity);
	}

	public static TEntity Merge<TEntity>(this TEntity existing, IDto modifier, State state, params object[] sources)
		where TEntity : IEntity
	{
		var newEntity = Activator.CreateInstance<TEntity>();

		return Serializer.Merge(newEntity, existing, modifier, new StateModifier { State = state }, sources);
	}

	public static async Task<ImmutableList<TSource>> AsEntities<TSource>(this IQueryable<TSource> source, CancellationToken cancellationToken = default)
	{
		if (source is null)
			return ImmutableList<TSource>.Empty;

		var list = new List<TSource>();

		await foreach (var element in source.AsAsyncEnumerable().WithCancellation(cancellationToken))
			list.Add(element);

		return list.ToImmutableList();
	}

	public static async Task<ImmutableList<TSource>> AsEntities<TSource>(this IEnumerable<TSource> source)
	{
		if (source is null)
			return ImmutableList<TSource>.Empty;

		await Task.CompletedTask;

		return source.ToImmutableList();
	}

	public static async Task<TSource?> AsEntity<TSource>(this IQueryable<TSource> source, CancellationToken cancellationToken = default)
	{
		if (source is null)
			return default;

		await Task.CompletedTask;

		return Execute<TSource, TSource>(QueryableMethods.SingleOrDefaultWithoutPredicate, source, cancellationToken);
	}

	public static async Task<TSource?> AsEntity<TSource>(this IEnumerable<TSource> source)
	{
		if (source is null)
			return default;

		await Task.CompletedTask;

		return source.FirstOrDefault();
	}

	public static IEnumerable<TEntity> WithArguments<TEntity>(this IEnumerable<TEntity> source, QueryArgs args)
	{
		return source.WithOrderBy(args).WithPaging(args);
	}

	private static IEnumerable<TEntity> WithPaging<TEntity>(this IEnumerable<TEntity> source, QueryArgs args)
	{
		if (args.Paging.Size < 1)
			return source;

		return source.Skip((args.Paging.Index - 1) * args.Paging.Size)
				.Take(args.Paging.Size);
	}

	private static IEnumerable<TEntity> WithOrderBy<TEntity>(this IEnumerable<TEntity> entities, QueryArgs args)
	{
		if (entities.AsQueryable() as IOrderedQueryable<TEntity> is not IOrderedQueryable<TEntity> result)
			return entities;

		var top = true;

		foreach (var criteria in args.OrderBy)
		{
			if (top)
			{
				if (criteria.Mode == OrderByMode.Ascending)
					result = result.OrderBy(ResolvePropertyPredicate<TEntity>(criteria.Property));
				else
					result = result.OrderByDescending(ResolvePropertyPredicate<TEntity>(criteria.Property));
			}
			else
			{
				if (criteria.Mode == OrderByMode.Ascending)
					result = result.ThenBy(ResolvePropertyPredicate<TEntity>(criteria.Property));
				else
					result = result.ThenByDescending(ResolvePropertyPredicate<TEntity>(criteria.Property));
			}

			top = false;
		}

		return result;
	}

	private static Expression<Func<T, object>> ResolvePropertyPredicate<T>(string propToOrder)
	{
		var param = Expression.Parameter(typeof(T));
		var memberAccess = Expression.Property(param, propToOrder);
		var convertedMemberAccess = Expression.Convert(memberAccess, typeof(object));
		var orderPredicate = Expression.Lambda<Func<T, object>>(convertedMemberAccess, param);

		return orderPredicate;
	}

	private static TResult? Execute<TSource, TResult>(MethodInfo operatorMethodInfo, IQueryable<TSource> source, Expression? expression, CancellationToken cancellationToken = default)
	{
		if (source.Provider is IAsyncQueryProvider provider)
		{
			if (operatorMethodInfo.IsGenericMethod)
			{
				operatorMethodInfo = operatorMethodInfo.GetGenericArguments().Length == 2
						  ? operatorMethodInfo.MakeGenericMethod(typeof(TSource), typeof(TResult).GetGenericArguments().Single())
						  : operatorMethodInfo.MakeGenericMethod(typeof(TSource));
			}

			return (TResult)provider.Execute(Expression.Call(instance: null, method: operatorMethodInfo, arguments: expression == null
							? new[] { source.Expression }
							: new[] { source.Expression, expression }), cancellationToken);
		}

		throw new InvalidOperationException();
	}

	private static TResult? Execute<TSource, TResult>(MethodInfo operatorMethodInfo, IQueryable<TSource> source, CancellationToken cancellationToken = default)
	{
		return Execute<TSource, TResult>(operatorMethodInfo, source, (Expression?)null, cancellationToken);
	}

	public static PropertyInfo? PrimaryKeyProperty(this IEntity entity)
	{
		foreach (var property in entity.GetType().GetInheritedProperites())
		{
			if (property.FindAttribute<PrimaryKeyAttribute>() is not null)
				return property;
		}

		return null;
	}

	public static object? PrimaryKeyValue(this IEntity entity)
	{
		if (PrimaryKeyProperty(entity) is not PropertyInfo property)
			return null;

		return property.GetValue(entity);
	}
	public static string EntityId(this IEntity entity)
	{
		var attribute = entity.GetSchemaAttribute();

		return $"{attribute.Schema}.{attribute.Name}";
	}
	public static SchemaAttribute GetSchemaAttribute(this IEntity entity)
	{
		var definedAttribute = entity.GetType().GetCustomAttribute<SchemaAttribute>();

		if (definedAttribute is not null && definedAttribute.Schema is not null && definedAttribute.Name is not null)
			return definedAttribute;

		var schema = string.IsNullOrEmpty(definedAttribute?.Schema) ? SchemaAttribute.DefaultSchema : definedAttribute.Schema;
		var name = string.IsNullOrEmpty(definedAttribute?.Name) ? entity.GetType().Name.ToPascalCase() : definedAttribute.Name;

		return new TableAttribute
		{
			Id = definedAttribute?.Id,
			Name = name,
			Schema = schema
		};
	}

	public static IAsyncEnumerable<TSource> AsAsyncEnumerable<TSource>(this IQueryable<TSource> source)
	{
		if (source is IAsyncEnumerable<TSource> asyncEnumerable)
			return asyncEnumerable;

		throw new InvalidOperationException();
	}
}