using System;

using System.Collections.Generic;

using System.Data.Entity;

using System.Data.Entity.Core.Objects;

using System.Data.Entity.Infrastructure;

using System.Linq;

using System.Reflection;

namespace JSONAPI.EntityFramework

{

/// <summary>

/// Extensions on DbContext useful for JSONAPI.NET

/// </summary>

public static class DbContextExtensions

{

/// <summary>

/// Gets the ID key names for an entity type

/// </summary>

/// <param name="dbContext"></param>

/// <param name="type"></param>

/// <returns></returns>

public static IEnumerable<string> GetKeyNames(this DbContext dbContext, Type type)

{

if (dbContext == null) throw new ArgumentNullException("dbContext");

if (type == null) throw new ArgumentNullException("type");

var originalType = type;

while (type != null)

{

var openMethod = typeof(DbContextExtensions).GetMethod("GetKeyNamesFromGeneric", BindingFlags.Public | BindingFlags.Static);

var method = openMethod.MakeGenericMethod(type);

try

{

return (IEnumerable<string>) method.Invoke(null, new object[] {dbContext});

}

catch (TargetInvocationException)

{

}

type = type.BaseType;

}

throw new Exception(string.Format("Failed to identify the key names for {0} or any of its parent classes.", originalType.Name));

}

/// <summary>

/// Gets the ID key names for an entity type

/// </summary>

/// <param name="dbContext"></param>

/// <typeparam name="T"></typeparam>

/// <returns></returns>

/// <exception cref="ArgumentException"></exception>

public static IEnumerable<string> GetKeyNamesFromGeneric<T>(this DbContext dbContext) where T : class

{

var objectContext = ((IObjectContextAdapter)dbContext).ObjectContext;

ObjectSet<T> objectSet;

try

{

objectSet = objectContext.CreateObjectSet<T>();

}

catch (InvalidOperationException e)

{

throw new ArgumentException(

String.Format("The Type {0} was not found in the DbContext with Type {1}", typeof(T).Name, dbContext.GetType().Name),

e

);

}

return objectSet.EntitySet.ElementType.KeyMembers.Select(k => k.Name).ToArray();

}

}

}