using System;

using System.Data.Common;

using System.Diagnostics.CodeAnalysis;

using System.Reflection;

namespace Npgsql;

/// <summary>

/// A factory to create instances of various Npgsql objects.

/// </summary>

[Serializable]

public sealed class NpgsqlFactory : DbProviderFactory, IServiceProvider

{

/// <summary>

/// Gets an instance of the <see cref="NpgsqlFactory"/>.

/// This can be used to retrieve strongly typed data objects.

/// </summary>

public static readonly NpgsqlFactory Instance = new();

NpgsqlFactory() {}

/// <summary>

/// Returns a strongly typed <see cref="DbCommand"/> instance.

/// </summary>

public override DbCommand CreateCommand() => new NpgsqlCommand();

/// <summary>

/// Returns a strongly typed <see cref="DbConnection"/> instance.

/// </summary>

public override DbConnection CreateConnection() => new NpgsqlConnection();

/// <summary>

/// Returns a strongly typed <see cref="DbParameter"/> instance.

/// </summary>

public override DbParameter CreateParameter() => new NpgsqlParameter();

/// <summary>

/// Returns a strongly typed <see cref="DbConnectionStringBuilder"/> instance.

/// </summary>

public override DbConnectionStringBuilder CreateConnectionStringBuilder() => new NpgsqlConnectionStringBuilder();

/// <summary>

/// Returns a strongly typed <see cref="DbCommandBuilder"/> instance.

/// </summary>

public override DbCommandBuilder CreateCommandBuilder() => new NpgsqlCommandBuilder();

/// <summary>

/// Returns a strongly typed <see cref="DbDataAdapter"/> instance.

/// </summary>

public override DbDataAdapter CreateDataAdapter() => new NpgsqlDataAdapter();

#if !NETSTANDARD2_0

/// <summary>

/// Specifies whether the specific <see cref="DbProviderFactory"/> supports the <see cref="DbDataAdapter"/> class.

/// </summary>

public override bool CanCreateDataAdapter => true;

/// <summary>

/// Specifies whether the specific <see cref="DbProviderFactory"/> supports the <see cref="DbCommandBuilder"/> class.

/// </summary>

public override bool CanCreateCommandBuilder => true;

#endif

#if NET6_0_OR_GREATER

/// <inheritdoc/>

public override bool CanCreateBatch => true;

/// <inheritdoc/>

public override DbBatch CreateBatch() => new NpgsqlBatch();

/// <inheritdoc/>

public override DbBatchCommand CreateBatchCommand() => new NpgsqlBatchCommand();

#endif

#if NET7_0_OR_GREATER

/// <inheritdoc/>

public override DbDataSource CreateDataSource(string connectionString)

=> NpgsqlDataSource.Create(connectionString);

#endif

#region IServiceProvider Members

/// <summary>

/// Gets the service object of the specified type.

/// </summary>

/// <param name="serviceType">An object that specifies the type of service object to get.</param>

/// <returns>A service object of type serviceType, or null if there is no service object of type serviceType.</returns>

[RequiresUnreferencedCode("Legacy EF5 method, not trimming-safe.")]

public object? GetService(Type serviceType)

{

if (serviceType == null)

throw new ArgumentNullException(nameof(serviceType));

// In legacy Entity Framework, this is the entry point for obtaining Npgsql's

// implementation of DbProviderServices. We use reflection for all types to

// avoid any dependencies on EF stuff in this project. EF6 (and of course EF Core) do not use this method.

if (serviceType.FullName != "System.Data.Common.DbProviderServices")

return null;

// User has requested a legacy EF DbProviderServices implementation. Check our cache first.

if (_legacyEntityFrameworkServices != null)

return _legacyEntityFrameworkServices;

// First time, attempt to find the EntityFramework5.Npgsql assembly and load the type via reflection

var assemblyName = typeof(NpgsqlFactory).GetTypeInfo().Assembly.GetName();

assemblyName.Name = "EntityFramework5.Npgsql";

Assembly npgsqlEfAssembly;

try {

npgsqlEfAssembly = Assembly.Load(new AssemblyName(assemblyName.FullName));

} catch {

return null;

}

Type? npgsqlServicesType;

if ((npgsqlServicesType = npgsqlEfAssembly.GetType("Npgsql.NpgsqlServices")) == null ||

npgsqlServicesType.GetProperty("Instance") == null)

throw new Exception("EntityFramework5.Npgsql assembly does not seem to contain the correct type!");

return _legacyEntityFrameworkServices = npgsqlServicesType

.GetProperty("Instance", BindingFlags.Public | BindingFlags.Static)!

.GetMethod!.Invoke(null, new object[0]);

}

static object? _legacyEntityFrameworkServices;

#endregion

}