using System;

using System.Data;

using System.Diagnostics;

using System.Threading;

using System.Threading.Tasks;

using Npgsql.Internal;

using NpgsqlTypes;

namespace Npgsql;

/// <summary>

/// A generic version of <see cref="NpgsqlParameter"/> which provides more type safety and

/// avoids boxing of value types. Use <see cref="TypedValue"/> instead of <see cref="NpgsqlParameter.Value"/>.

/// </summary>

/// <typeparam name="T">The type of the value that will be stored in the parameter.</typeparam>

public sealed class NpgsqlParameter<T> : NpgsqlParameter

{

/// <summary>

/// Gets or sets the strongly-typed value of the parameter.

/// </summary>

public T? TypedValue

{

get;

set

{

if (typeof(T) == typeof(object) && ShouldResetObjectTypeInfo(value))

ResetTypeInfo();

else

DisposeBindingState();

field = value;

}

}

/// <summary>

/// Gets or sets the value of the parameter. This delegates to <see cref="TypedValue"/>.

/// </summary>

public override object? Value

{

get => TypedValue;

set => TypedValue = (T)value!;

}

private protected override Type StaticValueType => typeof(T);

#region Constructors

/// <summary>

/// Initializes a new instance of <see cref="NpgsqlParameter{T}" />.

/// </summary>

public NpgsqlParameter() { }

/// <summary>

/// Initializes a new instance of <see cref="NpgsqlParameter{T}" /> with a parameter name and value.

/// </summary>

public NpgsqlParameter(string parameterName, T value)

{

ParameterName = parameterName;

TypedValue = value;

}

/// <summary>

/// Initializes a new instance of <see cref="NpgsqlParameter{T}" /> with a parameter name and type.

/// </summary>

public NpgsqlParameter(string parameterName, NpgsqlDbType npgsqlDbType)

{

ParameterName = parameterName;

NpgsqlDbType = npgsqlDbType;

}

/// <summary>

/// Initializes a new instance of <see cref="NpgsqlParameter{T}" /> with a parameter name and type.

/// </summary>

public NpgsqlParameter(string parameterName, DbType dbType)

{

ParameterName = parameterName;

DbType = dbType;

}

#endregion Constructors

private protected override PgConcreteTypeInfo MakeConcreteForTypedValue(PgTypeInfo typeInfo, out object? providerWriteState)

=> typeInfo.MakeConcreteForValue(

new() { NestedObjectDbNullHandling = ParameterDbNullHandling },

TypedValue,

out providerWriteState);

private protected override PgValueBinding BindTypedValue(PgConcreteTypeInfo concrete, object? providerWriteState, DataFormat? formatPreference)

=> concrete.BindParameterValue(TypedValue, providerWriteState, ParameterDbNullHandling, formatPreference);

private protected override ValueTask WriteTypedValue(bool async, PgConverter converter, PgWriter writer, CancellationToken cancellationToken)

{

Debug.Assert(TypedValue is not null);

if (async)

return converter.WriteAsync(writer, TypedValue, cancellationToken);

converter.Write(writer, TypedValue);

return new ValueTask();

}

private protected override void SetOutputTypedValue(NpgsqlDataReader reader, int ordinal)

=> TypedValue = reader.GetFieldValue<T>(ordinal);

private protected override NpgsqlParameter CloneCore() =>

// use fields instead of properties

// to avoid auto-initializing something like type_info

new NpgsqlParameter<T>

{

_precision = _precision,

_scale = _scale,

_size = _size,

_dbType = _dbType,

_npgsqlDbType = _npgsqlDbType,

_dataTypeName = _dataTypeName,

Direction = Direction,

IsNullable = IsNullable,

_name = _name,

TrimmedName = TrimmedName,

SourceColumn = SourceColumn,

SourceVersion = SourceVersion,

TypedValue = TypedValue,

SourceColumnNullMapping = SourceColumnNullMapping,

};

}