// <copyright file="System.Diagnostics.CodeAnalysis.Attributes.cs" company="OpenTelemetry Authors">
// Copyright The OpenTelemetry Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// </copyright>

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// https://github.com/dotnet/runtime/blob/bffa7cf52b3982597adc5447c25e7aaa3b063c1c/src/libraries/System.Private.CoreLib/src/System/Diagnostics/CodeAnalysis/NullableAttributes.cs

// This file contains attributes from the System.Diagnostics.CodeAnalysis namespace
// used by the compiler for null-state static analysis.
// This is a C# feature, but requires these attributes to be defined,
// so we define them here for older .NET runtimes.
// https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/attributes/nullable-analysis

#pragma warning disable SA1649 // file name should match first type name
#pragma warning disable SA1402 // file may only contain a single type

// ReSharper disable once CheckNamespace
namespace System.Diagnostics.CodeAnalysis;

#if !NETCOREAPP3_0_OR_GREATER
/// <summary>Specifies that null is allowed as an input even if the corresponding type disallows it.</summary>
[AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property)]
internal sealed class AllowNullAttribute : Attribute
{
}

/// <summary>Specifies that null is disallowed as an input even if the corresponding type allows it.</summary>
[AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property)]
internal sealed class DisallowNullAttribute : Attribute
{
}

/// <summary>Specifies that an output may be null even if the corresponding type disallows it.</summary>
[AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue)]
internal sealed class MaybeNullAttribute : Attribute
{
}

/// <summary>Specifies that an output will not be null even if the corresponding type allows it. Specifies that an input argument was not null when the call returns.</summary>
[AttributeUsage(AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue)]
internal sealed class NotNullAttribute : Attribute
{
}

/// <summary>Specifies that when a method returns <see cref="ReturnValue"/>, the parameter may be null even if the corresponding type disallows it.</summary>
[AttributeUsage(AttributeTargets.Parameter)]
internal sealed class MaybeNullWhenAttribute : Attribute
{
    /// <summary>Initializes a new instance of the <see cref="MaybeNullWhenAttribute"/> class with the specified return value condition.</summary>
    /// <param name="returnValue">
    /// The return value condition. If the method returns this value, the associated parameter may be null.
    /// </param>
    public MaybeNullWhenAttribute(bool returnValue) => ReturnValue = returnValue;

    /// <summary>Gets a value indicating whether the associated parameter may be null.</summary>
    public bool ReturnValue { get; }
}

/// <summary>Specifies that when a method returns <see cref="ReturnValue"/>, the parameter will not be null even if the corresponding type allows it.</summary>
[AttributeUsage(AttributeTargets.Parameter)]
internal sealed class NotNullWhenAttribute : Attribute
{
    /// <summary>Initializes a new instance of the <see cref="NotNullWhenAttribute"/> class with the specified return value condition.</summary>
    /// <param name="returnValue">
    /// The return value condition. If the method returns this value, the associated parameter will not be null.
    /// </param>
    public NotNullWhenAttribute(bool returnValue) => ReturnValue = returnValue;

    /// <summary>Gets a value indicating whether the associated parameter will not be null.</summary>
    public bool ReturnValue { get; }
}

/// <summary>Specifies that the output will be non-null if the named parameter is non-null.</summary>
[AttributeUsage(AttributeTargets.Parameter | AttributeTargets.Property | AttributeTargets.ReturnValue, AllowMultiple = true)]
internal sealed class NotNullIfNotNullAttribute : Attribute
{
    /// <summary>Initializes a new instance of the <see cref="NotNullIfNotNullAttribute"/> class with the associated parameter name.</summary>
    /// <param name="parameterName">
    /// The associated parameter name.  The output will be non-null if the argument to the parameter specified is non-null.
    /// </param>
    public NotNullIfNotNullAttribute(string parameterName) => ParameterName = parameterName;

    /// <summary>Gets the associated parameter name.</summary>
    public string ParameterName { get; }
}

/// <summary>Applied to a method that will never return under any circumstance.</summary>
[AttributeUsage(AttributeTargets.Method, Inherited = false)]
internal sealed class DoesNotReturnAttribute : Attribute
{
}

/// <summary>Specifies that the method will not return if the associated Boolean parameter is passed the specified value.</summary>
[AttributeUsage(AttributeTargets.Parameter)]
internal sealed class DoesNotReturnIfAttribute : Attribute
{
    /// <summary>Initializes a new instance of the <see cref="DoesNotReturnIfAttribute"/> class with the specified parameter value.</summary>
    /// <param name="parameterValue">
    /// The condition parameter value. Code after the method will be considered unreachable by diagnostics if the argument to
    /// the associated parameter matches this value.
    /// </param>
    public DoesNotReturnIfAttribute(bool parameterValue) => ParameterValue = parameterValue;

    /// <summary>Gets a value indicating whether the method will not return if the associated Boolean parameter is passed the specified value.</summary>
    public bool ParameterValue { get; }
}

/// <summary>Specifies that the method or property will ensure that the listed field and property members have not-null values.</summary>
[AttributeUsage(AttributeTargets.Method | AttributeTargets.Property, Inherited = false, AllowMultiple = true)]
internal sealed class MemberNotNullAttribute : Attribute
{
    /// <summary>Initializes a new instance of the <see cref="MemberNotNullAttribute"/> class with a field or property member.</summary>
    /// <param name="member">
    /// The field or property member that is promised to be not-null.
    /// </param>
    public MemberNotNullAttribute(string member) => Members = new[] { member };

    /// <summary>Initializes a new instance of the <see cref="MemberNotNullAttribute"/> class with the list of field and property members.</summary>
    /// <param name="members">
    /// The list of field and property members that are promised to be not-null.
    /// </param>
    public MemberNotNullAttribute(params string[] members) => Members = members;

    /// <summary>Gets field or property member names.</summary>
    public string[] Members { get; }
}
#endif
#if !NET5_0_OR_GREATER

/// <summary>Specifies that the method or property will ensure that the listed field and property members have not-null values when returning with the specified return value condition.</summary>
[AttributeUsage(AttributeTargets.Method | AttributeTargets.Property, Inherited = false, AllowMultiple = true)]
internal sealed class MemberNotNullWhenAttribute : Attribute
{
    /// <summary>Initializes a new instance of the <see cref="MemberNotNullWhenAttribute"/> class with the specified return value condition and a field or property member.</summary>
    /// <param name="returnValue">
    /// The return value condition. If the method returns this value, the associated parameter will not be null.
    /// </param>
    /// <param name="member">
    /// The field or property member that is promised to be not-null.
    /// </param>
    public MemberNotNullWhenAttribute(bool returnValue, string member)
    {
        ReturnValue = returnValue;
        Members = new[] { member };
    }

    /// <summary>Initializes a new instance of the <see cref="MemberNotNullWhenAttribute"/> class with the specified return value condition and list of field and property members.</summary>
    /// <param name="returnValue">
    /// The return value condition. If the method returns this value, the associated parameter will not be null.
    /// </param>
    /// <param name="members">
    /// The list of field and property members that are promised to be not-null.
    /// </param>
    public MemberNotNullWhenAttribute(bool returnValue, params string[] members)
    {
        ReturnValue = returnValue;
        Members = members;
    }

    /// <summary>Gets a value indicating whether the return value will be null or not.</summary>
    public bool ReturnValue { get; }

    /// <summary>Gets field or property member names.</summary>
    public string[] Members { get; }
}
#endif

#pragma warning restore SA1402
#pragma warning restore SA1649
