// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
using System;
using System.Composition;
using System.Threading.Tasks;
using Microsoft.CodeAnalysis.Completion;
using Microsoft.CodeAnalysis.Host.Mef;
using Microsoft.CodeAnalysis.Shared.Extensions;
 
namespace Microsoft.CodeAnalysis.CSharp.Completion.Providers
{
    [ExportArgumentProvider(nameof(DefaultArgumentProvider), LanguageNames.CSharp)]
    [ExtensionOrder(After = nameof(OutVariableArgumentProvider))]
    [Shared]
    internal sealed class DefaultArgumentProvider : AbstractDefaultArgumentProvider
    {
        [ImportingConstructor]
        [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
        public DefaultArgumentProvider()
        {
        }
 
        public override Task ProvideArgumentAsync(ArgumentContext context)
        {
            if (context.PreviousValue is { })
            {
                context.DefaultValue = context.PreviousValue;
            }
            else if (context.Parameter.Type.IsReferenceType || context.Parameter.Type.IsNullable())
            {
                context.DefaultValue = "null";
            }
            else
            {
                context.DefaultValue = context.Parameter.Type.SpecialType switch
                {
                    SpecialType.System_Boolean => "false",
                    SpecialType.System_Char => @"'\\0'",
                    SpecialType.System_Byte => "(byte)0",
                    SpecialType.System_SByte => "(sbyte)0",
                    SpecialType.System_Int16 => "(short)0",
                    SpecialType.System_UInt16 => "(ushort)0",
                    SpecialType.System_Int32 => "0",
                    SpecialType.System_UInt32 => "0U",
                    SpecialType.System_Int64 => "0L",
                    SpecialType.System_UInt64 => "0UL",
                    SpecialType.System_Decimal => "0.0m",
                    SpecialType.System_Single => "0.0f",
                    SpecialType.System_Double => "0.0",
                    _ => "default",
                };
            }
 
            return Task.CompletedTask;
        }
    }
}