// Copyright (c) .NET Foundation and contributors. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.FlowAnalysis;
 
namespace ILLink.RoslynAnalyzer.DataFlow
{
    // Copied from https://github.com/dotnet/roslyn/blob/fdd40b21d59c13e8fa6c718c7aaf9d50634da754/src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/ControlFlowGraphExtensions.cs
    internal static partial class ControlFlowGraphExtensions
    {
        public static BasicBlock EntryBlock(this ControlFlowGraph cfg)
        {
            var firstBlock = cfg.Blocks[0];
            Debug.Assert(firstBlock.Kind == BasicBlockKind.Entry);
            return firstBlock;
        }
 
        public static BasicBlock ExitBlock(this ControlFlowGraph cfg)
        {
            var lastBlock = cfg.Blocks.Last();
            Debug.Assert(lastBlock.Kind == BasicBlockKind.Exit);
            return lastBlock;
        }
 
        public static IEnumerable<IOperation> DescendantOperations(this ControlFlowGraph cfg)
            => cfg.Blocks.SelectMany(b => b.DescendantOperations());
 
        public static IEnumerable<T> DescendantOperations<T>(this ControlFlowGraph cfg, OperationKind operationKind)
            where T : IOperation
            => cfg.DescendantOperations().Where(d => d?.Kind == operationKind).Cast<T>();
    }
}