// 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.Linq;
using Microsoft.CodeAnalysis.Operations;

namespace Microsoft.CodeAnalysis.FlowAnalysis
{
    internal static partial class ControlFlowGraphExtensions
    {
        public static BasicBlock GetEntry(this ControlFlowGraph cfg) => cfg.Blocks.Single(b => b.Kind == BasicBlockKind.Entry);
        public static BasicBlock GetExit(this ControlFlowGraph cfg) => cfg.Blocks.Single(b => b.Kind == BasicBlockKind.Exit);

        internal static bool SupportsFlowAnalysis(this ControlFlowGraph cfg)
        {
            // Skip flow analysis for following root operation blocks:
            // 1. Null root operation (error case)
            // 2. OperationKindEx.Attribute or OperationKind.None (used for attributes before IAttributeOperation support).
            // 3. OperationKind.ParameterInitialzer (default parameter values).
            if (cfg.OriginalOperation == null ||
                cfg.OriginalOperation.Kind is OperationKind.Attribute or OperationKind.None or OperationKind.ParameterInitializer)
            {
                return false;
            }

            // Skip flow analysis for code with syntax/semantic errors
            if (cfg.OriginalOperation.Syntax.GetDiagnostics().Any(d => d.DefaultSeverity == DiagnosticSeverity.Error) ||
                cfg.OriginalOperation.HasAnyOperationDescendant(o => o is IInvalidOperation))
            {
                return false;
            }

            return true;
        }
    }
}