using System;
using System.Runtime.CompilerServices;
using System.Security;

namespace ETModel
{
    public struct ETAsyncTaskVoidMethodBuilder
    {
        private Action moveNext;

        // 1. Static Create method.
        //[DebuggerHidden]
        public static ETAsyncTaskVoidMethodBuilder Create()
        {
            ETAsyncTaskVoidMethodBuilder builder = new ETAsyncTaskVoidMethodBuilder();
            return builder;
        }

        // 2. TaskLike Task property(void)
        public ETTaskVoid Task => default;

        // 3. SetException
        //[DebuggerHidden]
        public void SetException(Exception exception)
        {
        }

        // 4. SetResult
        //[DebuggerHidden]
        public void SetResult()
        {
            // do nothing
        }

        // 5. AwaitOnCompleted
        //[DebuggerHidden]
        public void AwaitOnCompleted<TAwaiter, TStateMachine>(ref TAwaiter awaiter, ref TStateMachine stateMachine)
                where TAwaiter : INotifyCompletion
                where TStateMachine : IAsyncStateMachine
        {
            if (moveNext == null)
            {
                var runner = new MoveNextRunner<TStateMachine>();
                moveNext = runner.Run;
                runner.StateMachine = stateMachine; // set after create delegate.
            }

            awaiter.OnCompleted(moveNext);
        }

        // 6. AwaitUnsafeOnCompleted
        //[DebuggerHidden]
        [SecuritySafeCritical]
        public void AwaitUnsafeOnCompleted<TAwaiter, TStateMachine>(ref TAwaiter awaiter, ref TStateMachine stateMachine)
                where TAwaiter : ICriticalNotifyCompletion
                where TStateMachine : IAsyncStateMachine
        {
            if (moveNext == null)
            {
                var runner = new MoveNextRunner<TStateMachine>();
                moveNext = runner.Run;
                runner.StateMachine = stateMachine; // set after create delegate.
            }

            awaiter.UnsafeOnCompleted(moveNext);
        }

        // 7. Start
        //[DebuggerHidden]
        public void Start<TStateMachine>(ref TStateMachine stateMachine)
                where TStateMachine : IAsyncStateMachine
        {
            stateMachine.MoveNext();
        }

        // 8. SetStateMachine
        //[DebuggerHidden]
        public void SetStateMachine(IAsyncStateMachine stateMachine)
        {
        }
    }
}