using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Tango.Scripting.Basic
{
    public class ProjectSession<T> where T : IContext
    {
        private Action _abortAction;
        private TaskCompletionSource<object> _completion;

        public event EventHandler<ProjectSessionStateChangedEventArgs> StateChanged;

        public ProjectSessionState State { get; set; }

        public Project<T> Project { get; set; }

        public ProjectSession(Project<T> project, Action abortAction)
        {
            _completion = new TaskCompletionSource<object>();
            Project = project;
            _abortAction = abortAction;
        }

        public void Abort()
        {
            _abortAction();
            State = ProjectSessionState.Aborted;
            _completion.SetException(new OperationCanceledException("Project execution aborted."));
            RaiseStateChanged();
        }

        internal void Failed(Exception ex)
        {
            State = ProjectSessionState.Failed;
            _completion.SetException(ex);
            RaiseStateChanged(null, ex);
        }

        internal void Completed(object returnValue)
        {
            State = ProjectSessionState.Completed;
            _completion.SetResult(returnValue);
            RaiseStateChanged(returnValue, null);
        }

        private void RaiseStateChanged(object returnValue = null, Exception ex = null)
        {
            StateChanged?.Invoke(this,
                new ProjectSessionStateChangedEventArgs()
                {
                    ReturnValue = returnValue,
                    State = State,
                    Exception = ex
                });
        }

        public Task<Object> WaitForCompletion()
        {
            return _completion.Task;
        }
    }
}