using System;
using System.ComponentModel;

namespace Chernobyl.ComponentModel
{
    /// <summary>
    /// An interface for working with instances that represent work being done
    /// by some code. This code is often doing the work asynchronously but 
    /// not always.
    /// </summary>
    public interface ITask
    {
        /// <summary>
        /// Cancels the work being done but only if it has not been canceled 
        /// already and the <see cref="ITask.ProgressPercentage"/> has not 
        /// reached 100%. If cancellation is successful, the <see cref="Canceled"/> 
        /// event will be raised. Note that, when the work being done is on 
        /// another thread, it is possible that the work will finish just as 
        /// this method is invoked.
        /// </summary>
        void Cancel();

        /// <summary>
        /// True if the task has been canceled, false if otherwise.
        /// </summary>
        bool IsCanceled { get; }

        /// <summary>
        /// The percentage of work, from 0% to 100%, that has been completed on 
        /// this task. If the task is Canceled (i.e. <see cref="Cancel()"/> is
        /// invoked) the value of this property will be set to zero by this
        /// <see cref="ITask"/>.
        /// </summary>
        int ProgressPercentage { get; }

        /// <summary>
        /// An event that is raised when the <see cref="Cancel()"/> is invoked
        /// on this instance. Note that this event is only raised once,
        /// regardless of how many times <see cref="Cancel()"/> is invoked. This
        /// event will not be invoked if the <see cref="ITask.ProgressPercentage"/> 
        /// is at 100%.
        /// </summary>
        event EventHandler Canceled;

        /// <summary>
        /// An event that is raised when the progress of the task has changed.
        /// </summary>
        event ProgressChangedEventHandler ProgressChanged;
    }
}