using System;
using System.Collections.Generic;
using System.Text;
using ProcessHacker.Native.Api;
using ProcessHacker.Native.Objects;
using ProcessHacker.Native.Security;

namespace ProcessHacker.Native.Threading
{
    /// <summary>
    /// Represents a semaphore which can be used to control access to a shared resource.
    /// </summary>
    public class Semaphore : NativeObject<SemaphoreHandle>
    {
        /// <summary>
        /// Creates a binary semaphore.
        /// </summary>
        public Semaphore()
            : this(null)
        { }

        /// <summary>
        /// Creates a binary semaphore.
        /// </summary>
        /// <param name="initialCount">The initial count of the semaphore.</param>
        /// <param name="maximumCount">The maximum count of the semaphore.</param>
        public Semaphore(int initialCount, int maximumCount)
            : this(null, initialCount, maximumCount)
        { }

        /// <summary>
        /// Creates or opens a semaphore.
        /// </summary>
        /// <param name="name">
        /// The name of the new semaphore, or the name of an existing semaphore.
        /// </param>
        public Semaphore(string name)
            : this(name, 1, 1)
        { }

        /// <summary>
        /// Creates a semaphore.
        /// </summary>
        /// <param name="name">The name of the new semaphore.</param>
        /// <param name="initialCount">The initial count of the semaphore.</param>
        /// <param name="maximumCount">The maximum count of the semaphore.</param>
        public Semaphore(string name, int initialCount, int maximumCount)
        {
            this.Handle = SemaphoreHandle.Create(
                SemaphoreAccess.All,
                name,
                ObjectFlags.OpenIf,
                null,
                initialCount,
                maximumCount
                );
        }

        /// <summary>
        /// Gets the current count of the semaphore.
        /// </summary>
        public int Count
        {
            get { return this.Handle.GetBasicInformation().CurrentCount; }
        }

        /// <summary>
        /// Gets the maximum count of the semaphore.
        /// </summary>
        public int MaximumCount
        {
            get { return this.Handle.GetBasicInformation().MaximumCount; }
        }

        /// <summary>
        /// Releases the semaphore, incrementing the count.
        /// </summary>
        public void Release()
        {
            this.Handle.Release();
        }

        /// <summary>
        /// Releases the semaphore, incrementing the count by the 
        /// specified amount.
        /// </summary>
        /// <param name="count">The amount to increment the count by.</param>
        public void Release(int count)
        {
            this.Handle.Release(count);
        }
    }
}