using System;
using Umbraco.Core.Dynamics;

namespace Umbraco.Core
{
    /// <summary>
    /// Represents the result of an operation attempt.
    /// </summary>
    /// <typeparam name="T">The type of the attempted operation result.</typeparam>
    [Serializable]
	public struct Attempt<T>
	{
		private readonly bool _success;
		private readonly T _result;
		private readonly Exception _exception;

        /// <summary>
        /// Gets a value indicating whether this <see cref="Attempt{T}"/> was successful.
        /// </summary>
        public bool Success
		{
			get { return _success; }
		}

        /// <summary>
        /// Gets the exception associated with an unsuccessful attempt.
        /// </summary>
        public Exception Exception { get { return _exception; } }

        /// <summary>
        /// Gets the attempt result.
        /// </summary>
        public T Result
		{
			get { return _result; }
		}

        // optimize, use a singleton failed attempt
		private static readonly Attempt<T> Failed = new Attempt<T>(false, default(T), null);

        // private - use Succ() or Fail() methods to create attempts
        private Attempt(bool success, T result, Exception exception)
        {
            _success = success;
            _result = result;
            _exception = exception;
        }

        /// <summary>
        /// Creates a successful attempt.
        /// </summary>
        /// <returns>The successful attempt.</returns>
        public static Attempt<T> Succ()
        {
            return new Attempt<T>(true, default(T), null);
        }

        /// <summary>
        /// Creates a successful attempt with a result.
        /// </summary>
        /// <param name="result">The result of the attempt.</param>
        /// <returns>The successful attempt.</returns>
        public static Attempt<T> Succ(T result)
        {
            return new Attempt<T>(true, result, null);
        }

        /// <summary>
        /// Creates a failed attempt.
        /// </summary>
        /// <returns>The failed attempt.</returns>
        public static Attempt<T> Fail()
        {
            return Failed;
        }

        /// <summary>
        /// Creates a failed attempt with an exception.
        /// </summary>
        /// <param name="exception">The exception causing the failure of the attempt.</param>
        /// <returns>The failed attempt.</returns>
        public static Attempt<T> Fail(Exception exception)
        {
            return new Attempt<T>(false, default(T), exception);
        }

        /// <summary>
        /// Creates a failed attempt with a result.
        /// </summary>
        /// <param name="result">The result of the attempt.</param>
        /// <returns>The failed attempt.</returns>
        public static Attempt<T> Fail(T result)
        {
            return new Attempt<T>(false, result, null);
        }

        /// <summary>
        /// Creates a failed attempt with a result and an exception.
        /// </summary>
        /// <param name="result">The result of the attempt.</param>
        /// <param name="exception">The exception causing the failure of the attempt.</param>
        /// <returns>The failed attempt.</returns>
        public static Attempt<T> Fail(T result, Exception exception)
        {
            return new Attempt<T>(false, result, exception);
        }

        /// <summary>
        /// Creates a successful or a failed attempt.
        /// </summary>
        /// <param name="success">A value indicating whether the attempt is successful.</param>
        /// <returns>The attempt.</returns>
        public static Attempt<T> If(bool success)
        {
            return success ? new Attempt<T>(true, default(T), null) : Failed;
        }

        /// <summary>
        /// Creates a successful or a failed attempt, with a result.
        /// </summary>
        /// <param name="success">A value indicating whether the attempt is successful.</param>
        /// <param name="result">The result of the attempt.</param>
        /// <returns>The attempt.</returns>
        public static Attempt<T> If(bool success, T result)
        {
            return new Attempt<T>(success, result, null);
        }
    }
}