using System;
using System.ComponentModel;

namespace Chernobyl.Creation
{
    /// <summary>
    /// An <see cref="IFactory{TResult}"/> that uses a <see cref="Func{TResult}"/> for creation.
    /// </summary>
    public class FuncFactory<TResult> : FuncBuilder<Func<TResult>, TResult>, IFactory<TResult>
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="FuncFactory{TResult}"/> class.
        /// </summary>
        /// <param name="function">The method whose return value becomes the
        /// item that is returned by <c>this</c>. If this method throws an
        /// <see cref="Exception"/> then it is used as the
        /// <see cref="AsyncCompletedEventArgs.Error"/> value.</param>
        public FuncFactory(Func<TResult> function)
            : base(function)
        {}

        /// <summary>
        /// Performs an implicit conversion from <see cref="Func{TResult}"/> to
        /// <see cref="FuncFactory{TResult}"/>.
        /// </summary>
        /// <param name="function">The method whose return value becomes the
        /// item that is returned by <c>this</c>. If this method throws an
        /// <see cref="Exception"/> then it is used as the
        /// <see cref="AsyncCompletedEventArgs.Error"/> value.</param>
        /// <returns>The result of the conversion.</returns>
        public static implicit operator FuncFactory<TResult>(Func<TResult> function) => new FuncFactory<TResult>(function);

        /// <summary>
        /// Performs an implicit conversion from <see cref="FuncFactory{TResult}"/> to
        /// <see cref="Func{TResult}"/>.
        /// </summary>
        /// <param name="factory">The <see cref="FuncFactory{TResult}"/> whose
        /// <see cref="FuncBuilder{TFunc, TResult}.Function"/> is to be returned.
        /// </param>
        /// <returns>The result of the conversion.</returns>
        public static implicit operator Func<TResult>(FuncFactory<TResult> factory) => factory.Function;


        /// <inheritdoc />
        public TResult Create() => Create(Function, null);
    }

    /// <summary>
    /// An <see cref="IFactory{T1, TResult}"/> that uses a <see cref="Func{T1, TResult}"/> for creation.
    /// </summary>
    public class FuncFactory<T1, TResult> : FuncBuilder<Func<T1, TResult>, TResult>, IFactory<T1, TResult>
    {
        /// <param name="function">The method whose return value becomes the
        /// item that is returned by <c>this</c>. If this method throws an
        /// <see cref="Exception"/> then it is used as the
        /// <see cref="AsyncCompletedEventArgs.Error"/> value.</param>
        public FuncFactory(Func<T1, TResult> function)
            : base(function)
        {}

        /// <summary>
        /// Performs an implicit conversion from <see cref="Func{TResult}"/> to
        /// <see cref="FuncFactory{TResult}"/>.
        /// </summary>
        /// <param name="function">The method whose return value becomes the
        /// item that is returned by <c>this</c>. If this method throws an
        /// <see cref="Exception"/> then it is used as the
        /// <see cref="AsyncCompletedEventArgs.Error"/> value.</param>
        /// <returns>The result of the conversion.</returns>
        public static implicit operator FuncFactory<T1, TResult>(Func<T1, TResult> function) => new FuncFactory<T1, TResult>(function);

        /// <summary>
        /// Performs an implicit conversion from <see cref="FuncFactory{TResult}"/> to
        /// <see cref="Func{TResult}"/>.
        /// </summary>
        /// <param name="factory">The <see cref="FuncFactory{TResult}"/> whose
        /// <see cref="FuncBuilder{TFunc, TResult}.Function"/> is to be returned.
        /// </param>
        /// <returns>The result of the conversion.</returns>
        public static implicit operator Func<T1, TResult>(FuncFactory<T1, TResult> factory) => factory.Function;

        /// <inheritdoc />
        public TResult Create(T1 arg1) => Create(() => Function(arg1), arg1);
    }

    /// <summary>
    /// A type used to help create new <see cref="IBuilder{TResult}"/> types
    /// that build objects from methods.
    /// </summary>
    /// <typeparam name="TFunc">The type of the method whose return value
    /// becomes the item that is returned by <c>this</c>.</typeparam>
    /// <typeparam name="TResult">The type that is being constructed and/or configured.</typeparam>
    public abstract class FuncBuilder<TFunc, TResult> : Builder<TResult>
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="FuncFactory{TResult}"/> class.
        /// </summary>
        /// <param name="function">The method whose return value becomes the
        /// item that is returned by <c>this</c>. If this method throws an
        /// <see cref="Exception"/> then it is used as the
        /// <see cref="AsyncCompletedEventArgs.Error"/> value.</param>
        protected FuncBuilder(TFunc function)
        {
            Function = function;
        }

        /// <summary>
        /// Invokes the creation method provided and then reports the item
        /// created using <see cref="Builder{TResult}.ReportCreation(CreationEventArgs{TResult})" />.
        /// </summary>
        protected TResult Create(Func<TResult> creator, object userState)
        {
            TResult result;

            try
            {
                result = creator();
                ReportCreation(new CreationEventArgs<TResult>(result, userState));
            }
            catch (Exception e)
            {
                ReportCreation(new CreationEventArgs<TResult>(e, userState));
                throw;
            }

            return result;
        }

        /// <summary>
        /// The method whose return value becomes the item that is returned by
        /// <c>this</c>. If this method throws an <see cref="Exception"/> then
        /// it is used as the <see cref="AsyncCompletedEventArgs.Error"/> value.
        /// </summary>
        public TFunc Function { get; set; }
    }
}