using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using LinFu.IoC.Configuration.Interfaces;
using LinFu.IoC.Interfaces;

namespace LinFu.IoC.Configuration
{
    /// <summary>
    ///     A default implementation of the <see cref="IMemberInjectionFilter{TMember}" />
    ///     class that returns fields which have the <see cref="InjectAttribute" />
    ///     defined.
    /// </summary>
    public class AttributedFieldInjectionFilter : BaseMemberInjectionFilter<FieldInfo>
    {
        private readonly Type _attributeType;

        /// <summary>
        ///     Initializes the class and uses the <see cref="InjectAttribute" />
        ///     to specify which field should be automatically injected with
        ///     services from the container.
        /// </summary>
        public AttributedFieldInjectionFilter()
        {
            _attributeType = typeof(InjectAttribute);
        }

        /// <summary>
        ///     Initializes the class and uses the <paramref name="attributeType" />
        ///     to specify which fields should be automatically injected with
        ///     services from the container.
        /// </summary>
        /// <param name="attributeType">The custom property attribute that will be used to mark properties for automatic injection.</param>
        public AttributedFieldInjectionFilter(Type attributeType)
        {
            _attributeType = attributeType;
        }

        /// <summary>
        ///     Determines which members should be selected from the <paramref name="targetType" />
        ///     using the <paramref name="container" />
        /// </summary>
        /// <param name="targetType">The target type that will supply the list of members that will be filtered.</param>
        /// <param name="container">The target container.</param>
        /// <returns>A list of <see cref="FieldInfo" /> objects that pass the filter description.</returns>
        protected override IEnumerable<FieldInfo> GetMembers(Type targetType, IServiceContainer container)
        {
            // The field type must exist in the container and must be marked as public
            var results =
                from field in targetType.GetFields(BindingFlags.Public | BindingFlags.Instance)
                let fieldType = field.FieldType
                let attributes = field.GetCustomAttributes(_attributeType, false)
                where attributes != null && attributes.Length > 0 &&
                      container.Contains(fieldType)
                select field;

            return results;
        }
    }
}