using System;
using System.CodeDom;
using System.Reflection;

namespace Chernobyl.Reflection.Template.CodeDom
{
    /// <summary>
    /// An <see cref="IMember"/> that can take any <see cref="IMember"/>
    /// instance that represents a field and generate CodeDom for it.
    /// </summary>
    public class CodeDomField : CodeDomAssignableMember
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="CodeDomField"/> class.
        /// </summary>
        /// <param name="member">The <see cref="IMember"/> instance to
        /// generate CodeDom for and provide the <see cref="IMember"/>
        /// implementation for this class.</param>
        /// <exception cref="ArgumentException">Thrown if the member is not
        /// a field. In other words, the <see cref="MemberInfo.MemberType"/>
        /// on the <see cref="IMember.Info"/> is not equal to
        /// <see cref="MemberTypes.Field"/>.</exception>
        public CodeDomField(IMember member) : base(member)
        {
            if (Info.MemberType != MemberTypes.Field)
                throw new ArgumentException("The member must be a field.", "member");
        }

        /// <summary>
        /// The reference to the assignable member as a code expression. This
        /// reference will be used to generate code that can set the member.
        /// The reference to the property assumes the target object is
        /// <see cref="CodeDomMember.TheGenericInstancePropertyReference"/>.
        /// </summary>
        public override CodeExpression AssignableMemberReference
        {
            get { return _assignableMemberReference; }
        }

        /// <summary>
        /// Initializes the <see cref="CodeDomAssignableMember.MemberSetStatement"/>.
        /// Note to implementers: Base classes should invoke the base class 
        /// <see cref="Configure()"/> method when their 
        /// <see cref="AssignableMemberReference"/> is initialized.
        /// </summary>
        protected override void Configure()
        {
            // note that we don't configure the AssignableMemberReference if our  
            // Parent is not set to a CodeDomInstance because the property 
            // TheGenericInstancePropertyReference uses the CodeDomInstance 
            // Parent reference to generate the required code. 
            if (Parent != null && Parent is CodeDomInstance && _assignableMemberReference == null)
            {
                _assignableMemberReference =
                    new CodeFieldReferenceExpression(TheGenericInstancePropertyReference, Name);
                base.Configure();
            }
        }

        /// <summary>
        /// The backing field to <see cref="AssignableMemberReference"/>.
        /// </summary>
        CodeExpression _assignableMemberReference;
    }
}