using System;
using System.Collections.Generic;
using System.Text;
using System.Reflection;
using System.ComponentModel;

namespace LoreSoft.MathExpressions.Metadata
{
    /// <summary>
    /// A class to read attributes from type members.
    /// </summary>
    public static class AttributeReader
    {
        /// <summary>
        /// Gets the description from the <see cref="DescriptionAttribute"/> on an enum.
        /// </summary>
        /// <typeparam name="T">An enum type.</typeparam>
        /// <param name="instance">The value to get the description from.</param>
        /// <returns>The <see cref="DescriptionAttribute.Description"/> or the name of the instance.</returns>
        /// <seealso cref="DescriptionAttribute"/>
        public static string GetDescription<T>(T instance)
        {
            if (instance == null)
                throw new ArgumentNullException("instance");

            string result = instance.ToString();

            Type type = instance.GetType();
            MemberInfo[] members = type.GetMember(result);

            if (members == null || members.Length == 0)
                return result;
            
            return GetDescription(members[0]);
        }

        /// <summary>
        /// Gets the description from the <see cref="DescriptionAttribute"/> on a MemberInfo.
        /// </summary>
        /// <param name="info">The member info to look for the description.</param>
        /// <returns>The <see cref="DescriptionAttribute.Description"/> or the name of the member.</returns>
        /// <seealso cref="DescriptionAttribute"/>
        public static string GetDescription(MemberInfo info)
        {
            if (info == null)
                throw new ArgumentNullException("info");
            
            string result = info.Name;

            object[] attributes = info.GetCustomAttributes(typeof(DescriptionAttribute), false);
            if (attributes == null || attributes.Length == 0)
                return result;

            DescriptionAttribute description = attributes[0] as DescriptionAttribute;
            if (description == null || string.IsNullOrEmpty(description.Description))
                return result;

            return description.Description;
        }

        /// <summary>
        /// Gets the abbreviation from the <see cref="AbbreviationAttribute"/> on an enum.
        /// </summary>
        /// <typeparam name="T">An enum type.</typeparam>
        /// <param name="instance">The enum to get the abbreviation from.</param>
        /// <returns>The <see cref="AbbreviationAttribute.Text"/> or the name of the memeber.</returns>
        /// <seealso cref="AbbreviationAttribute"/>
        public static string GetAbbreviation<T>(T instance)
        {
            if (instance == null)
                throw new ArgumentNullException("instance");

            string result = instance.ToString();

            Type type = instance.GetType();
            MemberInfo[] members = type.GetMember(result);

            if (members == null || members.Length == 0)
                return result;

            return GetAbbreviation(members[0]);
        }

        /// <summary>
        /// Gets the abbreviation from the <see cref="AbbreviationAttribute"/> on a instance.
        /// </summary>
        /// <param name="info">The instance info look for the abbreviation.</param>
        /// <returns>The <see cref="AbbreviationAttribute.Text"/> or the name of the instance.</returns>
        /// <seealso cref="AbbreviationAttribute"/>
        public static string GetAbbreviation(MemberInfo info)
        {
            if (info == null)
                throw new ArgumentNullException("info");

            string result = info.Name;

            object[] attributes = info.GetCustomAttributes(typeof(AbbreviationAttribute), false);
            if (attributes == null || attributes.Length == 0)
                return result;

            AbbreviationAttribute abbreviation = attributes[0] as AbbreviationAttribute;
            if (abbreviation == null || string.IsNullOrEmpty(abbreviation.Text))
                return result;

            return abbreviation.Text;
        }
    }
}