using System;
using System.Collections.Generic;
using JD.Collections.Extensions;
using JD.Kernel.StaticHelpers;
using JD.Reflection.MefImplementations.Metadata;

namespace JD.Reflection.MefImplementations.Model
{
    public class ExportDefinition
    {
        #region Constants

        public const string ExportTypeIdentityMetadataKey = "ExportTypeIdentity";
        public const string TypeIdentityMetadataKey = "TypeIdentity";

        #endregion

        #region Variables

        private readonly PartDefinition m_part;
        private readonly string m_contractName;
        private readonly IReadOnlyDictionary<string, object> m_metadata;

        #endregion

        #region Constructor

        static ExportDefinition()
        {
            // Some validation
            Throw.InvalidProgramIf(typeof (ITypeIdentityMetadata).GetProperty(TypeIdentityMetadataKey) == null, "Inconsistent TypeIdentity Key");
        }

        public ExportDefinition(PartDefinition part, string contractName, IDictionary<string, object> metadata)
        {
            Throw.IfNull(part, "part");
            Throw.IfEmpty(contractName, "contractName");

            m_part = part;
            m_contractName = contractName;
            m_metadata = metadata == null ? new Dictionary<string, object>() : (IReadOnlyDictionary<string, object>)metadata.AsReadOnly();
        }

        #endregion

        #region Properties

        public PartDefinition Part
        {
            get { return m_part; }
        }

        public string ContractName
        {
            get { return m_contractName; }
        }

        public IReadOnlyDictionary<string, object> Metadata
        {
            get { return m_metadata; }
        }

        public string ExportTypeIdentity
        {
            get
            {
                object value;
                m_metadata.TryGetValue(ExportTypeIdentityMetadataKey, out value);
                return (string)value;
            }
        }

        public string TypeIdentity
        {
            get
            {
                object value;
                m_metadata.TryGetValue(TypeIdentityMetadataKey, out value);
                return (string)value;
            }
        }

        #endregion

        #region Methods

        public virtual object CreatePart()
        {
            return Activator.CreateInstance(Part.Type);
        }

        public override string ToString()
        {
            return $"{TypeIdentity} (Contract = {ContractName})";
        }

        #endregion
    }
}