Block.cs

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// 
//  Copyright 2010-2015 Deveel
// 
//    Licensed under the Apache License, Version 2.0 (the "License");
//    you may not use this file except in compliance with the License.
//    You may obtain a copy of the License at
// 
//        http://www.apache.org/licenses/LICENSE-2.0
// 
//    Unless required by applicable law or agreed to in writing, software
//    distributed under the License is distributed on an "AS IS" BASIS,
//    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//    See the License for the specific language governing permissions and
//    limitations under the License.
//

using System;
using System.Collections.Generic;

using Deveel.Data.Diagnostics;

namespace Deveel.Data {
    public class Block : IBlock {
        private IQuery query;

        public Block(IRequest request) {
            if (request == null)
                throw new ArgumentNullException("request");

            query = request as IQuery;
            
            Context = request.CreateBlockContext();
            Context.UnregisterService<IBlock>();
            Context.RegisterInstance<IBlock>(this);

            Parent = request as IBlock;
        }

        ~Block() {
            Dispose(false);
        }

        public IBlock Parent { get; private set; }

        public IBlock Next { get; set; }

        public IQuery Query {
            get {
                if (query != null)
                    return query;

                return Parent.Query;
            }
        }

        IEventSource IEventSource.ParentSource {
            get { return Parent; }
        }

        IEnumerable<KeyValuePair<string, object>> IEventSource.Metadata {
            get { return GetEventMetadata(); }
        }

        protected virtual IEnumerable<KeyValuePair<string, object>> GetEventMetadata() {
            return new KeyValuePair<string, object>[0];
        }

        public void Dispose() {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        protected virtual void Dispose(bool disposing) {
            if (disposing) {
                if (Context != null)
                    Context.Dispose();
            }

            Context = null;
            query = null;
        }

        public IBlockContext Context { get; private set; }

        IContext IEventSource.Context {
            get { return Context; }
        }

        IBlockContext IRequest.CreateBlockContext() {
            return Context.CreateBlockContext();
        }

        void IBlock.Execute(BlockExecuteContext context) {
            ExecuteBlock(context);
        }

        protected virtual void ExecuteBlock(BlockExecuteContext context) {
            // default implementation is an empty block, that does nothing
        }

        public virtual IBlock CreateBlock() {
            return new Block(this);
        }
    }
}