using System;
using System.Data;

namespace CoPackLibrary.DataAccessLayer
{
   public interface IQuery
   {
      void Prepare(IDbCommand command);
   }
   public interface IModifyQuery : IQuery
   {
      IQuery GetHistoryInsertUsing(DateTime updateDate);
   }
   public interface IResultQuery<ReturnType> : IQuery
   {
      ReturnType MapResult(IDataReader reader);
   }

   /******************************************************/
   /******************************************************/

   public static class Query
   {
      public static IQuery For(string sql)
      {
         return For(cmd => cmd.CommandText = sql);
      }

      public static IQuery For(Action<IDbCommand> prepare)
      {
         return new DynamicQuery(prepare);
      }

      /******************************************************/
      /******************************************************/

      public static IResultQuery<T> For<T>(string sql)
      {
         return For<T>(cmd => cmd.CommandText = sql);
      }

      public static IResultQuery<T> For<T>(IQuery query)
      {
         return For<T>(query.Prepare);
      }

      public static IResultQuery<T> For<T>(Action<IDbCommand> prepareMethod)
      {
         return new ScalarQuery<T>(prepareMethod);
      }

      /******************************************************/
      /******************************************************/

      public static IResultQuery<T> For<T>(string sql, Func<IDataReader, T> mappingMethod)
      {
         return For(cmd => cmd.CommandText = sql, mappingMethod);
      }

      public static IResultQuery<T> For<T>(Action<IDbCommand> prepareMethod, Func<IDataReader, T> mappingMethod)
      {
         return new ResultQuery<T>(prepareMethod, mappingMethod);
      }

      /******************************************************/
      /******************************************************/


      private class DynamicQuery : IQuery
      {
         public DynamicQuery(Action<IDbCommand> prepareMethod)
         {
            _prepareMethod = prepareMethod;
         }

         private readonly Action<IDbCommand> _prepareMethod;

         public void Prepare(IDbCommand command)
         {
            _prepareMethod(command);
         }
      }
      private class ScalarQuery<T> : IResultQuery<T>
      {
         public ScalarQuery(Action<IDbCommand> prepareMethod)
         {
            _prepareMethod = prepareMethod;
         }

         private readonly Action<IDbCommand> _prepareMethod;

         public void Prepare(IDbCommand command)
         {
            _prepareMethod(command);
         }

         public T MapResult(IDataReader reader)
         {
            return !reader.Read() ? default(T) : (T)Convert.ChangeType(reader[0], typeof(T));
         }
      }
      private class ResultQuery<T> : IResultQuery<T>
      {
         public ResultQuery(Action<IDbCommand> prepareMethod, Func<IDataReader, T> mappingMethod)
         {
            _prepareMethod = prepareMethod;
            _mappingMethod = mappingMethod;
         }

         private readonly Action<IDbCommand> _prepareMethod;
         private readonly Func<IDataReader, T> _mappingMethod;

         public void Prepare(IDbCommand command)
         {
            _prepareMethod(command);
         }

         public T MapResult(IDataReader reader)
         {
            return _mappingMethod(reader);
         }
      }
   }
}