/************************************************************************************
 * 
 *  Umbraco Data Layer
 *  MIT Licensed work
 *  ©2008 Ruben Verborgh
 * 
 ***********************************************************************************/

using System;
using System.Data;
using System.Diagnostics;
using System.IO;
using System.Xml;
using umbraco.DataLayer.Utility;

namespace umbraco.DataLayer
{
    /// <summary>
    /// Abstract base class for SQL helpers that use parameters implementing IDataParameter.
    /// </summary>
    /// <typeparam name="P">SQL parameter data type.</typeparam>
    public abstract class SqlHelper<P> : ISqlHelper where P : IDataParameter
    {
        #region Private Fields

        /// <summary>The connection string that provides access to the SQL database.</summary>
        private readonly string m_ConnectionString;

        #endregion

        #region Protected Fields

        /// <summary>Utility that provides access to complex database actions.</summary>
        protected IUtilitySet m_Utility;

        #endregion

        #region Public Properties
        /// <summary>
        /// Gets the connection string that provides access to the SQL database.
        /// </summary>
        /// <value>The connection string that provides access to the SQL database.</value>
        public string ConnectionString
        {
            get { return m_ConnectionString; }
        }

        /// <summary>
        /// Gets the Umbraco utility associated with this SQL helper.
        /// </summary>
        /// <value>The utilities.</value>
        public IUtilitySet Utility
        {
            get { return m_Utility; }
        }
        #endregion

        #region Public Constructors
        /// <summary>
        /// Initializes a new instance of the <see cref="SqlHelper&lt;P&gt;"/> class.
        /// </summary>
        /// <param name="connectionString">The connection string.</param>
        public SqlHelper(string connectionString) : this(connectionString, null)
        { }

        /// <summary>
        /// Initializes a new instance of the <see cref="SqlHelper&lt;P&gt;"/> class.
        /// </summary>
        /// <param name="connectionString">The connection string, cannot be <c>null</c>.</param>
        /// <param name="utility">The utility, a default utility will be used if <c>null</c>.</param>
        public SqlHelper(string connectionString, IUtilitySet utility)
        {
            // Check arguments
            if (connectionString == null)
                throw new ArgumentNullException("connectionString");
            if (utility == null)
                utility = new DefaultUtility<SqlHelper<P>>(this);

            // Initialize member fields
            m_ConnectionString = connectionString;
            m_Utility = utility;

            #if DEBUG && DebugDataLayer
                // Log creation
                Trace.TraceInformation(GetType().Name + " created.");
            #endif
        }

        /// <summary>
        /// Releases unmanaged resources and performs other cleanup operations before the
        /// <see cref="SqlHelper&lt;P&gt;"/> is reclaimed by garbage collection.
        /// </summary>
        ~SqlHelper()
        {
            Dispose();
        }
        #endregion

        #region Protected Methods
        /// <summary>
        /// Performs necessary conversion on the SQL command prior to its execution.
        /// </summary>
        /// <param name="commandText">The command text.</param>
        /// <returns>The original command text. Inheriting classes can change this behavior.</returns>
        protected virtual string ConvertCommand(string commandText)
        {
            if (commandText == null)
                throw new ArgumentNullException("commandText");
            return commandText;
        }

        /// <summary>
        /// Performs necessary conversion on the parameters prior to its execution.
        /// </summary>
        /// <param name="parameters">The parameters. Expected to be of type IParameterContainer.</param>
        /// <returns>The parameters, converted to the raw types of their containers.</returns>
        protected virtual P[] ConvertParameters(IParameter[] parameters)
        {
            // Check arguments
            if (parameters == null)
                throw new ArgumentNullException("parameters");

            // Add raw types of parameters to an array
            P[] newParams = new P[parameters.Length];
            for (int index = 0; index < parameters.Length; index++)
            {
                // Get raw type out of container
                IParameterContainer<P> parameter = parameters[index] as IParameterContainer<P>;
                if (parameter == null)
                    throw new ArgumentException(
                        String.Format("Element {0} of parameters has the wrong type. Expected: IParameterContainer<{1}>. Received: {2}.",
                                       index,
                                       typeof(P).Name,
                                       (parameter==null ? "null" : parameter.GetType().Name)),
                        "parameters");
                newParams[index] = parameter.RawParameter;
            }
            return newParams;
        }

        /// <summary>Converts the scalar value to the given type.</summary>
        /// <typeparam name="T">Desired type of the value.</typeparam>
        /// <param name="scalar">A scalar returned by ExecuteScalar.</param>
        /// <returns>The scalar, converted to type T.</returns>
        protected virtual T ConvertScalar<T>(object scalar)
        {
            if (scalar == null || (scalar == DBNull.Value && !typeof(T).IsAssignableFrom(typeof(DBNull))))
                return default(T);

            switch(typeof(T).FullName)
            {
                case "System.Int32": return (T)(object)int.Parse(scalar.ToString());
                case "System.Int64": return (T)(object)long.Parse(scalar.ToString());
                default: return (T)scalar;
            }
        }
        #endregion

        #region ISqlHelper Members
        /// <summary>
        /// Escapes a string for use in an SQL query.
        /// </summary>
        /// <param name="value">The value.</param>
        /// <returns>The escaped value.</returns>
        /// <remarks>You should use SQL parameters instead.</remarks>
        public virtual string EscapeString(string value)
        {
            return string.IsNullOrEmpty(value) ? string.Empty : value.Replace("'", "''");
        }

        /// <summary>
        /// Creates a new parameter for use with this specific implementation of ISqlHelper.
        /// </summary>
        /// <param name="parameterName">Name of the parameter.</param>
        /// <param name="value">Value of the parameter.</param>
        /// <returns>A new parameter of the correct type.</returns>
        /// <remarks>Abstract factory pattern</remarks>
        public abstract IParameter CreateParameter(string parameterName, object value);

        /// <summary>
        /// Executes a command that returns a single value.
        /// </summary>
        /// <typeparam name="T">The type of the value.</typeparam>
        /// <param name="commandText">The command text.</param>
        /// <param name="parameters">The parameters.</param>
        /// <returns>The return value of the command.</returns>
        /// <exception cref="umbraco.DataLayer.SqlHelperException">If a data source error occurs.</exception>
        public T ExecuteScalar<T>(string commandText, params IParameter[] parameters)
        {
            string commandConverted = ConvertCommand(commandText);
            P[] parametersConverted = ConvertParameters(parameters);
            try
            {
                return ConvertScalar<T>(ExecuteScalar(commandConverted, parametersConverted));
            }
            catch (Exception e)
            {
                throw new SqlHelperException("ExecuteScalar", commandText, parameters, e);
            }
        }

        /// <summary>
        /// Executes a command and returns the number of rows affected.
        /// </summary>
        /// <param name="commandText">The command text.</param>
        /// <param name="parameters">The parameters.</param>
        /// <returns>
        /// The number of rows affected by the command.
        /// </returns>
        /// <exception cref="umbraco.DataLayer.SqlHelperException">If a data source error occurs.</exception>
        public int ExecuteNonQuery(string commandText, params IParameter[] parameters)
        {
            string commandConverted = ConvertCommand(commandText);
            P[] parametersConverted = ConvertParameters(parameters);
            try
            {
                return ExecuteNonQuery(commandConverted, parametersConverted);
            }
            catch (Exception e)
            {
                throw new SqlHelperException("ExecuteNonQuery", commandText, parameters, e);
            }
        }

        /// <summary>
        /// Executes a command and returns a records reader containing the results.
        /// </summary>
        /// <param name="commandText">The command text.</param>
        /// <param name="parameters">The parameters.</param>
        /// <returns>
        /// A data reader containing the results of the command.
        /// </returns>
        /// <exception cref="umbraco.DataLayer.SqlHelperException">If a data source error occurs.</exception>
        public IRecordsReader ExecuteReader(string commandText, params IParameter[] parameters)
        {
            string commandConverted = ConvertCommand(commandText);
            P[] parametersConverted = ConvertParameters(parameters);
            try
            {
                return ExecuteReader(commandConverted, parametersConverted);
            }
            catch (Exception e)
            {
                throw new SqlHelperException("ExecuteReader", commandText, parameters, e);
            }
        }

        /// <summary>
        /// Executes a command that returns an XML value.
        /// </summary>
        /// <param name="commandText">The command text.</param>
        /// <param name="parameters">The parameters.</param>
        /// <returns>
        /// An XML reader containing the return value.
        /// </returns>
        /// <exception cref="umbraco.DataLayer.SqlHelperException">If a data source error occurs.</exception>
        public XmlReader ExecuteXmlReader(string commandText, params IParameter[] parameters)
        {
            string commandConverted = ConvertCommand(commandText);
            P[] parametersConverted = ConvertParameters(parameters);
            try
            {
                return ExecuteXmlReader(commandConverted, parametersConverted);
            }
            catch (Exception e)
            {
                throw new SqlHelperException("ExecuteXmlReader", commandText, parameters, e);
            }
        }
        #endregion

        #region Abstract Query Methods

        /// <summary>
        /// Executes a command that returns a single value.
        /// </summary>
        /// <param name="commandText">The command text.</param>
        /// <param name="parameters">The parameters.</param>
        /// <returns>The return value of the command.</returns>
        protected abstract object ExecuteScalar(string commandText, P[] parameters);

        /// <summary>
        /// Executes a command and returns the number of rows affected.
        /// </summary>
        /// <param name="commandText">The command text.</param>
        /// <param name="parameters">The parameters.</param>
        /// <returns>
        /// The number of rows affected by the command.
        /// </returns>
        protected abstract int ExecuteNonQuery(string commandText, params P[] parameters);

        /// <summary>
        /// Executes a command and returns a records reader containing the results.
        /// </summary>
        /// <param name="commandText">The command text.</param>
        /// <param name="parameters">The parameters.</param>
        /// <returns>
        /// A data reader containing the results of the command.
        /// </returns>
        protected abstract IRecordsReader ExecuteReader(string commandText, params P[] parameters);

        /// <summary>
        /// Executes a command that returns an XML value.
        /// </summary>
        /// <param name="commandText">The command text.</param>
        /// <param name="parameters">The parameters.</param>
        /// <returns>
        /// An XML reader containing the return value.
        /// </returns>
        protected virtual XmlReader ExecuteXmlReader(string commandText, params P[] parameters)
        {
            string xmlString = (string)ExecuteScalar(commandText, parameters);
            if (xmlString == null)
                throw new ArgumentException("The query didn't return a value.");

            return XmlReader.Create(new StringReader(xmlString));
        }

        #endregion

        #region IDisposable Members

        /// <summary>
        /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
        /// </summary>
        public virtual void Dispose()
        { }

        #endregion
    }
}