/*
 * DbExtensions.cs
 * Author: Josh Bush (digitalbush.com)
 */

using System;
using System.Data;
using System.Collections.Generic;

namespace Bush.Data{    
    public static class DbExtensions{        

        private delegate T DbAction<T>(IDbCommand cmd);

        /// <summary>
        /// Helper method that does the connection and paramter setup.
        /// </summary>
        private static T ExecuteDbAction<T>(IDbConnection conn, string commandText, IDbDataParameter[] parameters,DbAction<T> dba){
            if (conn.State != ConnectionState.Open)
                conn.Open();
            using (IDbCommand cmd = conn.CreateCommand()){
                cmd.CommandText = commandText;
                cmd.Connection = conn;
                if (parameters != null){
                    foreach (IDbDataParameter p in parameters)
                        cmd.Parameters.Add(p);
                }
                return dba(cmd);
            } 
        }
        
        /// <summary>
        /// Extension method to execute a query and return the resulting records
        /// </summary>
        public static IEnumerable<IDataRecord> Query(this IDbConnection conn, string commandText, params IDbDataParameter[] parameters){
            return ExecuteDbAction<IEnumerable<IDataRecord>>(
                conn,
                commandText,
                parameters,
                queryHelper  //ugh, can't use yield inside of an anonymous method
            );            
        }
        public static IEnumerable<IDataRecord> Query(this IDbConnection conn, string commandText){
            return conn.Query(commandText, null);
        }
        private static IEnumerable<IDataRecord> queryHelper(IDbCommand cmd){
            using (IDataReader r = cmd.ExecuteReader()){
                while (r.Read())
                    yield return r;                
            }
        }

        /// <summary>
        /// Extension method to execute scalar query.
        /// </summary>
        public static object QueryValue(this IDbConnection conn, string commandText, params IDbDataParameter[] parameters){
            return ExecuteDbAction<object>(
             conn,
             commandText,
             parameters,
             cmd=>cmd.ExecuteScalar()
         );  
        }
        public static object QueryValue(this IDbConnection conn, string commandText){
            return conn.QueryValue(commandText, null);
        }

        /// <summary>
        /// Extension method to execute a non-query.
        /// </summary>        
        public static int Execute(this IDbConnection conn, string commandText, params IDbDataParameter[] parameters){
            return ExecuteDbAction<int>(
                conn,
                commandText,
                parameters,
                cmd => cmd.ExecuteNonQuery()
            );
        }
        public static int Execute(this IDbConnection conn, string commandText){
            return conn.Execute(commandText, null);
        }
    }
}