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using System;
using System.Data;
using System.Data.OleDb;
using System.Windows.Forms;

namespace ExLab
{


    partial class FMSSDB_NewDataSet
    {
        partial class FILESDataTable
        {
            public override void EndInit()
            {
                base.EndInit();  //super class
                FILESRowChanged += MyRowChanged;
            }
            //  static int i=0;
            OleDbDataReader reader;
            public int GetNextCluster(OleDbCommand cmd,int currentCluster)
            {

                cmd.CommandText = "SELECT NextCluster, ClusterStatus FROM CLUSTERS WHERE [#C]=" + currentCluster;
                reader = cmd.ExecuteReader();
                reader.Read();

                if ("E".Equals(reader[1]))
                {
                    reader.Close();
                    return -1;
                }
                Console.WriteLine(reader[0]);
                int nextCluster = (int)reader[0];
                reader.Close();
                return nextCluster;
            }

            public Tuple<int,int> GetClusterChain(OleDbCommand cmd,int currentCluster)
            {
                int noClusters=1;

                while (true)
                {
                    int next = GetNextCluster(cmd, currentCluster);
                    if (next == -1)
                        break;
                    ++noClusters;
                    currentCluster = next;
                }
                return new Tuple<int, int>(currentCluster, noClusters);
            }


            public void LinkClusterAAfterB(OleDbCommand cmd,int clusterA, int clusterB)
            {
                cmd.CommandText = "UPDATE CLUSTERS SET NextCluster=" + clusterA + ",CLUSTER STATUS='C' WHERE [#C]=" + clusterB;
                cmd.ExecuteNonQuery();
            }


            public void MyRowChanged(object sender, FILESRowChangeEvent ev){

                //Console.WriteLine("bla"+(i++));
                //Console.WriteLine(ev.Row.File);
                //Console.WriteLine(ev.Row[0]);
                String conString = "Provider = Microsoft.ACE.OLEDB.12.0; Data Source =| DataDirectory |\\FMSSDB_New.accdb";
                OleDbConnection con = new OleDbConnection(conString);
                OleDbCommand cmd = new OleDbCommand();
                OleDbDataReader reader;
                cmd.CommandType =CommandType.Text;
                cmd.Connection = con;

                con.Open();
                cmd.CommandText = "SELECT FileSize FROM FILES WHERE [#F]=" + ev.Row[0];
                reader = cmd.ExecuteReader();
                reader.Read();
                int oldFileSize = (int)((float)reader[0]);
                reader.Close();
                int newFileSize = (int)ev.Row.FileSize;
                if(newFileSize==oldFileSize)
                {
                    con.Close();
                    return;
                }

                cmd.CommandText = "SELECT FirstFreeCluster FROM DRIVES WHERE [#LD]=" + ev.Row.LogicDrive;
                reader = cmd.ExecuteReader();
                reader.Read();
                int firstFreeCluster = (int)reader[0];
                reader.Close();

                Tuple<int, int> r = GetClusterChain(cmd, firstFreeCluster);
                int noFreeClusters = r.Item2;
                int lastFreeCluster = r.Item1;

                r = GetClusterChain(cmd, ev.Row.FileStart);
                int noFileClusters = r.Item2;
                int lastFileCluster = r.Item1;

                //    Console.WriteLine(GetNextCluster(cmd, 169432));

                int clusterSize = 10240;
                int oldClusterNr = (oldFileSize / clusterSize)+1;
                int newClusterNr = (newFileSize / clusterSize) + 1;

                if (newClusterNr > noFileClusters + noFreeClusters)
                {
                    MessageBox.Show("Not enough free clusters for the new file size");
                    ev.Row.RejectChanges();
                    return;
                }

                LinkClusterAAfterB(cmd, firstFreeCluster, lastFileCluster);

                int currentCluster = lastFileCluster;

                for(int i = 0; i < newClusterNr - noFileClusters; i++)
                {
                    lastFileCluster = firstFreeCluster;
                    firstFreeCluster = GetNextCluster(cmd, firstFreeCluster);
                }


                cmd.CommandText = "UPADATE CLUSTERS SET NextCluster= NULL, ClusterStatus= 'E' WHERE [#C]=" + lastFileCluster;
                cmd.ExecuteNonQuery();

                cmd.CommandText = "UPADATE DRIVES SET FirstFreeCluster="+firstFreeCluster+" WHERE [#LD]=" + ev.Row.LogicDrive;
                cmd.ExecuteNonQuery();

                cmd.CommandText = "UPADATE FILES SET FileSize= " + newFileSize + " WHERE [#F]=" + ev.Row[0];
                cmd.ExecuteNonQuery();

                con.Close();
            }
            }
        }
    }