protected static DataTable GetDiffgram()

in src/MIMConfigDocumenter/Documenter.cs [728:863]
101 lines of code
23 McCabe index (conditional complexity)

        protected static DataTable GetDiffgram(DataTable pilotTable, DataTable productionTable, int[] columnsIgnored)
        {
            Logger.Instance.WriteMethodEntry();

            DataTable diffgramTable = CreateDiffgramTable(pilotTable);

            try
            {
                if (columnsIgnored == null)
                {
                    columnsIgnored = new int[] { -1 };
                }

                // Unchanged rows in pilotTable: pilotRow PrimaryKey matches productionRow PrimaryKey AND pilotRow also matches productionRow:
                var unchangedPilotRows = from pilotRow in pilotTable.AsEnumerable()
                                         from productionRow in productionTable.AsEnumerable()
                                         where pilotTable.PrimaryKey.Aggregate(true, (match, keyColumn) => match && pilotRow[keyColumn].Equals(productionRow[keyColumn.Ordinal]))
                                               && pilotRow.ItemArray.Where((item, index) => !columnsIgnored.Contains(index)).SequenceEqual(productionRow.ItemArray.Where((item, index) => !columnsIgnored.Contains(index)))
                                         select pilotRow;

                // Unchanged rows in productionTable: pilotRow PrimaryKey matches productionRow PrimaryKey AND pilotRow also matches productionRow:
                var unchangedProductionRows = from pilotRow in pilotTable.AsEnumerable()
                                              from productionRow in productionTable.AsEnumerable()
                                              where pilotTable.PrimaryKey.Aggregate(true, (match, keyColumn) => match && pilotRow[keyColumn].Equals(productionRow[keyColumn.Ordinal]))
                                                    && pilotRow.ItemArray.Where((item, index) => !columnsIgnored.Contains(index)).SequenceEqual(productionRow.ItemArray.Where((item, index) => !columnsIgnored.Contains(index)))
                                              select productionRow;

                // Modified rows in pilotTable : pilotRow PrimaryKey matches productionRow PrimaryKey BUT pilotRow does not match productionRow:
                var modifiedPilotRows = from pilotRow in pilotTable.AsEnumerable()
                                        from productionRow in productionTable.AsEnumerable()
                                        where pilotTable.PrimaryKey.Aggregate(true, (match, keyColumn) => match && pilotRow[keyColumn].Equals(productionRow[keyColumn.Ordinal]))
                                              && !pilotRow.ItemArray.Where((item, index) => !columnsIgnored.Contains(index)).SequenceEqual(productionRow.ItemArray.Where((item, index) => !columnsIgnored.Contains(index)))
                                        select pilotRow;

                // Modified rows in productionTable : pilotRow PrimaryKey matches productionRow PrimaryKey BUT pilotRow does not match productionRow:
                var modifiedProductionRows = from pilotRow in pilotTable.AsEnumerable()
                                             from productionRow in productionTable.AsEnumerable()
                                             where pilotTable.PrimaryKey.Aggregate(true, (match, keyColumn) => match && pilotRow[keyColumn].Equals(productionRow[keyColumn.Ordinal]))
                                                 && !pilotRow.ItemArray.Where((item, index) => !columnsIgnored.Contains(index)).SequenceEqual(productionRow.ItemArray.Where((item, index) => !columnsIgnored.Contains(index)))
                                             select productionRow;

                // Added rows : rows in pilotTable not modified AND not unchanged
                var addedRows = pilotTable.AsEnumerable().Except(modifiedPilotRows, DataRowComparer.Default).Except(unchangedPilotRows, DataRowComparer.Default);

                // Deleted rows : rows in productionTable not modified AND not unchanged
                var deletedRows = productionTable.AsEnumerable().Except(modifiedProductionRows, DataRowComparer.Default).Except(unchangedProductionRows, DataRowComparer.Default);

                // Populate unchanged rows
                foreach (var row in unchangedPilotRows)
                {
                    var newRow = diffgramTable.NewRow();
                    newRow[Documenter.RowStateColumn] = DataRowState.Unchanged;
                    foreach (DataColumn column in pilotTable.Columns)
                    {
                        newRow[column.ColumnName] = row[column.ColumnName];
                    }

                    Documenter.AddRow(diffgramTable, newRow);
                }

                // Populate modified rows
                foreach (var row in modifiedPilotRows)
                {
                    // Match the unmodified version of the row via the PrimaryKey
                    ////var matchInProductionTable = modifiedProductionRows.Where(mondifiedProductionRow => productionTable.PrimaryKey.Aggregate(true, (match, keyColumn) => match && mondifiedProductionRow[keyColumn].Equals(row[keyColumn.Ordinal]))).First();
                    // revised query for perf improvements
                    var matchInProductionTable = (from productionRow in productionTable.AsEnumerable()
                                                  where productionTable.PrimaryKey.Aggregate(true, (match, keyColumn) => match && productionRow[keyColumn].Equals(row[keyColumn.Ordinal]))
                                                  select productionRow).First();
                    var newRow = diffgramTable.NewRow();
                    newRow[Documenter.RowStateColumn] = DataRowState.Modified;

                    // Set the row with the original values
                    foreach (DataColumn column in pilotTable.Columns)
                    {
                        if (!pilotTable.PrimaryKey.Contains(column))
                        {
                            newRow[Documenter.OldColumnPrefix + column.ColumnName] = matchInProductionTable[column.ColumnName];
                        }
                    }

                    // Set the modified values
                    foreach (DataColumn column in pilotTable.Columns)
                    {
                        newRow[column.ColumnName] = row[column.ColumnName];
                    }

                    Documenter.AddRow(diffgramTable, newRow);
                }

                // Populate added rows
                foreach (var row in addedRows)
                {
                    var newRow = diffgramTable.NewRow();
                    newRow[Documenter.RowStateColumn] = DataRowState.Added;
                    foreach (DataColumn column in pilotTable.Columns)
                    {
                        newRow[column.ColumnName] = row[column.ColumnName];
                    }

                    Documenter.AddRow(diffgramTable, newRow);
                }

                // Populate deleted rows
                foreach (var row in deletedRows)
                {
                    if (row.RowError == Documenter.VanityRow)
                    {
                        break;
                    }

                    var newRow = diffgramTable.NewRow();
                    newRow[Documenter.RowStateColumn] = DataRowState.Deleted;
                    foreach (DataColumn column in pilotTable.Columns)
                    {
                        if (!pilotTable.PrimaryKey.Contains(column))
                        {
                            newRow[column.ColumnName] = row[column.ColumnName]; // save the value in the orginal column as well in case it's used for Sorting table
                            newRow[Documenter.OldColumnPrefix + column.ColumnName] = row[column.ColumnName];
                        }
                        else
                        {
                            newRow[column.ColumnName] = row[column.ColumnName];
                        }
                    }

                    Documenter.AddRow(diffgramTable, newRow);
                }
            }
            finally
            {
                Logger.Instance.WriteMethodExit();
            }

            return diffgramTable;
        }