support some filtering

internal/report.go

@@ -50,7 +50,12 @@ type ReportWriter interface {
 	Write(context.Context, ReportItem) error
 }
 
-func BuildReport(ctx context.Context, reader RecordReader, writer ReportWriter) error {
+// Selector returns true if a record should be selected for processing, false otherwise.
+type Selector func(Record) bool
+
+// BuildReport reads records from a RecordReader and, if the record passes the Selector, it is
+// processed into the report
+func BuildReport(ctx context.Context, reader RecordReader, writer ReportWriter, s Selector) error {
 	buys := make(map[string]*FillerQueue)
 
 	for {
@@ -66,6 +71,10 @@ func BuildReport(ctx context.Context, reader RecordReader, writer ReportWriter)
 				return err
 			}
 
+			if !s(rec) {
+				continue
+			}
+
 			buyQueue, ok := buys[rec.Symbol()]
 			if !ok {
 				buyQueue = new(FillerQueue)