make use of the store optional

cmd/any2anexoj-cli/main.go

@@ -71,7 +71,7 @@ func run(ctx context.Context) error {
 	}
 
 	eg.Go(func() error {
-		return internal.BuildReport(ctx, reader, writer, selector)
+		return internal.BuildReport(ctx, reader, writer, internal.WithSelector(selector))
 	})
 
 	err = eg.Wait()

internal/ephemeral_store.go

@@ -0,0 +1,12 @@
+package internal
+
+// EphemeralStore loads an empty state and discards everything on save
+type EphemeralStore struct{}
+
+func (EphemeralStore) Load() (map[string]*FillerQueue, error) {
+	return make(map[string]*FillerQueue), nil
+}
+
+func (EphemeralStore) Save(map[string]*FillerQueue) error {
+	return nil
+}

internal/report.go

@@ -51,13 +51,52 @@ type ReportWriter interface {
 	Write(context.Context, ReportItem) error
 }
 
+type optionals struct {
+	selector Selector
+	store    Store
+}
+
+func applyOptions(defaults optionals, opts []Option) optionals {
+	for _, opt := range opts {
+		opt(&defaults)
+	}
+	return defaults
+}
+
+type Option func(*optionals)
+
 // Selector returns true if a record should be selected for processing, false otherwise.
 type Selector func(Record) bool
 
+func WithSelector(s Selector) Option {
+	return func(o *optionals) {
+		o.selector = s
+	}
+}
+
+type Store interface {
+	Load() (map[string]*FillerQueue, error)
+	Save(map[string]*FillerQueue) error
+}
+
+func WithStore(s Store) Option {
+	return func(o *optionals) {
+		o.store = s
+	}
+}
+
 // BuildReport reads records from a RecordReader and, if the record passes the Selector, it is
 // processed into the ReportWriter.
-func BuildReport(ctx context.Context, reader RecordReader, writer ReportWriter, sel Selector) error {
-	buys := make(map[string]*FillerQueue)
+func BuildReport(ctx context.Context, reader RecordReader, writer ReportWriter, options ...Option) error {
+	optionals := applyOptions(optionals{
+		selector: Any(),
+		store:    EphemeralStore{},
+	}, options)
+
+	buys, err := optionals.store.Load()
+	if err != nil {
+		return fmt.Errorf("loading state: %w", err)
+	}
 
 	var buysCount, sellsCount int64
 	var lastTimestamp time.Time
@@ -79,6 +118,11 @@ func BuildReport(ctx context.Context, reader RecordReader, writer ReportWriter,
 			rec, err := reader.ReadRecord(ctx)
 			if err != nil {
 				if errors.Is(err, io.EOF) {
+					err = optionals.store.Save(buys)
+					if err != nil {
+						return fmt.Errorf("saving state: %w", err)
+					}
+
 					return nil
 				}
 				return err
@@ -98,21 +142,18 @@ func BuildReport(ctx context.Context, reader RecordReader, writer ReportWriter,
 				buys[rec.Symbol()] = buyQueue
 			}
 
-			err = processRecord(ctx, buyQueue, rec, sel, writer)
+			err = processRecord(ctx, buyQueue, rec, optionals.selector, writer)
 			if err != nil {
 				return fmt.Errorf("processing record: %w", err)
 			}
-
 		}
 	}
+
+	return nil
 }
 
 // processRecord either adds buys to the queue or consumes buys from the queue when processing a
 // sell record.
-//
-// NOTE: Selectors are only applied when processing sell records for performance reasons. It's much
-// cheaper to just accumulate buys and only actually inspect any records once a sell happens. This
-// avoids potential network requests to for every single record.
 func processRecord(ctx context.Context, q *FillerQueue, rec Record, sel Selector, writer ReportWriter) error {
 	slog.Debug(
 		"Report: processing record",
@@ -122,6 +163,9 @@ func processRecord(ctx context.Context, q *FillerQueue, rec Record, sel Selector
 
 	switch rec.Kind() {
 	case KindBuy:
+		// Selectors are only applied when processing sell records for performance reasons. It's much
+		// cheaper to just accumulate buys and only actually inspect any records once a sell happens. This
+		// avoids potential network requests to for every single record.
 		q.Push(NewFiller(rec))
 
 	case KindSell:
@@ -142,7 +186,8 @@ func processRecord(ctx context.Context, q *FillerQueue, rec Record, sel Selector
 				return ErrInsufficientBoughtVolume
 			}
 
-			// Since we don't apply selectors while processing buys we need to apply them here.
+			// Since we don't apply selectors while processing buys we need to apply them here, befre we
+			// actually use them.
 			if !sel(buy) {
 				continue
 			}

internal/report_test.go

@@ -43,7 +43,7 @@ func TestBuildReport(t *testing.T) {
 		Taxes:         decimal.Decimal{},
 	})).Times(1)
 
-	gotErr := internal.BuildReport(t.Context(), reader, writer, internal.Any())
+	gotErr := internal.BuildReport(t.Context(), reader, writer)
 	if gotErr != nil {
 		t.Fatalf("got unexpected err: %v", gotErr)
 	}