Internal state persistence (#27)

Allow us to generate year over year reports without having to rerun everything from the beginning.

Co-authored-by: Natercio Moniz <[email protected]>

internal/report_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"reflect"
 	"testing"
 	"time"
 
@@ -43,7 +44,7 @@ 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)
 	}
@@ -98,3 +99,87 @@ func (m ReportItemMatcher) String() string {
 }
 
 var _ gomock.Matcher = (*ReportItemMatcher)(nil)
+
+// recordingStore is a test fake for internal.Store that records how many
+// times Load/Save were invoked and captures the maps it handed back so a
+// test can verify BuildReport wires the store correctly.
+type recordingStore struct {
+	loadCalls int
+	saveCalls int
+	loaded    map[string]*internal.FillerQueue
+	saved     map[string]*internal.FillerQueue
+}
+
+func (s *recordingStore) Load(_ context.Context) (map[string]*internal.FillerQueue, error) {
+	s.loadCalls++
+	if s.loaded == nil {
+		s.loaded = map[string]*internal.FillerQueue{}
+	}
+	return s.loaded, nil
+}
+
+func (s *recordingStore) Save(_ context.Context, queues map[string]*internal.FillerQueue) error {
+	s.saveCalls++
+	s.saved = queues
+	return nil
+}
+
+func TestBuildReport_WithStore(t *testing.T) {
+	now := time.Now()
+	ctrl := gomock.NewController(t)
+
+	reader := mocks.NewMockRecordReader(ctrl)
+	records := []internal.Record{
+		mockRecord(ctrl, 20.0, 10.0, internal.KindBuy, now),
+	}
+	reader.EXPECT().ReadRecord(gomock.Any()).DoAndReturn(func(ctx context.Context) (internal.Record, error) {
+		if len(records) > 0 {
+			r := records[0]
+			records = records[1:]
+			return r, nil
+		}
+		return nil, io.EOF
+	}).Times(2)
+
+	// No sells, so the writer must not be called.
+	writer := mocks.NewMockReportWriter(ctrl)
+
+	store := &recordingStore{}
+
+	gotErr := internal.BuildReport(t.Context(), reader, writer, internal.WithStore(store))
+	if gotErr != nil {
+		t.Fatalf("got unexpected err: %v", gotErr)
+	}
+
+	if store.loadCalls != 1 {
+		t.Errorf("Load calls: want 1 but got %d", store.loadCalls)
+	}
+	if store.saveCalls != 1 {
+		t.Errorf("Save calls: want 1 but got %d", store.saveCalls)
+	}
+
+	// Load must run before any records are read, so it has already been
+	// invoked by the time Save is observed.
+	if store.loadCalls < store.saveCalls {
+		t.Errorf("Load (%d) should be called at least as many times as Save (%d)", store.loadCalls, store.saveCalls)
+	}
+
+	if store.loaded == nil {
+		t.Fatalf("Load was not called or returned a nil map")
+	}
+	if store.saved == nil {
+		t.Fatalf("Save was not called or received a nil map")
+	}
+
+	// The map handed to Save must be the same map returned by Load so
+	// that buy-queue mutations done while processing flow into Save.
+	if reflect.ValueOf(store.loaded).Pointer() != reflect.ValueOf(store.saved).Pointer() {
+		t.Errorf("map passed to Save is not the same map returned by Load")
+	}
+
+	// Sanity: the buy record above should have populated an entry for the
+	// "TEST" symbol in the shared map.
+	if _, ok := store.saved["TEST"]; !ok {
+		t.Errorf("want saved map to contain symbol %q but it was missing", "TEST")
+	}
+}