[refactor] Conditionally implement interfaces in v1adapter (#6701)

## Which problem is this PR solving?
- Towards #6697

## Description of the changes
- This is a prequel to
#6699. This PR refactors the
`TraceReader` to conditionally propagate the implementations of
`storage.Purger` and `storage.SamplingStoreFactory`. Without this
change, the implementation of the aforementioned interfaces get lost
when we wrap a v1 `SpanReader`.

## How was this change tested?
- Added unit tests

## Checklist
- [x] I have read
https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md
- [x] I have signed all commits
- [x] I have added unit tests for the new functionality
- [x] I have run lint and test steps successfully
  - for `jaeger`: `make lint test`
  - for `jaeger-ui`: `npm run lint` and `npm run test`

---------

Signed-off-by: Mahad Zaryab <[email protected]>

internal/storage/v2/v1adapter/tracereader.go

@@ -11,6 +11,7 @@ import (
 	"go.opentelemetry.io/collector/pdata/ptrace"
 
 	"github.com/jaegertracing/jaeger-idl/model/v1"
+	"github.com/jaegertracing/jaeger/internal/storage/v1"
 	"github.com/jaegertracing/jaeger/internal/storage/v1/api/dependencystore"
 	"github.com/jaegertracing/jaeger/internal/storage/v1/api/spanstore"
 	"github.com/jaegertracing/jaeger/internal/storage/v2/api/depstore"
@@ -31,10 +32,35 @@ func GetV1Reader(reader tracestore.Reader) (spanstore.Reader, bool) {
 	return nil, false
 }
 
-func NewTraceReader(spanReader spanstore.Reader) *TraceReader {
-	return &TraceReader{
+func NewTraceReader(spanReader spanstore.Reader) tracestore.Reader {
+	traceReader := &TraceReader{
 		spanReader: spanReader,
 	}
+	var (
+		purger, isPurger   = spanReader.(storage.Purger)
+		sampler, isSampler = spanReader.(storage.SamplingStoreFactory)
+	)
+
+	switch {
+	case isPurger && isSampler:
+		return struct {
+			tracestore.Reader
+			storage.Purger
+			storage.SamplingStoreFactory
+		}{traceReader, purger, sampler}
+	case isPurger:
+		return struct {
+			tracestore.Reader
+			storage.Purger
+		}{traceReader, purger}
+	case isSampler:
+		return struct {
+			tracestore.Reader
+			storage.SamplingStoreFactory
+		}{traceReader, sampler}
+	default:
+		return traceReader
+	}
 }
 
 func (tr *TraceReader) GetTraces(

internal/storage/v2/v1adapter/tracereader_test.go

@@ -16,16 +16,80 @@ import (
 	"go.opentelemetry.io/collector/pdata/ptrace"
 
 	"github.com/jaegertracing/jaeger-idl/model/v1"
+	"github.com/jaegertracing/jaeger/internal/storage/v1"
 	dependencyStoreMocks "github.com/jaegertracing/jaeger/internal/storage/v1/api/dependencystore/mocks"
 	"github.com/jaegertracing/jaeger/internal/storage/v1/api/spanstore"
 	spanStoreMocks "github.com/jaegertracing/jaeger/internal/storage/v1/api/spanstore/mocks"
 	"github.com/jaegertracing/jaeger/internal/storage/v1/memory"
+	v1StorageMocks "github.com/jaegertracing/jaeger/internal/storage/v1/mocks"
 	"github.com/jaegertracing/jaeger/internal/storage/v2/api/depstore"
 	"github.com/jaegertracing/jaeger/internal/storage/v2/api/tracestore"
 	tracestoremocks "github.com/jaegertracing/jaeger/internal/storage/v2/api/tracestore/mocks"
 	"github.com/jaegertracing/jaeger/pkg/iter"
 )
 
+func TestNewTraceReader(t *testing.T) {
+	mockSpanReader := new(spanStoreMocks.Reader)
+	mockPurger := new(v1StorageMocks.Purger)
+	mockSamplingStoreFactory := new(v1StorageMocks.SamplingStoreFactory)
+
+	tests := []struct {
+		name               string
+		spanReader         spanstore.Reader
+		expectedInterfaces []any
+	}{
+		{
+			name:               "No extra interfaces",
+			spanReader:         mockSpanReader,
+			expectedInterfaces: []any{(*tracestore.Reader)(nil)},
+		},
+		{
+			name: "Implements Purger",
+			spanReader: struct {
+				spanstore.Reader
+				storage.Purger
+			}{mockSpanReader, mockPurger},
+			expectedInterfaces: []any{
+				(*tracestore.Reader)(nil),
+				(*storage.Purger)(nil),
+			},
+		},
+		{
+			name: "Implements SamplingStoreFactory",
+			spanReader: struct {
+				spanstore.Reader
+				storage.SamplingStoreFactory
+			}{mockSpanReader, mockSamplingStoreFactory},
+			expectedInterfaces: []any{
+				(*tracestore.Reader)(nil),
+				(*storage.SamplingStoreFactory)(nil),
+			},
+		},
+		{
+			name: "Implements both Purger and SamplingStoreFactory",
+			spanReader: struct {
+				spanstore.Reader
+				storage.Purger
+				storage.SamplingStoreFactory
+			}{mockSpanReader, mockPurger, mockSamplingStoreFactory},
+			expectedInterfaces: []any{
+				(*tracestore.Reader)(nil),
+				(*storage.Purger)(nil),
+				(*storage.SamplingStoreFactory)(nil),
+			},
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			traceReader := NewTraceReader(test.spanReader)
+			for _, i := range test.expectedInterfaces {
+				require.Implements(t, i, traceReader)
+			}
+		})
+	}
+}
+
 func TestGetV1Reader_NoError(t *testing.T) {
 	memstore := memory.NewStore()
 	traceReader := &TraceReader{