refactor: remove completed migration logic

internal/modules/lol/startup.go

@@ -24,9 +24,6 @@ const (
 // no-op.
 func InitStore(ctx context.Context, lolColl storage.Collection) error {
 	if mongoColl, ok := storage.MongoCollection(lolColl); ok {
-		if err := backfillMatchCacheFetchedAt(ctx, mongoColl); err != nil {
-			return err
-		}
 		if err := ensureMatchCacheTTLIndex(ctx, mongoColl); err != nil {
 			return err
 		}
@@ -34,26 +31,6 @@ func InitStore(ctx context.Context, lolColl storage.Collection) error {
 	return nil
 }
 
-func backfillMatchCacheFetchedAt(ctx context.Context, coll *mongo.Collection) error {
-	filter := bson.D{
-		{Key: "_id", Value: matchCacheIDRange()},
-		{Key: "fetchedAt", Value: bson.D{{Key: "$exists", Value: false}}},
-		{Key: "ts", Value: bson.D{
-			{Key: "$type", Value: "number"},
-			{Key: "$gt", Value: int64(0)},
-		}},
-	}
-	update := mongo.Pipeline{
-		bson.D{{Key: "$set", Value: bson.D{
-			{Key: "fetchedAt", Value: bson.D{{Key: "$toDate", Value: "$ts"}}},
-		}}},
-	}
-	if _, err := coll.UpdateMany(ctx, filter, update); err != nil {
-		return fmt.Errorf("lol match cache fetchedAt backfill: %w", err)
-	}
-	return nil
-}
-
 func ensureMatchCacheTTLIndex(ctx context.Context, coll *mongo.Collection) error {
 	model := mongo.IndexModel{
 		Keys: bson.D{{Key: "fetchedAt", Value: 1}},

internal/modules/lol/startup_mongo_test.go

@@ -41,48 +41,10 @@ func TestInitStore_MongoCreatesMatchCacheTTLIndex(t *testing.T) {
 		t.Fatal("lol collection is not Mongo-backed")
 	}
 
-	fetchedAt := time.Date(2026, 5, 9, 5, 0, 0, 0, time.UTC)
-	if _, err := rawLolColl.InsertMany(ctx, []any{
-		bson.M{
-			"_id":       "matches:2026-05-09T00:00:00Z:2026-05-10T00:00:00Z",
-			"version":   int64(1),
-			"updatedAt": time.Now().UTC(),
-			"ts":        fetchedAt.UnixMilli(),
-			"events":    bson.A{},
-		},
-		bson.M{
-			"_id":         "subscribers",
-			"version":     int64(1),
-			"updatedAt":   time.Now().UTC(),
-			"ts":          fetchedAt.UnixMilli(),
-			"subscribers": bson.A{},
-		},
-	}); err != nil {
-		t.Fatalf("seed legacy docs: %v", err)
-	}
-
 	if err := InitStore(ctx, lolColl); err != nil {
 		t.Fatalf("InitStore: %v", err)
 	}
 
-	var matchDoc struct {
-		FetchedAt time.Time `bson:"fetchedAt"`
-	}
-	if err := rawLolColl.FindOne(ctx, bson.M{"_id": "matches:2026-05-09T00:00:00Z:2026-05-10T00:00:00Z"}).Decode(&matchDoc); err != nil {
-		t.Fatalf("load backfilled match doc: %v", err)
-	}
-	if !matchDoc.FetchedAt.Equal(fetchedAt) {
-		t.Fatalf("backfilled fetchedAt = %s, want %s", matchDoc.FetchedAt, fetchedAt)
-	}
-
-	var subscriberDoc bson.M
-	if err := rawLolColl.FindOne(ctx, bson.M{"_id": "subscribers"}).Decode(&subscriberDoc); err != nil {
-		t.Fatalf("load subscriber doc: %v", err)
-	}
-	if _, ok := subscriberDoc["fetchedAt"]; ok {
-		t.Fatalf("subscriber doc was backfilled with fetchedAt: %#v", subscriberDoc)
-	}
-
 	cur, err := rawLolColl.Indexes().List(ctx)
 	if err != nil {
 		t.Fatalf("list indexes: %v", err)

internal/modules/lol/subscribers.go

@@ -2,7 +2,6 @@ package lol
 
 import (
 	"context"
-	"encoding/json"
 	"errors"
 	"fmt"
 
@@ -36,15 +35,6 @@ type SubscriberStore = storage.DocStore[subscribersDoc]
 
 // listSubscribers returns the current subscriber list, or an empty slice
 // if none have ever subscribed.
-//
-// Decoder accepts two shapes for forward-compatibility with rows written
-// before topic-aware subscriptions existed:
-//   - current: [{"chat_id":123,"thread_id":7}, ...]
-//   - legacy:  [123, 456, ...]   (decoded with ThreadID = 0)
-//
-// The decoder handles legacy rows indefinitely; any successful add/remove
-// rewrites the slot in the new shape, but a no-op duplicate add leaves the
-// legacy bytes in place — that's fine, the fallback path stays correct.
 func listSubscribers(ctx context.Context, store SubscriberStore) ([]Subscriber, error) {
 	doc, _, err := store.Get(ctx, subscribersKey)
 	switch {
@@ -59,25 +49,6 @@ func listSubscribers(ctx context.Context, store SubscriberStore) ([]Subscriber,
 	return nil, nil
 }
 
-// listSubscribersLegacy decodes a raw JSON byte slice that may be either the
-// current [{chat_id,thread_id}] shape or the legacy [int64] shape. Used by
-// the legacy-migration path when a key was written by an older version.
-func listSubscribersLegacy(raw []byte) ([]Subscriber, error) {
-	var subs []Subscriber
-	if err := json.Unmarshal(raw, &subs); err == nil {
-		return subs, nil
-	}
-	var legacy []int64
-	if err := json.Unmarshal(raw, &legacy); err != nil {
-		return nil, fmt.Errorf("lol listSubscribers decode: %w", err)
-	}
-	out := make([]Subscriber, len(legacy))
-	for i, id := range legacy {
-		out[i] = Subscriber{ChatID: id}
-	}
-	return out, nil
-}
-
 // addSubscriber appends (chatID, threadID) if that exact pair is absent.
 // Returns true on first-add, false when already subscribed (idempotent).
 //

internal/modules/lol/subscribers_test.go

@@ -2,7 +2,6 @@ package lol
 
 import (
 	"context"
-	"encoding/json"
 	"testing"
 
 	"github.com/tiennm99/miti99bot/internal/storage"
@@ -130,10 +129,7 @@ func TestSubscribers_RemoveAllForChat(t *testing.T) {
 	}
 }
 
-// TestSubscribers_LegacyDecode locks in backward-compat reads of rows
-// written before topic-aware subscriptions (raw []int64 JSON). The legacy
-// helper decodes both shapes independently of the store.
-func TestSubscribers_LegacyDecode(t *testing.T) {
+func TestSubscribers_CurrentShapeRoundTrip(t *testing.T) {
 	ctx := context.Background()
 	store := newSubscriberStore()
 
@@ -157,32 +153,7 @@ func TestSubscribers_LegacyDecode(t *testing.T) {
 		}
 	}
 
-	// Verify the legacy JSON helper handles the old []int64 shape.
-	legacyRaw := []byte(`[11,22,33]`)
-	legacySubs, err := listSubscribersLegacy(legacyRaw)
-	if err != nil {
-		t.Fatalf("listSubscribersLegacy: %v", err)
-	}
-	if len(legacySubs) != 3 {
-		t.Fatalf("legacy decode length = %d, want 3", len(legacySubs))
-	}
-	for i, s := range legacySubs {
-		if s != want[i] {
-			t.Errorf("legacy[%d]: got %v, want %v", i, s, want[i])
-		}
-	}
-
-	// Verify the legacy helper also handles the current [{chat_id,...}] shape.
-	currentRaw, _ := json.Marshal(currentSubs)
-	currentDecoded, err := listSubscribersLegacy(currentRaw)
-	if err != nil {
-		t.Fatalf("listSubscribersLegacy (current shape): %v", err)
-	}
-	if len(currentDecoded) != 3 {
-		t.Fatalf("current shape via legacy helper = %d, want 3", len(currentDecoded))
-	}
-
-	// Next mutation rewrites in the new shape — verify subscribers wrap correctly.
+	// Next mutation verifies subscribers wrap correctly.
 	if _, err := addSubscriber(ctx, store, 44, 7); err != nil {
 		t.Fatal(err)
 	}