Refactor AI summarizer client initialization to include MongoDB manager and add statistics endpoint

- Updated `InitAISummarizerClient` to accept `mongoManager` for tracking translation success.
- Introduced new `Statistics` endpoint in the dashboard to fetch scraping and translation statistics.
- Enhanced `TranslationWorker` to utilize the new success counter for tracking successful translations.
- Added necessary data structures and query forms for statistics reporting.

This refactor improves the tracking of AI translation success and provides new insights through the dashboard statistics.

pkg/mongo/counter.go

@@ -0,0 +1,130 @@
+package mongo
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"time"
+
+	"go.mongodb.org/mongo-driver/v2/bson"
+	mongodriver "go.mongodb.org/mongo-driver/v2/mongo"
+	"go.mongodb.org/mongo-driver/v2/mongo/options"
+)
+
+const (
+	metricsCountersCollection                   = "metrics_counters"
+	AITranslationSuccessCounterKey              = "ai_translation_successful_requests"
+	AITranslationSuccessCounterKeyDailyJob      = "ai_translation_successful_requests_daily_job"
+	AITranslationSuccessCounterKeyManualTrigger = "ai_translation_successful_requests_manual_trigger"
+)
+
+// Counter provides atomic increment/read operations for named metrics stored in MongoDB.
+type Counter struct {
+	mongo *ConnectionManager
+}
+
+// NewCounter creates a counter backed by the metrics_counters collection.
+func NewCounter(mongo *ConnectionManager) *Counter {
+	return &Counter{mongo: mongo}
+}
+
+// Increment atomically increments the counter identified by key and returns the new value.
+func (c *Counter) Increment(ctx context.Context, key string) (int64, error) {
+	if key == "" {
+		return 0, fmt.Errorf("mongo counter: key is required")
+	}
+
+	var res struct {
+		Count int64 `bson:"count"`
+	}
+	err := c.mongo.GetCollection(metricsCountersCollection).FindOneAndUpdate(
+		ctx,
+		bson.M{"_id": key},
+		bson.M{
+			"$inc":         bson.M{"count": 1},
+			"$set":         bson.M{"updated_at": time.Now().Unix()},
+			"$setOnInsert": bson.M{"_id": key},
+		},
+		options.FindOneAndUpdate().SetUpsert(true).SetReturnDocument(options.After),
+	).Decode(&res)
+	if err != nil {
+		return 0, fmt.Errorf("mongo counter increment %q: %w", key, err)
+	}
+
+	return res.Count, nil
+}
+
+// Get returns the current value of the counter identified by key (0 when missing).
+func (c *Counter) Get(ctx context.Context, key string) (int64, error) {
+	if key == "" {
+		return 0, fmt.Errorf("mongo counter: key is required")
+	}
+
+	var doc struct {
+		Count int64 `bson:"count"`
+	}
+	err := c.mongo.GetCollection(metricsCountersCollection).FindOne(ctx, bson.M{"_id": key}).Decode(&doc)
+	if err != nil {
+		if errors.Is(err, mongodriver.ErrNoDocuments) {
+			return 0, nil
+		}
+		return 0, fmt.Errorf("mongo counter get %q: %w", key, err)
+	}
+
+	return doc.Count, nil
+}
+
+// AITranslationSuccessCallback returns a callback that increments successful AI translation counters.
+func AITranslationSuccessCallback(counter *Counter) func(ctx context.Context, source string) error {
+	return func(ctx context.Context, source string) error {
+		if _, err := counter.Increment(ctx, AITranslationSuccessCounterKey); err != nil {
+			return err
+		}
+		if _, err := counter.Increment(ctx, AITranslationSuccessDailyCounterKey(time.Now().UTC())); err != nil {
+			return err
+		}
+		if key := AITranslationSuccessCounterKeyForSource(source); key != "" {
+			_, err := counter.Increment(ctx, key)
+			return err
+		}
+		return nil
+	}
+}
+
+// AITranslationSuccessDailyCounterKey returns the metrics key for successful translations on a given UTC day.
+func AITranslationSuccessDailyCounterKey(day time.Time) string {
+	return AITranslationSuccessCounterKey + "_day:" + day.UTC().Format("2006-01-02")
+}
+
+// GetDailyCounts returns counter values for each UTC day from start through end inclusive.
+func (c *Counter) GetDailyCounts(ctx context.Context, startDay, endDay time.Time) (map[string]int64, error) {
+	startDay = time.Date(startDay.Year(), startDay.Month(), startDay.Day(), 0, 0, 0, 0, time.UTC)
+	endDay = time.Date(endDay.Year(), endDay.Month(), endDay.Day(), 0, 0, 0, 0, time.UTC)
+	if endDay.Before(startDay) {
+		return map[string]int64{}, nil
+	}
+
+	counts := make(map[string]int64)
+	for day := startDay; !day.After(endDay); day = day.AddDate(0, 0, 1) {
+		date := day.Format("2006-01-02")
+		value, err := c.Get(ctx, AITranslationSuccessDailyCounterKey(day))
+		if err != nil {
+			return nil, err
+		}
+		counts[date] = value
+	}
+
+	return counts, nil
+}
+
+// AITranslationSuccessCounterKeyForSource maps a request source to its metrics counter key.
+func AITranslationSuccessCounterKeyForSource(source string) string {
+	switch source {
+	case "daily_job":
+		return AITranslationSuccessCounterKeyDailyJob
+	case "manual_trigger":
+		return AITranslationSuccessCounterKeyManualTrigger
+	default:
+		return ""
+	}
+}