rating

core/identity/domain/services/RatingSnapshotCalculator.ts

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+import { UserRating } from '../value-objects/UserRating';
+import { RatingEvent } from '../entities/RatingEvent';
+
+/**
+ * Domain Service: RatingSnapshotCalculator
+ * 
+ * Pure, stateless calculator that derives a UserRating snapshot from events.
+ * STUB IMPLEMENTATION - will be evolved in future slices.
+ */
+export class RatingSnapshotCalculator {
+  /**
+   * Calculate UserRating snapshot from events
+   * 
+   * STUB: Currently creates a basic snapshot by summing deltas per dimension.
+   * Future: Will implement:
+   * - Confidence calculation based on sample size
+   * - Trend detection from recent events
+   * - Exponential moving averages
+   * - Calculator version tracking
+   */
+  static calculate(userId: string, events: RatingEvent[]): UserRating {
+    // Start with default UserRating
+    let snapshot = UserRating.create(userId);
+
+    // Group events by dimension
+    const eventsByDimension = events.reduce((acc, event) => {
+      const dimension = event.dimension.value;
+      if (!acc[dimension]) acc[dimension] = [];
+      acc[dimension].push(event);
+      return acc;
+    }, {} as Record<string, RatingEvent[]>);
+
+    // Apply events to each dimension
+    for (const [dimension, dimensionEvents] of Object.entries(eventsByDimension)) {
+      const totalDelta = dimensionEvents.reduce((sum, e) => sum + e.delta.value, 0);
+      const sampleSize = dimensionEvents.length;
+      
+      // Calculate new value (base 50 + delta)
+      const newValue = Math.max(0, Math.min(100, 50 + totalDelta));
+
+      // Update the appropriate dimension
+      if (dimension === 'driving') {
+        snapshot = snapshot.updateDriverRating(newValue, sampleSize);
+      } else if (dimension === 'adminTrust') {
+        snapshot = snapshot.updateAdminRating(newValue, sampleSize);
+      } else if (dimension === 'stewardTrust') {
+        snapshot = snapshot.updateStewardRating(newValue, sampleSize);
+      } else if (dimension === 'broadcasterTrust') {
+        // Future dimension - would need to add to UserRating
+        // For now, skip
+      }
+    }
+
+    return snapshot;
+  }
+}