feat(recommendation): extend Score with SimilarityScore + SimilarityWeight

internal/recommendation/score_test.go

@@ -182,3 +182,37 @@ func TestScore_ContextualMatch_ZeroNoEffect(t *testing.T) {
 		t.Errorf("score-with-zero-ctx = %v, score-without = %v; should be equal", withCtx, withoutCtx)
 	}
 }
+
+func TestScore_SimilarityScore_PerfectMatchAtWeight2(t *testing.T) {
+	w := defaultWeights()
+	w.SimilarityWeight = 2.0
+	in := ScoringInputs{SimilarityScore: 1.0}
+	got := Score(in, w, time.Now(), fixedRNG(0.5))
+	// base 1.0 + recency 1.0 (never played) + similarity 2.0 = 4.0
+	want := 4.0
+	if math.Abs(got-want) > 1e-9 {
+		t.Errorf("score = %v, want %v", got, want)
+	}
+}
+
+func TestScore_SimilarityScore_HalfMatchAtWeight2(t *testing.T) {
+	w := defaultWeights()
+	w.SimilarityWeight = 2.0
+	in := ScoringInputs{SimilarityScore: 0.5}
+	got := Score(in, w, time.Now(), fixedRNG(0.5))
+	// base 1.0 + recency 1.0 + similarity 1.0 = 3.0
+	want := 3.0
+	if math.Abs(got-want) > 1e-9 {
+		t.Errorf("score = %v, want %v", got, want)
+	}
+}
+
+func TestScore_SimilarityScore_ZeroNoEffect(t *testing.T) {
+	wWithSim := defaultWeights()
+	wWithSim.SimilarityWeight = 2.0
+	withSim := Score(ScoringInputs{SimilarityScore: 0}, wWithSim, time.Now(), fixedRNG(0.5))
+	withoutSim := Score(ScoringInputs{}, defaultWeights(), time.Now(), fixedRNG(0.5))
+	if math.Abs(withSim-withoutSim) > 1e-9 {
+		t.Errorf("score-with-zero-sim = %v, score-without = %v; should be equal", withSim, withoutSim)
+	}
+}