feat: repair Redis candidates from durable source

server/store/candidate_projection_test.go

@@ -0,0 +1,48 @@
+package store
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/alicebob/miniredis/v2"
+	"github.com/cosmic-clash/cosmic-clash/server/domain"
+	"github.com/redis/go-redis/v9"
+)
+
+func TestCandidateProjectionRepairsPartialRedisStateFromDurableSource(t *testing.T) {
+	mini, err := miniredis.Run()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer mini.Close()
+	client := redis.NewClient(&redis.Options{Addr: mini.Addr()})
+	defer client.Close()
+	now := time.Unix(1000, 0).UTC()
+	candidate := domain.Candidate{TicketID: "repair-ticket", PlayerID: "repair-player", EnqueuedAt: now}
+	index := RedisCandidateIndex{Client: client, Prefix: "repair", TTL: time.Minute}
+	_, orderKey := index.keys()
+	if err := client.ZAdd(context.Background(), orderKey, redis.Z{Score: float64(now.UnixNano()), Member: candidate.TicketID}).Err(); err != nil {
+		t.Fatal(err)
+	}
+	projection := CandidateProjection{Index: index, Source: func(context.Context, time.Time) ([]domain.Candidate, error) {
+		return []domain.Candidate{candidate}, nil
+	}}
+	got, err := projection.Snapshot(context.Background(), now)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(got) != 1 || got[0].TicketID != candidate.TicketID {
+		t.Fatalf("repaired projection = %+v", got)
+	}
+}
+
+func TestCandidateProjectionDoesNotReturnCacheWhenRepairSourceFails(t *testing.T) {
+	index := RedisCandidateIndex{TTL: time.Minute}
+	projection := CandidateProjection{Index: index, Source: func(context.Context, time.Time) ([]domain.Candidate, error) {
+		return nil, context.DeadlineExceeded
+	}}
+	if _, err := projection.Snapshot(context.Background(), time.Unix(1000, 0)); err == nil {
+		t.Fatal("cache projection succeeded without a usable Redis/index source")
+	}
+}