feat: add rebuildable candidate cache

server/store/candidates_test.go

@@ -0,0 +1,39 @@
+package store
+
+import (
+	"testing"
+	"time"
+
+	"github.com/cosmic-clash/cosmic-clash/server/domain"
+)
+
+func TestCandidateCacheRebuildRepairsLossAndKeepsDeterministicOrder(t *testing.T) {
+	now := time.Unix(1000, 0)
+	cache := NewCandidateCache()
+	candidates := []domain.Candidate{{TicketID: "ticket-b", PlayerID: "player-b", EnqueuedAt: now}, {TicketID: "ticket-a", PlayerID: "player-a", EnqueuedAt: now}}
+	if err := cache.Rebuild(candidates); err != nil {
+		t.Fatal(err)
+	}
+	cache.Remove("ticket-a")
+	if got := cache.Snapshot(now); len(got) != 1 || got[0].TicketID != "ticket-b" {
+		t.Fatalf("stale cache snapshot = %+v", got)
+	}
+	if err := cache.Rebuild(candidates); err != nil {
+		t.Fatal(err)
+	}
+	got := cache.Snapshot(now)
+	if len(got) != 2 || got[0].TicketID != "ticket-a" || got[1].TicketID != "ticket-b" {
+		t.Fatalf("repaired order = %+v", got)
+	}
+}
+
+func TestCandidateCacheRejectsInvalidOrDuplicateDurableProjection(t *testing.T) {
+	cache := NewCandidateCache()
+	if err := cache.Upsert(domain.Candidate{TicketID: "", PlayerID: "p", EnqueuedAt: time.Unix(1000, 0)}); err == nil {
+		t.Fatal("invalid candidate accepted")
+	}
+	candidate := domain.Candidate{TicketID: "ticket-a", PlayerID: "player-a", EnqueuedAt: time.Unix(1000, 0)}
+	if err := cache.Rebuild([]domain.Candidate{candidate, candidate}); err == nil {
+		t.Fatal("duplicate candidate accepted")
+	}
+}