feat: enforce ranked admission policy

server/domain/ranked.go

@@ -0,0 +1,32 @@
+package domain
+
+import "fmt"
+
+type RankedParticipant struct {
+	PlayerID   string
+	SteamID    string
+	PartyID    string
+	IsBot      bool
+	IsBackfill bool
+}
+
+type RankedArena struct {
+	RandomEnabled bool
+	ElevatedGoals bool
+}
+
+func ValidateRankedAdmission(participants []RankedParticipant, arena RankedArena) error {
+	if len(participants) != 6 || !arena.RandomEnabled || arena.ElevatedGoals {
+		return fmt.Errorf("ranked admission requirements not met")
+	}
+	seenPlayers := make(map[string]bool, len(participants))
+	seenSteam := make(map[string]bool, len(participants))
+	for _, participant := range participants {
+		if participant.PlayerID == "" || participant.SteamID == "" || participant.PartyID != "" || participant.IsBot || participant.IsBackfill || seenPlayers[participant.PlayerID] || seenSteam[participant.SteamID] {
+			return fmt.Errorf("ranked requires six unique verified solo humans")
+		}
+		seenPlayers[participant.PlayerID] = true
+		seenSteam[participant.SteamID] = true
+	}
+	return nil
+}