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
+}

server/domain/ranked_test.go

@@ -0,0 +1,39 @@
+package domain
+
+import "testing"
+
+func rankedParticipants() []RankedParticipant {
+	result := make([]RankedParticipant, 6)
+	for i := range result {
+		result[i] = RankedParticipant{PlayerID: string(rune('a' + i)), SteamID: string(rune('A' + i))}
+	}
+	return result
+}
+
+func TestRankedAdmissionRequiresSixUniqueVerifiedSoloHumansAndEligibleArena(t *testing.T) {
+	if err := ValidateRankedAdmission(rankedParticipants(), RankedArena{RandomEnabled: true}); err != nil {
+		t.Fatal(err)
+	}
+	cases := []struct {
+		name string
+		edit func([]RankedParticipant, *RankedArena)
+	}{
+		{"five players", func(p []RankedParticipant, _ *RankedArena) { p[5].PlayerID = "" }},
+		{"party", func(p []RankedParticipant, _ *RankedArena) { p[0].PartyID = "party-1" }},
+		{"bot", func(p []RankedParticipant, _ *RankedArena) { p[0].IsBot = true }},
+		{"backfill", func(p []RankedParticipant, _ *RankedArena) { p[0].IsBackfill = true }},
+		{"duplicate identity", func(p []RankedParticipant, _ *RankedArena) { p[1].SteamID = p[0].SteamID }},
+		{"random disabled", func(_ []RankedParticipant, a *RankedArena) { a.RandomEnabled = false }},
+		{"elevated arena", func(_ []RankedParticipant, a *RankedArena) { a.ElevatedGoals = true }},
+	}
+	for _, test := range cases {
+		t.Run(test.name, func(t *testing.T) {
+			participants := rankedParticipants()
+			arena := RankedArena{RandomEnabled: true}
+			test.edit(participants, &arena)
+			if err := ValidateRankedAdmission(participants, arena); err == nil {
+				t.Fatal("invalid ranked admission accepted")
+			}
+		})
+	}
+}