feat: form matches from queue projections

server/domain/matcher.go

@@ -2,6 +2,7 @@ package domain
 
 import (
 	"fmt"
+	"math"
 	"sort"
 	"time"
 )
@@ -33,6 +34,33 @@ type Selection struct {
 	TotalWaitSeconds float64
 }
 
+type MatchFormation struct {
+	Selection Selection
+	Teams     Teams
+}
+
+// FormFromQueue is the queue-backed matcher boundary. Queue.Candidates owns
+// expiry and ordering; this method chooses the oldest projected candidate as
+// the anchor, then forms and partitions one deterministic match.
+func FormFromQueue(queue *Queue, size int, now time.Time) (MatchFormation, error) {
+	if queue == nil {
+		return MatchFormation{}, fmt.Errorf("queue is required")
+	}
+	candidates := queue.Candidates(now)
+	if len(candidates) == 0 {
+		return MatchFormation{}, fmt.Errorf("queue is empty")
+	}
+	selection, err := SelectCandidates(candidates[0], candidates[1:], size, now)
+	if err != nil {
+		return MatchFormation{}, err
+	}
+	teams, err := PartitionTeams(selection.Players)
+	if err != nil {
+		return MatchFormation{}, err
+	}
+	return MatchFormation{Selection: selection, Teams: teams}, nil
+}
+
 func RatingTolerance(waitSeconds float64) float64 {
 	if waitSeconds < 0 {
 		waitSeconds = 0
@@ -50,9 +78,11 @@ func SelectCandidates(anchor Candidate, candidates []Candidate, size int, now ti
 	}
 	pool := make([]Candidate, 0, len(candidates)+1)
 	seen := map[string]bool{}
+	seenPlayers := map[string]bool{}
 	add := func(candidate Candidate) {
-		if candidate.TicketID != "" && !seen[candidate.TicketID] {
+		if validCandidate(candidate) && !seen[candidate.TicketID] && !seenPlayers[candidate.PlayerID] {
 			seen[candidate.TicketID] = true
+			seenPlayers[candidate.PlayerID] = true
 			pool = append(pool, candidate)
 		}
 	}
@@ -97,6 +127,18 @@ func SelectCandidates(anchor Candidate, candidates []Candidate, size int, now ti
 	return best, nil
 }
 
+func validCandidate(candidate Candidate) bool {
+	if candidate.TicketID == "" || candidate.PlayerID == "" || candidate.EnqueuedAt.IsZero() || math.IsNaN(candidate.Rating) || math.IsInf(candidate.Rating, 0) {
+		return false
+	}
+	for region, rtt := range candidate.PredictedRTT {
+		if region != "EU" && region != "NA" || math.IsNaN(rtt) || math.IsInf(rtt, 0) || rtt < 0 {
+			return false
+		}
+	}
+	return len(candidate.PredictedRTT) > 0
+}
+
 func compatibleSet(players []Candidate, now time.Time) bool {
 	regions := commonRegions(players)
 	if len(regions) == 0 {

server/domain/matcher_test.go

@@ -66,3 +66,38 @@ func TestSelectCandidatesRejectsNoCommonRegion(t *testing.T) {
 		t.Fatal("selected players without a common <=100ms region")
 	}
 }
+
+func TestFormFromQueueUsesServerProjectionAndBalancesTeams(t *testing.T) {
+	now := time.Unix(100000, 0)
+	queue := NewQueue()
+	for _, id := range []string{"c", "a", "b", "d"} {
+		candidate := candidate(id, 1500, time.Second, 40, 45, now)
+		if _, err := queue.Create(candidate.PlayerID, candidate.TicketID, "create-key-"+id+"-123456", candidate, now.Add(-time.Duration(len(id))*time.Millisecond)); err != nil {
+			t.Fatal(err)
+		}
+	}
+	formation, err := FormFromQueue(queue, 4, now)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if formation.Selection.Players[0].TicketID != "a" || formation.Selection.Region != "EU" || len(formation.Teams.Team0) != 2 || len(formation.Teams.Team1) != 2 {
+		t.Fatalf("formation = %+v", formation)
+	}
+	seen := map[string]bool{}
+	for _, player := range append(formation.Teams.Team0, formation.Teams.Team1...) {
+		if seen[player.PlayerID] {
+			t.Fatalf("duplicate player in teams: %s", player.PlayerID)
+		}
+		seen[player.PlayerID] = true
+	}
+}
+
+func TestSelectCandidatesRejectsMalformedCandidateInsteadOfTrustingIt(t *testing.T) {
+	now := time.Unix(100000, 0)
+	anchor := candidate("a", 1500, 0, 40, 40, now)
+	malformed := candidate("b", 1500, 0, 40, 40, now)
+	malformed.PlayerID = anchor.PlayerID
+	if _, err := SelectCandidates(anchor, []Candidate{malformed}, 2, now); err == nil {
+		t.Fatal("duplicate player candidate accepted")
+	}
+}