feat: promote accepted proposals from API

server/domain/formation.go

@@ -2,6 +2,7 @@ package domain
 
 import (
 	"fmt"
+	"sort"
 	"time"
 )
 
@@ -68,5 +69,34 @@ func PrepareProposal(id string, playlist Playlist, formation MatchFormation, ran
 	if err != nil {
 		return PreparedProposal{}, err
 	}
+	if formation.Selection.Region == "" || len(formation.Selection.Players) == 0 || formation.Selection.Players[0].ProtocolVersion < 1 {
+		return PreparedProposal{}, fmt.Errorf("formed match metadata is incomplete")
+	}
+	proposal.Region = formation.Selection.Region
+	proposal.Protocol = formation.Selection.Players[0].ProtocolVersion
+	for _, player := range formation.Selection.Players {
+		if player.ProtocolVersion != proposal.Protocol {
+			return PreparedProposal{}, fmt.Errorf("formed match has mixed protocols")
+		}
+	}
+	assignProposalSlots(&proposal, formation.Teams)
 	return PreparedProposal{Proposal: proposal, CasualLineup: lineup}, nil
 }
+
+func assignProposalSlots(proposal *Proposal, teams Teams) {
+	assign := func(team int, players []Candidate) {
+		ordered := append([]Candidate(nil), players...)
+		sort.Slice(ordered, func(i, j int) bool { return ordered[i].PlayerID < ordered[j].PlayerID })
+		for index, player := range ordered {
+			for participant := range proposal.Participants {
+				if proposal.Participants[participant].PlayerID == player.PlayerID {
+					proposal.Participants[participant].Team = team
+					proposal.Participants[participant].Slot = team*3 + index
+					break
+				}
+			}
+		}
+	}
+	assign(0, teams.Team0)
+	assign(1, teams.Team1)
+}