OpenFrontIO/src/core/game/TeamAssignment.ts

import { PseudoRandom } from "../PseudoRandom";
import { simpleHash } from "../Util";
import { PlayerInfo, PlayerType, Team } from "./Game";

export function assignTeams(
  players: PlayerInfo[],
  teams: Team[],
): Map<PlayerInfo, Team | "kicked"> {
  const result = new Map<PlayerInfo, Team | "kicked">();
  const teamPlayerCount = new Map<Team, number>();

  // Group players by clan
  const clanGroups = new Map<string, PlayerInfo[]>();
  const noClanPlayers: PlayerInfo[] = [];

  // Sort players into clan groups or no-clan list
  for (const player of players) {
    if (player.clan) {
      if (!clanGroups.has(player.clan)) {
        clanGroups.set(player.clan, []);
      }
      clanGroups.get(player.clan)!.push(player);
    } else {
      noClanPlayers.push(player);
    }
  }

  const maxTeamSize = Math.ceil(players.length / teams.length);

  // Sort clans by size (largest first)
  const sortedClans = Array.from(clanGroups.entries()).sort(
    (a, b) => b[1].length - a[1].length,
  );

  // First, assign clan players
  for (const [_, clanPlayers] of sortedClans) {
    // Try to keep the clan together on the team with fewer players
    let team: Team | null = null;
    let teamSize = 0;
    for (const t of teams) {
      const p = teamPlayerCount.get(t) ?? 0;
      if (team !== null && teamSize <= p) continue;
      teamSize = p;
      team = t;
    }

    if (team === null) continue;

    for (const player of clanPlayers) {
      if (teamSize < maxTeamSize) {
        teamSize++;
        result.set(player, team);
      } else {
        result.set(player, "kicked");
      }
    }
    teamPlayerCount.set(team, teamSize);
  }

  // Then, assign non-clan players to balance teams
  let nationPlayers = noClanPlayers.filter(
    (player) => player.playerType === PlayerType.FakeHuman,
  );
  if (nationPlayers.length > 0) {
    // Shuffle only nations to randomize their team assignment
    const random = new PseudoRandom(simpleHash(nationPlayers[0].id));
    nationPlayers = random.shuffleArray(nationPlayers);
  }
  const otherPlayers = noClanPlayers.filter(
    (player) => player.playerType !== PlayerType.FakeHuman,
  );

  for (const player of otherPlayers.concat(nationPlayers)) {
    let team: Team | null = null;
    let teamSize = 0;
    for (const t of teams) {
      const p = teamPlayerCount.get(t) ?? 0;
      if (team !== null && teamSize <= p) continue;
      teamSize = p;
      team = t;
    }
    if (team === null) continue;
    teamPlayerCount.set(team, teamSize + 1);
    result.set(player, team);
  }

  return result;
}