import type { FactionId } from './catalog';
import { territory } from './board';
import { fighterCount } from './advisors';
import { presenceAt, type ForcePresence } from './force-presence';
import { ecazOccupancyIdentity, ecazOccupancyRelation } from './ecaz-occupy';
import { coalitionAllies, coalitionGroups, type CoalitionState } from './coalition-alliance';

/** Public board information only: a concealed No-Field contributes presence,
 * never its hidden denomination. Advisor groups do not fill strongholds. */
export type OccupancySeat = ForcePresence & {
  id: string;
  faction: FactionId;
  ally?: string | null;
  allySinceTurn?: number;
  advisors?: Readonly<Record<string, { lockedTurn?: number }>>;
};

/** Count the occupying factions after admitting a fighter from enteringId.
 * Ecaz and its reciprocal ally share a faction for board occupancy. Physical
 * forces and player ownership remain separate. This is not a combat side. */
export function occupyingFactionCount(
  players: readonly OccupancySeat[],
  to: string,
  enteringId?: string,
) {
  const where = { kind: 'territory' as const, id: to };
  const sides = new Set(
    players
      .filter((p) => fighterCount(p, to) > 0)
      .map((p) => ecazOccupancyIdentity(players, p.id, where).key),
  );
  if (enteringId)
    sides.add(ecazOccupancyIdentity(players, enteringId, where).key);
  return sides.size;
}

export function territoryEntryBlock(
  players: readonly OccupancySeat[],
  playerId: string,
  to: string,
  advisors = false,
  temporaryAlliedShipment = false,
  coalitionState?: CoalitionState,
): string | null {
  // Validate the complete identity roster even for an empty destination.
  ecazOccupancyIdentity(players, playerId, { kind: 'territory', id: to });
  const player = players.find((p) => p.id === playerId)!;
  const seats = players.map(p => ({ id: p.id, ally: p.ally ?? null, allySinceTurn: p.allySinceTurn }));
  if (coalitionState !== undefined) {
    const groups = coalitionGroups(seats, coalitionState);
    if (players.some(player => player.faction === 'ecaz') && groups.some(group => group.members.length >= 3))
      throw new Error('Three-member board rules do not yet support Ecaz.');
  }
  if (advisors) return null;
  const allies = coalitionState === undefined ? (player.ally ? [player.ally] : [])
    : coalitionAllies(seats, coalitionState, playerId);
  if (
    !temporaryAlliedShipment &&
    to !== 'polar_sink' &&
    allies.some(id => {
      const ally = players.find(p => p.id === id);
      return !!ally && presenceAt(ally, to) > 0 &&
    ecazOccupancyRelation(players, playerId, id, {
      kind: 'territory',
      id: to,
    }) !== 'ecazAlliance';
    })
  )
    return 'You cannot enter a territory occupied by your ally.';
  if (
    territory(to).type === 'stronghold' &&
    occupyingFactionCount(players, to, playerId) > 2
  )
    return 'A stronghold cannot contain three occupying factions.';
  return null;
}

/** Passing through a stronghold uses capacity, not allied destination rules. */
export function strongholdPathBlocked(
  players: readonly OccupancySeat[],
  playerId: string,
  to: string,
  advisors = false,
) {
  return (
    !advisors &&
    territory(to).type === 'stronghold' &&
    occupyingFactionCount(players, to, playerId) > 2
  );
}