/**
 * Resolve the winner of a PICK_WINNER award given all votes and the chair's userId.
 * Logic: count votes per project. If one project has the most, it wins.
 * If tied, the chair's pick wins among the tied projects.
 */
export function resolveAwardWinner(
  votes: Array<{ userId: string; projectId: string }>,
  chairUserId: string
): string {
  if (votes.length === 0) {
    throw new Error('Cannot resolve winner with no votes')
  }

  // Tally votes per project
  const tally = new Map<string, number>()
  for (const v of votes) {
    tally.set(v.projectId, (tally.get(v.projectId) || 0) + 1)
  }

  const maxVotes = Math.max(...tally.values())
  const topProjects = [...tally.entries()]
    .filter(([, count]) => count === maxVotes)
    .map(([pid]) => pid)

  if (topProjects.length === 1) {
    return topProjects[0]
  }

  // Tie: chair's pick wins if among tied projects
  const chairVote = votes.find((v) => v.userId === chairUserId)
  if (chairVote && topProjects.includes(chairVote.projectId)) {
    return chairVote.projectId
  }

  // Chair voted for a non-tied project — pick alphabetically for stability
  return topProjects.sort()[0]
}