interface ReactionRow {
    emoji: string;
    comment_id: number | null;
    user_id: number;
}

export function buildReactionCounts(
    reactions: ReactionRow[],
    commentId: number | null,
    userId: number | undefined,
): { emoji: string; count: number; userReacted: boolean }[] {
    const filtered = reactions.filter((r) =>
        commentId === null ? r.comment_id === null : r.comment_id === commentId,
    );
    const map = new Map<string, { count: number; userReacted: boolean }>();
    for (const r of filtered) {
        const entry = map.get(r.emoji) ?? { count: 0, userReacted: false };
        entry.count++;
        if (userId !== undefined && r.user_id === userId)
            entry.userReacted = true;
        map.set(r.emoji, entry);
    }
    return [...map.entries()].map(([emoji, d]) => ({ emoji, ...d }));
}