use std::fmt::Write as _;

use super::Uuid;

/// Insert mention rows for a post (batch insert). Ignores duplicates.
#[tracing::instrument(skip_all)]
pub async fn insert_mentions<'e, E: sqlx::PgExecutor<'e>>(
    executor: E,
    post_id: Uuid,
    user_ids: &[Uuid],
) -> Result<(), sqlx::Error> {
    if user_ids.is_empty() {
        return Ok(());
    }
    // runtime-checked: dynamic SQL (cannot use compile-time macro)
    // Build multi-row INSERT: VALUES ($1, $2), ($1, $3), ... ON CONFLICT DO NOTHING
    let mut sql = String::from("INSERT INTO post_mentions (post_id, mentioned_user_id) VALUES ");
    for (i, _) in user_ids.iter().enumerate() {
        if i > 0 {
            sql.push_str(", ");
        }
        let _ = write!(sql, "($1, ${})", i + 2);
    }
    sql.push_str(" ON CONFLICT DO NOTHING");
    let mut query = sqlx::query(&sql).bind(post_id);
    for user_id in user_ids {
        query = query.bind(user_id);
    }
    query.execute(executor).await?;
    Ok(())
}