use anyhow::Result;
use feedsignal_db::Db;
use uuid::Uuid;

/// Subscribes to a feed by URL: registers it (or updates its title if
/// already subscribed) and does an immediate first fetch so the reader
/// isn't empty until the next scheduled poll. Returns the number of
/// articles pulled in on this fetch.
///
/// Fetches under a throwaway id before writing anything, so there's exactly
/// one write to the `feeds` table (`upsert_feed` is the single source of
/// truth for the real id — the existing one on a re-subscribe, a fresh one
/// otherwise) and no half-registered row left behind if the fetch fails
/// (e.g. the URL is well-formed but points at nothing, or the feed no
/// longer exists — `fetch_feed` surfaces both as an `Err` via
/// `error_for_status`/feed-rs parse failure, which becomes the error
/// message shown in the subscribe form).
pub async fn subscribe(db: Db, url: String) -> Result<usize> {
    anyhow::ensure!(!url.trim().is_empty(), "feed URL is required");
    let url = url.trim();

    let (title, mut articles) = feedsignal_feeds::fetch_feed(url, Uuid::new_v4()).await?;
    let feed_id = db.upsert_feed(url, &title).await?;
    for article in &mut articles {
        article.feed_id = feed_id;
    }

    let count = articles.len();
    for article in &articles {
        db.insert_article(article).await?;
    }
    Ok(count)
}