// YoutubePlaylistLinkHandlerFactory — accepts:
//   * https://www.youtube.com/playlist?list=<PLid>
//   * https://www.youtube.com/watch?v=...&list=<PLid>
//   * https://music.youtube.com/playlist?list=<PLid>
//
// YT playlist IDs prefix:
//   * PL  user-curated playlists
//   * RD  mix / radio
//   * OLAK5uy_  album / single
//   * LL   liked-videos (private — won't extract anonymously)
//   * WL   watch-later (private)
//   * UU   uploads (auto-generated per channel)

use url::Url;

use crate::youtube::linkhandler::{host_is_youtube, LinkError};

pub fn extract_playlist_id(url_str: &str) -> Result<String, LinkError> {
    let url = Url::parse(url_str)
        .map_err(|e| LinkError::InvalidUrl(format!("{url_str}: {e}")))?;
    let host = url
        .host_str()
        .ok_or_else(|| LinkError::InvalidUrl("no host".into()))?;
    if !host_is_youtube(host) {
        return Err(LinkError::UnsupportedHost(host.into()));
    }
    url.query_pairs()
        .find(|(k, _)| k == "list")
        .map(|(_, v)| v.into_owned())
        .filter(|s| !s.is_empty())
        .ok_or_else(|| LinkError::MissingId(url_str.into()))
}

pub fn playlist_url(playlist_id: &str) -> String {
    format!("https://www.youtube.com/playlist?list={playlist_id}")
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn standalone_playlist() {
        let id = extract_playlist_id(
            "https://www.youtube.com/playlist?list=PLMC9KNkIncKtPzgY-5rmhvj7fax8fdxoj",
        )
        .unwrap();
        assert_eq!(id, "PLMC9KNkIncKtPzgY-5rmhvj7fax8fdxoj");
    }

    #[test]
    fn watch_with_list() {
        let id = extract_playlist_id(
            "https://www.youtube.com/watch?v=dQw4w9WgXcQ&list=PLxxx",
        )
        .unwrap();
        assert_eq!(id, "PLxxx");
    }

    #[test]
    fn music_subdomain() {
        let id = extract_playlist_id(
            "https://music.youtube.com/playlist?list=OLAK5uy_kFooBar",
        )
        .unwrap();
        assert_eq!(id, "OLAK5uy_kFooBar");
    }

    #[test]
    fn rejects_no_list_param() {
        let err = extract_playlist_id("https://www.youtube.com/watch?v=dQw4w9WgXcQ")
            .unwrap_err();
        assert!(matches!(err, LinkError::MissingId(_)));
    }

    #[test]
    fn rejects_non_youtube_host() {
        let err = extract_playlist_id("https://invidious.io/playlist?list=PLxxx").unwrap_err();
        assert!(matches!(err, LinkError::UnsupportedHost(_)));
    }
}