//! Accounts elsewhere on a profile (hub spec §6, oxygenhub#105): a
//! Bluesky handle, a Mastodon address and a GitHub username, checked and
//! normalised on the way in, and turned into links on the way out.

/// A Bluesky handle: a domain such as `andy.bsky.social`, with or
/// without a leading `@`. `None` when it is not one.
pub fn bluesky(input: &str) -> Option<String> {
    let h = input.trim().trim_start_matches('@').trim_end_matches('/');
    let h = h.strip_prefix("https://bsky.app/profile/").unwrap_or(h).to_ascii_lowercase();
    (!h.is_empty() && h.len() <= 253 && h.contains('.') && h.split('.').all(label_ok)).then_some(h)
}

/// A Mastodon address as `user@instance`, from `@user@instance`,
/// `user@instance` or `https://instance/@user`.
pub fn mastodon(input: &str) -> Option<String> {
    let s = input.trim().trim_end_matches('/');
    let (user, instance) = if let Some(rest) = s.strip_prefix("https://") {
        let (instance, user) = rest.split_once("/@")?;
        (user, instance)
    } else {
        s.trim_start_matches('@').split_once('@')?
    };
    let user_ok = !user.is_empty() && user.len() <= 64 && user.chars().all(|c| c.is_ascii_alphanumeric() || c == '_' || c == '.');
    let instance = instance.to_ascii_lowercase();
    let instance_ok = instance.contains('.') && instance.len() <= 253 && instance.split('.').all(label_ok);
    (user_ok && instance_ok).then(|| format!("{user}@{instance}"))
}

/// A GitHub username: 1 to 39 letters, digits and dashes, from the name
/// or a profile URL.
pub fn github(input: &str) -> Option<String> {
    let u = input.trim().trim_start_matches('@').trim_end_matches('/');
    let u = u.strip_prefix("https://github.com/").unwrap_or(u);
    let ok = !u.is_empty()
        && u.len() <= 39
        && u.chars().all(|c| c.is_ascii_alphanumeric() || c == '-')
        && !u.starts_with('-')
        && !u.ends_with('-');
    ok.then(|| u.to_string())
}

fn label_ok(l: &str) -> bool {
    !l.is_empty() && l.len() <= 63 && l.chars().all(|c| c.is_ascii_alphanumeric() || c == '-') && !l.starts_with('-') && !l.ends_with('-')
}

pub fn bluesky_url(handle: &str) -> String {
    format!("https://bsky.app/profile/{handle}")
}

/// `user@instance` → `https://instance/@user`.
pub fn mastodon_url(address: &str) -> String {
    match address.split_once('@') {
        Some((user, instance)) => format!("https://{instance}/@{user}"),
        None => String::new(),
    }
}

pub fn github_url(user: &str) -> String {
    format!("https://github.com/{user}")
}

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

    #[test]
    fn handles_are_checked_and_normalised() {
        assert_eq!(bluesky("@Andy.bsky.social").as_deref(), Some("andy.bsky.social"));
        assert_eq!(bluesky("https://bsky.app/profile/andy.example.org/").as_deref(), Some("andy.example.org"));
        assert_eq!(bluesky("andy"), None, "a handle is a domain");
        assert_eq!(bluesky("an dy.bsky.social"), None);
        assert_eq!(mastodon("@andy@mastodon.social").as_deref(), Some("andy@mastodon.social"));
        assert_eq!(mastodon("https://Fosstodon.org/@andy").as_deref(), Some("andy@fosstodon.org"));
        assert_eq!(mastodon("andy"), None);
        assert_eq!(mastodon("andy@nodot"), None);
        assert_eq!(github("https://github.com/andymccall/").as_deref(), Some("andymccall"));
        assert_eq!(github("@andy-mccall").as_deref(), Some("andy-mccall"));
        assert_eq!(github("-andy"), None);
        assert_eq!(github("andy mccall"), None);
        assert_eq!(mastodon_url("andy@fosstodon.org"), "https://fosstodon.org/@andy");
    }
}