//! 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("@[email protected]").as_deref(), Some("[email protected]"));

        assert_eq!(mastodon("https://Fosstodon.org/@andy").as_deref(), Some("[email protected]"));

        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("[email protected]"), "https://fosstodon.org/@andy");

    }

}