//! Names people give themselves (team links): what is accepted, and the key two
//! names collide on.
//!
//! A name is shown as the author of proposals, revisions and signals, so nobody
//! may take a name already there, even dressed differently: « émile » for
//! « Émile », an accent written apart, a Cyrillic « в » or a Greek « Υ » for a
//! Latin letter, full-width « Ｙｖｖ ». Hence a short alphabet — Latin letters
//! as French, English and Spanish write them, figures, space, hyphen,
//! apostrophe, dot — and a key that forgets case, accents and punctuation.

use unicode_normalization::UnicodeNormalization;
use unicode_normalization::char::is_combining_mark;

const MIN_NAME: usize = 2;
const MAX_NAME: usize = 60;

#[derive(Debug, PartialEq, Eq)]
pub struct Name {
    /// As shown: NFC, spaces collapsed.
    pub display: String,
    /// What two names collide on.
    pub key: String,
}

fn allowed(c: char) -> bool {
    c.is_ascii_alphanumeric()
        || (c.is_alphabetic() && matches!(c as u32, 0xC0..=0x17F))
        || matches!(c, ' ' | '-' | '\'' | '’' | '.')
}

/// Lowercase, no accents, letters and figures only: « Émile », « EMILE »,
/// « É-mile » share the key « emile ».
pub fn key(s: &str) -> String {
    s.nfkd().filter(|c| !is_combining_mark(*c)).flat_map(char::to_lowercase).filter(|c| c.is_alphanumeric()).collect()
}

/// A name a person may take, or `None`.
pub fn check(raw: &str) -> Option<Name> {
    let raw = raw.trim();
    // One line, ordinary spaces only (no line or paragraph separator).
    if raw.chars().any(|c| c.is_whitespace() && c != ' ') {
        return None;
    }
    let display = raw.nfc().collect::<String>().split(' ').filter(|w| !w.is_empty()).collect::<Vec<_>>().join(" ");
    let n = display.chars().count();
    if !(MIN_NAME..=MAX_NAME).contains(&n) || !display.chars().all(allowed) {
        return None;
    }
    let key = key(&display);
    if key.chars().count() < MIN_NAME {
        return None;
    }
    Some(Name { display, key })
}

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

    #[test]
    fn ordinary_names() {
        assert_eq!(check("  Émile   Zola ").map(|n| n.display), Some("Émile Zola".into()));
        assert_eq!(check("Jean-Marc O'Neil").map(|n| n.key), Some("jeanmarconeil".into()));
        assert_eq!(check("Núria").map(|n| n.key), Some("nuria".into()));
        assert!(check("Chiara 2").is_some());
    }

    #[test]
    fn the_same_name_dressed_differently_collides() {
        let emile = key("Émile");
        for other in ["émile", "EMILE", "E\u{301}mile", "É-mile", "Emile."] {
            assert_eq!(check(other).map(|n| n.key), Some(emile.clone()), "{other}");
        }
    }

    #[test]
    fn look_alikes_and_invisibles_are_refused() {
        // Eighth and ninth independent reviews, 2026-10-21.
        for name in ["Yvв", "Υvv", "Ｙｖｖ", "Yv\u{2028}v", "Yvv\u{fff9}", "Yv\u{200b}v", "Y\nvv", "Y", "--", "Yvv 🙂"]
        {
            assert_eq!(check(name), None, "{name:?}");
        }
    }
}