//! Owner and repository names (hub spec §3.2) and the top-level path
//! segments no owner may take.

use std::fmt;

/// `owner/name`, both validated.
#[derive(Clone, Debug, PartialEq, Eq, Hash, PartialOrd, Ord)]
pub struct RepoName {
    pub owner: String,
    pub name: String,
}

/// Top-level path segments reserved for the hub itself.
pub const RESERVED: &[&str] = &[
    "api",
    "static",
    "login",
    "logout",
    "register",
    "settings",
    "explore",
    "search",
    "notifications",
    "new",
    "orgs",
    "admin",
    "style.css",
    "favicon.ico",
    "favicon.svg",
    "health",
    "avatar",
    "help",
    "projects",
    "assets",
    ".well-known",
    // Live pages, CSP reports and the security pages (oxygenhub#204, #222, #224, #230).
    "live",
    "csp-report",
    "security.txt",
    "security-contact",
    // The transparency log, the metrics and Insights (oxygenhub#238, #212, #257).
    "log",
    "metrics",
    "insights",
    // Drops: `/drops` is the viewer's own (oxygenhub#279).
    "drops",
];

/// The repository name no repository may take: `/{owner}/drops` is the
/// owner's Drops page, and `/{owner}/drops/{id}` a drop (oxygenhub#279).
pub const DROPS: &str = "drops";

/// A drop's id: lowercase hex, 16 to 40 characters (they are made with
/// 24, 96 random bits, so a secret drop's address cannot be guessed).
pub fn valid_drop_id(s: &str) -> bool {
    (16..=40).contains(&s.len()) && s.bytes().all(|b| b.is_ascii_digit() || (b'a'..=b'f').contains(&b))
}

/// A repository name: a segment, not `drops`; or a drop's, `drops/ID`,
/// which no repository name can be, since it holds a slash.
pub fn valid_repo_name(s: &str) -> bool {
    match s.split_once('/') {
        Some((DROPS, id)) => valid_drop_id(id),
        Some(_) => false,
        None => valid_segment(s) && !s.eq_ignore_ascii_case(DROPS),
    }
}

/// `[A-Za-z0-9][A-Za-z0-9._-]{0,63}`, not `.`/`..`, not ending in `.git`.
pub fn valid_segment(s: &str) -> bool {
    let mut chars = s.chars();
    let Some(first) = chars.next() else { return false };
    if !first.is_ascii_alphanumeric() || s.len() > 64 {
        return false;
    }
    if !chars.all(|c| c.is_ascii_alphanumeric() || matches!(c, '.' | '_' | '-')) {
        return false;
    }
    s != "." && s != ".." && !s.ends_with(".git")
}

pub fn valid_owner(s: &str) -> bool {
    valid_segment(s) && !RESERVED.contains(&s)
}

impl RepoName {
    pub fn new(owner: &str, name: &str) -> Option<RepoName> {
        if valid_owner(owner) && valid_repo_name(name) {
            Some(RepoName { owner: owner.into(), name: name.into() })
        } else {
            None
        }
    }

    /// `owner/name`.
    pub fn parse(slug: &str) -> Option<RepoName> {
        let (owner, name) = slug.split_once('/')?;
        RepoName::new(owner, name)
    }

    pub fn url(&self) -> String {
        format!("/{}/{}", self.owner, self.name)
    }

    /// A drop's repository, `owner/drops/ID`.
    pub fn drop(owner: &str, id: &str) -> Option<RepoName> {
        RepoName::new(owner, &format!("{DROPS}/{id}"))
    }

    /// The drop's id, when this is a drop's repository.
    pub fn drop_id(&self) -> Option<&str> {
        self.name.strip_prefix(DROPS)?.strip_prefix('/')
    }
}

impl fmt::Display for RepoName {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}/{}", self.owner, self.name)
    }
}

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

    #[test]
    fn names() {
        assert!(RepoName::parse("andy/oxygen").is_some());
        assert!(RepoName::parse("andy/oxy.gen-2_x").is_some());
        assert!(RepoName::parse("api/x").is_none(), "reserved owner");
        assert!(RepoName::parse("andy/x.git").is_none(), "mirror URL");
        assert!(RepoName::parse("andy/..").is_none());
        assert!(RepoName::parse(".andy/x").is_none());
        assert!(RepoName::parse("andy/a b").is_none());
        assert!(RepoName::parse("andy").is_none());
        assert!(RepoName::parse(&format!("andy/{}", "a".repeat(65))).is_none());
        assert_eq!(RepoName::parse("andy/oxygen").unwrap().url(), "/andy/oxygen");
        // `drops` is the Drops page; a drop is `drops/ID` (#279).
        assert!(RepoName::parse("andy/drops").is_none() && RepoName::parse("andy/Drops").is_none());
        assert!(RepoName::parse("drops/x").is_none(), "reserved owner");
        let d = RepoName::parse("andy/drops/0123456789abcdef01234567").unwrap();
        assert_eq!(d.drop_id(), Some("0123456789abcdef01234567"));
        assert_eq!(d.url(), "/andy/drops/0123456789abcdef01234567");
        assert_eq!(RepoName::drop("andy", "0123456789abcdef01234567"), Some(d));
        assert!(RepoName::parse("andy/drops/short").is_none());
        assert!(RepoName::parse("andy/drops/0123456789ABCDEF01234567").is_none());
        assert!(RepoName::parse("andy/x/0123456789abcdef01234567").is_none());
        assert_eq!(RepoName::parse("andy/oxygen").unwrap().drop_id(), None);
    }
}