//! Debian version handling: splitting and validation of
//! `[epoch:]upstream[-revision]` version strings.

/// A Debian version, split into its `[epoch:]upstream[-revision]` parts.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct DebianVersion {
    /// Optional numeric epoch (part before the first `:`).
    pub epoch: Option<u32>,
    /// Upstream version (may itself contain `-` when there is no revision).
    pub upstream: String,
    /// Optional Debian revision (part after the last `-`).
    pub debian_revision: Option<String>,
}

impl DebianVersion {
    /// Parse and validate a Debian version string.
    pub fn parse(raw: &str) -> Result<DebianVersion, String> {
        let raw = raw.trim();
        if raw.is_empty() {
            return Err("empty version string".to_string());
        }

        let (epoch, rest) = match raw.split_once(':') {
            Some((e, r)) => {
                let epoch: u32 = e
                    .parse()
                    .map_err(|_| format!("invalid epoch '{}' in version '{}'", e, raw))?;
                (Some(epoch), r)
            }
            None => (None, raw),
        };

        // The revision is everything after the last hyphen.
        let (upstream, debian_revision) = match rest.rsplit_once('-') {
            Some((u, r)) => (u.to_string(), Some(r.to_string())),
            None => (rest.to_string(), None),
        };

        if upstream.is_empty() {
            return Err(format!("missing upstream version in '{}'", raw));
        }
        for c in upstream.chars() {
            if !(c.is_ascii_alphanumeric()
                || matches!(c, '.' | '+' | '-' | '~' | ':')
                || !c.is_ascii())
            {
                return Err(format!("invalid character '{}' in version '{}'", c, raw));
            }
        }
        if let Some(rev) = &debian_revision {
            for c in rev.chars() {
                if !(c.is_ascii_alphanumeric() || matches!(c, '.' | '+' | '~') || !c.is_ascii()) {
                    return Err(format!(
                        "invalid character '{}' in revision of version '{}'",
                        c, raw
                    ));
                }
            }
        }

        Ok(DebianVersion {
            epoch,
            upstream,
            debian_revision,
        })
    }

    /// Full version string, including the epoch (`[epoch:]upstream[-rev]`).
    pub fn full(&self) -> String {
        match (&self.epoch, &self.debian_revision) {
            (Some(e), Some(r)) => format!("{}:{}-{}", e, self.upstream, r),
            (Some(e), None) => format!("{}:{}", e, self.upstream),
            (None, Some(r)) => format!("{}-{}", self.upstream, r),
            (None, None) => self.upstream.clone(),
        }
    }

    /// Version string without the epoch (`upstream[-rev]`), used in artifact
    /// file names.
    pub fn no_epoch(&self) -> String {
        match &self.debian_revision {
            Some(r) => format!("{}-{}", self.upstream, r),
            None => self.upstream.clone(),
        }
    }
}

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

    #[test]
    fn version_splitting() {
        let v = DebianVersion::parse("1.2.3-4ubuntu5").unwrap();
        assert_eq!(v.epoch, None);
        assert_eq!(v.upstream, "1.2.3");
        assert_eq!(v.debian_revision.as_deref(), Some("4ubuntu5"));
        assert_eq!(v.full(), "1.2.3-4ubuntu5");
        assert_eq!(v.no_epoch(), "1.2.3-4ubuntu5");

        let v = DebianVersion::parse("3:2.10-3").unwrap();
        assert_eq!(v.epoch, Some(3));
        assert_eq!(v.upstream, "2.10");
        assert_eq!(v.no_epoch(), "2.10-3");
        assert_eq!(v.full(), "3:2.10-3");

        let v = DebianVersion::parse("1.0").unwrap();
        assert_eq!(v.debian_revision, None);
        assert_eq!(v.no_epoch(), "1.0");
    }

    #[test]
    fn version_validation() {
        assert!(DebianVersion::parse("").is_err());
        assert!(DebianVersion::parse(":1.0").is_err());
        assert!(DebianVersion::parse("a:_b").is_err());
        assert!(DebianVersion::parse("1.0").is_ok());
        assert!(DebianVersion::parse("1.0~rc1-2").is_ok());
    }
}