//! Utility helpers for claudbg.

/// Returns the first 8 characters of a session/agent ID for compact display.
///
/// If the ID is shorter than 8 characters, returns the full ID.
pub fn short_id(id: &str) -> &str {
    &id[..id.len().min(8)]
}

/// Escapes special XML characters in a string for safe embedding in XML content.
///
/// The following substitutions are applied:
/// - `&` → `&`
/// - `<` → `&lt;`
/// - `>` → `&gt;`
/// - `"` → `&quot;`
/// - `'` → `&apos;`
pub fn xml_escape(s: &str) -> String {
    let mut out = String::with_capacity(s.len());
    for ch in s.chars() {
        match ch {
            '&' => out.push_str("&amp;"),
            '<' => out.push_str("&lt;"),
            '>' => out.push_str("&gt;"),
            '"' => out.push_str("&quot;"),
            '\'' => out.push_str("&apos;"),
            other => out.push(other),
        }
    }
    out
}

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

    /// `short_id` returns the first 8 characters of a 36-character UUID.
    #[test]
    fn short_id_uuid() {
        let uuid = "550e8400-e29b-41d4-a716-446655440000";
        assert_eq!(short_id(uuid), "550e8400");
    }

    /// `short_id` returns the full string when it is shorter than 8 characters.
    #[test]
    fn short_id_short_string() {
        assert_eq!(short_id("abc"), "abc");
    }

    /// `short_id` returns an empty string for an empty input.
    #[test]
    fn short_id_empty_string() {
        assert_eq!(short_id(""), "");
    }

    /// `short_id` returns exactly 8 characters when input is exactly 8 characters.
    #[test]
    fn short_id_exact_length() {
        assert_eq!(short_id("12345678"), "12345678");
    }

    /// `xml_escape` replaces `&` with `&amp;`.
    #[test]
    fn xml_escape_ampersand() {
        assert_eq!(xml_escape("a & b"), "a &amp; b");
    }

    /// `xml_escape` replaces `<` with `&lt;` and `>` with `&gt;`.
    #[test]
    fn xml_escape_angle_brackets() {
        assert_eq!(xml_escape("<tag>"), "&lt;tag&gt;");
    }

    /// `xml_escape` replaces `"` with `&quot;`.
    #[test]
    fn xml_escape_double_quote() {
        assert_eq!(xml_escape(r#"say "hello""#), "say &quot;hello&quot;");
    }

    /// `xml_escape` replaces `'` with `&apos;`.
    #[test]
    fn xml_escape_single_quote() {
        assert_eq!(xml_escape("it's"), "it&apos;s");
    }

    /// `xml_escape` handles a string with multiple special characters.
    #[test]
    fn xml_escape_multiple() {
        assert_eq!(
            xml_escape(r#"<a href="x&y">it's</a>"#),
            "&lt;a href=&quot;x&amp;y&quot;&gt;it&apos;s&lt;/a&gt;"
        );
    }

    /// `xml_escape` returns the input unchanged if no special characters are present.
    #[test]
    fn xml_escape_no_special() {
        assert_eq!(xml_escape("hello world"), "hello world");
    }
}