//! Small, dependency-free encoding helpers shared across crates.
//!
//! v0.5.4: `pct_encode` and `xml_escape` were duplicated in the SAML
//! modules and the HTTP layer; they live here now. They're deliberately
//! hand-rolled rather than pulling in `percent-encoding` / `url`: the
//! unreserved set below is exactly the RFC 3986 set that iPXE's
//! `:uristring` modifier and the SAML HTTP-Redirect binding both expect,
//! and a general-purpose URL crate escapes a different set.

use std::fmt::Write as _;

/// Percent-encode `s` per RFC 3986: the unreserved set
/// (`A-Z` `a-z` `0-9` `-` `_` `.` `~`) passes through unchanged; every
/// other byte becomes `%XX` (uppercase hex).
#[must_use]
pub fn pct_encode(s: &str) -> String {
    let mut out = String::with_capacity(s.len());
    for b in s.bytes() {
        match b {
            b'A'..=b'Z' | b'a'..=b'z' | b'0'..=b'9' | b'-' | b'_' | b'.' | b'~' => {
                out.push(b as char);
            }
            _ => {
                let _ = write!(out, "%{b:02X}");
            }
        }
    }
    out
}

/// Escape the five XML predefined entities so `s` is safe inside element
/// text or a double-quoted attribute value.
#[must_use]
pub fn xml_escape(s: &str) -> String {
    let mut out = String::with_capacity(s.len());
    for c in s.chars() {
        match c {
            '&' => out.push_str("&"),
            '<' => out.push_str("&lt;"),
            '>' => out.push_str("&gt;"),
            '"' => out.push_str("&quot;"),
            '\'' => out.push_str("&apos;"),
            _ => out.push(c),
        }
    }
    out
}

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

    #[test]
    fn pct_encode_unreserved_passthrough_else_hex() {
        assert_eq!(pct_encode("node-7.lab_1~"), "node-7.lab_1~");
        assert_eq!(pct_encode("aa:bb cc/?&="), "aa%3Abb%20cc%2F%3F%26%3D");
        assert_eq!(pct_encode(""), "");
    }

    #[test]
    fn xml_escape_all_five_entities() {
        assert_eq!(xml_escape("a&b<c>\"d'e"), "a&amp;b&lt;c&gt;&quot;d&apos;e");
        assert_eq!(xml_escape("plain text"), "plain text");
    }
}