//! JSON minification by whitespace removal only. The input must parse as strict JSON first;
//! then every byte outside insignificant whitespace is kept, so duplicate keys, number spelling
//! and string escapes reach the game exactly as written.

/// The minified bytes, or `None` when `bytes` is not strict JSON (comments, a BOM, trailing
/// commas): such files ship as they are.
pub fn minify(bytes: &[u8]) -> Option<Vec<u8>> {
    serde_json::from_slice::<serde::de::IgnoredAny>(bytes).ok()?;
    let mut out = Vec::with_capacity(bytes.len());
    let mut in_string = false;
    let mut escaped = false;
    for &b in bytes {
        if in_string {
            out.push(b);
            if escaped {
                escaped = false;
            } else if b == b'\\' {
                escaped = true;
            } else if b == b'"' {
                in_string = false;
            }
        } else if b == b'"' {
            in_string = true;
            out.push(b);
        } else if !matches!(b, b' ' | b'\t' | b'\n' | b'\r') {
            out.push(b);
        }
    }
    Some(out)
}

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

    #[test]
    fn strips_only_insignificant_whitespace() {
        let input = br#"{ "a b" : [ 1.50 , 2e3 ],
            "esc\" x" : "\\ y", "a b": null }"#;
        assert_eq!(minify(input).unwrap(), br#"{"a b":[1.50,2e3],"esc\" x":"\\ y","a b":null}"#);
    }

    #[test]
    fn lenient_json_ships_unchanged() {
        assert_eq!(minify(b"{ // c\n }"), None);
        assert_eq!(minify(b"\xef\xbb\xbf{}"), None);
        assert_eq!(minify(b"[1,]"), None);
    }
}