//! Minimal JSON string quoting, so the proof of concept needs no crates.

/// The JSON string literal for `value`, quotes included.
pub fn quote(value: &str) -> String {
    let mut out = String::with_capacity(value.len() + 2);
    out.push('"');
    for ch in value.chars() {
        match ch {
            '"' => out.push_str("\\\""),
            '\\' => out.push_str("\\\\"),
            '\n' => out.push_str("\\n"),
            '\r' => out.push_str("\\r"),
            '\t' => out.push_str("\\t"),
            c if c < ' ' => out.push_str(&format!("\\u{:04x}", c as u32)),
            c => out.push(c),
        }
    }
    out.push('"');
    out
}

/// `Some` as its JSON literal, `None` as `null`.
pub fn option(value: Option<&str>) -> String {
    value.map(quote).unwrap_or_else(|| "null".to_string())
}

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

    #[test]
    fn quotes() {
        assert_eq!(quote("a"), "\"a\"");
        assert_eq!(quote("a\"b\\c\n"), "\"a\\\"b\\\\c\\n\"");
        assert_eq!(option(None), "null");
        assert_eq!(option(Some("x")), "\"x\"");
    }
}