fn as_headers()

in sdk/cosmos/azure_data_cosmos/src/partition_key.rs [102:154]
44 lines of code
5 McCabe index (conditional complexity)

    fn as_headers(&self) -> Result<Self::Iter, Self::Error> {
        // We have to do some manual JSON serialization here.
        // The partition key is sent in an HTTP header, when used to set the partition key for a query.
        // It's not safe to use non-ASCII characters in HTTP headers, and serde_json will not escape non-ASCII characters if they are otherwise valid as UTF-8.
        // So, we do some conversion by hand, with the help of Rust's own `encode_utf16` method which gives us the necessary code points for non-ASCII values, and produces surrogate pairs as needed.

        let mut json = String::new();
        let mut utf_buf = [0; 2]; // A buffer for encoding UTF-16 characters.
        json.push('[');
        for key in &self.0 {
            match key.0 {
                InnerPartitionKeyValue::Null => json.push_str("null"),
                InnerPartitionKeyValue::String(ref string_key) => {
                    json.push('"');
                    for char in string_key.chars() {
                        match char {
                            '\x08' => json.push_str(r#"\b"#),
                            '\x0c' => json.push_str(r#"\f"#),
                            '\n' => json.push_str(r#"\n"#),
                            '\r' => json.push_str(r#"\r"#),
                            '\t' => json.push_str(r#"\t"#),
                            '"' => json.push_str(r#"\""#),
                            '\\' => json.push('\\'),
                            c if c.is_ascii() => json.push(c),
                            c => {
                                let encoded = c.encode_utf16(&mut utf_buf);
                                for code_unit in encoded {
                                    json.push_str(&format!(r#"\u{:04x}"#, code_unit));
                                }
                            }
                        }
                    }
                    json.push('"');
                }
                InnerPartitionKeyValue::Number(ref num) => {
                    json.push_str(
                        serde_json::to_string(&serde_json::Value::Number(num.clone()))?.as_str(),
                    );
                }
            }

            json.push(',');
        }

        // Pop the trailing ','
        json.pop();
        json.push(']');

        Ok(std::iter::once((
            constants::PARTITION_KEY,
            HeaderValue::from_cow(json),
        )))
    }