Easy function to call GitHub's GraphQL server in Rust.

github_graphql.rs

// Example usage:
//     let github_details = github_graphql_query(
//        &"some_oauth_access_token",
//        &"query { viewer { email name login id location websiteUrl } }",
//    )?;
// 
// Cargo.toml:
// .. 
// [dependencies]
// rocket = "0.3.11"
// curl = "0.4"
// ..

extern crate curl;

use curl::easy::{Easy, List};

const CONTENT_TYPE_JSON: &str = "application/json";
const GITHUB_GRAPHQL_API: &str = "https://api.github.com/graphql";
const GITHUB_APP_NAME: &str = "Example-App";

// handles any Error Result and converts to a 500 error in Rocket (for use within a Rocket Web Application).
// CHANGEME to return any other type of useful error
macro_rules! error_to_500 {
    ($x:expr) => {
        match $x {
            Err(err) => {
                eprintln!("{}", err.to_string());
                return Err(rocket::http::Status::InternalServerError);
            }
            Ok(_) => (),
        }
    };
}


fn github_graphql_query(access_token: &str, graphql_query: &str) -> Result<String, Status> {
    let mut easy = Easy::new();
    match easy.url(GITHUB_GRAPHQL_API) {
        Err(err) => {
            eprintln!("{}", err.to_string());
            return Err(rocket::http::Status::InternalServerError);
        }
        Ok(_) => (),
    };

    let mut headers = List::new();
    error_to_500!(headers.append(&format!("User-Agent: {}", GITHUB_APP_NAME)));
    error_to_500!(headers.append(&format!("Authorization: bearer {}", access_token)));
    error_to_500!(headers.append(&format!("Accept: {}", CONTENT_TYPE_JSON)));
    error_to_500!(easy.http_headers(headers));
    error_to_500!(easy.post(true));
    let query_json_str = format!("{{ \"query\": \"{}\" }}", graphql_query);
    let mut query_json = query_json_str.as_bytes();
    error_to_500!(easy.post_field_size(query_json.len() as u64));

    let mut data = Vec::new();
    {
        let mut transfer = easy.transfer();

        error_to_500!(transfer.read_function(|buf| Ok(query_json.read(buf).unwrap_or(0))));

        error_to_500!(transfer.write_function(|new_data| {
            data.extend_from_slice(new_data);
            Ok(new_data.len())
        }));

        error_to_500!(transfer.perform());
    }

    let http_status_response = easy.response_code();
    error_to_500!(http_status_response);
    let response_code = http_status_response.unwrap();
    if response_code != 200 {
        eprintln!(
            "Github API returned {} : {}",
            response_code,
            String::from_utf8_lossy(data.as_slice())
        );
        return Err(rocket::http::Status::InternalServerError);
    }

    Ok(String::from_utf8_lossy(data.as_slice()).to_string())
}