cargo add parcelwing
cargo add tokio --features macros,rt-multi-thread

use parcelwing::{Client, EmailSendRequest};
use serde::Deserialize;
use std::convert::Infallible;
use warp::Filter;
 
#[derive(Clone, Deserialize)]
struct WelcomeRequest {
    email: String,
    first_name: Option<String>,
}
 
#[tokio::main]
async fn main() -> Result<(), parcelwing::Error> {
    let client = Client::new(std::env::var("PARCELWING_API_KEY").unwrap())?;
    let client_filter = warp::any().map(move || client.clone());
 
    let send_welcome = warp::path("send-welcome")
        .and(warp::post())
        .and(client_filter)
        .and(warp::body::json())
        .and_then(send_welcome);
 
    warp::serve(send_welcome).run(([0, 0, 0, 0], 8080)).await;
    Ok(())
}
 
async fn send_welcome(client: Client, payload: WelcomeRequest) -> Result<impl warp::Reply, Infallible> {
    let response = match client
        .emails()
        .send(
            EmailSendRequest::new(std::env::var("PARCELWING_FROM_EMAIL").unwrap(), payload.email)
                .template_alias("welcome")
                .template_param("first_name", payload.first_name.unwrap_or_else(|| "friend".to_string())),
        )
        .await
    {
        Ok(emails) => serde_json::json!({ "id": emails[0].id }),
        Err(error) => serde_json::json!({ "error": error.to_string() }),
    };
 
    Ok(warp::reply::json(&response))
}