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

use axum::{extract::State, routing::post, Json, Router};
use parcelwing::{Client, EmailSendRequest};
use serde::Deserialize;
use serde_json::{json, Value};
 
#[derive(Clone)]
struct AppState {
    parcelwing: Client,
}
 
#[derive(Deserialize)]
struct WelcomeRequest {
    email: String,
    first_name: Option<String>,
}
 
#[tokio::main]
async fn main() -> Result<(), parcelwing::Error> {
    let state = AppState {
        parcelwing: Client::new(std::env::var("PARCELWING_API_KEY").unwrap())?,
    };
 
    let app = Router::new()
        .route("/send-welcome", post(send_welcome))
        .with_state(state);
 
    let listener = tokio::net::TcpListener::bind("0.0.0.0:8080").await.unwrap();
    axum::serve(listener, app).await.unwrap();
    Ok(())
}
 
async fn send_welcome(
    State(state): State<AppState>,
    Json(payload): Json<WelcomeRequest>,
) -> Result<Json<Value>, String> {
    let emails = state
        .parcelwing
        .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
        .map_err(|error| error.to_string())?;
 
    Ok(Json(json!({ "id": emails[0].id })))
}