Add some example code

README.md

@@ -25,3 +25,135 @@ specification.
 
 * Only tested with DNS challenges against Let's Encrypt so far (staging and production)
 * Only supports ECDSA keys for now
+
+## Getting started
+
+```rust
+use std::time::Duration;
+
+use rcgen::{Certificate, CertificateParams, DistinguishedName};
+use tokio::time::sleep;
+use tracing::{error, info};
+
+use acme::{
+    Account, AuthorizationStatus, ChallengeType, Identifier, LetsEncrypt, NewAccount, NewOrder,
+    OrderStatus,
+};
+
+async fn provision(names: Vec<String>) -> anyhow::Result<()> {
+    // Create a new account. This will generate a fresh ECDSA key for you.
+    // Alternatively, restore an account from serialized credentials by
+    // using `Account::from_credentials()`.
+
+    let account = Account::create(
+        &NewAccount {
+            contact: &[],
+            terms_of_service_agreed: true,
+            only_return_existing: false,
+        },
+        LetsEncrypt::Staging.url(),
+    )
+    .await?;
+
+    // Create the ACME order based on the given domain names.
+    // Note that this only needs an `&Account`, so the library will let you
+    // process multiple orders in parallel for a single account.
+
+    let identifiers = names
+        .iter()
+        .map(|name| Identifier::Dns(name.into()))
+        .collect::<Vec<_>>();
+    let (mut order, state) = account
+        .new_order(&NewOrder {
+            identifiers: &identifiers,
+        })
+        .await
+        .unwrap();
+
+    info!("order state: {:#?}", state);
+    assert!(matches!(state.status, OrderStatus::Pending));
+
+    // Pick the desired challenge type and prepare the response.
+
+    let authorizations = order.authorizations(&state.authorizations).await.unwrap();
+    let mut challenges = Vec::with_capacity(authorizations.len());
+    for authz in &authorizations {
+        match authz.status {
+            AuthorizationStatus::Pending => {}
+            AuthorizationStatus::Valid => continue,
+            _ => todo!(),
+        }
+
+        // We'll use the DNS challenges for this example, but you could
+        // pick something else to use here.
+
+        let challenge = authz
+            .challenges
+            .iter()
+            .find(|c| c.r#type == ChallengeType::Dns01)
+            .ok_or_else(|| anyhow::anyhow!("no dns01 challenge found"))?;
+
+        let Identifier::Dns(identifier) = &authz.identifier;
+        // TODO: set up the challenge response here.
+        challenges.push((identifier, &challenge.url));
+    }
+
+    // Let the server know we're ready to accept the challenges.
+
+    for (_, url) in &challenges {
+        order.set_challenge_ready(url).await.unwrap();
+    }
+
+    // Exponentially back off until the order becomes ready or invalid.
+
+    let mut tries = 1u8;
+    let mut delay = Duration::from_millis(250);
+    let state = loop {
+        sleep(delay).await;
+        let state = order.state().await.unwrap();
+        if let OrderStatus::Ready | OrderStatus::Invalid = state.status {
+            info!("order state: {:#?}", state);
+            break state;
+        }
+
+        delay *= 2;
+        tries += 1;
+        match tries < 5 {
+            true => info!(?state, tries, "order is not ready, waiting {delay:?}"),
+            false => {
+                error!(?state, tries, "order is not ready");
+                return Err(anyhow::anyhow!("order is not ready"));
+            }
+        }
+    };
+
+    if state.status == OrderStatus::Invalid {
+        return Err(anyhow::anyhow!("order is invalid"));
+    }
+
+    let mut names = Vec::with_capacity(challenges.len());
+    for (identifier, _) in challenges {
+        names.push(identifier.to_owned());
+    }
+
+    // If the order is ready, we can provision the certificate.
+    // Use the rcgen library to create a Certificate Signing Request.
+
+    let mut params = CertificateParams::new(names.clone());
+    params.distinguished_name = DistinguishedName::new();
+    let cert = Certificate::from_params(params).unwrap();
+    let csr = cert.serialize_request_der()?;
+
+    // Finalize the order and print certificate chain, private key and account credentials.
+
+    let cert_chain_pem = order.finalize(&csr, &state.finalize).await.unwrap();
+    info!("certficate chain:\n\n{}", cert_chain_pem,);
+    info!("private key:\n\n{}", cert.serialize_private_key_pem());
+    info!(
+        "account credentials:\n\n{}",
+        serde_json::to_string_pretty(&account.credentials()).unwrap()
+    );
+
+    Ok(())
+}
+```