266 lines
9 KiB
Rust
266 lines
9 KiB
Rust
use anyhow::{Context, Result};
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use axum::extract::FromRef;
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use futures::Future;
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use lettre::{AsyncSmtpTransport, AsyncTransport, Tokio1Executor};
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use regex::Regex;
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use serde::{Serialize, Serializer};
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use crate::app_state::AppState;
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const POSTMARK_EMAIL_BATCH_URL: &str = "https://api.postmarkapp.com/email/batch";
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/// Returns true if the email address matches a format recognized as "valid".
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/// Not all "legal" email addresses will be accepted, but addresses that are
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/// "illegal" and/or could result in unexpected behavior should be rejected.
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pub fn is_permissible_email(address: &str) -> bool {
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let re = Regex::new(r"^[a-zA-Z0-9._+-]+@([a-zA-Z0-9_-]+.)+[a-zA-Z]+$")
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.expect("email validation regex should parse");
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re.is_match(address)
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}
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#[derive(Clone, Serialize)]
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pub struct Message {
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#[serde(rename = "From")]
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pub from: lettre::message::Mailbox,
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#[serde(rename = "To")]
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#[serde(serialize_with = "serialize_mailboxes")]
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pub to: lettre::message::Mailboxes,
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#[serde(rename = "Subject")]
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pub subject: String,
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#[serde(rename = "TextBody")]
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pub text_body: String,
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}
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pub trait MailSender: Clone + Sync {
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/// Attempt to send all messages defined by the input Vec. Send as many as
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/// possible, returning exactly one Result<()> for each message.
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fn send_batch(&self, emails: Vec<Message>) -> impl Future<Output = Vec<Result<()>>>;
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}
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#[derive(Clone, Debug)]
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pub enum Mailer {
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Smtp(SmtpSender),
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Postmark(PostmarkSender),
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}
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impl Mailer {
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pub fn new_smtp(opts: SmtpOptions) -> Result<Self> {
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Ok(Self::Smtp(SmtpSender::new(opts)?))
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}
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pub fn new_postmark(server_token: String) -> Result<Self> {
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Ok(Self::Postmark(PostmarkSender::new(server_token)?))
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}
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pub fn with_reqwest_client(self, client: reqwest::Client) -> Self {
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match self {
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Self::Postmark(sender) => Self::Postmark(sender.with_reqwest_client(client)),
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_ => self,
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}
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}
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}
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impl MailSender for Mailer {
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async fn send_batch(&self, emails: Vec<Message>) -> Vec<Result<()>> {
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match self {
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Mailer::Smtp(sender) => sender.send_batch(emails).await,
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Mailer::Postmark(sender) => sender.send_batch(emails).await,
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}
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}
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}
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#[derive(Clone, Debug)]
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pub struct SmtpSender {
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transport: AsyncSmtpTransport<Tokio1Executor>,
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}
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#[derive(Debug)]
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pub struct SmtpOptions {
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pub server: String,
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pub username: String,
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pub password: String,
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}
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impl SmtpSender {
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fn new(opts: SmtpOptions) -> Result<Self> {
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let mailer_creds =
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lettre::transport::smtp::authentication::Credentials::new(opts.username, opts.password);
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let transport = lettre::AsyncSmtpTransport::<Tokio1Executor>::starttls_relay(&opts.server)
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.context("unable to initialize starttls_relay")?
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.credentials(mailer_creds)
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.build();
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Ok(Self { transport })
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}
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}
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impl TryInto<lettre::Message> for Message {
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type Error = anyhow::Error;
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fn try_into(self) -> Result<lettre::Message, Self::Error> {
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let mut builder = lettre::Message::builder()
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.from(self.from.clone())
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.subject(self.subject)
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.header(lettre::message::header::ContentType::TEXT_PLAIN);
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for to_addr in self.to {
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builder = builder.to(to_addr);
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}
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let message = builder.body(self.text_body)?;
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Ok(message)
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}
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}
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fn serialize_mailboxes<S>(t: &lettre::message::Mailboxes, s: S) -> Result<S::Ok, S::Error>
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where
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S: Serializer,
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{
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s.serialize_str(&t.to_string())
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}
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impl MailSender for SmtpSender {
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async fn send_batch(&self, emails: Vec<Message>) -> Vec<Result<()>> {
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let mut results: Vec<Result<()>> = Vec::with_capacity(emails.len());
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for email in emails {
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match TryInto::<lettre::Message>::try_into(email) {
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Ok(email) => {
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results.push(
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self.transport
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.send(email)
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.await
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.map(|_| ())
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.map_err(Into::<anyhow::Error>::into),
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);
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}
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Err(err) => {
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results.push(Err(err));
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}
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}
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}
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results
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}
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}
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#[derive(Clone, Debug)]
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pub struct PostmarkSender {
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client: reqwest::Client,
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server_token: String,
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}
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impl PostmarkSender {
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fn new(server_token: String) -> Result<Self> {
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Ok(Self {
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client: reqwest::ClientBuilder::new().https_only(true).build()?,
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server_token,
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})
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}
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pub fn with_reqwest_client(self, client: reqwest::Client) -> Self {
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Self { client, ..self }
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}
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}
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impl MailSender for PostmarkSender {
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/// Recursively attempts to send messages, breaking them into smaller and
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/// smaller batches as needed.
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async fn send_batch(&self, mut emails: Vec<Message>) -> Vec<Result<()>> {
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/// Constructs a Vec with Ok(()) repeated n times.
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macro_rules! all_ok {
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() => {{
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let mut collection: Vec<Result<_>> = Vec::with_capacity(emails.len());
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for _ in 0..emails.len() {
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collection.push(Ok(()));
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}
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collection
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}};
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}
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/// Constructs a Vec with a single specific error, followed by n-1
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/// generic errors referring back to it.
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macro_rules! cascade_err {
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($err:expr) => {{
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let mut collection: Vec<Result<_>> = Vec::with_capacity(emails.len());
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collection.push(Err($err));
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for _ in 1..emails.len() {
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collection.push(Err(anyhow::anyhow!("could not send due to previous error")));
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}
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collection
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}};
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}
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/// Recursively splits the email batch in half and tries to send each
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/// half independently, allowing both to run to completion and then
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/// returning the first error of the two results, if present.
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macro_rules! split_and_retry {
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// This is implemented as a macro in order to avoid unstable async
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// closures.
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() => {
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if emails.len() < 2 {
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tracing::warn!("Postmark send batch cannot be split any further");
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vec![Err(anyhow::anyhow!(
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"unable to split Postmark batch into smaller slices"
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))]
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} else {
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tracing::debug!("retrying Postmark send with smaller batches");
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let mut results =
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Box::pin(self.send_batch(emails.split_off(emails.len() / 2))).await;
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results.extend(Box::pin(self.send_batch(emails)).await);
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results
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}
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};
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}
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// https://postmarkapp.com/support/article/1056-what-are-the-attachment-and-email-size-limits
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const POSTMARK_MAX_BATCH_ENTRIES: usize = 500;
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const POSTMARK_MAX_REQUEST_BYTES: usize = 50 * 1000 * 1000;
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// TODO: Check email subject and body size against Postmark limits
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if emails.is_empty() {
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tracing::debug!("no Postmark messages to send");
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vec![Ok(())]
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} else if emails.len() > POSTMARK_MAX_BATCH_ENTRIES {
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split_and_retry!()
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} else {
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let body = match serde_json::to_string(&emails) {
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Ok(body) => body,
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Err(err) => return cascade_err!(err.into()),
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};
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if body.len() > POSTMARK_MAX_REQUEST_BYTES {
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if emails.len() > 1 {
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split_and_retry!()
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} else {
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vec![Err(anyhow::anyhow!(
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"Postmark requests may not exceed {} bytes",
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POSTMARK_MAX_REQUEST_BYTES
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))]
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}
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} else {
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tracing::debug!("sending Postmark batch of {} messages", emails.len());
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let resp = match self
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.client
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.post(POSTMARK_EMAIL_BATCH_URL)
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.header("X-Postmark-Server-Token", &self.server_token)
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.header(reqwest::header::CONTENT_TYPE, "application/json")
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.body(body)
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.send()
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.await
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{
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Ok(resp) => resp,
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Err(err) => return cascade_err!(err.into()),
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};
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if resp.status().is_client_error() && emails.len() > 1 {
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split_and_retry!()
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} else if let Err(err) = resp.error_for_status() {
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cascade_err!(err.into())
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} else {
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tracing::debug!("sent Postmark batch of {} messages", emails.len());
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all_ok!()
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}
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}
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}
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}
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}
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impl FromRef<AppState> for Mailer {
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fn from_ref(state: &AppState) -> Mailer {
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state.mailer.clone()
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}
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}
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