zero2prod/src/email_client.rs

use crate::{configuration::EmailClientSettings, domain::SubscriberEmail};
use reqwest::Client;
use secrecy::{ExposeSecret, SecretString};
use std::time::Duration;

pub struct EmailClient {
    http_client: Client,
    base_url: reqwest::Url,
    sender: SubscriberEmail,
    authorization_token: SecretString,
}

impl EmailClient {
    pub fn build(config: EmailClientSettings) -> Result<Self, anyhow::Error> {
        let client = Self {
            http_client: Client::builder()
                .timeout(Duration::from_millis(config.timeout_milliseconds))
                .build()
                .unwrap(),
            base_url: reqwest::Url::parse(&config.base_url)?,
            sender: config.sender().map_err(|e| anyhow::anyhow!(e))?,
            authorization_token: config.authorization_token,
        };
        Ok(client)
    }

    pub async fn send_email(
        &self,
        recipient: &SubscriberEmail,
        subject: &str,
        html_content: &str,
        text_content: &str,
    ) -> Result<(), reqwest::Error> {
        let url = self.base_url.join("email").unwrap();
        let request_body = SendEmailRequest {
            from: EmailField {
                email: self.sender.as_ref(),
            },
            to: vec![EmailField {
                email: recipient.as_ref(),
            }],
            subject,
            text: text_content,
            html: html_content,
        };

        self.http_client
            .post(url)
            .header("X-Requested-With", "XMLHttpRequest")
            .header(
                "Authorization",
                format!("Bearer {}", self.authorization_token.expose_secret()),
            )
            .json(&request_body)
            .send()
            .await?
            .error_for_status()?;
        Ok(())
    }
}

#[derive(serde::Serialize)]
struct SendEmailRequest<'a> {
    from: EmailField<'a>,
    to: Vec<EmailField<'a>>,
    subject: &'a str,
    text: &'a str,
    html: &'a str,
}

#[derive(serde::Serialize)]
struct EmailField<'a> {
    email: &'a str,
}

#[cfg(test)]
mod tests {
    use crate::{
        configuration::EmailClientSettings, domain::SubscriberEmail, email_client::EmailClient,
    };
    use claims::{assert_err, assert_ok};
    use fake::{
        Fake, Faker,
        faker::{
            internet::en::SafeEmail,
            lorem::en::{Paragraph, Sentence},
        },
    };
    use std::time::Duration;
    use wiremock::{
        Mock, MockServer, ResponseTemplate,
        matchers::{any, header, header_exists, method, path},
    };

    struct SendEmailBodyMatcher;

    impl wiremock::Match for SendEmailBodyMatcher {
        fn matches(&self, request: &wiremock::Request) -> bool {
            let result: Result<serde_json::Value, _> = serde_json::from_slice(&request.body);
            if let Ok(body) = result {
                body.get("from").is_some()
                    && body.get("to").is_some()
                    && body.get("subject").is_some()
                    && body.get("html").is_some()
                    && body.get("text").is_some()
            } else {
                false
            }
        }
    }

    fn subject() -> String {
        Sentence(1..2).fake()
    }

    fn content() -> String {
        Paragraph(1..10).fake()
    }

    fn email() -> SubscriberEmail {
        SubscriberEmail::parse(SafeEmail().fake()).unwrap()
    }

    fn email_client(base_url: String) -> EmailClient {
        let sender_email = SafeEmail().fake();
        let token: String = Faker.fake();
        let settings = EmailClientSettings::new(base_url, sender_email, token, 200);
        EmailClient::build(settings).unwrap()
    }

    #[tokio::test]
    async fn send_email_sends_the_expected_request() {
        let mock_server = MockServer::start().await;
        let email_client = email_client(mock_server.uri());

        Mock::given(header_exists("Authorization"))
            .and(header("Content-Type", "application/json"))
            .and(header("X-Requested-With", "XMLHttpRequest"))
            .and(path("email"))
            .and(method("POST"))
            .and(SendEmailBodyMatcher)
            .respond_with(ResponseTemplate::new(200))
            .expect(1)
            .mount(&mock_server)
            .await;

        email_client
            .send_email(&email(), &subject(), &content(), &content())
            .await
            .unwrap();
    }

    #[tokio::test]
    async fn send_email_succeeds_if_the_server_returns_200() {
        let mock_server = MockServer::start().await;
        let email_client = email_client(mock_server.uri());

        Mock::given(any())
            .respond_with(ResponseTemplate::new(200))
            .expect(1)
            .mount(&mock_server)
            .await;

        let response = email_client
            .send_email(&email(), &subject(), &content(), &content())
            .await;

        assert_ok!(response);
    }

    #[tokio::test]
    async fn send_email_fails_if_the_server_retuns_500() {
        let mock_server = MockServer::start().await;
        let email_client = email_client(mock_server.uri());

        Mock::given(any())
            .respond_with(ResponseTemplate::new(500))
            .expect(1)
            .mount(&mock_server)
            .await;

        let response = email_client
            .send_email(&email(), &subject(), &content(), &content())
            .await;

        assert_err!(response);
    }

    #[tokio::test]
    async fn send_email_times_out_if_the_server_takes_too_long() {
        let mock_server = MockServer::start().await;
        let email_client = email_client(mock_server.uri());

        Mock::given(any())
            .respond_with(ResponseTemplate::new(200).set_delay(Duration::from_secs(180)))
            .expect(1)
            .mount(&mock_server)
            .await;

        let response = email_client
            .send_email(&email(), &subject(), &content(), &content())
            .await;

        assert_err!(response);
    }
}