zero2prod/src/routes/subscriptions.rs

use crate::{
    domain::{NewSubscriber, SubscriberEmail},
    email_client::EmailClient,
    routes::{AppError, generate_token},
    startup::AppState,
    templates::MessageTemplate,
};
use anyhow::Context;
use askama::Template;
use axum::{
    Form,
    extract::State,
    response::{Html, IntoResponse, Response},
};
use chrono::Utc;
use serde::Deserialize;
use sqlx::{Executor, Postgres, Transaction};
use uuid::Uuid;

#[tracing::instrument(
    name = "Adding a new subscriber",
    skip(connection_pool, email_client, base_url, form),
    fields(
        subscriber_email = %form.email,
    )
)]
pub async fn subscribe(
    State(AppState {
        connection_pool,
        email_client,
        base_url,
        ..
    }): State<AppState>,
    Form(form): Form<SubscriptionFormData>,
) -> Result<Response, AppError> {
    let new_subscriber = form
        .try_into()
        .context("Failed to parse subscription form data.")
        .map_err(AppError::FormError)?;
    let mut transaction = connection_pool
        .begin()
        .await
        .context("Failed to acquire a Postgres connection from the pool.")?;
    if let Some(subscriber_id) = insert_subscriber(&mut transaction, &new_subscriber)
        .await
        .context("Failed to insert new subscriber in the database.")
        .map_err(AppError::unexpected_message)?
    {
        let subscription_token = generate_token();
        store_token(&mut transaction, &subscription_token, &subscriber_id)
            .await
            .context("Failed to store the confirmation token for a new subscriber.")
            .map_err(AppError::unexpected_message)?;
        send_confirmation_email(
            &email_client,
            &new_subscriber,
            &base_url,
            &subscription_token,
        )
        .await
        .context("Failed to send a confirmation email.")?;

        transaction
            .commit()
            .await
            .context("Failed to commit the database transaction to store a new subscriber.")?;
    }

    let template = MessageTemplate::Success {
        message: "You'll receive a confirmation email shortly.".to_string(),
    };
    Ok(Html(template.render().unwrap()).into_response())
}

#[tracing::instrument(
    name = "Saving new subscriber details in the database",
    skip(transaction, new_subscriber)
)]
pub async fn insert_subscriber(
    transaction: &mut Transaction<'_, Postgres>,
    new_subscriber: &NewSubscriber,
) -> Result<Option<Uuid>, sqlx::Error> {
    let query = sqlx::query!(
        "SELECT id FROM subscriptions WHERE email = $1",
        new_subscriber.email.as_ref()
    );
    let existing = transaction.fetch_optional(query).await?;
    if existing.is_some() {
        return Ok(None);
    }
    let subscriber_id = Uuid::new_v4();
    let query = sqlx::query!(
        r#"
        INSERT INTO subscriptions (id, email, subscribed_at, status)
        VALUES ($1, $2, $3, 'pending_confirmation')
        "#,
        subscriber_id,
        new_subscriber.email.as_ref(),
        Utc::now()
    );
    transaction.execute(query).await?;
    Ok(Some(subscriber_id))
}

#[tracing::instrument(
    name = "Store subscription token in the database",
    skip(transaction, subscription_token)
)]
async fn store_token(
    transaction: &mut Transaction<'_, Postgres>,
    subscription_token: &str,
    subscriber_id: &Uuid,
) -> Result<(), sqlx::Error> {
    let query = sqlx::query!(
        r#"
        INSERT INTO subscription_tokens (subscription_token, subscriber_id)
        VALUES ($1, $2)
        "#,
        subscription_token,
        subscriber_id,
    );
    transaction.execute(query).await?;
    Ok(())
}

#[tracing::instrument(
    name = "Send a confirmation email to a new subscriber",
    skip(email_client, new_subscriber, base_url, subscription_token)
)]
pub async fn send_confirmation_email(
    email_client: &EmailClient,
    new_subscriber: &NewSubscriber,
    base_url: &str,
    subscription_token: &str,
) -> Result<(), reqwest::Error> {
    let confirmation_link = format!(
        "{}/subscriptions/confirm?subscription_token={}",
        base_url, subscription_token
    );
    let html_content = format!(
        "Welcome to our newsletter!<br />\
Click <a href=\"{}\">here</a> to confirm your subscription.",
        confirmation_link
    );
    let text_content = format!(
        "Welcome to our newsletter!\nVisit {} to confirm your subscription.",
        confirmation_link
    );
    email_client
        .send_email(
            &new_subscriber.email,
            "Welcome!",
            &html_content,
            &text_content,
        )
        .await
}

#[derive(Debug, Deserialize)]
pub struct SubscriptionFormData {
    email: String,
}

impl TryFrom<SubscriptionFormData> for NewSubscriber {
    type Error = anyhow::Error;

    fn try_from(value: SubscriptionFormData) -> Result<Self, Self::Error> {
        let email = SubscriberEmail::parse(value.email)?;
        Ok(Self { email })
    }
}