feat: add authentication

2 files changed, 185 insertions, 0 deletions

diff --git a/src/auth/mod.rs b/src/auth/mod.rs
new file mode 100644
index 0000000..c5beeb3
--- /dev/null
+++ b/src/auth/mod.rs
@@ -0,0 +1,145 @@
+//! Deezer API authentication.
+use std::error::Error;
+use std::fmt::Display;
+use std::time::Duration;
+
+use actix_web::web::Data;
+use actix_web::{App, HttpServer};
+use serde::Deserialize;
+use tokio::sync::mpsc;
+use tokio::task::JoinHandle;
+use tokio::{select, spawn};
+
+use crate::auth::service::retrieve_auth_code;
+use crate::errors::auth::{AccessTokenRequestError, AuthPromptHandlerError};
+
+mod service;
+
+const AUTH_URL: &str = "https://connect.deezer.com/oauth/auth.php";
+const ACCESS_TOKEN_URL: &str = "https://connect.deezer.com/oauth/access_token.php";
+
+/// A Deezer authentication code.
+#[derive(Debug, Deserialize, Clone)]
+pub struct AuthCode(String);
+
+impl Display for AuthCode
+{
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result
+    {
+        self.0.fmt(f)
+    }
+}
+
+/// A Deezer authentication prompt handler.
+pub struct AuthPromptHandler
+{
+    /// URL to the Deezer authentication prompt.
+    pub auth_prompt_url: String,
+
+    /// Handle for the running authentication prompt handler.
+    ///
+    /// Finishes when a single authentication has occurred.
+    pub handler: JoinHandle<Result<AuthCode, Box<dyn Error + Send + Sync>>>,
+}
+
+impl AuthPromptHandler
+{
+    /// Runs a web server that handles a Deezer authentication prompt.
+    ///
+    /// The argument `address` must be in the same domain as the domain you defined when
+    /// you created the application with the ID `app_id`.
+    ///
+    /// # Errors
+    /// Will return Err if the web server created is unable to bind to `address`.
+    pub async fn run(
+        app_id: u32,
+        address: String,
+        port: u16,
+        uri_scheme: String,
+    ) -> Result<Self, AuthPromptHandlerError>
+    {
+        let (done_tx, mut done_rx) = mpsc::channel::<AuthCode>(1);
+
+        let done_tx_data = Data::new(done_tx);
+
+        let server = HttpServer::new(move || {
+            App::new()
+                .app_data(done_tx_data.clone())
+                .service(retrieve_auth_code)
+        })
+        .bind((address.clone(), port))
+        .map_err(|_| AuthPromptHandlerError::BindAddressFailed)?;
+
+        let server_future = server.run();
+
+        let handle = spawn(async move {
+            let opt_auth_code = select! {
+                result = server_future => {
+                    result.map(|_| None)
+                },
+                auth_code = async {
+                    done_rx.recv().await
+                } => Ok(auth_code)
+            }?;
+
+            Ok(opt_auth_code.map_or_else(|| Err("No auth code was received"), Ok)?)
+        });
+
+        Ok(Self {
+            auth_prompt_url: format!(
+                "{}?app_id={}&redirect_uri={}://{}:{}&perms=basic_access",
+                AUTH_URL, app_id, uri_scheme, address, port
+            ),
+            handler: handle,
+        })
+    }
+}
+
+/// A Deezer access token.
+pub struct AccessToken
+{
+    /// The access token.
+    pub access_token: String,
+
+    /// The duration until the access token expires.
+    pub expires: Duration,
+}
+
+/// Sends a request for a access token.
+///
+/// # Errors
+/// Will return Err if either sending the request fails or parsing the response fails.
+pub async fn request_access_token(
+    app_id: u32,
+    secret_key: String,
+    auth_code: AuthCode,
+) -> Result<AccessToken, AccessTokenRequestError>
+{
+    let response = reqwest::get(format!(
+        "{}?app_id={}&secret={}&code={}&output=json",
+        ACCESS_TOKEN_URL, app_id, secret_key, auth_code
+    ))
+    .await?
+    .json::<AccessTokenResponse>()
+    .await?;
+
+    Ok(response.into())
+}
+
+#[derive(Debug, Deserialize)]
+struct AccessTokenResponse
+{
+    pub access_token: String,
+    pub expires: u64,
+}
+
+impl From<AccessTokenResponse> for AccessToken
+{
+    fn from(response: AccessTokenResponse) -> Self
+    {
+        Self {
+            access_token: response.access_token,
+            expires: Duration::from_secs(response.expires),
+        }
+    }
+}
diff --git a/src/auth/service.rs b/src/auth/service.rs
new file mode 100644
index 0000000..b9b44d4
--- /dev/null
+++ b/src/auth/service.rs
@@ -0,0 +1,40 @@
+use actix_web::web::{Data, Query};
+use actix_web::{get, HttpResponse};
+use serde::Deserialize;
+use tokio::sync::mpsc;
+
+use crate::auth::AuthCode;
+
+#[derive(Debug, Deserialize)]
+struct AuthCodeQuery
+{
+    error_reason: Option<String>,
+    code: Option<AuthCode>,
+}
+
+#[get("/")]
+async fn retrieve_auth_code(
+    query: Query<AuthCodeQuery>,
+    done_tx: Data<mpsc::Sender<AuthCode>>,
+) -> HttpResponse
+{
+    if let Some(error_reason) = &query.error_reason {
+        return HttpResponse::Unauthorized().body(format!(
+            "Error: No authentication code was retrieved. Reason: {}\n\nYou can close this tab",
+            error_reason
+        ));
+    }
+
+    let auth_code = match &query.code {
+        Some(auth_code) => auth_code,
+        None => {
+            return HttpResponse::BadRequest()
+                .body("Error: No authentication code was retrieved");
+        }
+    };
+
+    done_tx.send(auth_code.clone()).await.unwrap();
+
+    HttpResponse::Ok()
+        .body("Authentication code was successfully retrieved.\n\nYou can close this tab")
+}