add opengraph metadata for preview cards

src/main.rs

@@ -30,6 +30,7 @@ struct AppState {
 }
 
 struct Config {
+    base_url: String,
     max_upload_size: u64,
     max_lifetime: u16,
     upload_password: String,
@@ -58,12 +59,14 @@ pub fn log_auth_failure(ip_addr: &str) {
 #[template(path = "index.html")]
 struct IndexPage {
     cachebuster: String,
+    base_url: String,
 }
 
 #[get("/")]
 async fn index(data: web::Data<AppState>) -> impl Responder {
     IndexPage {
         cachebuster: data.config.cachebuster.clone(),
+        base_url: data.config.base_url.clone(),
     }
 }
 
@@ -78,6 +81,7 @@ struct DownloadRequest {
 struct DownloadPage<'a> {
     info: DownloadInfo,
     cachebuster: &'a str,
+    base_url: &'a str,
 }
 
 #[derive(Serialize)]
@@ -134,6 +138,7 @@ async fn handle_download(
                 offsets,
             },
             cachebuster: &data.config.cachebuster,
+            base_url: &data.config.base_url,
         }
         .to_response())
     }
@@ -175,6 +180,7 @@ async fn download_info(
 #[template(path = "404.html")]
 struct NotFoundPage<'a> {
     cachebuster: &'a str,
+    base_url: &'a str,
 }
 
 fn not_found<T>(req: HttpRequest, data: web::Data<AppState>, report: bool) -> actix_web::Result<T> {
@@ -184,6 +190,7 @@ fn not_found<T>(req: HttpRequest, data: web::Data<AppState>, report: bool) -> ac
     }
     let mut resp = NotFoundPage {
         cachebuster: &data.config.cachebuster,
+        base_url: &data.config.base_url,
     }
     .to_response();
     *resp.status_mut() = StatusCode::NOT_FOUND;
@@ -269,6 +276,14 @@ where
         .unwrap_or_else(default)
 }
 
+fn env_or_panic<T: FromStr>(var: &str) -> T
+where
+    <T as FromStr>::Err: Debug,
+{
+    let val = std::env::var(var).unwrap_or_else(|_| panic!("{} must be set!", var));
+    val.parse::<T>().unwrap_or_else(|_| panic!("Invalid value {} for variable {}", val, var))
+}
+
 #[actix_web::main]
 async fn main() -> std::io::Result<()> {
     dotenv::dotenv().ok();
@@ -276,6 +291,7 @@ async fn main() -> std::io::Result<()> {
 
     let static_dir: PathBuf = env_or_else("TRANSBEAM_STATIC_DIR", || PathBuf::from("static"));
     let storage_dir: PathBuf = env_or_else("TRANSBEAM_STORAGE_DIR", || PathBuf::from("storage"));
+    let base_url: String = env_or_panic("TRANSBEAM_BASE_URL");
     let port: u16 = env_or("TRANSBEAM_PORT", 8080);
     let mnemonic_codes: bool = env_or("TRANSBEAM_MNEMONIC_CODES", true);
     let reverse_proxy: bool = env_or("TRANSBEAM_REVERSE_PROXY", true);
@@ -284,13 +300,13 @@ async fn main() -> std::io::Result<()> {
         env_or::<ByteSize>("TRANSBEAM_MAX_UPLOAD_SIZE", ByteSize(16 * bytesize::GB)).as_u64();
     let max_storage_size: u64 =
         env_or::<ByteSize>("TRANSBEAM_MAX_STORAGE_SIZE", ByteSize(64 * bytesize::GB)).as_u64();
-    let upload_password: String =
-        std::env::var("TRANSBEAM_UPLOAD_PASSWORD").expect("TRANSBEAM_UPLOAD_PASSWORD must be set!");
+    let upload_password: String = env_or_panic("TRANSBEAM_UPLOAD_PASSWORD");
     let cachebuster: String = env_or_else("TRANSBEAM_CACHEBUSTER", String::new);
 
     let data = web::Data::new(AppState {
         file_store: RwLock::new(FileStore::load(storage_dir.clone(), max_storage_size).await?),
         config: Config {
+            base_url,
             max_upload_size,
             max_lifetime,
             upload_password,