Improve packaging (#328)

* Add gpgui-helper (#326)

* Add packaging

apps/gpgui-helper/src-tauri/src/downloader.rs

@@ -0,0 +1,87 @@
+use std::io::Write;
+
+use anyhow::bail;
+use futures_util::StreamExt;
+use log::info;
+use tempfile::NamedTempFile;
+use tokio::sync::RwLock;
+
+type OnProgress = Box<dyn Fn(Option<f64>) + Send + Sync + 'static>;
+
+pub struct FileDownloader<'a> {
+  url: &'a str,
+  on_progress: RwLock<Option<OnProgress>>,
+}
+
+impl<'a> FileDownloader<'a> {
+  pub fn new(url: &'a str) -> Self {
+    Self {
+      url,
+      on_progress: Default::default(),
+    }
+  }
+
+  pub fn on_progress<T>(&self, on_progress: T)
+  where
+    T: Fn(Option<f64>) + Send + Sync + 'static,
+  {
+    if let Ok(mut guard) = self.on_progress.try_write() {
+      *guard = Some(Box::new(on_progress));
+    } else {
+      info!("Failed to acquire on_progress lock");
+    }
+  }
+
+  pub async fn download(&self) -> anyhow::Result<NamedTempFile> {
+    let res = reqwest::get(self.url).await?.error_for_status()?;
+    let content_length = res.content_length().unwrap_or(0);
+
+    info!("Content length: {}", content_length);
+
+    let mut current_length = 0;
+    let mut stream = res.bytes_stream();
+
+    let mut file = NamedTempFile::new()?;
+
+    while let Some(item) = stream.next().await {
+      let chunk = item?;
+      let chunk_size = chunk.len() as u64;
+
+      file.write_all(&chunk)?;
+
+      current_length += chunk_size;
+      let progress = current_length as f64 / content_length as f64 * 100.0;
+
+      if let Some(on_progress) = &*self.on_progress.read().await {
+        let progress = if content_length > 0 { Some(progress) } else { None };
+
+        on_progress(progress);
+      }
+    }
+
+    if content_length > 0 && current_length != content_length {
+      bail!("Download incomplete");
+    }
+
+    info!("Downloaded to: {:?}", file.path());
+
+    Ok(file)
+  }
+}
+
+pub struct ChecksumFetcher<'a> {
+  url: &'a str,
+}
+
+impl<'a> ChecksumFetcher<'a> {
+  pub fn new(url: &'a str) -> Self {
+    Self { url }
+  }
+
+  pub async fn fetch(&self) -> anyhow::Result<String> {
+    let res = reqwest::get(self.url).await?.error_for_status()?;
+    let checksum = res.text().await?.trim().to_string();
+
+    Ok(checksum)
+  }
+}