Add DownloadRequestBuilder for more complex download support

src/client/object.rs

@@ -1,5 +1,5 @@
+use bytes::Bytes;
 use futures_util::{stream, Stream, TryStream};
-use reqwest::StatusCode;
 
 use crate::{
     error::GoogleResponse,
@@ -276,24 +276,8 @@ impl<'a> ObjectClient<'a> {
     /// # }
     /// ```
     pub async fn download(&self, bucket: &str, file_name: &str) -> crate::Result<Vec<u8>> {
-        let url = format!(
-            "{}/b/{}/o/{}?alt=media",
-            crate::BASE_URL,
-            percent_encode(bucket),
-            percent_encode(file_name),
-        );
-        let resp = self
-            .0
-            .client
-            .get(&url)
-            .headers(self.0.get_headers().await?)
-            .send()
-            .await?;
-        if resp.status() == StatusCode::NOT_FOUND {
-            Err(crate::Error::Other(resp.text().await?))
-        } else {
-            Ok(resp.error_for_status()?.bytes().await?.to_vec())
-        }
+        let resp = self.download_request(bucket, file_name);
+        Ok(resp.bytes().await?.to_vec())
     }
 
     /// Download the content of the object with the specified name in the specified bucket, without
@@ -322,22 +306,9 @@ impl<'a> ObjectClient<'a> {
         &self,
         bucket: &str,
         file_name: &str,
-    ) -> crate::Result<impl Stream<Item = crate::Result<u8>> + Unpin> {
+    ) -> crate::Result<impl Stream<Item=crate::Result<u8>> + Unpin> {
         use futures_util::{StreamExt, TryStreamExt};
-        let url = format!(
-            "{}/b/{}/o/{}?alt=media",
-            crate::BASE_URL,
-            percent_encode(bucket),
-            percent_encode(file_name),
-        );
-        let response = self
-            .0
-            .client
-            .get(&url)
-            .headers(self.0.get_headers().await?)
-            .send()
-            .await?
-            .error_for_status()?;
+        let response = self.download_request(bucket, file_name).send().await?;
         let size = response.content_length();
         let bytes = response
             .bytes_stream()
@@ -346,6 +317,33 @@ impl<'a> ObjectClient<'a> {
         Ok(SizedByteStream::new(bytes, size))
     }
 
+    /// Returns a [`DownloadRequestBuilder`] which can be used to download the content of the
+    /// object with the specified name in the specified bucket, with additional options
+    ///
+    /// ### Example
+    /// ```no_run
+    /// # #[tokio::main]
+    /// # async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    /// use cloud_storage::Client;
+    /// use cloud_storage::Object;
+    /// use futures_util::stream::StreamExt;
+    /// use tokio::fs::File;
+    /// use tokio::io::{AsyncWriteExt, BufWriter};
+    ///
+    /// let client = Client::default();
+    /// let mut stream = client.object().download_request("my_bucket", "path/to/my/file.png").with_range(0..100).bytes_stream().await?;
+    /// let mut file = BufWriter::new(File::create("file.png").await.unwrap());
+    /// while let Some(bytes) = stream.next().await {
+    ///     file.write_all(&bytes.unwrap()).await.unwrap();
+    /// }
+    /// file.flush().await?;
+    /// # Ok(())
+    /// # }
+    /// ```
+    pub fn download_request(&self, bucket: &str, file_name: &str) -> DownloadRequestBuilder<'_> {
+        DownloadRequestBuilder::new(self.0, bucket, file_name)
+    }
+
     /// Updates a single object with the specified name in the specified bucket with the new
     /// information in `object`.
     ///
@@ -588,3 +586,63 @@ impl<'a> ObjectClient<'a> {
         // }
     }
 }
+
+/// A builder used to construct a download request
+pub struct DownloadRequestBuilder<'a> {
+    url: String,
+    range: Option<String>,
+    gcs_client: &'a super::Client,
+}
+
+impl<'a> DownloadRequestBuilder<'a> {
+    /// Create a new request builder
+    fn new(gcs_client: &'a super::Client, bucket: &str, file_name: &str) -> Self {
+        let url = format!(
+            "{}/b/{}/o/{}?alt=media",
+            crate::BASE_URL,
+            percent_encode(bucket),
+            percent_encode(file_name),
+        );
+
+        Self {
+            url,
+            gcs_client,
+            range: None,
+        }
+    }
+
+    /// Specify a range of bytes to download
+    ///
+    /// See https://cloud.google.com/storage/docs/json_api/v1/parameters#range
+    pub fn with_range(self, range: impl Into<String>) -> Self {
+        Self {
+            range: Some(range.into()),
+            ..self
+        }
+    }
+
+    /// Dispatch the request and return the response
+    async fn send(self) -> crate::Result<reqwest::Response> {
+        let headers = self.gcs_client.get_headers().await?;
+        let mut builder = self.gcs_client.client.get(self.url).headers(headers);
+
+        if let Some(range) = self.range {
+            builder = builder.header(reqwest::header::RANGE, range)
+        }
+
+        let resp = builder.send().await?.error_for_status()?;
+
+        Ok(resp)
+    }
+
+    /// Get the full response body as [`Bytes`]
+    pub async fn bytes(self) -> crate::Result<Bytes> {
+        Ok(self.send().await?.bytes().await?)
+    }
+
+    /// Return a stream of the downloaded bytes
+    pub async fn bytes_stream(self) -> crate::Result<impl Stream<Item=crate::Result<Bytes>>> {
+        use futures_util::stream::TryStreamExt;
+        Ok(self.send().await?.bytes_stream().map_err(Into::into))
+    }
+}