Merge pull request #232 from Songtronix/songtronix/add-download-example

Add example for download with progress tracking

1 files changed, 110 insertions, 0 deletions

diff --git a/examples/download_progress/src/download.rs b/examples/download_progress/src/download.rs
new file mode 100644
index 00000000..96e1dc28
--- /dev/null
+++ b/examples/download_progress/src/download.rs
@@ -0,0 +1,110 @@
+use iced_futures::futures;
+
+// Just a little utility function
+pub fn file<T: ToString>(url: T) -> iced::Subscription<Progress> {
+    iced::Subscription::from_recipe(Download {
+        url: url.to_string(),
+    })
+}
+
+pub struct Download {
+    url: String,
+}
+
+// Make sure iced can use our download stream
+impl<H, I> iced_native::subscription::Recipe<H, I> for Download
+where
+    H: std::hash::Hasher,
+{
+    type Output = Progress;
+
+    fn hash(&self, state: &mut H) {
+        use std::hash::Hash;
+        std::any::TypeId::of::<Self>().hash(state);
+    }
+
+    fn stream(
+        self: Box<Self>,
+        _input: futures::stream::BoxStream<'static, I>,
+    ) -> futures::stream::BoxStream<'static, Self::Output> {
+        Box::pin(futures::stream::unfold(
+            State::Ready(self.url),
+            |state| async move {
+                match state {
+                    State::Ready(url) => {
+                        let response = reqwest::get(&url).await;
+
+                        match response {
+                            Ok(response) => {
+                                if let Some(total) = response.content_length() {
+                                    Some((
+                                        Progress::Started,
+                                        State::Downloading {
+                                            response,
+                                            total,
+                                            downloaded: 0,
+                                        },
+                                    ))
+                                } else {
+                                    Some((Progress::Errored, State::Finished))
+                                }
+                            }
+                            Err(_) => {
+                                Some((Progress::Errored, State::Finished))
+                            }
+                        }
+                    }
+                    State::Downloading {
+                        mut response,
+                        total,
+                        downloaded,
+                    } => match response.chunk().await {
+                        Ok(Some(chunk)) => {
+                            let downloaded = downloaded + chunk.len() as u64;
+
+                            let percentage =
+                                (downloaded as f32 / total as f32) * 100.0;
+
+                            Some((
+                                Progress::Advanced(percentage),
+                                State::Downloading {
+                                    response,
+                                    total,
+                                    downloaded,
+                                },
+                            ))
+                        }
+                        Ok(None) => Some((Progress::Finished, State::Finished)),
+                        Err(_) => Some((Progress::Errored, State::Finished)),
+                    },
+                    State::Finished => {
+                        // We do not let the stream die, as it would start a
+                        // new download repeatedly if the user is not careful
+                        // in case of errors.
+                        let _: () = iced::futures::future::pending().await;
+
+                        None
+                    }
+                }
+            },
+        ))
+    }
+}
+
+#[derive(Debug, Clone)]
+pub enum Progress {
+    Started,
+    Advanced(f32),
+    Finished,
+    Errored,
+}
+
+pub enum State {
+    Ready(String),
+    Downloading {
+        response: reqwest::Response,
+        total: u64,
+        downloaded: u64,
+    },
+    Finished,
+}