Implement file downloading (and also add Bot::get_file)

Cargo.toml

@@ -14,3 +14,4 @@ apply = "0.2.2"
 derive_more = "0.15.0"
 tokio = "0.2.0-alpha.4"
 bytes = "0.4.12"
+futures-preview = "0.3.0-alpha.18"

src/bot/mod.rs

@@ -1,5 +1,7 @@
 use reqwest::r#async::Client;
 
+use crate::core::network::{download_file, download_file_stream};
+use crate::core::requests::get_file::GetFile;
 use crate::core::{
     requests::{
         edit_message_live_location::EditMessageLiveLocation,
@@ -11,6 +13,10 @@ use crate::core::{
     },
     types::{InputFile, InputMedia},
 };
+use crate::DownloadError;
+use reqwest::r#async::Chunk;
+use tokio::io::AsyncWrite;
+use tokio::stream::Stream;
 
 pub struct Bot {
     token: String,
@@ -42,6 +48,62 @@ impl Bot {
 
 /// Telegram functions
 impl Bot {
+    /// Download file from telegram into `destination`.
+    /// `path` can be obtained from [`get_file`] method.
+    ///
+    /// For downloading as Stream of Chunks see [`download_file_stream`].
+    ///
+    /// ## Examples
+    ///
+    /// ```no_run
+    /// use async_telegram_bot::{
+    ///     bot::Bot,
+    ///     core::{requests::Request, types::File as TgFile},
+    /// };
+    /// use tokio::fs::File;
+    /// # use async_telegram_bot::core::requests::RequestError;
+    ///
+    /// # async fn run() -> Result<(), Box<dyn std::error::Error>> {
+    /// let bot = Bot::new("TOKEN");
+    /// let mut file = File::create("/home/waffle/Pictures/test.png").await?;
+    ///
+    /// let TgFile { file_path, .. } = bot.get_file("*file_id*").send().await?;
+    /// bot.download_file(&file_path, &mut file).await?;
+    /// # Ok(()) }
+    /// ```
+    ///
+    /// [`get_file`]: crate::bot::Bot::get_file
+    /// [`download_file_stream`]: crate::bot::Bot::download_file_stream
+    pub async fn download_file<D>(
+        &self,
+        path: &str,
+        destination: &mut D,
+    ) -> Result<(), DownloadError>
+    where
+        D: AsyncWrite + Unpin,
+    {
+        download_file(&self.client, &self.token, path, destination).await
+    }
+
+    /// Download file from telegram.
+    ///
+    /// `path` can be obtained from [`get_file`] method.
+    ///
+    /// For downloading into [`AsyncWrite`] (e.g. [`tokio::fs::File`])
+    /// see  [`download_file`].
+    ///
+    /// [`get_file`]: crate::bot::Bot::get_file
+    /// [`AsyncWrite`]: tokio::io::AsyncWrite
+    /// [`tokio::fs::File`]: tokio::fs::File
+    /// [`download_file`]: crate::bot::Bot::download_file
+    pub async fn download_file_stream(
+        &self,
+        path: &str,
+    ) -> Result<impl Stream<Item = Result<Chunk, reqwest::Error>>, reqwest::Error>
+    {
+        download_file_stream(&self.client, &self.token, path).await
+    }
+
     pub fn get_me(&self) -> GetMe {
         GetMe::new(self.ctx())
     }
@@ -135,4 +197,11 @@ impl Bot {
     pub fn stop_message_live_location(&self) -> StopMessageLiveLocation {
         StopMessageLiveLocation::new(self.ctx())
     }
+
+    pub fn get_file<F>(&self, file_id: F) -> GetFile
+    where
+        F: Into<String>,
+    {
+        GetFile::new(self.ctx(), file_id.into())
+    }
 }

src/core/mod.rs

@@ -1,3 +1,3 @@
-mod network;
+pub(crate) mod network;
 pub mod requests;
 pub mod types;

src/core/network/mod.rs

@@ -3,12 +3,19 @@ use crate::core::{
     types::ResponseParameters,
 };
 
+use crate::DownloadError;
 use apply::Apply;
+use bytes::Buf;
+use futures::StreamExt;
+use reqwest::r#async::Chunk;
 use reqwest::{
     r#async::{multipart::Form, Client},
     StatusCode,
 };
 use serde::{de::DeserializeOwned, Serialize};
+use tokio::io::AsyncWriteExt;
+use tokio::prelude::AsyncWrite;
+use tokio::stream::Stream;
 
 const TELEGRAM_API_URL: &str = "https://api.telegram.org";
 
@@ -102,6 +109,34 @@ enum TelegramResponse<R> {
     },
 }
 
+pub async fn download_file<D>(
+    client: &Client,
+    token: &str,
+    path: &str,
+    destination: &mut D,
+) -> Result<(), DownloadError>
+where
+    D: AsyncWrite + Unpin,
+{
+    let mut stream = download_file_stream(client, token, path).await?;
+
+    while let Some(chunk) = stream.next().await {
+        destination.write_all(chunk?.bytes()).await?;
+    }
+
+    Ok(())
+}
+
+pub(crate) async fn download_file_stream(
+    client: &Client,
+    token: &str,
+    path: &str,
+) -> Result<impl Stream<Item = Result<Chunk, reqwest::Error>>, reqwest::Error> {
+    let url = file_url(TELEGRAM_API_URL, token, path);
+    let resp = client.get(&url).send().await?.error_for_status()?;
+    Ok(resp.into_body())
+}
+
 impl<R> Into<ResponseResult<R>> for TelegramResponse<R> {
     fn into(self) -> Result<R, RequestError> {
         match self {

src/errors.rs

@@ -0,0 +1,17 @@
+#[derive(Debug, Display, From)]
+pub enum DownloadError {
+    #[display(fmt = "Network error: {err}", err = _0)]
+    NetworkError(reqwest::Error),
+
+    #[display(fmt = "IO Error: {err}", err = _0)]
+    Io(std::io::Error),
+}
+
+impl std::error::Error for DownloadError {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        match self {
+            DownloadError::NetworkError(err) => Some(err),
+            DownloadError::Io(err) => Some(err),
+        }
+    }
+}

src/lib.rs

@@ -5,3 +5,6 @@ extern crate serde;
 
 pub mod bot;
 pub mod core;
+pub mod errors;
+
+pub use errors::DownloadError;