1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131

use std::future::Future;

use bytes::Bytes;
use futures::{
    future::{ready, Either},
    stream::{once, unfold},
    FutureExt, Stream, StreamExt,
};
use reqwest::{Client, Response, Url};
use tokio::io::{AsyncWrite, AsyncWriteExt};

use crate::{errors::DownloadError, net::file_url};

/// A trait for downloading files from Telegram.
pub trait Download<'w>
/* FIXME(waffle): ideally, this lifetime ('w) shouldn't be here, but we can't help it without
 * GATs */
{
    /// An error returned from [`download_file`](Self::download_file).
    type Err;

    /// A future returned from [`download_file`](Self::download_file).
    type Fut: Future<Output = Result<(), Self::Err>> + Send;

    /// Download a file from Telegram into `destination`.
    ///
    /// `path` can be obtained from [`GetFile`].
    ///
    /// To download as a stream of chunks, see [`download_file_stream`].
    ///
    /// ## Examples
    ///
    /// ```no_run
    /// use teloxide_core::{
    ///     net::Download,
    ///     requests::{Request, Requester},
    ///     types::File,
    ///     Bot,
    /// };
    /// use tokio::fs;
    ///
    /// # async fn run() -> Result<(), Box<dyn std::error::Error>> {
    /// let bot = Bot::new("TOKEN");
    ///
    /// let file = bot.get_file("*file_id*").await?;
    /// let mut dst = fs::File::create("/tmp/test.png").await?;
    /// bot.download_file(&file.path, &mut dst).await?;
    /// # Ok(()) }
    /// ```
    ///
    /// [`GetFile`]: crate::payloads::GetFile
    /// [`download_file_stream`]: Self::download_file_stream
    fn download_file(
        &self,
        path: &str,
        destination: &'w mut (dyn AsyncWrite + Unpin + Send),
    ) -> Self::Fut;

    /// An error returned from
    /// [`download_file_stream`](Self::download_file_stream).
    type StreamErr;

    /// A stream returned from [`download_file_stream`].
    ///
    ///[`download_file_stream`]: (Self::download_file_stream)
    type Stream: Stream<Item = Result<Bytes, Self::StreamErr>> + Send;

    /// Download a file from Telegram as [`Stream`].
    ///
    /// `path` can be obtained from the [`GetFile`].
    ///
    /// To download into an [`AsyncWrite`] (e.g. [`tokio::fs::File`]), see
    /// [`download_file`].
    ///
    /// [`GetFile`]: crate::payloads::GetFile
    /// [`AsyncWrite`]: tokio::io::AsyncWrite
    /// [`tokio::fs::File`]: tokio::fs::File
    /// [`download_file`]: Self::download_file
    fn download_file_stream(&self, path: &str) -> Self::Stream;
}

/// Download a file from Telegram into `dst`.
///
/// Note: if you don't need to use a different (from you're bot) client and
/// don't need to get *all* performance (and you don't, c'mon it's very io-bound
/// job), then it's recommended to use [`Download::download_file`].
pub fn download_file<'o, D>(
    client: &Client,
    api_url: Url,
    token: &str,
    path: &str,
    dst: &'o mut D,
) -> impl Future<Output = Result<(), DownloadError>> + 'o
where
    D: ?Sized + AsyncWrite + Unpin,
{
    client.get(file_url(api_url, token, path)).send().then(move |r| async move {
        let mut res = r?.error_for_status()?;

        while let Some(chunk) = res.chunk().await? {
            dst.write_all(&chunk).await?;
        }

        Ok(())
    })
}

/// Download a file from Telegram as [`Stream`].
///
/// Note: if you don't need to use a different (from you're bot) client and
/// don't need to get *all* performance (and you don't, c'mon it's very io-bound
/// job), then it's recommended to use [`Download::download_file_stream`].
pub fn download_file_stream(
    client: &Client,
    api_url: Url,
    token: &str,
    path: &str,
) -> impl Stream<Item = reqwest::Result<Bytes>> + 'static {
    client.get(file_url(api_url, token, path)).send().into_stream().flat_map(|res| {
        match res.and_then(Response::error_for_status) {
            Ok(res) => Either::Left(unfold(res, |mut res| async {
                match res.chunk().await {
                    Err(err) => Some((Err(err), res)),
                    Ok(Some(c)) => Some((Ok(c), res)),
                    Ok(None) => None,
                }
            })),
            Err(err) => Either::Right(once(ready(Err(err)))),
        }
    })
}