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

use futures_util::StreamExt;
use indicatif::{ProgressBar, ProgressStyle};
use reqwest::Client;
use std::cmp::min;
use std::fs::File;
use std::io::{Seek, Write};
use std::time::Duration;

#[derive(Debug, thiserror::Error)]
pub enum DownloadError {
    #[error(transparent)]
    NetworkError(#[from] reqwest::Error),

    #[error(transparent)]
    IOError(#[from] std::io::Error),

    #[error("{0}")]
    GenericError(String),
}

impl DownloadError {
    fn from_string(s: String) -> Self {
        DownloadError::GenericError(s)
    }
}

pub async fn download_file(
    client: &Client,
    url: &str,
    path: &str,
    title: &str,
) -> Result<(), DownloadError> {
    const RETRY_SECONDS: u64 = 5;
    let mut retries = 3;

    loop {
        let res = _download_file(client, url, path, title).await;

        retries -= 1;
        if retries < 0 {
            return res;
        }

        match res {
            Err(DownloadError::NetworkError(ref net_err))
                if net_err.is_connect() || net_err.is_timeout() =>
            {
                println!("  Will retry in {} seconds...", RETRY_SECONDS);
                tokio::time::sleep(Duration::from_secs(RETRY_SECONDS)).await;
                continue;
            }
            _ => return res,
        };
    }
}

async fn _download_file(
    client: &Client,
    url: &str,
    path: &str,
    title: &str,
) -> Result<(), DownloadError> {
    let (mut file, mut downloaded) = open_file_for_write(path)?;
    let total_size = get_content_length(client, url).await?;

    if downloaded >= total_size {
        println!("  Nothing to do. File already exists.");
        return Ok(());
    }

    // Start the download
    let res = client
        .get(url)
        .header("Range", format!("bytes={}-", downloaded))
        .send()
        .await?;

    let mut stream = res.bytes_stream();

    let pb = get_progress_bar(total_size);
    pb.set_message(format!("Downloading {}", title));

    while let Some(chunk) = stream.next().await {
        let chunk = chunk?;
        let _ = file.write(&chunk)?;

        downloaded = min(downloaded + (chunk.len() as u64), total_size);
        pb.set_position(downloaded);
    }

    pb.finish_and_clear();
    println!("  Downloaded {}", title);
    Ok(())
}

fn open_file_for_write(path: &str) -> Result<(File, u64), std::io::Error> {
    if std::path::Path::new(path).exists() {
        let mut file = std::fs::OpenOptions::new()
            .read(true)
            .append(true)
            .open(path)?;

        let file_size = std::fs::metadata(path)?.len();
        file.seek(std::io::SeekFrom::Start(file_size))?;
        Ok((file, file_size))
    } else {
        let file = File::create(path)?;
        Ok((file, 0))
    }
}

async fn get_content_length(client: &Client, url: &str) -> Result<u64, DownloadError> {
    let res = client.get(url).send().await?;
    res.content_length().ok_or_else(|| {
        DownloadError::from_string(format!("Failed to get content length from '{}'", &url))
    })
}

fn get_progress_bar(total_size: u64) -> ProgressBar {
    let pb = ProgressBar::new(total_size);
    let pb_template =
        "  {msg}\n  {spinner:.green} [{elapsed}] [{bar}] {bytes} / {total_bytes} ({bytes_per_sec})";

    pb.set_style(
        ProgressStyle::default_bar()
            .template(pb_template)
            .progress_chars("=> "),
    );
    pb
}