youtube-legend-cli 0.2.8

Non-interactive Rust CLI that downloads YouTube subtitles through third-party providers, using a native Unix stdin/stdout interface.
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
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155

//! Extract and validate the 11-character YouTube video id from any
//! recognized YouTube URL form.

use crate::error::{AppError, AppResult};

/// Parse a YouTube URL and return the 11-character video id.
///
/// Supports the following URL forms:
///
/// - `https://www.youtube.com/watch?v=<id>`
/// - `https://youtube.com/watch?v=<id>`
/// - `https://m.youtube.com/watch?v=<id>`
/// - `https://www.youtube.com/shorts/<id>`
/// - `https://www.youtube.com/embed/<id>`
/// - `https://youtu.be/<id>`
///
/// # Errors
///
/// - [`AppError::InvalidUrl`] if the input is not a syntactically valid URL,
///   does not point to a YouTube host, or does not carry a video id in any
///   of the supported forms, or if the extracted id is not exactly 11
///   characters of `[A-Za-z0-9_-]`.
///
/// # Examples
///
/// ```
/// use youtube_legend_cli::parse::video_id::extract_video_id;
///
/// let id = extract_video_id("https://youtu.be/dQw4w9WgXcQ").unwrap();
/// assert_eq!(id, "dQw4w9WgXcQ");
/// ```
#[tracing::instrument(level = "debug", err, skip(input), fields(input = %input.chars().take(64).collect::<String>()))]
pub fn extract_video_id(input: &str) -> AppResult<String> {
    let url = url::Url::parse(input)
        .map_err(|e| AppError::InvalidUrl(format!("could not parse url: {e}")))?;

    let host = url
        .host_str()
        .ok_or_else(|| AppError::InvalidUrl("url has no host".to_string()))?
        .to_lowercase();

    let path_segments: Vec<&str> = url
        .path_segments()
        .map(|s| s.filter(|p| !p.is_empty()).collect())
        .unwrap_or_default();

    let video_id = match host.as_str() {
        "youtu.be" => path_segments
            .first()
            .copied()
            .ok_or_else(|| AppError::InvalidUrl("youtu.be url has no id".to_string()))?
            .to_string(),
        "youtube.com" | "www.youtube.com" | "m.youtube.com" => {
            if let Some(query_id) = url.query_pairs().find(|(k, _)| k == "v") {
                query_id.1.into_owned()
            } else if path_segments.first().copied() == Some("shorts")
                || path_segments.first().copied() == Some("embed")
            {
                path_segments
                    .get(1)
                    .copied()
                    .ok_or_else(|| {
                        AppError::InvalidUrl(format!(
                            "{} path has no id",
                            path_segments.first().copied().unwrap_or("path")
                        ))
                    })?
                    .to_string()
            } else {
                return Err(AppError::InvalidUrl(
                    "youtube.com url has neither ?v= nor /shorts/ nor /embed/".to_string(),
                ));
            }
        }
        _ => {
            return Err(AppError::InvalidUrl(format!(
                "domain is not youtube: {host}"
            )));
        }
    };

    validate_video_id(&video_id)?;
    Ok(video_id)
}

fn validate_video_id(id: &str) -> AppResult<()> {
    if id.len() != 11 {
        return Err(AppError::InvalidUrl(format!(
            "video id must be 11 characters, got {}: {id}",
            id.len()
        )));
    }
    if !id
        .chars()
        .all(|c| c.is_ascii_alphanumeric() || c == '_' || c == '-')
    {
        return Err(AppError::InvalidUrl(format!(
            "video id contains invalid characters: {id}"
        )));
    }
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn extracts_watch_url() {
        let id = extract_video_id("https://www.youtube.com/watch?v=dQw4w9WgXcQ").unwrap();
        assert_eq!(id, "dQw4w9WgXcQ");
    }

    #[test]
    fn extracts_short_url() {
        let id = extract_video_id("https://youtu.be/dQw4w9WgXcQ").unwrap();
        assert_eq!(id, "dQw4w9WgXcQ");
    }

    #[test]
    fn extracts_shorts_url() {
        let id = extract_video_id("https://www.youtube.com/shorts/dQw4w9WgXcQ").unwrap();
        assert_eq!(id, "dQw4w9WgXcQ");
    }

    #[test]
    fn extracts_embed_url() {
        let id = extract_video_id("https://www.youtube.com/embed/dQw4w9WgXcQ").unwrap();
        assert_eq!(id, "dQw4w9WgXcQ");
    }

    #[test]
    fn rejects_non_youtube() {
        let err = extract_video_id("https://example.com/watch?v=ABC123DEF45").unwrap_err();
        assert!(matches!(err, AppError::InvalidUrl(_)));
    }

    #[test]
    fn rejects_short_id() {
        let err = extract_video_id("https://youtu.be/abc").unwrap_err();
        assert!(matches!(err, AppError::InvalidUrl(_)));
    }

    #[test]
    fn rejects_special_chars() {
        let err = extract_video_id("https://www.youtube.com/watch?v=abc!@#$%^&*()").unwrap_err();
        assert!(matches!(err, AppError::InvalidUrl(_)));
    }

    #[test]
    fn rejects_invalid_url() {
        let err = extract_video_id("not a url at all").unwrap_err();
        assert!(matches!(err, AppError::InvalidUrl(_)));
    }
}