| 1 | //! Parser for LRC (synced lyrics) files. |
| 2 | |
| 3 | use std::time::Duration; |
| 4 | |
| 5 | #[derive(Clone, Debug, PartialEq, Eq)] |
| 6 | pub struct LyricLine { |
| 7 | pub time: Duration, |
| 8 | pub text: String, |
| 9 | } |
| 10 | |
| 11 | #[derive(Clone, Debug, PartialEq, Eq)] |
| 12 | pub enum Lyrics { |
| 13 | /// Lines with timestamps, sorted by time. |
| 14 | Synced(Vec<LyricLine>), |
| 15 | Plain(Vec<String>), |
| 16 | } |
| 17 | |
| 18 | impl Lyrics { |
| 19 | /// Parses LRC text. Text without any timestamps is treated as plain |
| 20 | /// lyrics. |
| 21 | pub fn parse(text: &str) -> Self { |
| 22 | let mut offset_ms: i64 = 0; |
| 23 | let mut synced = Vec::new(); |
| 24 | for raw in text.lines() { |
| 25 | let mut rest = raw.trim(); |
| 26 | let mut times = Vec::new(); |
| 27 | while let Some(tag) = rest.strip_prefix('[').and_then(|r| r.split_once(']')) { |
| 28 | let (inner, tail) = tag; |
| 29 | if let Some(time) = parse_timestamp(inner) { |
| 30 | times.push(time); |
| 31 | } else if let Some(value) = inner.strip_prefix("offset:") { |
| 32 | offset_ms = value.trim().parse().unwrap_or(0); |
| 33 | } else if !is_id_tag(inner) { |
| 34 | break; |
| 35 | } |
| 36 | rest = tail; |
| 37 | } |
| 38 | let text = rest.trim().to_owned(); |
| 39 | synced.extend(times.into_iter().map(|time| (time, text.clone()))); |
| 40 | } |
| 41 | if synced.is_empty() { |
| 42 | return Self::Plain(text.lines().map(|l| l.trim_end().to_owned()).collect()); |
| 43 | } |
| 44 | // A positive offset makes lyrics appear sooner. |
| 45 | let mut lines: Vec<LyricLine> = synced |
| 46 | .into_iter() |
| 47 | .map(|(time, text)| LyricLine { |
| 48 | time: shift(time, -offset_ms), |
| 49 | text, |
| 50 | }) |
| 51 | .collect(); |
| 52 | lines.sort_by_key(|line| line.time); |
| 53 | Self::Synced(lines) |
| 54 | } |
| 55 | |
| 56 | pub fn is_empty(&self) -> bool { |
| 57 | match self { |
| 58 | Self::Synced(lines) => lines.is_empty(), |
| 59 | Self::Plain(lines) => lines.iter().all(|l| l.trim().is_empty()), |
| 60 | } |
| 61 | } |
| 62 | |
| 63 | pub fn len(&self) -> usize { |
| 64 | match self { |
| 65 | Self::Synced(lines) => lines.len(), |
| 66 | Self::Plain(lines) => lines.len(), |
| 67 | } |
| 68 | } |
| 69 | |
| 70 | /// The index of the line being sung at `elapsed`. |
| 71 | pub fn current_line(&self, elapsed: Duration) -> Option<usize> { |
| 72 | match self { |
| 73 | Self::Synced(lines) => lines |
| 74 | .partition_point(|line| line.time <= elapsed) |
| 75 | .checked_sub(1), |
| 76 | Self::Plain(_) => None, |
| 77 | } |
| 78 | } |
| 79 | |
| 80 | pub fn line(&self, index: usize) -> &str { |
| 81 | match self { |
| 82 | Self::Synced(lines) => lines.get(index).map_or("", |l| l.text.as_str()), |
| 83 | Self::Plain(lines) => lines.get(index).map_or("", String::as_str), |
| 84 | } |
| 85 | } |
| 86 | } |
| 87 | |
| 88 | /// `mm:ss`, `mm:ss.xx` or `mm:ss.xxx`. |
| 89 | fn parse_timestamp(tag: &str) -> Option<Duration> { |
| 90 | let (minutes, seconds) = tag.split_once(':')?; |
| 91 | let minutes: u64 = minutes.trim().parse().ok()?; |
| 92 | let (secs, fraction) = seconds.split_once(['.', ':']).unwrap_or((seconds, "0")); |
| 93 | let secs: u64 = secs.trim().parse().ok()?; |
| 94 | if secs >= 60 || fraction.is_empty() || !fraction.chars().all(|c| c.is_ascii_digit()) { |
| 95 | return None; |
| 96 | } |
| 97 | let millis = match fraction.len() { |
| 98 | 1 => fraction.parse::<u64>().ok()? * 100, |
| 99 | 2 => fraction.parse::<u64>().ok()? * 10, |
| 100 | _ => fraction[..3].parse::<u64>().ok()?, |
| 101 | }; |
| 102 | Some(Duration::from_millis((minutes * 60 + secs) * 1000 + millis)) |
| 103 | } |
| 104 | |
| 105 | fn is_id_tag(tag: &str) -> bool { |
| 106 | tag.split_once(':') |
| 107 | .is_some_and(|(key, _)| !key.is_empty() && key.chars().all(|c| c.is_ascii_alphabetic())) |
| 108 | } |
| 109 | |
| 110 | fn shift(time: Duration, ms: i64) -> Duration { |
| 111 | let shifted = time.as_millis() as i64 + ms; |
| 112 | Duration::from_millis(shifted.max(0) as u64) |
| 113 | } |
| 114 | |
| 115 | #[cfg(test)] |
| 116 | mod tests { |
| 117 | use super::*; |
| 118 | |
| 119 | fn ms(ms: u64) -> Duration { |
| 120 | Duration::from_millis(ms) |
| 121 | } |
| 122 | |
| 123 | #[test] |
| 124 | fn parses_synced_lyrics() { |
| 125 | let lyrics = Lyrics::parse( |
| 126 | "[ar:Someone]\n[ti:Song]\n[00:12.50]First\n[00:05.1][01:00.000]Chorus\n\n[00:20]Last", |
| 127 | ); |
| 128 | let Lyrics::Synced(lines) = &lyrics else { |
| 129 | panic!("expected synced lyrics"); |
| 130 | }; |
| 131 | let times: Vec<_> = lines.iter().map(|l| l.time).collect(); |
| 132 | assert_eq!(times, [ms(5_100), ms(12_500), ms(20_000), ms(60_000)]); |
| 133 | assert_eq!(lines[0].text, "Chorus"); |
| 134 | assert_eq!(lyrics.current_line(ms(0)), None); |
| 135 | assert_eq!(lyrics.current_line(ms(12_500)), Some(1)); |
| 136 | assert_eq!(lyrics.current_line(ms(90_000)), Some(3)); |
| 137 | } |
| 138 | |
| 139 | #[test] |
| 140 | fn applies_offset() { |
| 141 | let lyrics = Lyrics::parse("[offset:+500]\n[00:01.00]a\n[00:00.20]b"); |
| 142 | let Lyrics::Synced(lines) = lyrics else { |
| 143 | panic!("expected synced lyrics"); |
| 144 | }; |
| 145 | assert_eq!(lines[0].time, ms(0)); |
| 146 | assert_eq!(lines[1].time, ms(500)); |
| 147 | } |
| 148 | |
| 149 | #[test] |
| 150 | fn falls_back_to_plain() { |
| 151 | let lyrics = Lyrics::parse("Just some\nwords [not a tag]\n"); |
| 152 | assert_eq!( |
| 153 | lyrics, |
| 154 | Lyrics::Plain(vec!["Just some".into(), "words [not a tag]".into()]) |
| 155 | ); |
| 156 | assert_eq!(lyrics.current_line(ms(1000)), None); |
| 157 | } |
| 158 | |
| 159 | #[test] |
| 160 | fn rejects_bad_timestamps() { |
| 161 | assert_eq!(parse_timestamp("1:75.00"), None); |
| 162 | assert_eq!(parse_timestamp("ab:10"), None); |
| 163 | assert_eq!(parse_timestamp("02:03.4567"), Some(ms(123_456))); |
| 164 | } |
| 165 | } |