tact 0.1.1

Terminal interface for Nanocodex
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

//! Reusable demand-driven text wave for compact status labels.

use ratatui::{
    style::{Color, Modifier, Style},
    text::Span,
};
use std::time::{Duration, Instant};

const FRAME_INTERVAL: Duration = Duration::from_millis(140);
const SHADE_PERCENTAGES: [u16; 8] = [100, 85, 70, 55, 40, 48, 62, 80];

pub(super) struct WavedText {
    text: String,
    base_color: Color,
    active: bool,
    started_at: Instant,
    next_frame: Instant,
    frame: usize,
}

impl WavedText {
    pub(super) fn new(text: impl Into<String>, base_color: Color) -> Self {
        let now = Instant::now();
        Self {
            text: text.into(),
            base_color,
            active: false,
            started_at: now,
            next_frame: now + FRAME_INTERVAL,
            frame: 0,
        }
    }

    pub(super) fn set_active(&mut self, active: bool, now: Instant) {
        if self.active == active {
            return;
        }
        self.active = active;
        self.started_at = now;
        self.next_frame = now + FRAME_INTERVAL;
        self.frame = 0;
    }

    pub(super) const fn is_active(&self) -> bool {
        self.active
    }

    pub(super) fn animation_deadline(&self) -> Option<Instant> {
        self.active.then_some(self.next_frame)
    }

    pub(super) fn advance(&mut self, now: Instant) -> bool {
        if !self.active || now < self.next_frame {
            return false;
        }

        let ticks =
            now.saturating_duration_since(self.started_at).as_millis() / FRAME_INTERVAL.as_millis();
        let frame = usize::try_from(ticks).unwrap_or(usize::MAX) % SHADE_PERCENTAGES.len();
        self.next_frame = now + FRAME_INTERVAL;
        if frame == self.frame {
            return false;
        }
        self.frame = frame;
        true
    }

    pub(super) fn spans(&self) -> Vec<Span<'static>> {
        self.text
            .chars()
            .enumerate()
            .map(|(index, character)| {
                let style = if self.active {
                    let percentage =
                        SHADE_PERCENTAGES[(index + self.frame) % SHADE_PERCENTAGES.len()];
                    shade(self.base_color, percentage)
                } else {
                    Style::default().fg(self.base_color)
                };
                Span::styled(character.to_string(), style)
            })
            .collect()
    }
}

fn shade(color: Color, percentage: u16) -> Style {
    if let Color::Rgb(red, green, blue) = color {
        return Style::default().fg(Color::Rgb(
            scale(red, percentage),
            scale(green, percentage),
            scale(blue, percentage),
        ));
    }

    let style = Style::default().fg(color);
    if percentage < 60 {
        style.add_modifier(Modifier::DIM)
    } else if percentage > 90 {
        style.add_modifier(Modifier::BOLD)
    } else {
        style
    }
}

fn scale(channel: u8, percentage: u16) -> u8 {
    let scaled = u16::from(channel).saturating_mul(percentage) / 100;
    u8::try_from(scaled).unwrap_or(u8::MAX)
}

#[cfg(test)]
mod tests {
    use super::{Color, FRAME_INTERVAL, WavedText};
    use std::time::Instant;

    #[test]
    fn inactive_text_uses_its_base_color_without_scheduling_frames() {
        let base = Color::Rgb(200, 100, 50);
        let waved = WavedText::new("wave", base);

        assert_eq!(waved.animation_deadline(), None);
        assert!(waved.spans().iter().all(|span| span.style.fg == Some(base)));
    }

    #[test]
    fn active_text_shades_the_base_color_and_advances_on_demand() {
        let now = Instant::now();
        let mut waved = WavedText::new("wave", Color::Rgb(200, 100, 50));
        waved.set_active(true, now);
        let initial = waved.spans();

        assert_eq!(waved.animation_deadline(), Some(now + FRAME_INTERVAL));
        assert_eq!(initial[0].style.fg, Some(Color::Rgb(200, 100, 50)));
        assert_eq!(initial[1].style.fg, Some(Color::Rgb(170, 85, 42)));
        assert!(waved.advance(now + FRAME_INTERVAL));
        assert_ne!(waved.spans(), initial);

        waved.set_active(false, now + FRAME_INTERVAL);
        assert_eq!(waved.animation_deadline(), None);
        assert!(!waved.advance(now + FRAME_INTERVAL * 2));
    }
}