ced/src/app/theme.rs

use eframe::egui;

#[derive(Debug, Clone, Copy, PartialEq, serde::Serialize, serde::Deserialize, Default)]
pub enum Theme {
    #[default]
    System,
    Light,
    Dark,
}

pub fn apply(theme: Theme, ctx: &egui::Context) {
    match theme {
        Theme::System => {
            if let Some(system_visuals) = get_system_colors() {
                ctx.set_visuals(system_visuals);
            } else {
                let is_dark = detect_system_dark_mode();
                if is_dark {
                    ctx.set_visuals(egui::Visuals::dark());
                } else {
                    ctx.set_visuals(egui::Visuals::light());
                }
            }
        }
        Theme::Light => {
            ctx.set_visuals(egui::Visuals::light());
        }
        Theme::Dark => {
            ctx.set_visuals(egui::Visuals::dark());
        }
    }
}

fn get_system_colors() -> Option<egui::Visuals> {
    if let Some(visuals) = get_pywal_colors() {
        return Some(visuals);
    }

    #[cfg(target_os = "linux")]
    {
        if let Some(visuals) = get_gtk_colors() {
            return Some(visuals);
        }
    }
    None
}

fn get_pywal_colors() -> Option<egui::Visuals> {
    use std::fs;
    use std::path::Path;

    let home = std::env::var("HOME").ok()?;
    let colors_path = Path::new(&home).join(".cache/wal/colors");

    if !colors_path.exists() {
        return None;
    }

    let colors_content = fs::read_to_string(&colors_path).ok()?;
    let colors: Vec<&str> = colors_content.lines().collect();

    if colors.len() < 8 {
        return None;
    }

    let parse_color = |hex: &str| -> Option<egui::Color32> {
        if hex.len() != 7 || !hex.starts_with('#') {
            return None;
        }
        let r = u8::from_str_radix(&hex[1..3], 16).ok()?;
        let g = u8::from_str_radix(&hex[3..5], 16).ok()?;
        let b = u8::from_str_radix(&hex[5..7], 16).ok()?;
        Some(egui::Color32::from_rgb(r, g, b))
    };

    let bg = parse_color(colors[0])?;
    let fg = parse_color(colors.get(7).unwrap_or(&colors[0]))?;
    let bg_alt = parse_color(colors.get(8).unwrap_or(&colors[0]))?;
    let accent = parse_color(colors.get(1).unwrap_or(&colors[0]))?;
    let secondary = parse_color(colors.get(2).unwrap_or(&colors[0]))?;

    let mut visuals = if is_dark_color(bg) {
        egui::Visuals::dark()
    } else {
        egui::Visuals::light()
    };

    visuals.window_fill = bg;
    visuals.extreme_bg_color = bg;
    visuals.code_bg_color = bg;
    visuals.panel_fill = bg;

    visuals.faint_bg_color = blend_colors(bg, bg_alt, 0.15);
    visuals.error_fg_color = parse_color(colors.get(1).unwrap_or(&colors[0]))?;

    visuals.override_text_color = Some(fg);

    visuals.hyperlink_color = accent;
    visuals.selection.bg_fill = blend_colors(accent, bg, 0.3);
    visuals.selection.stroke.color = accent;

    let separator_color = blend_colors(fg, bg, 0.3);

    visuals.widgets.noninteractive.bg_stroke = egui::Stroke::new(1.0, separator_color);
    visuals.widgets.noninteractive.bg_fill = bg;
    visuals.widgets.noninteractive.fg_stroke.color = fg;

    visuals.widgets.inactive.bg_fill = blend_colors(bg, accent, 0.2);
    visuals.widgets.inactive.fg_stroke.color = fg;
    visuals.widgets.inactive.bg_stroke = egui::Stroke::new(1.0, blend_colors(accent, bg, 0.4));
    visuals.widgets.inactive.weak_bg_fill = blend_colors(bg, accent, 0.1);

    visuals.widgets.hovered.bg_fill = blend_colors(bg, accent, 0.3);
    visuals.widgets.hovered.fg_stroke.color = fg;
    visuals.widgets.hovered.bg_stroke = egui::Stroke::new(1.0, accent);
    visuals.widgets.hovered.weak_bg_fill = blend_colors(bg, accent, 0.15);

    visuals.widgets.active.bg_fill = blend_colors(bg, accent, 0.4);
    visuals.widgets.active.fg_stroke.color = fg;
    visuals.widgets.active.bg_stroke = egui::Stroke::new(1.0, accent);
    visuals.widgets.active.weak_bg_fill = blend_colors(bg, accent, 0.2);

    visuals.window_stroke = egui::Stroke::new(1.0, separator_color);

    visuals.widgets.open.bg_fill = blend_colors(bg, accent, 0.25);
    visuals.widgets.open.fg_stroke.color = fg;
    visuals.widgets.open.bg_stroke = egui::Stroke::new(1.0, accent);
    visuals.widgets.open.weak_bg_fill = blend_colors(bg, accent, 0.15);

    visuals.striped = true;

    visuals.button_frame = true;
    visuals.collapsing_header_frame = false;

    Some(visuals)
}

fn get_gtk_colors() -> Option<egui::Visuals> {
    None
}

fn is_dark_color(color: egui::Color32) -> bool {
    let r = color.r() as f32 / 255.0;
    let g = color.g() as f32 / 255.0;
    let b = color.b() as f32 / 255.0;

    let r_lin = if r <= 0.04045 {
        r / 12.92
    } else {
        ((r + 0.055) / 1.055).powf(2.4)
    };
    let g_lin = if g <= 0.04045 {
        g / 12.92
    } else {
        ((g + 0.055) / 1.055).powf(2.4)
    };
    let b_lin = if b <= 0.04045 {
        b / 12.92
    } else {
        ((b + 0.055) / 1.055).powf(2.4)
    };

    let luminance = 0.2126 * r_lin + 0.7152 * g_lin + 0.0722 * b_lin;

    luminance < 0.5
}

fn blend_colors(base: egui::Color32, blend: egui::Color32, factor: f32) -> egui::Color32 {
    let factor = factor.clamp(0.0, 1.0);
    let inv_factor = 1.0 - factor;

    egui::Color32::from_rgb(
        (base.r() as f32 * inv_factor + blend.r() as f32 * factor) as u8,
        (base.g() as f32 * inv_factor + blend.g() as f32 * factor) as u8,
        (base.b() as f32 * inv_factor + blend.b() as f32 * factor) as u8,
    )
}

fn detect_system_dark_mode() -> bool {
    #[cfg(target_os = "windows")]
    {
        true
    }
    #[cfg(target_os = "macos")]
    {
        true
    }
    #[cfg(target_os = "linux")]
    {
        true
    }
    #[cfg(not(any(target_os = "windows", target_os = "macos", target_os = "linux")))]
    {
        true
    }
}