発達障害（ADHD・ASD・ディスレクシア）や感覚過敏のある方が疲れずに読める
「低刺激・3行要点・集中読書UI」の認知科学

#![forbid(unsafe_code)]
/// sRGB 8-bit color triplet for psychophysical contrast and glare verification.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct SrgbColor {
    pub r: u8,
    pub g: u8,
    pub b: u8,
}
impl SrgbColor {
    #[inline]
    fn linearize_channel(c: u8) -> f64 {
        let v = (c as f64) / 255.0;
        if v <= 0.04045 {
            v / 12.92
        } else {
            ((v + 0.055) / 1.055).powf(2.4)
        }
    }
    /// Computes ITU-R BT.709 / WCAG 2.2 relative luminance Y in [0.0, 1.0].
    #[inline]
    pub fn relative_luminance(self) -> f64 {
        0.2126 * Self::linearize_channel(self.r)
            + 0.7152 * Self::linearize_channel(self.g)
            + 0.0722 * Self::linearize_channel(self.b)
    }
    /// Computes WCAG 2.2 contrast ratio between two colors in [1.0, 21.0].
    #[inline]
    pub fn contrast_ratio(self, other: Self) -> f64 {
        let y1 = self.relative_luminance();
        let y2 = other.relative_luminance();
        let (lighter, darker) = if y1 >= y2 { (y1, y2) } else { (y2, y1) } ;
        (lighter + 0.05) / (darker + 0.05)
    }
}
/// Typography & layout metrics for a reading container.
#[derive(Debug, Clone, Copy)]
pub struct ReadingContainerSpec {
    pub background: SrgbColor,
    pub foreground: SrgbColor,
    pub cjk_chars_per_line: usize,
    pub line_height_ratio: f64,
    pub takeaway_bullet_count: usize,
    pub max_paragraph_lines: usize,
    pub has_autoplay_or_blinking_media: bool,
}
#[derive(Debug, Clone, Copy, PartialEq)]
pub enum CognitiveReadabilityReport {
    OptimalComfort {
        contrast_ratio: f64,
        estimated_extraneous_load: f64,
    },
    Violation(&'static str),
}
/// Verifies that a reading layout satisfies both WCAG 2.2 AAA contrast (>= 7.0)
/// and Neurodivergent Low-Glare / Saccadic Ergonomics constraints.
pub fn verify_neurodivergent_reading_ux(spec: &ReadingContainerSpec) -> CognitiveReadabilityReport {
    if spec.has_autoplay_or_blinking_media {
        return CognitiveReadabilityReport::Violation(
            "Autoplay or blinking media causes involuntary saccadic distraction.",
        );
    }
    if spec.takeaway_bullet_count == 0 || spec.takeaway_bullet_count > 4 {
        return CognitiveReadabilityReport::Violation(
            "Advance organizer must contain 1..=4 takeaway chunks (Cowan working memory bound).",
        );
    }
    let bg_lum = spec.background.relative_luminance();
    let ratio = spec.background.contrast_ratio(spec.foreground);
    // Must meet WCAG AAA (>= 7.0) while avoiding pure-white scotopic glare (Y_bg > 0.97 or ratio > 19.5)
    if ratio < 7.0 {
        return CognitiveReadabilityReport::Violation("Contrast ratio below WCAG 2.2 AAA (7.0:1).");
    }
    if bg_lum > 0.97 || spec.background.b > spec.background.r {
        return CognitiveReadabilityReport::Violation(
            "Background exceeds anti-glare luminance cap or has cold blue-dominant tint.",
        );
    }
    if !(32..=46).contains(&spec.cjk_chars_per_line) {
        return CognitiveReadabilityReport::Violation(
            "CJK line length outside optimal saccadic return-sweep range (32..=46 chars).",
        );
    }
    if spec.line_height_ratio < 1.85 || spec. max_paragraph_lines > 6 {
        return CognitiveReadabilityReport::Violation(
            "Insufficient line-height (< 1.85) or dense wall-of-text paragraph (> 6 lines).",
        );
    }
    let line_dev = ((spec.cjk_chars_per_line as f64) - 39.0).abs() / 39.0;
    let estimated_extraneous_load = (line_dev * 0.15) + (1.0 / spec.line_height_ratio) * 0.10;
    CognitiveReadabilityReport::OptimalComfort {
        contrast_ratio: ratio,
        estimated_extraneous_load,
    }
}