手話の「表情という文法」と、腕の微弱な電気信号。
映画『もしもの話』が紡ぐ、心の壁を溶かす科学。

#![forbid(unsafe_code)]

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum JslSentenceModality {
    DeclarativeAffirmative, // 平叙文（肯定）
    PolarYesNoQuestion,     // Yes/No 疑問文（眉挙上 + 頭部前傾）
    WhContentQuestion,      // Wh 疑問文（眉顰め + 顎引き）
    ConditionalIfClause,    // 条件節「もし〜ならば」（眉挙上保持 + 節末ポーズ）
}

#[derive(Debug, Clone, Copy)]
pub struct NmmFacialState {
    pub brow_raise_zscore: f32,  // Positive = raised (AU1+2), Negative = furrowed (AU4)
    pub head_pitch_deg: f32,     // Forward nod / chin posture
    pub clause_boundary_pause_ms: u16,
}

/// Classifies the grammatical clause modality of Japanese Sign Language (JSL)
/// from Non-Manual Markers (NMM) synchronized with forearm sEMG onset/offset.
#[inline]
pub fn classify_jsl_nmm_modality(nmm: &NmmFacialState) -> JslSentenceModality {
    if nmm.brow_raise_zscore >= 1.2 && nmm.clause_boundary_pause_ms >= 180 {
        JslSentenceModality::ConditionalIfClause
    } else if nmm.brow_raise_zscore >= 1.0 && nmm.head_pitch_deg >= 4.0 {
        JslSentenceModality::PolarYesNoQuestion
    } else if nmm.brow_raise_zscore <= -0.9 {
        JslSentenceModality::WhContentQuestion
    } else {
        JslSentenceModality::DeclarativeAffirmative
    }
}

/// Computes the Waveform Length (WL) complexity feature of a filtered sEMG frame:
/// WL = ∑_k=1^N-1 |x[k] - x[k-1]|, reflecting motor unit recruitment density.
#[inline]
pub fn compute_semg_waveform_length(samples: &[f32]) -> f32 {
    let mut wl: f32 = 0.0;
    for pair in samples.windows(2) {
        wl += (pair[1] - pair[0]).abs();
    }
    wl
}