災害時・救急医療で「音が聞こえない・声が出せない」方を孤立させないために
——視覚アラートと双方向デジタル安否・医療伝達シート

#![forbid(unsafe_code)]

/// Communication and medical alert flags for instant paramedic & shelter triage.
pub const FLAG_REQUIRES_SIGN_LANGUAGE_JSL: u16 = 1 << 0;
pub const FLAG_REQUIRES_WRITTEN_TEXT_BOARD: u16 = 1 << 1;
pub const FLAG_HAS_DRUG_OR_FOOD_ALLERGY: u16    = 1 << 2;
pub const FLAG_REQUIRES_CONTINUOUS_MEDS: u16    = 1 << 3;
pub const FLAG_WEARS_COCHLEAR_OR_HEARING_AID: u16 = 1 << 4;

/// Compact 16-byte offline emergency triage frame designed for BLE Mesh & QR broadcast.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct EmergencyTriageFrame {
    pub triage_severity: u8,     // 0=Safe, 1=Minor, 2=Delayed, 3=Immediate(Red)
    pub hop_ttl: u8,             // Remaining DTN relay hops (max 15)
    pub medical_comm_flags: u16, // Bitmask of communication & medical requirements
    pub lat_e7: i32,             // Latitude * 1e7
    pub lon_e7: i32,             // Longitude * 1e7
    pub semg_intent_code: u16,   // Recognized JSL emergency sign ID (e.g., 101=Chest Pain)
}

/// Computes CRC-16-CCITT (polynomial 0x1021, initial 0xFFFF) over a byte slice.
pub const fn crc16_ccitt(bytes: &[u8]) -> u16 {
    let mut crc: u16 = 0xFFFF;
    let mut i = 0;
    while i < bytes.len() {
        crc ^= (bytes[i] as u16) << 8;
        let mut bit = 0;
        while bit < 8 {
            if (crc & 0x8000) != 0 {
                crc = (crc << 1) ^ 0x1021;
            } else {
                crc <<= 1;
            }
            bit += 1;
        }
        i += 1;
    }
    crc
}

impl EmergencyTriageFrame {
    /// Encodes the frame into a 16-byte wire format with CRC-16 integrity protection.
    pub fn to_wire_bytes(self) -> [u8; 16] {
        let mut buf = [0u8; 16];
        buf[0] = 0x4F; // 'O'
        buf[1] = ((self.triage_severity & 0x0F) << 4) | (self.hop_ttl & 0x0F);
        let flags = self.medical_comm_flags.to_be_bytes();
        buf[2] = flags[0];
        buf[3] = flags[1];
        let lat = self.lat_e7.to_be_bytes();
        buf[4..8].copy_from_slice(&lat);
        let lon = self.lon_e7.to_be_bytes();
        buf[8..12].copy_from_slice(&lon);
        let intent = self.semg_intent_code.to_be_bytes();
        buf[12] = intent[0];
        buf[13] = intent[1];

        let crc = crc16_ccitt(&buf[0..14]).to_be_bytes();
        buf[14] = crc[0];
        buf[15] = crc[1];
        buf
    }

    /// Decodes and verifies a 16-byte wire frame. Returns None on magic or CRC mismatch.
    pub fn from_wire_bytes(buf: &[u8; 16]) -> Option<Self> {
        if buf[0] != 0x4F {
            return None;
        }
        let expected_crc = crc16_ccitt(&buf[0..14]);
        let actual_crc = u16::from_be_bytes([buf[14], buf[15]]);
        if expected_crc != actual_crc {
            return None;
        }
        Some(Self {
            triage_severity: (buf[1] >> 4) & 0x0F,
            hop_ttl: buf[1] & 0x0F,
            medical_comm_flags: u16::from_be_bytes([buf[2], buf[3]]),
            lat_e7: i32::from_be_bytes([buf[4], buf[5], buf[6], buf[7]]),
            lon_e7: i32::from_be_bytes([buf[8], buf[9], buf[10], buf[11]]),
            semg_intent_code: u16::from_be_bytes([buf[12], buf[13]]),
        })
    }
}