70代・80代・90代のご家族と読む
「スマートフォンとインターネットを安心して楽しむための3つの約束」

#![forbid(unsafe_code)]

/// Telemetry representing an incoming phone call, SMS, or payment prompt on a senior's device.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct IncomingEventTelemetry<'a> {
    pub caller_e164: &'a str,
    pub is_in_family_address_book: bool,
    pub contains_url_in_sms: bool,
    pub mentions_posa_gift_card: bool,
    pub mentions_urgent_account_freeze: bool,
    pub triggers_fullscreen_audio_alarm: bool,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ShieldAction {
    /// Safe communication from known contact or normal browsing.
    AllowPassThrough,
    /// Quarantines suspicious event and sends a warm, blameless check request to family members.
    HoldForBlamelessFamilyCoSign {
        risk_score: u8,
        reassurance_code: &'static str,
    },
    /// Immediately blocks confirmed scam vector (e.g., fullscreen fake virus alarm or POSA demand).
    BlockScamImmediately {
        risk_score: u8,
        reason: &'static str,
    },
}

/// Evaluates an incoming call, SMS, or web prompt to protect senior users without inducing shame.
pub fn evaluate_senior_safety_event(ev: &IncomingEventTelemetry<'_>) -> ShieldAction {
    if ev.triggers_fullscreen_audio_alarm {
        return ShieldAction::BlockScamImmediately {
            risk_score: 100,
            reason: "Fake browser virus alarm (Tech Support Scam) neutralized.",
        };
    }

    if ev.mentions_posa_gift_card {
        return ShieldAction::BlockScamImmediately {
            risk_score: 100,
            reason: "Public agencies and utilities never request gift card numbers.",
        };
    }

    if ev.is_in_family_address_book && !ev.contains_url_in_sms {
        return ShieldAction::AllowPassThrough;
    }

    let mut score: u8 = 0;

    // Check for international prefix outside Japan (+81) from unknown caller
    if ev.caller_e164.starts_with('+') && !ev.caller_e164.starts_with("+81") {
        score = score.saturating_add(65);
    }

    if ev.contains_url_in_sms && !ev.is_in_family_address_book {
        score = score.saturating_add(45);
    }

    if ev.mentions_urgent_account_freeze {
        score = score.saturating_add(40);
    }

    if score >= 85 {
        ShieldAction::BlockScamImmediately {
            risk_score: score,
            reason: "High-confidence international spoofing or smishing pattern.",
        }
    } else if score >= 40 {
        ShieldAction::HoldForBlamelessFamilyCoSign {
            risk_score: score,
            reassurance_code: "BLAMELESS_FAMILY_CHECK_188",
        }
    } else {
        ShieldAction::AllowPassThrough
    }
}