import { Platform } from 'react-native';

type SmsRetrieverModule = {
    requestPhoneNumber: () => Promise<string>;
    startSmsRetriever: () => Promise<boolean>;
    addSmsListener: (callback: (event: { message?: string }) => void) => Promise<boolean>;
    removeSmsListener: () => void;
};

function getModule(): SmsRetrieverModule | null {
    if (Platform.OS !== 'android') return null;
    return require('react-native-sms-retriever').default as SmsRetrieverModule;
}

export function extractOtpFromMessage(message: string, length: number): string | null {
    const exact = new RegExp(`(?:^|[^\\d])(\\d{${length}})(?:[^\\d]|$)`);
    const m = message.match(exact);
    if (m) return m[1];
    const any = message.match(/(\d{4,8})/);
    if (!any) return null;
    const digits = any[1];
    if (digits.length >= length) return digits.slice(0, length);
    if (digits.length === length) return digits;
    return null;
}

/** SMS Retriever：无需 READ_SMS，短信需含 app hash（见 Google 文档） */
export async function startOtpSmsListener(
    otpLength: number,
    onOtp: (otp: string) => void,
): Promise<() => void> {
    const mod = getModule();
    if (!mod) return () => {};

    const stop = () => {
        try {
            mod.removeSmsListener();
        } catch {
            /* ignore */
        }
    };

    try {
        const registered = await mod.startSmsRetriever();
        if (!registered) return stop;
        await mod.addSmsListener((event) => {
            const msg = event.message ?? '';
            const otp = extractOtpFromMessage(msg, otpLength);
            if (otp) {
                onOtp(otp);
                stop();
            }
        });
    } catch {
        stop();
    }
    return stop;
}

/** 系统号码选择器，一次性授权，无需 READ_SMS */
export async function requestPhoneNumberHint(): Promise<string> {
    const mod = getModule();
    if (!mod) throw new Error('仅支持 Android');
    return mod.requestPhoneNumber();
}

export function normalizeHintPhone(raw: string, mobileLength = 10): string {
    return raw.replace(/\D/g, '').slice(-mobileLength);
}