import crypto from 'crypto';
import fetch from 'node-fetch';

const DEDUPE_TTL_MS = 24 * 60 * 60 * 1000;

export function verifyWebhookSignature(rawBody, signatureHeader, secret) {
    if (!secret) {
        return false;
    }

    if (!signatureHeader || !rawBody) {
        return false;
    }

    const expected = crypto.createHmac('sha1', secret).update(rawBody).digest('hex');

    try {
        const expectedBuffer = Buffer.from(expected, 'utf8');
        const actualBuffer = Buffer.from(signatureHeader, 'utf8');

        if (expectedBuffer.length !== actualBuffer.length) {
            return false;
        }

        return crypto.timingSafeEqual(expectedBuffer, actualBuffer);
    } catch {
        return false;
    }
}

export function createMessageDeduper() {
    const seen = new Map();

    function cleanup() {
        const now = Date.now();
        for (const [messageId, expiresAt] of seen.entries()) {
            if (expiresAt <= now) {
                seen.delete(messageId);
            }
        }
    }

    function has(messageId) {
        cleanup();
        return seen.has(messageId);
    }

    function add(messageId) {
        cleanup();
        seen.set(messageId, Date.now() + DEDUPE_TTL_MS);
    }

    return { has, add };
}

export async function fetchWebexMessage(token, messageId) {
    const response = await fetch(`https://webexapis.com/v1/messages/${encodeURIComponent(messageId)}`, {
        headers: {
            Authorization: `Bearer ${token}`,
            Accept: 'application/json',
        },
    });

    const responseText = await response.text();
    let data;

    try {
        data = responseText ? JSON.parse(responseText) : {};
    } catch {
        throw new Error(`Invalid JSON from Webex messages API: ${responseText}`);
    }

    if (!response.ok) {
        const error = new Error(data.message || responseText || `Webex API error (${response.status})`);
        error.status = response.status;
        throw error;
    }

    return data;
}

export function extractMessageFromWebhook(body) {
    const resource = body?.resource;
    const event = body?.event;
    const data = body?.data || {};

    if (resource !== 'messages' || event !== 'created') {
        return { supported: false, reason: 'unsupported_event' };
    }

    return {
        supported: true,
        messageId: data.id,
        roomId: data.roomId,
        personId: data.personId,
        personEmail: data.personEmail,
        text: data.text,
        parentId: data.parentId,
    };
}