'use strict';
const crypto = require('crypto');

/**
 * Stripe Webhook ハンドラー
 *
 * 処理するイベント:
 *   checkout.session.completed
 *     - metadata.product === 'ponshu_room_pro'
 *         -> ponshu_licenses にライセンスキーを発行し Resend でメール送信
 *     - それ以外
 *         -> users テーブルに購入記録（既存の Posimai 購読フロー）
 *   customer.subscription.deleted
 *     -> users.plan を free に戻す
 *
 * 使用方法:
 *   const { handleWebhook } = require('./routes/stripe')(pool);
 *   app.post('/api/stripe/webhook', express.raw({ type: 'application/json' }),
 *     (req, res) => handleWebhook(req, res));
 */
module.exports = function createStripeHandler(pool) {
    const STRIPE_WEBHOOK_SECRET = process.env.STRIPE_WEBHOOK_SECRET || '';
    const RESEND_API_KEY        = process.env.RESEND_API_KEY || '';
    const APP_SUPPORT_EMAIL     = process.env.APP_SUPPORT_EMAIL || 'support@posimai.soar-enrich.com';
    const FROM_EMAIL            = process.env.FROM_EMAIL || 'noreply@posimai.soar-enrich.com';

    // ── ライセンスキー生成 (PONSHU-XXXX-XXXX-XXXX) ──
    function generateLicenseKey() {
        const hex = crypto.randomBytes(6).toString('hex').toUpperCase();
        return `PONSHU-${hex.slice(0, 4)}-${hex.slice(4, 8)}-${hex.slice(8, 12)}`;
    }

    // ── Resend でライセンスキーをメール送信 ──
    async function sendLicenseEmail(toEmail, licenseKey) {
        if (!RESEND_API_KEY) {
            console.warn('[Stripe] RESEND_API_KEY not set — skipping license email');
            return;
        }
        const emailRes = await fetch('https://api.resend.com/emails', {
            method: 'POST',
            headers: {
                'Content-Type': 'application/json',
                'Authorization': `Bearer ${RESEND_API_KEY}`,
            },
            body: JSON.stringify({
                from: FROM_EMAIL,
                to: toEmail,
                subject: 'Ponshu Room Pro ライセンスキーのお知らせ',
                html: `
                    <p>この度は Ponshu Room Pro をご購入いただきありがとうございます。</p>
                    <p>以下のライセンスキーをアプリ内「設定 → ライセンスを有効化」から入力してください。</p>
                    <p style="font-size:24px;font-weight:bold;letter-spacing:4px;font-family:monospace;
                              background:#f5f5f5;padding:16px;border-radius:8px;display:inline-block;">
                        ${licenseKey}
                    </p>
                    <p>ご不明な点は <a href="mailto:${APP_SUPPORT_EMAIL}">${APP_SUPPORT_EMAIL}</a> までお問い合わせください。</p>
                `,
            }),
        });
        if (!emailRes.ok) {
            const errBody = await emailRes.text();
            console.error('[Stripe] Resend API error:', emailRes.status, errBody);
        } else {
            console.log(`[Stripe] License email sent to ${toEmail}`);
        }
    }

    // ── Ponshu Room Pro 購入処理 ──
    async function handlePonshuPurchase(session) {
        const email = session.customer_details?.email?.toLowerCase();
        if (!email) {
            console.error('[Stripe] Ponshu purchase: no email in session', session.id);
            return;
        }

        // 冪等性チェック — Stripe がリトライしても重複発行しない
        const existing = await pool.query(
            `SELECT license_key FROM ponshu_licenses WHERE stripe_session_id = $1`,
            [session.id]
        );
        if (existing.rows.length > 0) {
            console.log(`[Stripe] Ponshu: duplicate webhook for session ${session.id}, skipping`);
            return;
        }

        const licenseKey = generateLicenseKey();
        await pool.query(
            `INSERT INTO ponshu_licenses (license_key, email, plan, status, stripe_session_id)
             VALUES ($1, $2, 'pro', 'active', $3)`,
            [licenseKey, email, session.id]
        );

        console.log(`[Stripe] Ponshu license issued: ${licenseKey.substring(0, 12)}... -> ${email}`);
        await sendLicenseEmail(email, licenseKey);
    }

    // ── 購入完了メール（マジックリンク付き）送信 ──
    async function sendWelcomeMagicLink(email) {
        if (!RESEND_API_KEY) {
            console.warn('[Stripe] RESEND_API_KEY not set — skipping welcome email');
            return;
        }
        try {
            // マジックリンク用トークンを生成（15分有効）
            const token = crypto.randomBytes(32).toString('hex');
            const expiresAt = new Date(Date.now() + 15 * 60 * 1000);
            await pool.query(
                `INSERT INTO magic_link_tokens (email, token, expires_at) VALUES ($1, $2, $3)`,
                [email, token, expiresAt]
            );

            const loginBase = process.env.MAGIC_LINK_BASE_URL || 'https://posimai.soar-enrich.com';
            const magicLinkUrl = `${loginBase}/auth/verify?token=${token}&redirect=${encodeURIComponent('https://brief.posimai.soar-enrich.com')}`;

            const emailRes = await fetch('https://api.resend.com/emails', {
                method: 'POST',
                headers: {
                    'Content-Type': 'application/json',
                    'Authorization': `Bearer ${RESEND_API_KEY}`,
                },
                body: JSON.stringify({
                    from: FROM_EMAIL,
                    to: email,
                    subject: 'Posimai へようこそ — ログインリンク',
                    html: `
                        <div style="font-family:sans-serif;max-width:480px;margin:0 auto;padding:24px">
                            <h2 style="font-size:20px;font-weight:600;margin-bottom:8px">ご購入ありがとうございます</h2>
                            <p style="color:#555;line-height:1.6">Posimai パスの購入が完了しました。<br>
                            下のボタンをクリックするとすぐにアプリをご利用いただけます。</p>
                            <div style="margin:24px 0">
                                <a href="${magicLinkUrl}"
                                   style="display:inline-block;background:#6EE7B7;color:#0D0D0D;
                                          font-weight:600;padding:12px 28px;border-radius:8px;
                                          text-decoration:none;font-size:15px">
                                    Posimai を開く
                                </a>
                            </div>
                            <p style="font-size:12px;color:#888">このリンクは15分間有効です。<br>
                            期限切れの場合は <a href="${loginBase}/login">${loginBase}/login</a> からログインしてください。</p>
                            <hr style="border:none;border-top:1px solid #eee;margin:24px 0">
                            <p style="font-size:12px;color:#aaa">
                                ご不明な点は <a href="mailto:${APP_SUPPORT_EMAIL}">${APP_SUPPORT_EMAIL}</a> までお問い合わせください。
                            </p>
                        </div>
                    `,
                }),
            });

            if (!emailRes.ok) {
                const errBody = await emailRes.text();
                console.error('[Stripe] Welcome email error:', emailRes.status, errBody);
            } else {
                console.log(`[Stripe] Welcome magic link sent to ${email}`);
            }
        } catch (e) {
            console.error('[Stripe] sendWelcomeMagicLink error:', e.message);
        }
    }

    // ── Posimai 購読購入処理（既存フロー） ──
    async function handlePosiPurchase(session) {
        const email = session.customer_details?.email?.toLowerCase();
        if (!email) return;

        const existing = await pool.query(
            `SELECT user_id FROM users WHERE email = $1`, [email]
        );
        let userId;
        if (existing.rows.length > 0) {
            userId = existing.rows[0].user_id;
        } else {
            const baseId = email.split('@')[0].replace(/[^a-zA-Z0-9_-]/g, '').substring(0, 30);
            userId = `${baseId}_${Date.now().toString(36)}`;
            await pool.query(
                `INSERT INTO users (user_id, name, email, email_verified) VALUES ($1, $2, $3, true)
                 ON CONFLICT (user_id) DO NOTHING`,
                [userId, baseId, email]
            );
        }
        await pool.query(
            `UPDATE users SET purchased_at = NOW(), stripe_session_id = $1,
             plan = 'premium', stripe_customer_id = $2, stripe_subscription_id = $3
             WHERE user_id = $4`,
            [session.id, session.customer, session.subscription, userId]
        );
        console.log(`[Stripe] Plan upgraded to premium for ${email}`);

        // 購入完了メールにマジックリンクを同梱（非同期・失敗しても購入処理には影響しない）
        sendWelcomeMagicLink(email).catch(e =>
            console.error('[Stripe] Welcome email failed (non-critical):', e.message)
        );
    }

    // ── Webhook エントリーポイント ──
    async function handleWebhook(req, res) {
        const sig = req.headers['stripe-signature'];
        if (!STRIPE_WEBHOOK_SECRET) {
            console.warn('[Stripe] STRIPE_WEBHOOK_SECRET not set — webhook disabled');
            return res.status(503).json({ error: 'Webhook not configured' });
        }
        if (!sig) return res.status(400).json({ error: 'Missing stripe-signature' });

        // 署名検証（stripe ライブラリ不使用・軽量実装）
        let event;
        try {
            const rawBody = req.body; // Buffer (express.raw が渡す)
            const match = sig.match(/t=(\d+).*?,.*?v1=([a-fA-F0-9]+)/);
            if (!match || match.length < 3) throw new Error('Invalid signature format');
            const [, tsStr, v1Sig] = match;
            const tolerance = 300; // 5 分
            if (Math.abs(Date.now() / 1000 - parseInt(tsStr)) > tolerance) {
                throw new Error('Timestamp too old');
            }
            const payload  = `${tsStr}.${rawBody.toString('utf8')}`;
            const expected = crypto.createHmac('sha256', STRIPE_WEBHOOK_SECRET).update(payload).digest('hex');
            if (!crypto.timingSafeEqual(Buffer.from(expected), Buffer.from(v1Sig))) {
                throw new Error('Signature mismatch');
            }
            event = JSON.parse(rawBody.toString('utf8'));
        } catch (e) {
            console.error('[Stripe] Webhook verification failed:', e.message);
            return res.status(400).json({ error: 'Webhook verification failed' });
        }

        if (event.type === 'checkout.session.completed') {
            const session = event.data.object;
            try {
                if (session.metadata?.product === 'ponshu_room_pro') {
                    await handlePonshuPurchase(session);
                } else {
                    await handlePosiPurchase(session);
                }
            } catch (e) {
                console.error('[Stripe] Error processing checkout session:', e.message);
                return res.status(500).json({ error: 'Processing error' });
            }
        }

        if (event.type === 'customer.subscription.deleted') {
            const subscription = event.data.object;
            try {
                await pool.query(
                    `UPDATE users SET plan = 'free', stripe_subscription_id = NULL
                     WHERE stripe_customer_id = $1`,
                    [subscription.customer]
                );
                console.log(`[Stripe] Plan downgraded to free for customer: ${subscription.customer}`);
            } catch (e) {
                console.error('[Stripe] DB error downgrading plan:', e.message);
            }
        }

        res.json({ received: true });
    }

    return { handleWebhook };
};