import { NextResponse } from 'next/server';
import { z } from 'zod';
import { eq } from 'drizzle-orm';
import crypto from 'node:crypto';

import { withAuth } from '@/lib/api/helpers';
import { parseBody } from '@/lib/api/route-helpers';
import { db } from '@/lib/db';
import { user, userEmailChanges } from '@/lib/db/schema/users';
import { createAuditLog } from '@/lib/audit';
import { ConflictError, errorResponse, ValidationError } from '@/lib/errors';
import { env } from '@/lib/env';

const updateEmailSchema = z.object({
  email: z.string().email().toLowerCase(),
});

const VERIFY_TOKEN_TTL_MINUTES = 60;
const REQUIRES_VERIFICATION = process.env.EMAIL_CHANGE_INSTANT !== 'true';

/**
 * Initiate an email-change for the signed-in user.
 *
 * Production flow (REQUIRES_VERIFICATION=true, default):
 *   1. Create a user_email_changes row with sha256(token)
 *   2. Email OLD address with a cancel link
 *   3. Email NEW address with a confirm link
 *   4. Change applies only when /api/v1/me/email/confirm/<token> is called
 *
 * Dev shortcut (set EMAIL_CHANGE_INSTANT=true):
 *   - Updates user.email immediately, skipping the email round-trip.
 *   - Useful for local testing where SMTP isn't wired.
 */
export const PATCH = withAuth(async (req, ctx) => {
  try {
    const { email } = await parseBody(req, updateEmailSchema);
    if (email === ctx.user.email) {
      return NextResponse.json({ ok: true, unchanged: true });
    }

    // Reject if another account already owns this address.
    const conflict = await db.query.user.findFirst({ where: eq(user.email, email) });
    if (conflict && conflict.id !== ctx.userId) {
      throw new ConflictError('That email is already in use by another account');
    }

    if (!REQUIRES_VERIFICATION) {
      // Instant change - dev only.
      const [updated] = await db
        .update(user)
        .set({ email, emailVerified: false, updatedAt: new Date() })
        .where(eq(user.id, ctx.userId))
        .returning({ email: user.email });
      if (!updated) throw new ValidationError('Failed to update email');
      void createAuditLog({
        userId: ctx.userId,
        portId: ctx.portId || null,
        action: 'update',
        entityType: 'user',
        entityId: ctx.userId,
        oldValue: { email: ctx.user.email },
        newValue: { email: updated.email },
        metadata: { type: 'email_change_instant' },
        ipAddress: ctx.ipAddress,
        userAgent: ctx.userAgent,
      });
      return NextResponse.json({ data: { email: updated.email, instant: true } });
    }

    // Verification flow - generate a single-use token, hash it, persist.
    const rawToken = crypto.randomBytes(32).toString('base64url');
    const tokenHash = crypto.createHash('sha256').update(rawToken).digest('hex');
    const expiresAt = new Date(Date.now() + VERIFY_TOKEN_TTL_MINUTES * 60 * 1000);

    const [pending] = await db
      .insert(userEmailChanges)
      .values({
        userId: ctx.userId,
        oldEmail: ctx.user.email,
        newEmail: email,
        confirmTokenHash: tokenHash,
        expiresAt,
      })
      .returning();
    if (!pending) throw new ValidationError('Failed to create pending email-change row');

    const baseUrl = env.APP_URL.replace(/\/+$/, '');
    const confirmUrl = `${baseUrl}/api/v1/me/email/confirm/${rawToken}`;
    const cancelUrl = `${baseUrl}/api/v1/me/email/cancel/${rawToken}`;

    try {
      const [{ sendEmail }, { renderShell, safeUrl }, { resolveAuthShellBranding }] =
        await Promise.all([
          import('@/lib/email'),
          import('@/lib/email/shell'),
          import('@/lib/email/auth-shell-branding'),
        ]);
      const branding = await resolveAuthShellBranding();
      const appName = branding?.appName?.trim() || 'CRM';
      const brandingShell = branding
        ? {
            logoUrl: branding.logoUrl,
            backgroundUrl: branding.backgroundUrl,
            primaryColor: null,
            emailHeaderHtml: null,
            emailFooterHtml: null,
          }
        : null;
      const safeOldEmail = ctx.user.email.replace(/[<>&]/g, '');
      const safeNewEmail = email.replace(/[<>&]/g, '');
      const confirmBody = `
        <p style="margin-bottom:16px;">Hi,</p>
        <p style="margin-bottom:16px;">You (or someone using your account) requested to change the sign-in email on your ${appName} account from <strong>${safeOldEmail}</strong> to <strong>${safeNewEmail}</strong>.</p>
        <p style="margin-bottom:16px;"><a href="${safeUrl(confirmUrl)}" style="color:#2563eb;font-weight:600;">Click here to confirm this change</a> - the link expires in ${VERIFY_TOKEN_TTL_MINUTES} minutes.</p>
        <p style="color:#64748b;">If you didn't request this, ignore this email.</p>
      `;
      const cancelBody = `
        <p style="margin-bottom:16px;">Hi,</p>
        <p style="margin-bottom:16px;">A change to your sign-in email was requested. If this wasn't you, <a href="${safeUrl(cancelUrl)}" style="color:#2563eb;font-weight:600;">click here to cancel the change</a> immediately and consider rotating your password.</p>
      `;
      const confirmSubject = `Confirm your new ${appName} email address`;
      const noticeSubject = `A change to your ${appName} email was requested`;
      await Promise.allSettled([
        sendEmail(
          email,
          confirmSubject,
          renderShell({ title: confirmSubject, body: confirmBody, branding: brandingShell }),
          undefined,
          `Confirm new email: ${confirmUrl}`,
        ),
        sendEmail(
          ctx.user.email,
          noticeSubject,
          renderShell({ title: noticeSubject, body: cancelBody, branding: brandingShell }),
          undefined,
          `Cancel email change: ${cancelUrl}`,
        ),
      ]);
    } catch {
      // Email send is best-effort; the row stays so the user can re-request.
    }

    void createAuditLog({
      userId: ctx.userId,
      portId: ctx.portId || null,
      action: 'create',
      entityType: 'user_email_change',
      entityId: pending.id,
      newValue: { newEmail: email },
      metadata: { type: 'email_change_requested' },
      ipAddress: ctx.ipAddress,
      userAgent: ctx.userAgent,
    });

    return NextResponse.json({
      data: {
        pendingChangeId: pending.id,
        verificationSentTo: email,
      },
    });
  } catch (error) {
    return errorResponse(error);
  }
});