import { NextRequest, NextResponse } from "next/server";
import { eq } from "drizzle-orm";

import { db } from "@/lib/db";
import { stripeAccounts } from "@/lib/schema";
import { getUserFromSession } from "@/lib/auth/get-user";

type StripeOAuthResponse = {
  access_token: string;
  refresh_token: string;
  stripe_user_id: string;
  scope: string;
};

export async function GET(req: NextRequest) {
  const user = await getUserFromSession();

  if (!user) {
    return NextResponse.redirect(
      new URL("/login", process.env.APP_URL)
    );
  }

  const { searchParams } = new URL(req.url);
  const code = searchParams.get("code");
  const error = searchParams.get("error");

  if (error) {
    console.error("Stripe OAuth error:", error);
    return NextResponse.redirect(
      new URL(
        "/connect/stripe?error=oauth_failed",
        process.env.APP_URL
      )
    );
  }

  if (!code) {
    return NextResponse.json(
      { error: "Missing OAuth code" },
      { status: 400 }
    );
  }

  // --------------------------------------------------
  // Exchange OAuth code for Stripe account
  // --------------------------------------------------
  const tokenRes = await fetch("https://connect.stripe.com/oauth/token", {
    method: "POST",
    headers: { "Content-Type": "application/x-www-form-urlencoded" },
    body: new URLSearchParams({
      grant_type: "authorization_code",
      code,
      client_secret: process.env.STRIPE_SECRET_KEY!,
    }),
  });

  if (!tokenRes.ok) {
    const text = await tokenRes.text();
    console.error("Stripe token exchange failed:", text);

    return NextResponse.redirect(
      new URL(
        "/connect/stripe?error=token_exchange_failed",
        process.env.APP_URL
      )
    );
  }

  const data = (await tokenRes.json()) as StripeOAuthResponse;
  const stripeAccountId = data.stripe_user_id;

  // --------------------------------------------------
  // Check for existing Stripe account connection
  // --------------------------------------------------
  const existing = await db
    .select()
    .from(stripeAccounts)
    .where(eq(stripeAccounts.stripeAccountId, stripeAccountId))
    .limit(1);

  if (existing.length > 0) {
    const record = existing[0];

    // Same user → idempotent success
    if (record.userId === user.id) {
      console.log("Stripe already connected for this user", {
        stripeAccountId,
        userId: user.id,
      });

      return NextResponse.redirect(
        new URL("/connect/stripe/success", process.env.APP_URL)
      );
    }

    // Different user → block
    console.warn("Stripe account already linked to another user", {
      stripeAccountId,
      existingUserId: record.userId,
      currentUserId: user.id,
    });

    return NextResponse.redirect(
      new URL(
        "/connect/stripe?error=already_connected",
        process.env.APP_URL
      )
    );
  }

  // --------------------------------------------------
  // Insert new Stripe connection
  // --------------------------------------------------
  await db
    .insert(stripeAccounts)
    .values({
      userId: user.id,
      stripeAccountId: data.stripe_user_id,
    })
    .onConflictDoUpdate({
      target: stripeAccounts.userId,
      set: {
        stripeAccountId: data.stripe_user_id,
      },
    });


  console.log("Stripe OAuth connected", {
    stripeAccountId,
    userId: user.id,
    scope: data.scope,
  });

  return NextResponse.redirect(
    new URL("/connect/stripe/success", process.env.APP_URL)
  );
}