import { cookies } from "next/headers";
import { NextRequest, NextResponse } from "next/server";
import { db } from "@/lib/db";
import { xeroConnections } from "@/lib/schema/xeroConnections";
import { eq } from "drizzle-orm";

type XeroTokenResponse = {
  access_token: string;
  refresh_token: string;
};

type XeroTenant = {
  tenantId: string;
};

export async function GET(req: NextRequest) {
  const cookieStore = await cookies();
  const session = cookieStore.get("session");

  // Must be logged in
  if (!session) {
    return NextResponse.redirect(
      new URL("/login", process.env.APP_URL)
    );
  }

  const userId = session.value;

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

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

  // Exchange code for token
  const tokenRes = await fetch("https://identity.xero.com/connect/token", {
    method: "POST",
    headers: {
      Authorization:
        "Basic " +
        Buffer.from(
          `${process.env.XERO_CLIENT_ID}:${process.env.XERO_CLIENT_SECRET}`
        ).toString("base64"),
      "Content-Type": "application/x-www-form-urlencoded",
    },
    body: new URLSearchParams({
      grant_type: "authorization_code",
      code,
      redirect_uri: process.env.XERO_REDIRECT_URI!,
    }),
  });

  if (!tokenRes.ok) {
    const text = await tokenRes.text();
    console.error("Xero token exchange failed:", text);
    return NextResponse.redirect(
      new URL("/connect/xero?error=token_failed", process.env.APP_URL)
    );
  }

  const tokenData = (await tokenRes.json()) as XeroTokenResponse;

  // Fetch connected tenants (organisations)
  const tenantRes = await fetch(
    "https://api.xero.com/connections",
    {
      headers: {
        Authorization: `Bearer ${tokenData.access_token}`,
      },
    }
  );

  const tenants = (await tenantRes.json()) as XeroTenant[];
  const tenantId = tenants[0]?.tenantId;

  if (!tenantId) {
    return NextResponse.json(
      { error: "No Xero organisation found" },
      { status: 400 }
    );
  }

  // Save user ↔ tenant (minimal MVP)
  await db
    .insert(xeroConnections)
    .values({
      userId,
      tenantId,
    })
    .onConflictDoUpdate({
      target: xeroConnections.userId,
      set: { tenantId },
    });

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