import { timingSafeEqual } from "node:crypto"
import { NextResponse } from "next/server"
import { hasConvexUrl } from "@/lib/convex-config"

function readBearerToken(request: Request) {
  const authHeader = request.headers.get("authorization") || ""
  if (!authHeader.toLowerCase().startsWith("bearer ")) {
    return ""
  }

  return authHeader.slice("bearer ".length).trim()
}

function tokensMatch(expected: string, provided: string) {
  const expectedBuffer = Buffer.from(expected)
  const providedBuffer = Buffer.from(provided)

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

  return timingSafeEqual(expectedBuffer, providedBuffer)
}

export function getGhlSyncToken() {
  return String(process.env.GHL_SYNC_CRON_TOKEN || "").trim()
}

export async function requireGhlSyncAuth(request: Request) {
  if (!hasConvexUrl()) {
    return NextResponse.json(
      { error: "Convex is not configured for GHL sync" },
      { status: 503 }
    )
  }

  const configuredToken = getGhlSyncToken()
  if (!configuredToken) {
    return NextResponse.json(
      { error: "GHL sync token is not configured" },
      { status: 503 }
    )
  }

  const providedToken = readBearerToken(request)
  if (!providedToken || !tokensMatch(configuredToken, providedToken)) {
    return NextResponse.json({ error: "Unauthorized" }, { status: 401 })
  }

  return null
}