/**
 * Map an inbound deep link (custom scheme or universal/app link) to an in-app
 * route for the Next router.
 *
 * Conventions:
 *  - Custom scheme:   `ulti<app>://go/<route>`        -> `/<route>`
 *                     `ulti<app>://<seg>/<rest>`      -> `/<seg>/<rest>`
 *  - Universal link:  `https://<host>/app/<app>/<rest>` -> `/<rest>`
 *
 * The OAuth callback (`ulti<app>://oauth/callback`) is consumed by the native
 * auth flow and intentionally returns null here.
 */
export function routeForDeepLink(rawUrl: string): string | null {
  let u: URL
  try {
    u = new URL(rawUrl)
  } catch {
    return null
  }

  // Custom scheme (e.g. ultimail:, ultidrive:)
  if (u.protocol.startsWith("ulti") && u.protocol.endsWith(":")) {
    if (u.hostname === "oauth") return null // handled by native-auth
    const host = u.hostname
    const path = u.pathname.replace(/^\/+/, "")
    let route: string
    if (host === "go" || host === "") {
      route = `/${path}`
    } else {
      route = `/${host}${path ? `/${path}` : ""}`
    }
    return normalize(route, u.search)
  }

  // Universal / App link: https://host/app/<app>/<rest>
  if (u.protocol === "https:" || u.protocol === "http:") {
    const parts = u.pathname.split("/").filter(Boolean)
    const appIdx = parts.indexOf("app")
    if (appIdx >= 0 && parts.length > appIdx + 1) {
      const rest = parts.slice(appIdx + 2).join("/")
      return normalize(`/${rest}`, u.search)
    }
    return normalize(u.pathname, u.search)
  }

  return null
}

function normalize(route: string, search: string): string {
  const cleaned = route.replace(/\/{2,}/g, "/")
  const path = cleaned === "/" || cleaned === "" ? "/" : cleaned.replace(/\/$/, "")
  return `${path}${search ?? ""}`
}