// Presentation of the backend's server-compatibility verdict.
//
// The decision is Rust's — see `ServerCompatibility` in `auth/mod.rs`. This file
// decides only how it *reads*, which is presentation and changes only if the UI
// is redesigned. Nothing here compares a version number, and nothing here may
// start to: the backend sends an opaque state precisely so the frontend cannot.
//
// TRACES: UR-085 | DR-286

import type { ServerCompatibility } from "$lib/api/bindings";

export interface CompatibilityNotice {
  /** Blocks going on to the login step. Only a server below the floor does. */
  blocking: boolean;
  tone: "error" | "warning";
  message: string;
}

/**
 * What to show the user about a server's version, or `null` when there is
 * nothing worth saying — which is the common case.
 */
export function compatibilityNotice(
  compatibility: ServerCompatibility,
  serverVersion: string,
): CompatibilityNotice | null {
  switch (compatibility.type) {
    case "supported":
      return null;

    case "unknownVersion":
      // Not worth interrupting anyone over: the server almost certainly works,
      // and we simply could not read what it called itself.
      return null;

    case "newerThanKnown":
      return {
        blocking: false,
        tone: "warning",
        message:
          `This server (${serverVersion}) is newer than this version of JellyTau. ` +
          `It should work normally — update the app if anything looks wrong.`,
      };

    case "tooOld":
      return {
        blocking: true,
        tone: "error",
        message:
          `This server runs Jellyfin ${serverVersion}. JellyTau needs ` +
          `${compatibility.minimum} or newer.`,
      };
  }
}