import { computed, onMounted, onUnmounted, readonly, shallowRef } from "vue";

import { createPreviewRuntimeSnapshot } from "../mock/runtime-preview";
import type { DesktopRuntimeSnapshot } from "../types";

const snapshot = shallowRef<DesktopRuntimeSnapshot | null>(null);
const loading = shallowRef(false);
const error = shallowRef<string | null>(null);

let intervalHandle: ReturnType<typeof setInterval> | null = null;
let subscribers = 0;

async function refreshRuntimeSnapshot() {
  loading.value = true;
  error.value = null;

  try {
    if (window.desktopBridge?.app?.runtimeSnapshot) {
      snapshot.value = await window.desktopBridge.app.runtimeSnapshot();
      return;
    }

    snapshot.value = createPreviewRuntimeSnapshot();
  } catch (err) {
    error.value = err instanceof Error ? err.message : "runtime snapshot unavailable";
  } finally {
    loading.value = false;
  }
}

function startPolling() {
  if (intervalHandle) {
    return;
  }

  intervalHandle = setInterval(() => {
    void refreshRuntimeSnapshot();
  }, 15_000);
}

function stopPolling() {
  if (subscribers > 0 || !intervalHandle) {
    return;
  }

  clearInterval(intervalHandle);
  intervalHandle = null;
}

export function useDesktopRuntime() {
  onMounted(() => {
    subscribers += 1;
    if (!snapshot.value && !loading.value) {
      void refreshRuntimeSnapshot();
    }
    startPolling();
  });

  onUnmounted(() => {
    subscribers = Math.max(0, subscribers - 1);
    stopPolling();
  });

  return {
    snapshot: readonly(snapshot),
    loading: readonly(loading),
    error: readonly(error),
    refresh: refreshRuntimeSnapshot,
    hasSnapshot: computed(() => snapshot.value !== null),
  };
}