import {
  inject,
  onBeforeUnmount,
  onMounted,
  onScopeDispose,
  watch,
  type InjectionKey,
} from "vue";
import { nativeRouterKey } from "../runtime";
import type { NativeRouterRuntime, NativeViewLifecycle } from "../types";

export const nativeViewLifecycleKey: InjectionKey<NativeViewLifecycle> = Symbol(
  "native-view-lifecycle",
);

export function useNativeRouter() {
  const runtime = inject<NativeRouterRuntime>(nativeRouterKey);
  if (!runtime)
    throw new Error(
      "Native Vue Router is not installed. Call app.use(nativeRouter).",
    );
  return runtime;
}

export function useNativeViewLifecycle() {
  const lifecycle = inject<NativeViewLifecycle>(nativeViewLifecycleKey);
  if (!lifecycle)
    throw new Error(
      "Native view lifecycle APIs must be used inside NativeRouterView.",
    );
  return lifecycle;
}

type NativeViewHook = () => void;

function onNativeViewState(
  source: Readonly<{ value: boolean }>,
  entering: boolean,
  hook: NativeViewHook,
) {
  onMounted(() => {
    if (entering && source.value) hook();
  });
  watch(
    () => source.value,
    (value, previous) => {
      if (value === entering && previous !== entering) hook();
    },
    { flush: "sync" },
  );
}

export function onNativeViewActivate(hook: NativeViewHook) {
  onNativeViewState(useNativeViewLifecycle().isActive, true, hook);
}

export function onNativeViewDeactivate(hook: NativeViewHook) {
  onNativeViewState(useNativeViewLifecycle().isActive, false, hook);
}

export function onNativeViewShow(hook: NativeViewHook) {
  onNativeViewState(useNativeViewLifecycle().isVisible, true, hook);
}

export function onNativeViewHide(hook: NativeViewHook) {
  onNativeViewState(useNativeViewLifecycle().isVisible, false, hook);
}

export function onNativeViewEvict(
  hook: (reason: NativeViewLifecycle["evictionReason"]["value"]) => void,
) {
  const lifecycle = useNativeViewLifecycle();
  onBeforeUnmount(() => {
    if (lifecycle.status.value === "evicted")
      hook(lifecycle.evictionReason.value);
  });
}

function useNativeViewEffect(
  source: Readonly<{ value: boolean }>,
  effect: () => void | (() => void),
) {
  let cleanup: void | (() => void);
  const stopEffect = () => {
    cleanup?.();
    cleanup = undefined;
  };
  const stopWatch = watch(
    () => source.value,
    (enabled) => {
      stopEffect();
      if (enabled) cleanup = effect();
    },
    { immediate: true, flush: "sync" },
  );
  onScopeDispose(() => {
    stopWatch();
    stopEffect();
  });
}

/** Runs an effect only while this route is the semantically active route. */
export function useNativeViewActiveEffect(effect: () => void | (() => void)) {
  useNativeViewEffect(useNativeViewLifecycle().isActive, effect);
}

/** Runs an effect while this route is active or participating in a transition. */
export function useNativeViewVisibleEffect(effect: () => void | (() => void)) {
  useNativeViewEffect(useNativeViewLifecycle().isVisible, effect);
}