import AsyncStorage from "@react-native-async-storage/async-storage";
import { AppState, AppStateStatus, Platform } from "react-native";
import * as Sentry from "@sentry/react-native";
import * as Updates from "expo-updates";
import { lastObservedRootRouteRef } from "@/lib/rootNavigation";

const STORAGE_KEY = "@jrshikoku/app_crash_sentinel_v1";
const HEARTBEAT_INTERVAL_MS = 7000;
const RECENT_HEARTBEAT_MS = 120000;
const MIN_SESSION_AGE_MS = 5000;

type RootNavigationSnapshot = {
  rootRoute: string | null;
  nestedRoute?: string | null;
  rootIndex?: number;
  nestedIndex?: number;
  source?: string;
  updatedAt: string;
};

type CrashSentinelState = {
  app_session_active: boolean;
  normal_background: boolean;
  sessionStartedAt: string;
  lastHeartbeatAt: string;
  lastKnownAppState: AppStateStatus | "unknown";
  lastRootTab: string | null;
  previousRootNavigation: RootNavigationSnapshot | null;
  activeWebViews: string[];
  nativeScreensMode: string;
  reportedUnexpectedExitForSessionStartedAt?: string;
};

type StartOptions = {
  nativeScreensMode: string;
};

let currentState: CrashSentinelState | null = null;
let heartbeatTimer: ReturnType<typeof setInterval> | null = null;
let appStateSubscription: { remove: () => void } | null = null;
let latestNavigationSnapshot: RootNavigationSnapshot | null = null;
const activeWebViews = new Set<string>();

const nowIso = () => new Date().toISOString();

const safeJsonParse = <T>(value: string | null): T | null => {
  if (!value) return null;
  try {
    return JSON.parse(value) as T;
  } catch {
    return null;
  }
};

const getExpoUpdateContext = () => ({
  update_id: (Updates as any).updateId ?? null,
  updateId: (Updates as any).updateId ?? null,
  channel: (Updates as any).channel ?? null,
  runtimeVersion: (Updates as any).runtimeVersion ?? null,
  createdAt: (Updates as any).createdAt ?? null,
  isEmbeddedLaunch: (Updates as any).isEmbeddedLaunch ?? null,
});

const getMemoryInfo = () => {
  const performanceMemory = (globalThis as any)?.performance?.memory;
  if (!performanceMemory) return null;
  return {
    jsHeapSizeLimit: performanceMemory.jsHeapSizeLimit ?? null,
    totalJSHeapSize: performanceMemory.totalJSHeapSize ?? null,
    usedJSHeapSize: performanceMemory.usedJSHeapSize ?? null,
  };
};

const getRootTab = () => lastObservedRootRouteRef.current ?? currentState?.lastRootTab ?? "unknown";

const persistCurrentState = async (patch?: Partial<CrashSentinelState>) => {
  if (!currentState) return;
  currentState = {
    ...currentState,
    ...patch,
    lastRootTab: getRootTab(),
    previousRootNavigation: latestNavigationSnapshot ?? currentState.previousRootNavigation,
    activeWebViews: Array.from(activeWebViews).sort(),
  };
  try {
    await AsyncStorage.setItem(STORAGE_KEY, JSON.stringify(currentState));
  } catch (error) {
    Sentry.addBreadcrumb({
      category: "app.lifecycle",
      level: "warning",
      message: "crash sentinel persist failed",
      data: {
        errorMessage: error instanceof Error ? error.message : String(error),
      },
    });
  }
};

const shouldReportUnexpectedExit = (previous: CrashSentinelState, nowMs: number) => {
  if (!previous.app_session_active) return false;
  if (previous.normal_background) return false;
  if (previous.reportedUnexpectedExitForSessionStartedAt === previous.sessionStartedAt) return false;

  const heartbeatMs = Date.parse(previous.lastHeartbeatAt);
  const startedMs = Date.parse(previous.sessionStartedAt);
  if (!Number.isFinite(heartbeatMs) || !Number.isFinite(startedMs)) return false;

  const heartbeatAgeMs = nowMs - heartbeatMs;
  const sessionAgeMs = heartbeatMs - startedMs;
  return heartbeatAgeMs >= 0 && heartbeatAgeMs <= RECENT_HEARTBEAT_MS && sessionAgeMs >= MIN_SESSION_AGE_MS;
};

const reportUnexpectedExit = async (previous: CrashSentinelState, nativeScreensMode: string) => {
  const rootTab = getRootTab();
  Sentry.captureMessage("app.previous_session_unexpected_exit", {
    level: "warning",
    tags: {
      area: "app_lifecycle",
      result: "unexpected_exit",
      platform: Platform.OS,
      root_tab: rootTab,
      last_root_tab: previous.lastRootTab ?? "unknown",
      native_screens_mode: nativeScreensMode,
    },
    contexts: {
      app_lifecycle: {
        lastHeartbeatAt: previous.lastHeartbeatAt,
        sessionStartedAt: previous.sessionStartedAt,
        previousRootNavigation: previous.previousRootNavigation,
        lastKnownAppState: previous.lastKnownAppState,
        activeWebViews: previous.activeWebViews,
        memory: getMemoryInfo(),
        expoUpdate: getExpoUpdateContext(),
        normalBackground: previous.normal_background,
        heartbeatAgeMs: Date.now() - Date.parse(previous.lastHeartbeatAt),
      },
    },
    fingerprint: ["app_lifecycle", "unexpected_exit", Platform.OS],
  });

  await AsyncStorage.setItem(
    STORAGE_KEY,
    JSON.stringify({
      ...previous,
      reportedUnexpectedExitForSessionStartedAt: previous.sessionStartedAt,
    })
  );
};

export async function startAppLifecycleCrashSentinel(options: StartOptions) {
  const startedAt = nowIso();
  const previous = safeJsonParse<CrashSentinelState>(await AsyncStorage.getItem(STORAGE_KEY));

  if (previous && shouldReportUnexpectedExit(previous, Date.now())) {
    await reportUnexpectedExit(previous, options.nativeScreensMode);
  }

  currentState = {
    app_session_active: true,
    normal_background: false,
    sessionStartedAt: startedAt,
    lastHeartbeatAt: startedAt,
    lastKnownAppState: AppState.currentState ?? "unknown",
    lastRootTab: getRootTab(),
    previousRootNavigation: latestNavigationSnapshot,
    activeWebViews: Array.from(activeWebViews).sort(),
    nativeScreensMode: options.nativeScreensMode,
  };

  Sentry.setContext("app_lifecycle_sentinel", {
    sessionStartedAt: currentState.sessionStartedAt,
    lastHeartbeatAt: currentState.lastHeartbeatAt,
    lastKnownAppState: currentState.lastKnownAppState,
    activeWebViews: currentState.activeWebViews,
    expoUpdate: getExpoUpdateContext(),
  });

  await persistCurrentState();

  if (heartbeatTimer) clearInterval(heartbeatTimer);
  heartbeatTimer = setInterval(() => {
    void persistCurrentState({
      lastHeartbeatAt: nowIso(),
      lastKnownAppState: AppState.currentState ?? "unknown",
      normal_background: AppState.currentState === "background" ? true : currentState?.normal_background ?? false,
    });
  }, HEARTBEAT_INTERVAL_MS);

  appStateSubscription?.remove();
  appStateSubscription = AppState.addEventListener("change", (nextState) => {
    const patch: Partial<CrashSentinelState> = {
      lastKnownAppState: nextState,
      lastHeartbeatAt: nowIso(),
    };
    if (nextState === "background") {
      patch.normal_background = true;
    } else if (nextState === "active") {
      patch.normal_background = false;
    }
    void persistCurrentState(patch);
  });
}

export function stopAppLifecycleCrashSentinel() {
  if (heartbeatTimer) {
    clearInterval(heartbeatTimer);
    heartbeatTimer = null;
  }
  appStateSubscription?.remove();
  appStateSubscription = null;
}

export function recordAppLifecycleRootNavigation(snapshot: Omit<RootNavigationSnapshot, "updatedAt">) {
  latestNavigationSnapshot = {
    ...snapshot,
    updatedAt: nowIso(),
  };
  if (snapshot.rootRoute) {
    lastObservedRootRouteRef.current = snapshot.rootRoute;
  }
  void persistCurrentState();
}

export function setAppLifecycleWebViewActive(name: string, active: boolean) {
  if (active) {
    activeWebViews.add(name);
  } else {
    activeWebViews.delete(name);
  }
  Sentry.setContext("active_webviews", {
    names: Array.from(activeWebViews).sort(),
  });
  void persistCurrentState();
}