type IdleCallbackHandle = number;

type IdleCallbackOptions = {
  timeout?: number;
};

type WindowWithIdleCallback = Window & {
  requestIdleCallback?: (
    callback: () => void,
    options?: IdleCallbackOptions,
  ) => IdleCallbackHandle;
};

type NavigatorWithConnection = Navigator & {
  connection?: {
    effectiveType?: string;
    saveData?: boolean;
  };
  deviceMemory?: number;
};

const prefetchedGroups = new Set<string>();
const scheduledGroups = new Set<string>();

type PrefetchTask = {
  key: string;
  load: () => Promise<unknown>;
};

const corePrefetchTasks: PrefetchTask[] = [
  { key: 'system-user', load: () => import('#/views/_core/user/index.vue') },
  { key: 'system-menu', load: () => import('#/views/_core/menu/index.vue') },
  { key: 'system-role', load: () => import('#/views/_core/role/index.vue') },
];

const aiPrefetchTasks = {
  agent: {
    key: 'ai-agent',
    load: () => import('#/views/ai-platform/agent/index.vue'),
  },
  agentChat: {
    key: 'agent-chat',
    load: () => import('#/views/_core/agent-chat/index.vue'),
  },
  aiChatPanel: {
    key: 'ai-chat-panel',
    load: () => import('#/components/ai-chat-panel/AiChatPanel.vue'),
  },
  knowledge: {
    key: 'ai-knowledge',
    load: () => import('#/views/ai-platform/knowledge/index.vue'),
  },
  model: {
    key: 'ai-model',
    load: () => import('#/views/ai-platform/model/index.vue'),
  },
  workflow: {
    key: 'ai-workflow',
    load: () => import('#/views/ai-platform/workflow/index.vue'),
  },
  workflowRuns: {
    key: 'ai-workflow-runs',
    load: () => import('#/views/ai-platform/workflow-runs/index.vue'),
  },
} as const;

function scheduleIdle(callback: () => void) {
  const browserWindow = window as WindowWithIdleCallback;

  if (browserWindow.requestIdleCallback) {
    browserWindow.requestIdleCallback(callback, { timeout: 8000 });
    return;
  }

  window.setTimeout(callback, 8000);
}

function canPrefetch() {
  if (typeof document !== 'undefined' && document.visibilityState !== 'visible') {
    return false;
  }

  const connection = (navigator as NavigatorWithConnection).connection;
  if (connection?.saveData) {
    return false;
  }

  const deviceMemory = (navigator as NavigatorWithConnection).deviceMemory;
  if (deviceMemory && deviceMemory < 4) {
    return false;
  }

  return !/(^|-)2g$/.test(connection?.effectiveType || '');
}

async function runTasksSequentially(tasks: PrefetchTask[]) {
  for (const task of tasks) {
    if (!canPrefetch()) {
      return;
    }
    if (prefetchedGroups.has(task.key)) {
      continue;
    }
    prefetchedGroups.add(task.key);
    await task.load().catch(() => undefined);
    await new Promise((resolve) => window.setTimeout(resolve, 300));
  }
}

function delayedPrefetch(groupKey: string, tasks: PrefetchTask[], delay: number) {
  if (!tasks.length || typeof window === 'undefined') {
    return;
  }
  if (scheduledGroups.has(groupKey)) {
    return;
  }
  scheduledGroups.add(groupKey);

  window.setTimeout(() => {
    scheduleIdle(() => {
      void runTasksSequentially(tasks);
    });
  }, delay);
}

function isSystemRoute(path: string) {
  return path.startsWith('/system/') || path.startsWith('/message/');
}

function isAiPlatformRoute(path: string) {
  return path.startsWith('/ai-platform/');
}

function isAgentChatRoute(path: string) {
  return path.startsWith('/agent-chat/');
}

function getAiRoutePrefetchTasks(path: string): PrefetchTask[] {
  if (path.startsWith('/ai-platform/agent')) {
    return [aiPrefetchTasks.workflow, aiPrefetchTasks.model];
  }
  if (path.startsWith('/ai-platform/workflow-runs')) {
    return [aiPrefetchTasks.workflow];
  }
  if (path.startsWith('/ai-platform/workflow')) {
    return [aiPrefetchTasks.workflowRuns, aiPrefetchTasks.agent];
  }
  if (path.startsWith('/ai-platform/model')) {
    return [aiPrefetchTasks.agent, aiPrefetchTasks.workflow];
  }
  if (path.startsWith('/ai-platform/knowledge')) {
    return [aiPrefetchTasks.agent];
  }
  return [aiPrefetchTasks.agent, aiPrefetchTasks.workflow];
}

function prefetchAiPlatformPages(currentPath = '') {
  if (typeof window === 'undefined') {
    return;
  }

  if (isSystemRoute(currentPath)) {
    delayedPrefetch(`core:${currentPath}`, corePrefetchTasks, 18_000);
    return;
  }

  if (isAgentChatRoute(currentPath)) {
    delayedPrefetch(
      `agent-chat:${currentPath}`,
      [aiPrefetchTasks.agentChat, aiPrefetchTasks.aiChatPanel],
      14_000,
    );
    return;
  }

  if (isAiPlatformRoute(currentPath)) {
    delayedPrefetch(
      `ai:${currentPath}`,
      getAiRoutePrefetchTasks(currentPath),
      14_000,
    );
    return;
  }

  delayedPrefetch('core:home', corePrefetchTasks, 22_000);
}

export { prefetchAiPlatformPages };