// src/hooks/useHostApp.ts
import { useState, useEffect } from 'react';
import { connectToHostApp, type HostAppAPI } from '@cognite/app-sdk';

export function useHostApp(): HostAppAPI | null {
  const [api, setApi] = useState<HostAppAPI | null>(null);

  useEffect(() => {
    connectToHostApp({ applicationName: 'my-app' })
      .then(({ api: resolvedApi }) => setApi(() => resolvedApi))
      .catch(() => { /* outside Fusion — no-op */ });
  }, []);

  return api;
}

await api.sendAgentLayoutMode({ mode: 'sidebar' });

await api.sendAgentLayoutMode({ mode: 'sidebar' });
await api.sendAgentMessage({
  message: `Analyse the schedule for "${itemName}" and suggest how to reduce total duration.`,
  newSession: true,
});

src/features/agent/
  agentActions.ts     — (deps) => Action[]
  agentResources.ts   — (deps) => Resource[]
  useAgentServer.ts   — register / unregister

// src/features/agent/agentResources.ts
import { createAgentResource } from '@cognite/app-sdk';

export function buildAgentResources(storage: StorageService) {
  return [
    createAgentResource({
      uri: 'my-app://current-state',
      name: 'Current application state',
      description:
        'Items currently visible, their statuses, and active filters. Read before answering questions about what the user is looking at.',
      async read() {
        return [{ type: 'json', data: storage.getAll() }];
      },
    }),
  ];
}

// src/features/agent/agentActions.ts
import { createAgentAction } from '@cognite/app-sdk';
import { z } from 'zod';

export function buildAgentActions(dataService: DataService) {
  return [
    createAgentAction({
      name: 'get_item_details',
      description: 'Full details for an item by ID, including history.',
      parameters: z.object({
        item_id: z.string().describe('The ID of the item to retrieve'),
      }),
      async handler({ item_id }) {
        const item = await dataService.getItem(item_id);
        return { content: [{ type: 'json', data: item }] };
      },
    }),
  ];
}

createAgentAction({
  name: 'update_item_status',
  description:
    'Update item status. Call ONLY when the user has explicitly approved the change.',
  parameters: z.object({
    item_id: z.string().describe('The item to update'),
    status: z.enum(['active', 'closed', 'pending']).describe('The new status'),
  }),
  async handler({ item_id, status }) {
    storage.updateStatus(item_id, status);
    return { content: [{ type: 'json', data: { success: true } }] };
  },
})

// src/features/agent/useAgentServer.ts
import { useEffect } from 'react';
import { createAgentServer, registerAgentServer, type HostAppAPI } from '@cognite/app-sdk';
import { buildAgentActions } from './agentActions';
import { buildAgentResources } from './agentResources';
import { useStorageService } from '../storage/StorageServiceContext';
import { useDataService } from '../data/DataServiceContext';

export function useAgentServer(api: HostAppAPI | null): void {
  const storage = useStorageService();
  const dataService = useDataService();

  useEffect(() => {
    if (!api) return;
    const server = createAgentServer({
      uri: 'my-app', // Fusion namespaces with instance ID
      actions: buildAgentActions(dataService),
      resources: buildAgentResources(storage),
    });
    void registerAgentServer(api, server).catch((err: unknown) => {
      console.warn('[agent] registerAgentServer failed:', err);
    });
    return () => {
      void api.unregisterAgentServer('my-app').catch((err: unknown) => {
        console.warn('[agent] unregisterAgentServer failed:', err);
      });
    };
  }, [api, storage, dataService]);
}

function App() {
  const api = useHostApp();
  useAgentServer(api);

  return (
    <AppLayout>
      <MainContent onAnalyseItem={async (item) => {
        if (!api) return;
        await api.sendAgentLayoutMode({ mode: 'sidebar' });
        await api.sendAgentMessage({
          message: `Analyse "${item.name}" (id: ${item.id}).`,
          newSession: true,
        });
      }} />
    </AppLayout>
  );
}

const [getItemAction] = buildAgentActions({
  getItem: vi.fn().mockResolvedValue({ id: '1', name: 'Test' }),
});
const result = await getItemAction.handler({ item_id: '1' });
expect(result.content[0].data).toEqual({ id: '1', name: 'Test' });