import { describe, it, expect, vi, beforeEach } from 'vitest';
import type { Cluster, EmbeddingMap } from '../types/domain.js';

type StreamEvent = {
  type: string;
  delta?: { type: string; text: string };
};

const { streamMock, mockEmbeddings } = vi.hoisted(() => {
  const embeddings = new Map<string, number[]>([
    ['note_001', [1.0, 0.0, 0.0]],
    ['note_002', [0.0, 1.0, 0.0]],
  ]);
  return { streamMock: vi.fn(), mockEmbeddings: embeddings as EmbeddingMap };
});

vi.mock('@anthropic-ai/sdk', () => {
  return {
    default: class MockAnthropic {
      messages = { stream: streamMock };
    },
  };
});

vi.mock('../services/embedding.service.js', () => ({
  embedNotes: vi.fn().mockResolvedValue(mockEmbeddings),
}));

import { clusterNotes } from '../services/clustering.service.js';

const MOCK_NOTES = [
  { id: 'note_001', text: 'Login is broken' },
  { id: 'note_002', text: 'Export fails' },
];

const MOCK_CLUSTERS: Cluster[] = [
  { label: 'Auth Issues', noteIds: ['note_001'] },
  { label: 'Export Issues', noteIds: ['note_002'] },
];

// Splits text into several text_delta events so the service is exercised
// against a genuinely incremental stream rather than one whole payload.
const textEvents = (text: string, pieces = 4): StreamEvent[] => {
  const size = Math.max(1, Math.ceil(text.length / pieces));
  const events: StreamEvent[] = [];
  for (let i = 0; i < text.length; i += size) {
    events.push({
      type: 'content_block_delta',
      delta: { type: 'text_delta', text: text.slice(i, i + size) },
    });
  }
  return events;
};

const mockStreamOf = (text: string): void => {
  const events: StreamEvent[] = [
    { type: 'message_start' },
    ...textEvents(text),
    { type: 'message_stop' },
  ];
  streamMock.mockImplementation(() => ({
    async *[Symbol.asyncIterator]() {
      for (const event of events) yield event;
    },
  }));
};

const mockStreamThrowing = (err: Error): void => {
  streamMock.mockImplementation(() => ({
    async *[Symbol.asyncIterator]() {
      throw err;
    },
  }));
};

describe('clusterNotes service', () => {

  beforeEach(() => {
    vi.clearAllMocks();
  });

  it('should call Anthropic messages.stream with the correct model', async () => {
    mockStreamOf(JSON.stringify(MOCK_CLUSTERS));

    await clusterNotes(MOCK_NOTES);

    expect(streamMock).toHaveBeenCalledOnce();
    const callArgs = streamMock.mock.calls[0][0];
    expect(callArgs.model).toBe('claude-sonnet-5');
    expect(callArgs.max_tokens).toBe(4096);
  });

  it('should forward an abort signal to the LLM request', async () => {
    mockStreamOf(JSON.stringify(MOCK_CLUSTERS));
    const controller = new AbortController();

    await clusterNotes(MOCK_NOTES, { signal: controller.signal });

    expect(streamMock.mock.calls[0][1]).toEqual({ signal: controller.signal });
  });

  it('should include all note texts in prompt sent to the LLM API', async () => {
    mockStreamOf(JSON.stringify(MOCK_CLUSTERS));

    await clusterNotes(MOCK_NOTES);

    const prompt = streamMock.mock.calls[0][0].messages[0].content;
    expect(prompt).toContain('note_001');
    expect(prompt).toContain('Login is broken');
    expect(prompt).toContain('note_002');
    expect(prompt).toContain('Export fails');
  });

  it('should return clusters and a cohesion score', async () => {
    mockStreamOf(JSON.stringify(MOCK_CLUSTERS));

    const result = await clusterNotes(MOCK_NOTES);

    expect(result.clusters).toEqual(MOCK_CLUSTERS);
    expect(typeof result.score).toBe('number');
    expect(result.score).toBeGreaterThanOrEqual(-1);
    expect(result.score).toBeLessThanOrEqual(1);
  });

  it('should reassemble clusters split across many stream deltas', async () => {
    const json = JSON.stringify(MOCK_CLUSTERS);
    streamMock.mockImplementation(() => ({
      async *[Symbol.asyncIterator]() {
        for (const char of json) {
          yield { type: 'content_block_delta', delta: { type: 'text_delta', text: char } };
        }
      },
    }));

    const result = await clusterNotes(MOCK_NOTES);

    expect(result.clusters).toEqual(MOCK_CLUSTERS);
  });

  it('should throw error when the API returns non-JSON', async () => {
    mockStreamOf('An unknown error occured when generting structured response.');

    await expect(clusterNotes(MOCK_NOTES)).rejects.toThrow('non-JSON response');
  });

  it('should throw error when the API response has no text content', async () => {
    mockStreamOf('');

    await expect(clusterNotes(MOCK_NOTES)).rejects.toThrow('no text content returned');
  });

  it('should throw error when Anthropic API authentication fails', async () => {
    mockStreamThrowing(new Error('401 Unauthorized'));

    await expect(clusterNotes(MOCK_NOTES)).rejects.toThrow('401 Unauthorized');
  });

  it('should throw a validation error when a note is missing from clusters', async () => {
    const incompleteClusters: Cluster[] = [
      { label: 'Auth Issues', noteIds: ['note_001'] },
    ];
    mockStreamOf(JSON.stringify(incompleteClusters));

    await expect(clusterNotes(MOCK_NOTES)).rejects.toThrow('Cluster validation failed');
  });

  it('should throw when the API returns a JSON array of the wrong shape', async () => {
    mockStreamOf(JSON.stringify([{ name: 'Auth Issues', ids: ['note_001'] }]));

    await expect(clusterNotes(MOCK_NOTES)).rejects.toThrow('unexpected shape');
  });
});