/**
 * @license
 * Copyright 2025 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */

import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
import {
  ChatCompressionService,
  findCompressSplitPoint,
} from './chatCompressionService.js';
import type { Content, GenerateContentResponse } from '@google/genai';
import { CompressionStatus } from '../core/turn.js';
import { tokenLimit } from '../core/tokenLimits.js';
import type { GeminiChat } from '../core/geminiChat.js';
import type { Config } from '../config/config.js';
import { getInitialChatHistory } from '../utils/environmentContext.js';
import type { ContentGenerator } from '../core/contentGenerator.js';

vi.mock('../core/tokenLimits.js');
vi.mock('../telemetry/loggers.js');
vi.mock('../utils/environmentContext.js');

describe('findCompressSplitPoint', () => {
  it('should throw an error for non-positive numbers', () => {
    expect(() => findCompressSplitPoint([], 0)).toThrow(
      'Fraction must be between 0 and 1',
    );
  });

  it('should throw an error for a fraction greater than or equal to 1', () => {
    expect(() => findCompressSplitPoint([], 1)).toThrow(
      'Fraction must be between 0 and 1',
    );
  });

  it('should handle an empty history', () => {
    expect(findCompressSplitPoint([], 0.5)).toBe(0);
  });

  it('should handle a fraction in the middle', () => {
    const history: Content[] = [
      { role: 'user', parts: [{ text: 'This is the first message.' }] }, // JSON length: 66 (19%)
      { role: 'model', parts: [{ text: 'This is the second message.' }] }, // JSON length: 68 (40%)
      { role: 'user', parts: [{ text: 'This is the third message.' }] }, // JSON length: 66 (60%)
      { role: 'model', parts: [{ text: 'This is the fourth message.' }] }, // JSON length: 68 (80%)
      { role: 'user', parts: [{ text: 'This is the fifth message.' }] }, // JSON length: 65 (100%)
    ];
    expect(findCompressSplitPoint(history, 0.5)).toBe(4);
  });

  it('should handle a fraction of last index', () => {
    const history: Content[] = [
      { role: 'user', parts: [{ text: 'This is the first message.' }] }, // JSON length: 66 (19%)
      { role: 'model', parts: [{ text: 'This is the second message.' }] }, // JSON length: 68 (40%)
      { role: 'user', parts: [{ text: 'This is the third message.' }] }, // JSON length: 66 (60%)
      { role: 'model', parts: [{ text: 'This is the fourth message.' }] }, // JSON length: 68 (80%)
      { role: 'user', parts: [{ text: 'This is the fifth message.' }] }, // JSON length: 65 (100%)
    ];
    expect(findCompressSplitPoint(history, 0.9)).toBe(4);
  });

  it('should handle a fraction of after last index', () => {
    const history: Content[] = [
      { role: 'user', parts: [{ text: 'This is the first message.' }] }, // JSON length: 66 (24%)
      { role: 'model', parts: [{ text: 'This is the second message.' }] }, // JSON length: 68 (50%)
      { role: 'user', parts: [{ text: 'This is the third message.' }] }, // JSON length: 66 (74%)
      { role: 'model', parts: [{ text: 'This is the fourth message.' }] }, // JSON length: 68 (100%)
    ];
    expect(findCompressSplitPoint(history, 0.8)).toBe(4);
  });

  it('should return earlier splitpoint if no valid ones are after threshhold', () => {
    const history: Content[] = [
      { role: 'user', parts: [{ text: 'This is the first message.' }] },
      { role: 'model', parts: [{ text: 'This is the second message.' }] },
      { role: 'user', parts: [{ text: 'This is the third message.' }] },
      { role: 'model', parts: [{ functionCall: { name: 'foo', args: {} } }] },
    ];
    // Can't return 4 because the previous item has a function call.
    expect(findCompressSplitPoint(history, 0.99)).toBe(2);
  });

  it('should handle a history with only one item', () => {
    const historyWithEmptyParts: Content[] = [
      { role: 'user', parts: [{ text: 'Message 1' }] },
    ];
    expect(findCompressSplitPoint(historyWithEmptyParts, 0.5)).toBe(0);
  });

  it('should handle history with weird parts', () => {
    const historyWithEmptyParts: Content[] = [
      { role: 'user', parts: [{ text: 'Message 1' }] },
      {
        role: 'model',
        parts: [{ fileData: { fileUri: 'derp', mimeType: 'text/plain' } }],
      },
      { role: 'user', parts: [{ text: 'Message 2' }] },
    ];
    expect(findCompressSplitPoint(historyWithEmptyParts, 0.5)).toBe(2);
  });
});

describe('ChatCompressionService', () => {
  let service: ChatCompressionService;
  let mockChat: GeminiChat;
  let mockConfig: Config;
  const mockModel = 'gemini-pro';
  const mockPromptId = 'test-prompt-id';

  beforeEach(() => {
    service = new ChatCompressionService();
    mockChat = {
      getHistory: vi.fn(),
      getLastPromptTokenCount: vi.fn().mockReturnValue(500),
    } as unknown as GeminiChat;
    mockConfig = {
      getChatCompression: vi.fn(),
      getContentGenerator: vi.fn(),
    } as unknown as Config;

    vi.mocked(tokenLimit).mockReturnValue(1000);
    vi.mocked(getInitialChatHistory).mockImplementation(
      async (_config, extraHistory) => extraHistory || [],
    );
  });

  afterEach(() => {
    vi.restoreAllMocks();
  });

  it('should return NOOP if history is empty', async () => {
    vi.mocked(mockChat.getHistory).mockReturnValue([]);
    const result = await service.compress(
      mockChat,
      mockPromptId,
      false,
      mockModel,
      mockConfig,
      false,
    );
    expect(result.info.compressionStatus).toBe(CompressionStatus.NOOP);
    expect(result.newHistory).toBeNull();
  });

  it('should return NOOP if previously failed and not forced', async () => {
    vi.mocked(mockChat.getHistory).mockReturnValue([
      { role: 'user', parts: [{ text: 'hi' }] },
    ]);
    const result = await service.compress(
      mockChat,
      mockPromptId,
      false,
      mockModel,
      mockConfig,
      true,
    );
    expect(result.info.compressionStatus).toBe(CompressionStatus.NOOP);
    expect(result.newHistory).toBeNull();
  });

  it('should return NOOP if under token threshold and not forced', async () => {
    vi.mocked(mockChat.getHistory).mockReturnValue([
      { role: 'user', parts: [{ text: 'hi' }] },
    ]);
    vi.mocked(mockChat.getLastPromptTokenCount).mockReturnValue(600);
    vi.mocked(tokenLimit).mockReturnValue(1000);
    // Threshold is 0.7 * 1000 = 700. 600 < 700, so NOOP.

    const result = await service.compress(
      mockChat,
      mockPromptId,
      false,
      mockModel,
      mockConfig,
      false,
    );
    expect(result.info.compressionStatus).toBe(CompressionStatus.NOOP);
    expect(result.newHistory).toBeNull();
  });

  it('should compress if over token threshold', async () => {
    const history: Content[] = [
      { role: 'user', parts: [{ text: 'msg1' }] },
      { role: 'model', parts: [{ text: 'msg2' }] },
      { role: 'user', parts: [{ text: 'msg3' }] },
      { role: 'model', parts: [{ text: 'msg4' }] },
    ];
    vi.mocked(mockChat.getHistory).mockReturnValue(history);
    vi.mocked(mockChat.getLastPromptTokenCount).mockReturnValue(800);
    vi.mocked(tokenLimit).mockReturnValue(1000);
    const mockGenerateContent = vi.fn().mockResolvedValue({
      candidates: [
        {
          content: {
            parts: [{ text: 'Summary' }],
          },
        },
      ],
    } as unknown as GenerateContentResponse);
    vi.mocked(mockConfig.getContentGenerator).mockReturnValue({
      generateContent: mockGenerateContent,
    } as unknown as ContentGenerator);

    const result = await service.compress(
      mockChat,
      mockPromptId,
      false,
      mockModel,
      mockConfig,
      false,
    );

    expect(result.info.compressionStatus).toBe(CompressionStatus.COMPRESSED);
    expect(result.newHistory).not.toBeNull();
    expect(result.newHistory![0].parts![0].text).toBe('Summary');
    expect(mockGenerateContent).toHaveBeenCalled();
  });

  it('should force compress even if under threshold', async () => {
    const history: Content[] = [
      { role: 'user', parts: [{ text: 'msg1' }] },
      { role: 'model', parts: [{ text: 'msg2' }] },
      { role: 'user', parts: [{ text: 'msg3' }] },
      { role: 'model', parts: [{ text: 'msg4' }] },
    ];
    vi.mocked(mockChat.getHistory).mockReturnValue(history);
    vi.mocked(mockChat.getLastPromptTokenCount).mockReturnValue(100);
    vi.mocked(tokenLimit).mockReturnValue(1000);

    const mockGenerateContent = vi.fn().mockResolvedValue({
      candidates: [
        {
          content: {
            parts: [{ text: 'Summary' }],
          },
        },
      ],
    } as unknown as GenerateContentResponse);
    vi.mocked(mockConfig.getContentGenerator).mockReturnValue({
      generateContent: mockGenerateContent,
    } as unknown as ContentGenerator);

    const result = await service.compress(
      mockChat,
      mockPromptId,
      true, // forced
      mockModel,
      mockConfig,
      false,
    );

    expect(result.info.compressionStatus).toBe(CompressionStatus.COMPRESSED);
    expect(result.newHistory).not.toBeNull();
  });

  it('should return FAILED if new token count is inflated', async () => {
    const history: Content[] = [
      { role: 'user', parts: [{ text: 'msg1' }] },
      { role: 'model', parts: [{ text: 'msg2' }] },
    ];
    vi.mocked(mockChat.getHistory).mockReturnValue(history);
    vi.mocked(mockChat.getLastPromptTokenCount).mockReturnValue(10);
    vi.mocked(tokenLimit).mockReturnValue(1000);

    const longSummary = 'a'.repeat(1000); // Long summary to inflate token count
    const mockGenerateContent = vi.fn().mockResolvedValue({
      candidates: [
        {
          content: {
            parts: [{ text: longSummary }],
          },
        },
      ],
    } as unknown as GenerateContentResponse);
    vi.mocked(mockConfig.getContentGenerator).mockReturnValue({
      generateContent: mockGenerateContent,
    } as unknown as ContentGenerator);

    const result = await service.compress(
      mockChat,
      mockPromptId,
      true,
      mockModel,
      mockConfig,
      false,
    );

    expect(result.info.compressionStatus).toBe(
      CompressionStatus.COMPRESSION_FAILED_INFLATED_TOKEN_COUNT,
    );
    expect(result.newHistory).toBeNull();
  });
});