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

import {
  vi,
  describe,
  it,
  expect,
  beforeEach,
  afterEach,
  Mocked,
} from 'vitest';

import {
  type CommandContext,
  MessageActionReturn,
  SlashCommand,
} from './types.js';
import { createMockCommandContext } from '../../test-utils/mockCommandContext.js';
import { Content } from '@google/genai';
import { GeminiClient } from '@google/gemini-cli-core';

import * as fsPromises from 'fs/promises';
import { chatCommand } from './chatCommand.js';
import { Stats } from 'fs';
import { HistoryItemWithoutId } from '../types.js';

vi.mock('fs/promises', () => ({
  stat: vi.fn(),
  readdir: vi.fn().mockResolvedValue(['file1.txt', 'file2.txt'] as string[]),
}));

describe('chatCommand', () => {
  const mockFs = fsPromises as Mocked<typeof fsPromises>;

  let mockContext: CommandContext;
  let mockGetChat: ReturnType<typeof vi.fn>;
  let mockSaveCheckpoint: ReturnType<typeof vi.fn>;
  let mockLoadCheckpoint: ReturnType<typeof vi.fn>;
  let mockGetHistory: ReturnType<typeof vi.fn>;

  const getSubCommand = (name: 'list' | 'save' | 'resume'): SlashCommand => {
    const subCommand = chatCommand.subCommands?.find(
      (cmd) => cmd.name === name,
    );
    if (!subCommand) {
      throw new Error(`/memory ${name} command not found.`);
    }
    return subCommand;
  };

  beforeEach(() => {
    mockGetHistory = vi.fn().mockReturnValue([]);
    mockGetChat = vi.fn().mockResolvedValue({
      getHistory: mockGetHistory,
    });
    mockSaveCheckpoint = vi.fn().mockResolvedValue(undefined);
    mockLoadCheckpoint = vi.fn().mockResolvedValue([]);

    mockContext = createMockCommandContext({
      services: {
        config: {
          getProjectTempDir: () => '/tmp/gemini',
          getGeminiClient: () =>
            ({
              getChat: mockGetChat,
            }) as unknown as GeminiClient,
        },
        logger: {
          saveCheckpoint: mockSaveCheckpoint,
          loadCheckpoint: mockLoadCheckpoint,
          initialize: vi.fn().mockResolvedValue(undefined),
        },
      },
    });
  });

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

  it('should have the correct main command definition', () => {
    expect(chatCommand.name).toBe('chat');
    expect(chatCommand.description).toBe('Manage conversation history.');
    expect(chatCommand.subCommands).toHaveLength(3);
  });

  describe('list subcommand', () => {
    let listCommand: SlashCommand;

    beforeEach(() => {
      listCommand = getSubCommand('list');
    });

    it('should inform when no checkpoints are found', async () => {
      mockFs.readdir.mockImplementation(
        (async (_: string): Promise<string[]> =>
          [] as string[]) as unknown as typeof fsPromises.readdir,
      );
      const result = await listCommand?.action?.(mockContext, '');
      expect(result).toEqual({
        type: 'message',
        messageType: 'info',
        content: 'No saved conversation checkpoints found.',
      });
    });

    it('should list found checkpoints', async () => {
      const fakeFiles = ['checkpoint-test1.json', 'checkpoint-test2.json'];
      const date = new Date();

      mockFs.readdir.mockImplementation(
        (async (_: string): Promise<string[]> =>
          fakeFiles as string[]) as unknown as typeof fsPromises.readdir,
      );
      mockFs.stat.mockImplementation((async (path: string): Promise<Stats> => {
        if (path.endsWith('test1.json')) {
          return { mtime: date } as Stats;
        }
        return { mtime: new Date(date.getTime() + 1000) } as Stats;
      }) as unknown as typeof fsPromises.stat);

      const result = (await listCommand?.action?.(
        mockContext,
        '',
      )) as MessageActionReturn;

      const content = result?.content ?? '';
      expect(result?.type).toBe('message');
      expect(content).toContain('List of saved conversations:');
      const isoDate = date
        .toISOString()
        .match(/(\d{4}-\d{2}-\d{2})T(\d{2}:\d{2}:\d{2})/);
      const formattedDate = isoDate ? `${isoDate[1]} ${isoDate[2]}` : '';
      expect(content).toContain(formattedDate);
      const index1 = content.indexOf('- \u001b[36mtest1\u001b[0m');
      const index2 = content.indexOf('- \u001b[36mtest2\u001b[0m');
      expect(index1).toBeGreaterThanOrEqual(0);
      expect(index2).toBeGreaterThan(index1);
    });

    it('should handle invalid date formats gracefully', async () => {
      const fakeFiles = ['checkpoint-baddate.json'];
      const badDate = {
        toISOString: () => 'an-invalid-date-string',
      } as Date;

      mockFs.readdir.mockResolvedValue(fakeFiles);
      mockFs.stat.mockResolvedValue({ mtime: badDate } as Stats);

      const result = (await listCommand?.action?.(
        mockContext,
        '',
      )) as MessageActionReturn;

      const content = result?.content ?? '';
      expect(content).toContain('(saved on Invalid Date)');
    });
  });
  describe('save subcommand', () => {
    let saveCommand: SlashCommand;
    const tag = 'my-tag';
    beforeEach(() => {
      saveCommand = getSubCommand('save');
    });

    it('should return an error if tag is missing', async () => {
      const result = await saveCommand?.action?.(mockContext, '  ');
      expect(result).toEqual({
        type: 'message',
        messageType: 'error',
        content: 'Missing tag. Usage: /chat save <tag>',
      });
    });

    it('should inform if conversation history is empty', async () => {
      mockGetHistory.mockReturnValue([]);
      const result = await saveCommand?.action?.(mockContext, tag);
      expect(result).toEqual({
        type: 'message',
        messageType: 'info',
        content: 'No conversation found to save.',
      });
    });

    it('should save the conversation', async () => {
      const history: HistoryItemWithoutId[] = [
        {
          type: 'user',
          text: 'hello',
        },
      ];
      mockGetHistory.mockReturnValue(history);
      const result = await saveCommand?.action?.(mockContext, tag);

      expect(mockSaveCheckpoint).toHaveBeenCalledWith(history, tag);
      expect(result).toEqual({
        type: 'message',
        messageType: 'info',
        content: `Conversation checkpoint saved with tag: ${tag}.`,
      });
    });
  });

  describe('resume subcommand', () => {
    const goodTag = 'good-tag';
    const badTag = 'bad-tag';

    let resumeCommand: SlashCommand;
    beforeEach(() => {
      resumeCommand = getSubCommand('resume');
    });

    it('should return an error if tag is missing', async () => {
      const result = await resumeCommand?.action?.(mockContext, '');

      expect(result).toEqual({
        type: 'message',
        messageType: 'error',
        content: 'Missing tag. Usage: /chat resume <tag>',
      });
    });

    it('should inform if checkpoint is not found', async () => {
      mockLoadCheckpoint.mockResolvedValue([]);

      const result = await resumeCommand?.action?.(mockContext, badTag);

      expect(result).toEqual({
        type: 'message',
        messageType: 'info',
        content: `No saved checkpoint found with tag: ${badTag}.`,
      });
    });

    it('should resume a conversation', async () => {
      const conversation: Content[] = [
        { role: 'user', parts: [{ text: 'hello gemini' }] },
        { role: 'model', parts: [{ text: 'hello world' }] },
      ];
      mockLoadCheckpoint.mockResolvedValue(conversation);

      const result = await resumeCommand?.action?.(mockContext, goodTag);

      expect(result).toEqual({
        type: 'load_history',
        history: [
          { type: 'user', text: 'hello gemini' },
          { type: 'gemini', text: 'hello world' },
        ] as HistoryItemWithoutId[],
        clientHistory: conversation,
      });
    });

    describe('completion', () => {
      it('should provide completion suggestions', async () => {
        const fakeFiles = ['checkpoint-alpha.json', 'checkpoint-beta.json'];
        mockFs.readdir.mockImplementation(
          (async (_: string): Promise<string[]> =>
            fakeFiles as string[]) as unknown as typeof fsPromises.readdir,
        );

        mockFs.stat.mockImplementation(
          (async (_: string): Promise<Stats> =>
            ({
              mtime: new Date(),
            }) as Stats) as unknown as typeof fsPromises.stat,
        );

        const result = await resumeCommand?.completion?.(mockContext, 'a');

        expect(result).toEqual(['alpha']);
      });

      it('should suggest filenames sorted by modified time (newest first)', async () => {
        const fakeFiles = ['checkpoint-test1.json', 'checkpoint-test2.json'];
        const date = new Date();
        mockFs.readdir.mockImplementation(
          (async (_: string): Promise<string[]> =>
            fakeFiles as string[]) as unknown as typeof fsPromises.readdir,
        );
        mockFs.stat.mockImplementation((async (
          path: string,
        ): Promise<Stats> => {
          if (path.endsWith('test1.json')) {
            return { mtime: date } as Stats;
          }
          return { mtime: new Date(date.getTime() + 1000) } as Stats;
        }) as unknown as typeof fsPromises.stat);

        const result = await resumeCommand?.completion?.(mockContext, '');
        // Sort items by last modified time (newest first)
        expect(result).toEqual(['test2', 'test1']);
      });
    });
  });
});