/**
 * Tests for encryption service
 */

import { encrypt, decrypt, isEncrypted, clearEncryptionKey } from '../encryption';
import * as SecureStore from 'expo-secure-store';
import * as Crypto from 'expo-crypto';

// expo-crypto and expo-secure-store are already mocked in jest.setup.js

describe('Encryption Service', () => {
  beforeEach(() => {
    jest.clearAllMocks();
    // Reset SecureStore mock to return null (no existing key)
    (SecureStore.getItemAsync as jest.Mock).mockResolvedValue(null);
  });

  afterEach(async () => {
    // Clear encryption key after each test
    await clearEncryptionKey();
  });

  describe('encrypt', () => {
    it('should encrypt a string successfully', async () => {
      const plaintext = 'MySecurePassword123';
      const encrypted = await encrypt(plaintext);

      // Should return base64 string
      expect(typeof encrypted).toBe('string');
      expect(encrypted.length).toBeGreaterThan(0);

      // Should not be the same as plaintext
      expect(encrypted).not.toBe(plaintext);

      // Should be base64
      expect(() => Buffer.from(encrypted, 'base64')).not.toThrow();
    });

    it('should generate a master key and store it', async () => {
      const plaintext = 'test password';
      await encrypt(plaintext);

      // Should have stored the master key
      expect(SecureStore.setItemAsync).toHaveBeenCalledWith(
        'WELLNUO_ENCRYPTION_KEY',
        expect.any(String)
      );
    });

    it('should encrypt empty string', async () => {
      const plaintext = '';
      const encrypted = await encrypt(plaintext);

      expect(typeof encrypted).toBe('string');
      expect(encrypted.length).toBeGreaterThan(0);
    });

    it('should encrypt unicode characters', async () => {
      const plaintext = '密码 🔐 пароль';
      const encrypted = await encrypt(plaintext);

      expect(typeof encrypted).toBe('string');
      expect(encrypted.length).toBeGreaterThan(0);
    });

    it('should produce different ciphertext for same input (due to random IV)', async () => {
      const plaintext = 'same password';

      // Mock to return different random bytes each time
      let callCount = 0;
      (Crypto.getRandomBytesAsync as jest.Mock).mockImplementation((size: number) => {
        callCount++;
        const bytes = new Uint8Array(size);
        for (let i = 0; i < size; i++) {
          bytes[i] = (i * callCount + 13) % 256;
        }
        return Promise.resolve(bytes);
      });

      const encrypted1 = await encrypt(plaintext);
      const encrypted2 = await encrypt(plaintext);

      expect(encrypted1).not.toBe(encrypted2);
    });
  });

  describe('decrypt', () => {
    it('should decrypt encrypted data correctly', async () => {
      const plaintext = 'MySecurePassword123';
      const encrypted = await encrypt(plaintext);
      const decrypted = await decrypt(encrypted);

      expect(decrypted).toBe(plaintext);
    });

    it('should decrypt empty string', async () => {
      const plaintext = '';
      const encrypted = await encrypt(plaintext);
      const decrypted = await decrypt(encrypted);

      expect(decrypted).toBe(plaintext);
    });

    it('should decrypt unicode characters', async () => {
      const plaintext = '密码 🔐 пароль';
      const encrypted = await encrypt(plaintext);
      const decrypted = await decrypt(encrypted);

      expect(decrypted).toBe(plaintext);
    });

    it('should handle long strings', async () => {
      const plaintext = 'A'.repeat(10000);
      const encrypted = await encrypt(plaintext);
      const decrypted = await decrypt(encrypted);

      expect(decrypted).toBe(plaintext);
    });

    it('should throw error for invalid ciphertext', async () => {
      const invalidCiphertext = 'not-valid-base64!@#$';

      await expect(decrypt(invalidCiphertext)).rejects.toThrow();
    });

    it('should throw error for corrupted data', async () => {
      const plaintext = 'test';
      const encrypted = await encrypt(plaintext);

      // Corrupt the ciphertext
      const buffer = Buffer.from(encrypted, 'base64');
      buffer[buffer.length - 1] ^= 0xFF; // Flip bits in last byte
      const corrupted = buffer.toString('base64');

      await expect(decrypt(corrupted)).rejects.toThrow();
    });

    it('should throw error if ciphertext is too short', async () => {
      // Create invalid ciphertext (too short)
      const tooShort = Buffer.from('short').toString('base64');

      await expect(decrypt(tooShort)).rejects.toThrow();
    });
  });

  describe('isEncrypted', () => {
    it('should return true for encrypted data', async () => {
      const plaintext = 'test password';
      const encrypted = await encrypt(plaintext);

      expect(isEncrypted(encrypted)).toBe(true);
    });

    it('should return false for plaintext', () => {
      const plaintext = 'just a regular password';

      expect(isEncrypted(plaintext)).toBe(false);
    });

    it('should return false for short base64 strings', () => {
      const shortBase64 = Buffer.from('short').toString('base64');

      expect(isEncrypted(shortBase64)).toBe(false);
    });

    it('should return false for invalid base64', () => {
      const invalid = 'not-base64!@#$%';

      expect(isEncrypted(invalid)).toBe(false);
    });

    it('should return false for empty string', () => {
      expect(isEncrypted('')).toBe(false);
    });
  });

  describe('clearEncryptionKey', () => {
    it('should clear the master encryption key', async () => {
      // First encrypt something to generate a key
      await encrypt('test');

      // Clear the key
      await clearEncryptionKey();

      // Should have called deleteItemAsync
      expect(SecureStore.deleteItemAsync).toHaveBeenCalledWith('WELLNUO_ENCRYPTION_KEY');
    });
  });

  describe('key persistence', () => {
    it('should reuse existing master key', async () => {
      const existingKey = Buffer.from('existing-master-key-32-bytes!!').toString('base64');
      (SecureStore.getItemAsync as jest.Mock).mockResolvedValue(existingKey);

      await encrypt('test');

      // Should have retrieved existing key
      expect(SecureStore.getItemAsync).toHaveBeenCalledWith('WELLNUO_ENCRYPTION_KEY');

      // Should NOT have set a new key
      expect(SecureStore.setItemAsync).not.toHaveBeenCalledWith(
        'WELLNUO_ENCRYPTION_KEY',
        expect.any(String)
      );
    });
  });

  describe('round-trip encryption', () => {
    const testCases = [
      { name: 'simple password', value: 'password123' },
      { name: 'complex password', value: 'P@ssw0rd!#$%^&*()' },
      { name: 'unicode', value: '密码 🔐 пароль ñoño' },
      { name: 'empty string', value: '' },
      { name: 'spaces', value: '   spaces   ' },
      { name: 'newlines', value: 'line1\nline2\nline3' },
      { name: 'long string', value: 'x'.repeat(1000) },
      { name: 'WiFi password', value: 'MyHomeWiFi2024!' },
    ];

    testCases.forEach(({ name, value }) => {
      it(`should correctly encrypt and decrypt: ${name}`, async () => {
        const encrypted = await encrypt(value);
        const decrypted = await decrypt(encrypted);

        expect(decrypted).toBe(value);
      });
    });
  });
});