defmodule Odinsea.CryptoTest do
  @moduledoc """
  Test module for MapleStory crypto implementation.
  Run with: mix test test/crypto_test.exs
  """

  use ExUnit.Case

  alias Odinsea.Net.Cipher.{ClientCrypto, IGCipher, ShandaCipher, AESCipher}
  alias Odinsea.Util.BitTools

  describe "IGCipher (IV transformation)" do
    test "inno_hash transforms IV correctly" do
      iv = <<0x34, 0x9A, 0x0F, 0x0C>>
      result = IGCipher.inno_hash(iv)
      
      # Result should be 4 bytes
      assert byte_size(result) == 4
      
      # Result should be different from input (usually)
      assert result != iv
    end
    
    test "inno_hash produces deterministic results" do
      iv = <<0xA8, 0xBC, 0x0D, 0xB3>>
      result1 = IGCipher.inno_hash(iv)
      result2 = IGCipher.inno_hash(iv)
      
      assert result1 == result2
    end
  end
  
  describe "ShandaCipher" do
    test "encrypt and decrypt are inverse operations" do
      original = <<1, 0, 7, 112, 0, 4, 0>>  # CP_PermissionRequest payload
      encrypted = ShandaCipher.encrypt(original)
      decrypted = ShandaCipher.decrypt(encrypted)
      
      assert decrypted == original
    end
    
    test "encrypt produces different output" do
      original = <<1, 0, 7, 112, 0, 4, 0>>
      encrypted = ShandaCipher.encrypt(original)
      
      assert encrypted != original
    end
  end
  
  describe "AESCipher" do
    test "crypt is self-inverse (XOR property)" do
      data = <<1, 0, 7, 112, 0, 4, 0>>
      iv = <<0xA8, 0xBC, 0x0D, 0xB3>>
      
      encrypted = AESCipher.crypt(data, iv)
      decrypted = AESCipher.crypt(encrypted, iv)
      
      assert decrypted == data
    end
  end
  
  describe "ClientCrypto" do
    test "new creates crypto with random IVs" do
      crypto = ClientCrypto.new(112)
      
      assert byte_size(crypto.send_iv) == 4
      assert byte_size(crypto.recv_iv) == 4
      assert crypto.version == 112
    end
    
    test "new_from_ivs creates crypto with specified IVs" do
      send_iv = <<0x34, 0x9A, 0x0F, 0x0C>>
      recv_iv = <<0xA8, 0xBC, 0x0D, 0xB3>>
      
      crypto = ClientCrypto.new_from_ivs(112, send_iv, recv_iv)
      
      assert crypto.send_iv == send_iv
      assert crypto.recv_iv == recv_iv
    end
    
    test "new_from_client_ivs swaps IVs correctly" do
      # Client's perspective
      client_send_iv = <<0xA8, 0xBC, 0x0D, 0xB3>>
      client_recv_iv = <<0x34, 0x9A, 0x0F, 0x0C>>
      
      # Server's perspective (should be swapped)
      crypto = ClientCrypto.new_from_client_ivs(112, client_send_iv, client_recv_iv)
      
      # Server's send = client's recv
      assert crypto.send_iv == client_recv_iv
      # Server's recv = client's send
      assert crypto.recv_iv == client_send_iv
    end
    
    test "decrypt updates recv_iv" do
      crypto = ClientCrypto.new(112)
      original_recv_iv = crypto.recv_iv
      
      encrypted_data = <<0x7C, 0xA8, 0x7B, 0xA8, 0xBF, 0x0A, 0xCD, 0xDE>>
      {new_crypto, _decrypted} = ClientCrypto.decrypt(crypto, encrypted_data)
      
      # IV should be updated after decryption
      assert new_crypto.recv_iv != original_recv_iv
    end
    
    test "encrypt updates send_iv" do
      crypto = ClientCrypto.new(112)
      original_send_iv = crypto.send_iv
      
      data = <<1, 0, 7, 112, 0, 4, 0>>
      {new_crypto, _encrypted, _header} = ClientCrypto.encrypt(crypto, data)
      
      # IV should be updated after encryption
      assert new_crypto.send_iv != original_send_iv
    end
    
    test "header encoding produces 4 bytes" do
      crypto = ClientCrypto.new(112)
      data = <<1, 0, 7, 112, 0, 4, 0>>
      
      {_new_crypto, _encrypted, header} = ClientCrypto.encrypt(crypto, data)
      
      assert byte_size(header) == 4
    end
    
    test "header validation works correctly" do
      crypto = ClientCrypto.new(112)
      data = <<1, 0, 7, 112, 0, 4, 0>>
      
      {new_crypto, encrypted, header} = ClientCrypto.encrypt(crypto, data)
      
      # Extract raw_seq from header
      <<raw_seq::little-16, _raw_len::little-16>> = header
      
      # Validation should pass
      assert ClientCrypto.decode_header_valid?(new_crypto, raw_seq)
    end
    
    test "full encrypt/decrypt roundtrip" do
      # Create crypto instances with same IVs
      send_iv = <<0x34, 0x9A, 0x0F, 0x0C>>
      recv_iv = <<0xA8, 0xBC, 0x0D, 0xB3>>
      
      # Server's crypto (for sending)
      server_crypto = ClientCrypto.new_from_ivs(112, send_iv, recv_iv)
      
      # Client's crypto would have swapped IVs
      # For testing, we'll use the same crypto to verify roundtrip
      original_data = <<1, 0, 7, 112, 0, 4, 0>>
      
      # Encrypt
      {server_crypto_after, encrypted, header} = ClientCrypto.encrypt(server_crypto, original_data)
      
      # Decrypt (using recv_iv which should match server's send_iv after swap)
      # For this test, we'll create a matching client crypto
      client_crypto = ClientCrypto.new_from_ivs(112, recv_iv, send_iv)
      {client_crypto_after, decrypted} = ClientCrypto.decrypt(client_crypto, encrypted)
      
      assert decrypted == original_data
    end
  end
  
  describe "BitTools" do
    test "roll_left rotates bits correctly" do
      # 0b11001101 = 205
      # rotate left by 3: 0b01101101 = 109 (wrapping around)
      result = BitTools.roll_left(205, 3)
      assert result == 109
    end
    
    test "roll_right rotates bits correctly" do
      # Test that roll_right is inverse of roll_left
      original = 205
      rotated = BitTools.roll_left(original, 3)
      back = BitTools.roll_right(rotated, 3)
      assert back == original
    end
    
    test "multiply_bytes repeats correctly" do
      input = <<1, 2, 3, 4>>
      result = BitTools.multiply_bytes(input, 4, 2)
      assert result == <<1, 2, 3, 4, 1, 2, 3, 4>>
    end
  end
end