#include "kernel/devices/block_device_utils.hpp"

#include "kernel/test_support/cpu.hpp"
#include "kernel/test_support/devices/block_device.hpp"

#include <kstd/memory>
#include <kstd/print>
#include <kstd/vector>

#include <catch2/catch_test_macros.hpp>

#include <cstddef>
#include <cstdint>

SCENARIO("reading from a block device with block_device_utils", "[devices][block_device_utils]")
{
  GIVEN("a block device with known data")
  {
    auto const block_size = 512;
    auto device = kstd::make_shared<kernel::tests::devices::block_device>(0, 0, "test_block_device", block_size);
    kstd::vector<uint8_t> block_data(block_size);
    for (size_t i = 0; i < block_data.size(); ++i)
    {
      block_data[i] = static_cast<uint8_t>(i % 256);
    }
    device->write_block(0, block_data.data());
    device->write_block(1, block_data.data());

    WHEN("reading from the block device using block_device_utils")
    {
      kstd::vector<uint8_t> read_buffer(block_size);
      auto bytes_read = kernel::devices::block_device_utils::read(device, read_buffer.data(), 0, read_buffer.size());

      THEN("the correct number of bytes is read")
      {
        REQUIRE(bytes_read == read_buffer.size());
      }

      THEN("the data read matches the data written to the block device")
      {
        REQUIRE(read_buffer == block_data);
      }
    }

    WHEN("reading over block boundaries")
    {
      kstd::vector<uint8_t> read_buffer(1024);
      auto bytes_read = kernel::devices::block_device_utils::read(device, read_buffer.data(), 256, read_buffer.size());

      THEN("the correct number of bytes is read")
      {
        REQUIRE(bytes_read == 1.5 * block_size);
      }

      THEN("the data read matches the expected data across block boundaries")
      {
        for (size_t i = 0; i < bytes_read; ++i)
        {
          uint8_t expected_value = static_cast<uint8_t>((256 + i) % 256);
          REQUIRE(read_buffer[i] == expected_value);
        }
      }
    }

    WHEN("reading beyond the device capacity")
    {
      kstd::vector<uint8_t> read_buffer(block_size);
      auto bytes_read = kernel::devices::block_device_utils::read(device, read_buffer.data(), 1024, read_buffer.size());

      THEN("no bytes are read")
      {
        REQUIRE(bytes_read == 0);
      }
    }

    WHEN("reading nothing")
    {
      kstd::vector<uint8_t> read_buffer(block_size);
      auto bytes_read = kernel::devices::block_device_utils::read(device, read_buffer.data(), 0, 0);

      THEN("no bytes are read")
      {
        REQUIRE(bytes_read == 0);
      }
    }

    WHEN("reading with a null buffer")
    {
      THEN("the system panics")
      {
        REQUIRE_THROWS_AS(kernel::devices::block_device_utils::read(device, nullptr, 0, 512), kernel::tests::cpu::halt);
      }
    }
  }
}

SCENARIO("writing to a block device using block_device_utils", "[devices][block_device_utils]")
{
  GIVEN("a block device")
  {
    auto const block_size = 512;
    auto device = kstd::make_shared<kernel::tests::devices::block_device>(0, 0, "test_block_device", block_size);
    device->data.resize(2 * block_size);

    WHEN("writing to the block device using block_device_utils")
    {
      kstd::vector<uint8_t> write_buffer(block_size);
      for (size_t i = 0; i < write_buffer.size(); ++i)
      {
        write_buffer[i] = static_cast<uint8_t>(i % 256);
      }

      auto bytes_written =
          kernel::devices::block_device_utils::write(device, write_buffer.data(), 0, write_buffer.size());

      THEN("the correct number of bytes is written")
      {
        REQUIRE(bytes_written == write_buffer.size());
      }

      THEN("the data written matches the data read back from the block device")
      {
        kstd::vector<uint8_t> read_buffer(block_size);
        device->read_block(0, read_buffer.data());
        REQUIRE(read_buffer == write_buffer);
      }
    }

    WHEN("writing over block boundaries")
    {
      kstd::vector<uint8_t> write_buffer(2 * block_size);
      for (size_t i = 0; i < write_buffer.size(); ++i)
      {
        write_buffer[i] = static_cast<uint8_t>(i % 256);
      }

      auto bytes_written =
          kernel::devices::block_device_utils::write(device, write_buffer.data(), 256, write_buffer.size());

      THEN("the correct number of bytes is written")
      {
        REQUIRE(bytes_written == 1.5 * block_size);
      }

      THEN("the data written matches the data read back from the block device across block boundaries")
      {
        kstd::vector<uint8_t> read_buffer(2 * block_size);
        auto bytes_read = kernel::devices::block_device_utils::read(device, read_buffer.data(), 256, 2 * block_size);

        for (size_t i = 0; i < bytes_read; ++i)
        {
          REQUIRE(read_buffer[i] == write_buffer[i]);
        }
      }
    }

    WHEN("writing beyond the device capacity")
    {
      kstd::vector<uint8_t> write_buffer(block_size);
      auto bytes_written =
          kernel::devices::block_device_utils::write(device, write_buffer.data(), 1024, write_buffer.size());

      THEN("no bytes are written")
      {
        REQUIRE(bytes_written == 0);
      }
    }

    WHEN("writing nothing")
    {
      kstd::vector<uint8_t> write_buffer(block_size);
      auto bytes_written = kernel::devices::block_device_utils::write(device, write_buffer.data(), 0, 0);

      THEN("no bytes are written")
      {
        REQUIRE(bytes_written == 0);
      }
    }

    WHEN("writing with a null buffer")
    {
      THEN("the system panics")
      {
        REQUIRE_THROWS_AS(kernel::devices::block_device_utils::write(device, nullptr, 0, block_size),
                          kernel::tests::cpu::halt);
      }
    }
  }
}