#include <kernel/devices/storage/management.hpp>
#include <kernel/filesystem/device_inode.hpp>
#include <kernel/filesystem/file_descriptor_table.hpp>
#include <kernel/filesystem/open_file_descriptor.hpp>
#include <kernel/filesystem/vfs.hpp>
#include <kernel/memory.hpp>

#include <kapi/boot_modules.hpp>
#include <kapi/cio.hpp>
#include <kapi/cpu.hpp>
#include <kapi/devices.hpp>
#include <kapi/filesystem.hpp>
#include <kapi/interrupts.hpp>
#include <kapi/memory.hpp>
#include <kapi/system.hpp>

#include <kstd/format>
#include <kstd/memory>
#include <kstd/os/error.hpp>
#include <kstd/print>
#include <kstd/units>
#include <kstd/vector>

#include <algorithm>
#include <cstddef>
#include <string_view>

using namespace kstd::units_literals;

auto test_device_names() -> void
{
  auto storage_mgmt = kernel::devices::storage::management::get();
  std::ranges::for_each(storage_mgmt.all_controllers(), [](auto const & controller) {
    std::ranges::for_each(controller->all_devices(),
                          [](auto const & device) { kstd::println("{}", device->name().view()); });
  });
}

auto test_file_descriptor_manually() -> void
{
  // setup
  auto fd_table = kernel::filesystem::file_descriptor_table::get();
  auto storage_mgmt = kernel::devices::storage::management::get();
  auto device = storage_mgmt.device_by_major_minor(1, 0);

  auto dev_node = kstd::make_shared<kernel::filesystem::device_inode>(device);

  auto ofd = kstd::make_shared<kernel::filesystem::open_file_descriptor>(dev_node);
  auto fd_index = fd_table.add_file(ofd);

  // use: read two bytes and write two again
  auto fd = fd_table.get_file(fd_index);
  if (!fd)
  {
    kstd::os::panic("test code failed");
  }

  kstd::vector<std::byte> buffer{2};
  auto number_of_read_bytes = fd->read(buffer.data(), buffer.size());
  kstd::println("read bytes: {}", number_of_read_bytes);
  kstd::println("buffer: {::#04x}", buffer);

  // write half of the file new
  auto const value1 = std::byte{0xAA};
  auto const value2 = std::byte{0xBB};
  kstd::vector<std::byte> write_buffer{value1, value2};
  auto written_bytes = fd->write(write_buffer.data(), write_buffer.size());

  kstd::println("written bytes: {}", written_bytes);

  fd_table.remove_file(fd_index);

  // use: read four bytes again -> two old bytes two new bytes
  auto ofd1 = kstd::make_shared<kernel::filesystem::open_file_descriptor>(dev_node);
  fd_index = fd_table.add_file(ofd1);
  auto fd1 = fd_table.get_file(fd_index);

  if (!fd1)
  {
    kstd::os::panic("test code failed");
  }

  kstd::vector<std::byte> buffer1{4};
  number_of_read_bytes = fd1->read(buffer1.data(), buffer1.size());
  kstd::println("read bytes: {}", number_of_read_bytes);
  kstd::println("buffer: {::#04x}", buffer1);
}

auto test_device_with_vfs() -> void
{
  auto vfs = kernel::filesystem::vfs::get();
  auto dentry = vfs.open("/dev/ram0");
  if (!dentry)
  {
    kstd::os::panic("test code failed");
  }

  auto fd_table = kernel::filesystem::file_descriptor_table::get();
  auto ofd = kstd::make_shared<kernel::filesystem::open_file_descriptor>(dentry->get_inode());
  auto fd = fd_table.add_file(ofd);
  kstd::vector<std::byte> buffer{2};
  auto file = fd_table.get_file(fd);
  if (!file)
  {
    kstd::os::panic("test code failed");
  }

  auto number_of_read_bytes = file->read(buffer.data(), buffer.size());
  kstd::println("read bytes: {}", number_of_read_bytes);
  kstd::println("buffer: {::#04x}", buffer);
}

auto test_file_lookup() -> void
{
  auto vfs = kernel::filesystem::vfs::get();
  auto read_and_write_file = [&vfs](std::string_view path) {
    kstd::println("[TEST] Reading and writing file at path: {}", path);
    auto dentry = vfs.open(path);
    if (!dentry)
    {
      kstd::os::panic("test code failed");
    }

    kstd::vector<std::byte> buffer{32};
    auto ofd = kstd::make_shared<kernel::filesystem::open_file_descriptor>(dentry->get_inode());
    auto number_of_read_bytes = ofd->read(buffer.data(), buffer.size());
    kstd::println("read bytes: {}", number_of_read_bytes);
    kstd::println("buffer: {::#04x}", buffer);

    std::string_view buffer_as_str{reinterpret_cast<char *>(buffer.data()), number_of_read_bytes};
    kstd::println("buffer_as_str: {}", buffer_as_str);
  };

  read_and_write_file("/info.txt");
  read_and_write_file("/enclosures/info.txt");
  read_and_write_file("/enclosures/aquarium/tank_1/fish_4.txt");
  read_and_write_file("/enclosures/elephant_house/elephant_1.txt");
  read_and_write_file(
      "/enclosures/aquarium/tank_2/"
      "this_is_a_very_very_long_fish_filename_that_keeps_going_and_going_until_it_almost_breaks_linux_filesystem_"
      "limits_for_testing_purposes_and_we_add_more_characters_to_make_it_even_longer_30.txt");

  vfs.do_mount("/dev/ram16", "/enclosures/aquarium");
  read_and_write_file("/enclosures/aquarium/closed.txt");
  read_and_write_file("/enclosures/aquarium/information/info_2.txt");

  vfs.unmount("/enclosures/aquarium");
  read_and_write_file("/enclosures/aquarium/tank_1/fish_4.txt");

  vfs.do_mount("/dev/ram32", "/enclosures/elephant_house");
  read_and_write_file("/enclosures/elephant_house/monkey_house/infrastructure/info.txt");

  vfs.do_mount("/dev/ram16", "/enclosures/elephant_house/monkey_house");
  read_and_write_file("/enclosures/elephant_house/monkey_house/information/info_2.txt");

  auto result = vfs.unmount("/enclosures/elephant_house");
  if (result == kernel::filesystem::vfs::operation_result::unmount_failed)
  {
    kstd::println("[TEST] Unmount failed as expected due to active child mount.");
  }

  vfs.unmount("/enclosures/elephant_house/monkey_house");
  result = vfs.unmount("/enclosures/elephant_house");
  if (result == kernel::filesystem::vfs::operation_result::success)
  {
    kstd::println("[TEST] Unmount succeeded after unmounting child mount.");
  }
}

auto run_test_code() -> void
{
  kstd::println("[TEST] Running test code...");

  kstd::println("[TEST] device names");
  test_device_names();
  kstd::println("---------------------------------");

  kstd::println("[TEST] file descriptor manually");
  test_file_descriptor_manually();
  kstd::println("---------------------------------");

  kstd::println("[TEST] device with VFS");
  test_device_with_vfs();
  kstd::println("---------------------------------");

  kstd::println("[TEST] file lookup");
  test_file_lookup();
  kstd::println("---------------------------------");
}

auto run_demo() -> void
{
  // 1) open a file
  auto fd_1 = kapi::filesystem::open("/entrance/tickets.txt");
  if (fd_1 == -1)
  {
    kstd::os::panic("demo failed");
  }

  // 2) read from the file
  kstd::vector<std::byte> buffer_1{10};
  auto bytes_read = kapi::filesystem::read(fd_1, buffer_1.data(), buffer_1.size());
  auto buffer_as_str = std::string_view{reinterpret_cast<char *>(buffer_1.data()), static_cast<size_t>(bytes_read)};
  kstd::println("Read {} bytes from /entrance/tickets.txt: {}", bytes_read, buffer_as_str);

  // 3) show that /entrance/information/info_1.txt is not accessible before mounting
  auto fd_before_mount = kapi::filesystem::open("/entrance/information/info_1.txt");
  if (fd_before_mount == -1)
  {
    kstd::println("/entrance/information/info_1.txt is not accessible before mounting, as expected.");
  }

  // 4) mount a new filesystem on top of /entrance
  kapi::filesystem::mount("/dev/ram16", "/entrance");

  // 5) open a file from the new filesystem
  auto fd_2 = kapi::filesystem::open("/entrance/information/info_1.txt");
  if (fd_2 == -1)
  {
    kstd::os::panic("demo failed");
  }

  // 6) read from the new file
  kstd::vector<std::byte> buffer_2{10};
  bytes_read = kapi::filesystem::read(fd_2, buffer_2.data(), buffer_2.size());
  buffer_as_str = std::string_view{reinterpret_cast<char *>(buffer_2.data()), static_cast<size_t>(bytes_read)};
  kstd::println("Read {} bytes from /entrance/information/info_1.txt: {}", bytes_read, buffer_as_str);

  // 7) open device as file
  auto fd_3 = kapi::filesystem::open("/dev/ram48");
  if (fd_3 == -1)
  {
    kstd::os::panic("demo failed");
  }

  // 8) read from the device file
  kstd::vector<std::byte> buffer_3{2};
  bytes_read = kapi::filesystem::read(fd_3, buffer_3.data(), buffer_3.size());
  kstd::println("Read {} bytes from /dev/ram48: {::#04x}", bytes_read, buffer_3);

  // 9) write to the device file
  kstd::vector<std::byte> write_buffer{std::byte{0xAA}, std::byte{0xAA}};
  auto bytes_written = kapi::filesystem::write(fd_3, write_buffer.data(), write_buffer.size());
  kstd::println("Written {} bytes to /dev/ram48: {::#04x}", bytes_written, write_buffer);

  // 10) do memory dump to show that the write to the device file had an effect
}

auto main() -> int
{
  kapi::cio::init();
  kstd::println("[OS] IO subsystem initialized.");

  kapi::cpu::init();

  kapi::memory::init();
  kernel::memory::init_heap(kapi::memory::heap_base);
  kapi::system::memory_initialized();
  kapi::memory::init_mmio(kapi::memory::mmio_base, 1_GiB / kapi::memory::page::size);
  kstd::println("[OS] Memory subsystem initialized.");

  kapi::devices::init();
  kstd::println("[OS] System root bus initialized.");

  kapi::devices::init_platform_devices();
  kstd::println("[OS] Platform devices initialized.");

  kapi::interrupts::enable();
  kstd::println("[OS] Interrupts enabled.");

  kapi::boot_modules::init();
  kstd::println("[OS] Boot module registry initialized.");

  kernel::devices::storage::management::init();
  kstd::println("[OS] Storage management initialized.");

  kernel::filesystem::file_descriptor_table::init();
  kstd::println("[OS] Global file descriptor table initialized.");

  kernel::filesystem::vfs::init();
  kstd::println("[OS] Virtual filesystem initialized.");

  // TODO BA-FS26 remove demo and test code again?
  // run_demo();

  // TODO BA-FS26 remove demo and test code again?
  run_test_code();
  kstd::println("[TEST] All tests completed.");

  kapi::system::panic("Returning from kernel main!");
}