#include <hilbert/kernel/application.hpp>
#include <hilbert/kernel/framebuffer.hpp>
#include <hilbert/kernel/paging.hpp>
#include <hilbert/kernel/vfile.hpp>

namespace hilbert::kernel::syscall {

  enum file_result : uint64_t {
    file_result_success,
    file_result_bad_file_handle,
    file_result_device_error,
    file_result_file_system_corrupt,
    file_result_out_of_bounds,
    file_result_does_not_exist,
    file_result_directory
  };

  bool is_range_owned_by_application(uint64_t start, uint64_t end) {
    auto *app = application::running_app;
    uint64_t pstart = (start / 4096) * 4096;
    uint64_t pend = ((end - 1) / 4096 + 1) * 4096;
    for (uint64_t p = pstart; p < pend; p += 4096)
      if (!app->is_page_owned(p))
        return false;
    return true;
  }

  void set_zero(uint64_t &rax, uint64_t &rdi, uint64_t &rsi, uint64_t &rdx) {
    rax = 0;
    rdi = 0;
    rsi = 0;
    rdx = 0;
  }

  void encode_color_syscall(
    uint64_t &rax, uint64_t &rdi, uint64_t &rsi, uint64_t &rdx
  ) {
    rax = (uint64_t)framebuffer::encode_color(
      rdi & 0xff, (rdi >> 8) & 0xff, (rdi >> 16) & 0xff);
    rdi = 0;
    rsi = 0;
    rdx = 0;
  }

  void get_framebuffer_syscall(
    uint64_t &rax, uint64_t &rdi, uint64_t &rsi, uint64_t &rdx
  ) {

    auto *app = application::running_app;
    if (app->framebuffer_vaddr == 0) {
      uint64_t pages_needed =
        (framebuffer::dword_pitch * framebuffer::height * 4 - 1) / 4096 + 1;
      uint64_t vaddr = app->get_free_vaddr_pages(pages_needed);
      for (uint64_t i = 0; i < pages_needed; ++i)
        app->map_page(
          vaddr + i * 4096, framebuffer::paddr + i * 4096, true, false, false);
      app->framebuffer_vaddr = vaddr;
    }

    rax = app->framebuffer_vaddr;
    rdi =
      (uint64_t)(uint32_t)framebuffer::width |
      ((uint64_t)(uint32_t)framebuffer::height << 32);
    rsi = (uint32_t)framebuffer::dword_pitch;
    rdx = 0;

  }

  void open_file_syscall(
    uint64_t &rax, uint64_t &rdi, uint64_t &rsi, uint64_t &rdx
  ) {

    if (!is_range_owned_by_application(rdi, rdi + rsi)) {
      set_zero(rax, rdi, rsi, rdx);
      return;
    }

    utility::string path((const char *)rdi, rsi);
    vfile::canon_path cp;
    vfile::canonize_path(path, cp);

    set_zero(rax, rdi, rsi, rdx);

    vfile::vfile file;
    switch (vfile::lookup_path(cp, file)) {
    case storage::fs_result::success:
      break;
    case storage::fs_result::device_error:
      rax = file_result_device_error;
      return;
    case storage::fs_result::fs_corrupt:
      rax = file_result_file_system_corrupt;
      return;
    case storage::fs_result::does_not_exist:
      rax = file_result_does_not_exist;
      return;
    }

    vfile::vfile real_file;
    switch (file.follow_symlinks(real_file)) {
    case storage::fs_result::success:
      break;
    case storage::fs_result::device_error:
      rax = file_result_device_error;
      return;
    case storage::fs_result::fs_corrupt:
      rax = file_result_file_system_corrupt;
      return;
    case storage::fs_result::does_not_exist:
      rax = file_result_does_not_exist;
      return;
    }

    if (real_file.dir_entry.type != storage::file_type::regular_file) {
      rax = file_result_directory;
      return;
    }

    unsigned handler =
      application::running_app->open_files.add_new(utility::move(real_file));
    rax = file_result_success;
    rdi = (uint64_t)handler;

  }

  void get_file_length_syscall(
    uint64_t &rax, uint64_t &rdi, uint64_t &rsi, uint64_t &rdx
  ) {

    auto &open_files = application::running_app->open_files;
    unsigned handle = (unsigned)rdi;

    set_zero(rax, rdi, rsi, rdx);

    if (!open_files.has_id(handle)) {
      rax = file_result_bad_file_handle;
      return;
    }

    rax = file_result_success;
    rdi = open_files.get(handle).dir_entry.length;

  }

  void read_from_file_syscall(
    uint64_t &rax, uint64_t &rdi, uint64_t &rsi, uint64_t &rdx
  ) {

    if (!is_range_owned_by_application(rdi, rdi + 32)) {
      set_zero(rax, rdi, rsi, rdx);
      return;
    }

    const uint64_t *request = (const uint64_t *)rdi;
    unsigned handle = (unsigned)request[0];
    uint64_t start = request[1];
    uint64_t length = request[2];
    uint64_t buffer_vaddr = request[3];

    set_zero(rax, rdi, rsi, rdx);

    if (!is_range_owned_by_application(buffer_vaddr, buffer_vaddr + length))
      return;

    auto &open_files = application::running_app->open_files;

    if (!open_files.has_id(handle))
      rax = file_result_bad_file_handle;

    vfile::vfile &file = open_files.get(handle);

    if (start + length > file.dir_entry.length)
      rax = file_result_out_of_bounds;

    switch (file.read_file(start, length, (void *)buffer_vaddr)) {
    case storage::fs_result::success:
      rax = file_result_success;
      return;
    case storage::fs_result::device_error:
      rax = file_result_device_error;
      return;
    case storage::fs_result::fs_corrupt:
    case storage::fs_result::does_not_exist:
      rax = file_result_file_system_corrupt;
      return;
    }

  }

  [[noreturn]] void end_this_process_syscall(
    uint64_t &, uint64_t &, uint64_t &, uint64_t &
  ) {

    //TODO
    while (1)
      ;

  }

  void get_new_pages_syscall(
    uint64_t &rax, uint64_t &rdi, uint64_t &rsi, uint64_t &rdx
  ) {

    uint64_t count = rdi;
    set_zero(rax, rdi, rsi, rdx);

    auto *app = application::running_app;
    uint64_t vaddr = app->get_free_vaddr_pages(count);

    for (uint64_t i = 0; i < count; ++i) {
      uint64_t paddr = paging::take_pram_page();
      app->map_page(vaddr + i * 4096, paddr, true, false, true);
    }

    rax = vaddr;

  }

  void close_file_syscall(
    uint64_t &rax, uint64_t &rdi, uint64_t &rsi, uint64_t &rdx
  ) {

    unsigned handle = rdi;
    set_zero(rax, rdi, rsi, rdx);
    application::running_app->open_files.remove_id(handle);

  }

  typedef void (*syscall_handler)(
    uint64_t &rax, uint64_t &rdi, uint64_t &rsi, uint64_t &rdx);

  syscall_handler handlers[] = {
    &encode_color_syscall,
    &get_framebuffer_syscall,
    &open_file_syscall,
    &get_file_length_syscall,
    &read_from_file_syscall,
    &end_this_process_syscall,
    &get_new_pages_syscall,
    &close_file_syscall
  };

  static constexpr int max_syscall_number = 7;

}

using namespace hilbert::kernel::syscall;

extern "C" void do_syscall(
  uint64_t &rax, uint64_t &rdi, uint64_t &rsi, uint64_t &rdx
) {

  if (rax <= max_syscall_number && handlers[rax] != 0)
    handlers[rax](rax, rdi, rsi, rdx);
  else
    set_zero(rax, rdi, rsi, rdx);

}