#include <sys/mman.h>
#include <unistd.h>
#include <stdlib.h>
#include <time.h>
#include <dirent.h>
#include <errno.h>
#include <string.h>
#include <linux/limits.h>

#define POSIX_PAGE_SIZE 4096

function B32
os_write_file(String filename, String filecontent){
  FILE *f = fopen((const char *)filename.str, "w");
  if(f){
    fwrite(filecontent.str, 1, filecontent.len, f);
    fclose(f);
    return true;
  }
  return false;
}

function String
os_read_file(Arena *a, String name){
  String result = {0};
  FILE *f = fopen((char *)name.str, "rb");
  if(f){
    fseek(f, 0, SEEK_END);
    result.len = ftell(f);
    fseek(f, 0, SEEK_SET);
    result.str = (U8 *)arena_push_size(a, result.len + 1);
    fread(result.str, result.len, 1, f);
    fclose(f);
    result.str[result.len] = 0;
  }

  return result;
}

function String
os_get_exe_dir(Arena *a){
  char buffer[PATH_MAX] = {};
  if (readlink("/proc/self/exe", buffer, PATH_MAX) == -1) {
    log_info("Failed to retrieve the path of the executable, the method used is fetching /proc/self/exe, very likely you are using an OS that doesn't follow this convention and as such it is currently not supported");
  }
  String exe = string_from_cstring(buffer);
  exe = string_chop_last_slash(exe);
  String result = string_copy(a, exe);

  log_trace("Retrieved executable path %Q", result);
  return result;
}

function String
os_get_absolute_path(Arena *a, String path){
  assert(path.str[path.len] == 0);
  char buffer[PATH_MAX] = {};
  realpath((char *)path.str, buffer);
  String abs = string_from_cstring(buffer);
  String result = string_copy(a, abs);
  return result;
}

function B32
os_does_file_exist(String path){
  B32 result = false;
  assert(path.str[path.len] == 0);
  if (access((char *)path.str, F_OK) == 0) {
    result = true;
  }
  log_trace("Does file exist? %Q %d", path, result);
  return result;
}

function String
os_get_working_dir(Arena *allocator){
  char *buffer = arena_push_array(allocator, char, PATH_MAX);
  char *result = getcwd(buffer, PATH_MAX);
  return string_from_cstring(result);
}

function Array<OS_File_Info>
os_list_dir(Arena *a, String dir, U32 flags = LIST_RECURSE_INTO_DIRS){
  Scratch scratch(a);
  Array<String> dirs_to_read = {scratch};
  dirs_to_read.add(dir);

  Array<OS_File_Info> result = {a};
  for(auto it = dirs_to_read.begin(); it != dirs_to_read.end(); it++){
    assert(it->str[it->len] == 0);
    dirent *dir;
    DIR *d = opendir((char *)it->str);
    if(d){
      while ((dir = readdir(d)) != NULL) {
        if(dir->d_name[0] == '.'){
          if(dir->d_name[1] == '.'){
            if(dir->d_name[2] == 0)
              continue;
          }

          if(dir->d_name[1] == 0)
            continue;
        }

        OS_File_Info entry = {};
        entry.relative_path = string_fmt(a, "%Q/%s", *it, dir->d_name);
        entry.absolute_path = os_get_absolute_path(a, entry.relative_path);

        if(dir->d_type == DT_DIR){
          entry.is_directory = true;

          if(flags & LIST_RECURSE_INTO_DIRS){
            dirs_to_read.add(entry.absolute_path);
          }
        }

        result.add(entry);
        log_trace("%Q %d", entry.absolute_path, entry.is_directory);
      }
      closedir(d);
    }
    else{
      log_info("ERROR Failed to read dir: %Q, errno: %s", *it, strerror(errno));
    }
  }

  return result;
}

function U8 *
os_advance_commit(OS_Memory *m, size_t *commit_size, size_t page_size) {
  size_t aligned_up_commit                            = align_up(*commit_size, page_size);
  size_t to_be_total_commited_size                    = aligned_up_commit + m->commit;
  size_t to_be_total_commited_size_clamped_to_reserve = clamp_top(to_be_total_commited_size, m->reserve);
  size_t adjusted_to_boundary_commit                  = to_be_total_commited_size_clamped_to_reserve - m->commit;
  assert_message(adjusted_to_boundary_commit, "Debug WIN32 Error: Reached the virtual memory reserved boundary");
  U8 *result = m->data + m->commit;
  if (adjusted_to_boundary_commit == 0)
    result = 0;
  *commit_size = adjusted_to_boundary_commit;
  return result;
}

function OS_Memory
os_reserve(size_t size) {
  OS_Memory result       = {};
  size_t    size_aligned = align_up(size, POSIX_PAGE_SIZE);
  result.data            = (U8 *)mmap(0, size_aligned, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
  assert_message(result.data, POSIX_ERROR "Failed to reserve memory using mmap!!");
  if (result.data) {
    result.reserve = size_aligned;
  }
  return result;
}

function B32
os_commit(OS_Memory *m, size_t commit) {
  B32 result   = false;
  U8 * pointer = os_advance_commit(m, &commit, POSIX_PAGE_SIZE);
  if (pointer) {
    int mprotect_result = mprotect(pointer, commit, PROT_READ | PROT_WRITE);
    assert_message(mprotect_result == 0, "OS1 POSIX Debug Error: Failed to commit more memory using mmap");
    if (mprotect_result == 0) {
      m->commit += commit;
      result = true;
    }
  }
  return result;
}

function void
os_release(OS_Memory *m) {
  int result = munmap(m->data, m->reserve);
  assert_message(result == 0, "OS1 POSIX Debug Error: Failed to release virtual memory using munmap");
  if (result == 0) {
    memory_zero(m, sizeof(*m));
  }
}

function U64
os_get_microseconds() {
  timespec ts;
  clock_gettime(CLOCK_MONOTONIC, &ts);
  U64 result = (((U64)ts.tv_sec) * 1000000ull) + ((U64)ts.tv_nsec) / 1000ull;
  return result;
}

function F64
os_time(){
  F64 time = (F64)os_get_microseconds();
  F64 result = time / 1000000.0; // Microseconds to seconds
  return result;
}