#include <fcntl.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <unistd.h>

#include "read_file.h"

#define CHECK_OOM(ptr) \
  if (ptr == NULL) { \
    fprintf(stderr, "geheugen is op\n"); \
    /* I think I should free the original memory here, but whatever */ \
    return NULL; \
  }

struct filebuf *stream_to_filebuf(FILE *restrict stream) {
  size_t sz = 0;
  size_t cap = 4096;
  char *buf = malloc(cap);
  CHECK_OOM(buf);

  while (!feof(stream)) {
    if (cap-sz == 0) {
      cap *= 2;
      buf = realloc(buf, cap);
      CHECK_OOM(buf);
    }

    const size_t amount = cap-sz;
    const size_t n = fread(buf+sz, 1, amount, stream);
    sz += n;

    if (n != amount && !feof(stream)) {
      fprintf(stderr, "fout tijdens lezen van standaard invoer.\n");
      free(buf);
      return NULL;
    }
  }

  buf = realloc(buf, sz);

  struct filebuf *res = calloc(1, sizeof(struct filebuf));
  res->buf = buf;
  res->sz = sz;
  res->mapping_type = MT_OWNED;
  return res;
}

static void *fd_to_mmap(const int fd, struct stat sb) {
  void *addr = mmap(NULL, sb.st_size, PROT_READ, MAP_SHARED, fd, 0);
  if (addr == MAP_FAILED) {
    return NULL;
  }

  close(fd);
  return addr;
}

struct filebuf *file_to_filebuf(char *fname) {
  const int fd = open(fname, O_RDONLY);

  struct stat sb;
  if (fstat(fd, &sb) == -1) {
    goto stream;
  }

  void *addr;
  if ((addr = fd_to_mmap(fd, sb)) != NULL) {
    struct filebuf *res = calloc(1, sizeof(struct filebuf));
    res->buf = addr;
    res->sz = sb.st_size;
    res->mapping_type = MT_MMAP;
    return res;
  }

stream: {
  FILE *stream = fdopen(fd, "rb");
  struct filebuf *res = stream_to_filebuf(stream);
  fclose(stream);
  return res;
}
}

void free_filebuf(struct filebuf *fb) {
  switch (fb->mapping_type) {
    case MT_MMAP:
      munmap(fb->buf, fb->sz);
      break;
    case MT_OWNED:
      free(fb->buf);
      break;
  }
  free(fb);
}