#ifndef _DEFAULT_SOURCE
#define _DEFAULT_SOURCE
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "cst_agent.h"
#include "os_compat.h"

int cst_sandbox_resolve(const char *workspace_root, const char *rel_or_abs,
                        char *out, size_t out_sz) {
  if (!workspace_root || !rel_or_abs || !out || out_sz < 2)
    return -1;

  char root_real[OS_PATH_MAX];
  if (os_realpath(workspace_root, root_real, sizeof(root_real)) != 0)
    return -1;
  os_path_norm_slashes(root_real);
  size_t root_len = strlen(root_real);

  char candidate[OS_PATH_MAX];
  if (os_path_is_abs(rel_or_abs)) {
    snprintf(candidate, sizeof(candidate), "%s", rel_or_abs);
  } else if (os_path_join(candidate, sizeof(candidate), root_real, rel_or_abs) !=
             0) {
    return -1;
  }
  os_path_norm_slashes(candidate);

  char resolved[OS_PATH_MAX];
  if (os_realpath(candidate, resolved, sizeof(resolved)) == 0) {
    os_path_norm_slashes(resolved);
    if (!os_path_under(root_real, resolved))
      return -1;
    if (strlen(resolved) + 1 > out_sz)
      return -1;
    memcpy(out, resolved, strlen(resolved) + 1);
    return 0;
  }

  /* Parent exists, leaf may be new file. */
  char tmp[OS_PATH_MAX];
  snprintf(tmp, sizeof(tmp), "%s", candidate);
  char *slash = strrchr(tmp, '/');
  if (!slash)
    return -1;
  *slash = 0;
  const char *base = slash + 1;
  char parent_real[OS_PATH_MAX];
  if (os_realpath(tmp, parent_real, sizeof(parent_real)) != 0)
    return -1;
  os_path_norm_slashes(parent_real);
  if (!os_path_under(root_real, parent_real) &&
      strcmp(parent_real, root_real) != 0)
    return -1;
  (void)root_len;
  int n = snprintf(out, out_sz, "%s/%s", parent_real, base);
  if (n < 0 || (size_t)n >= out_sz)
    return -1;
  return 0;
}