#ifndef _DEFAULT_SOURCE
#define _DEFAULT_SOURCE
#endif
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif

#ifdef __APPLE__
#include <mach-o/dyld.h>
#include <stdint.h>
#endif
#include "os_compat.h"
#include "os_internal.h"

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

#ifdef _WIN32
#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif
#include <direct.h>
#include <fcntl.h>
#include <io.h>
#include <process.h>
#include <windows.h>
#else
#include <dirent.h>
#include <fcntl.h>
#include <poll.h>
#include <pthread.h>
#include <signal.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <time.h>
#include <unistd.h>
#endif

void os_run_result_free(os_run_result_t *r) {
  if (!r)
    return;
  free(r->out);
  r->out = NULL;
  r->out_len = 0;
}

int os_path_is_abs(const char *p) {
  if (!p || !p[0])
    return 0;
#ifdef _WIN32
  if (p[0] == '/' || p[0] == '\\')
    return 1;
  if (((p[0] >= 'A' && p[0] <= 'Z') || (p[0] >= 'a' && p[0] <= 'z')) &&
      p[1] == ':' && (p[2] == '/' || p[2] == '\\' || p[2] == '\0'))
    return 1;
  return 0;
#else
  return p[0] == '/';
#endif
}

void os_path_norm_slashes(char *p) {
  if (!p)
    return;
  for (; *p; p++) {
    if (*p == '\\')
      *p = '/';
  }
}

int os_path_join(char *out, size_t out_sz, const char *a, const char *b) {
  if (!out || out_sz < 2 || !a)
    return -1;
  if (!b || !b[0]) {
    snprintf(out, out_sz, "%s", a);
    return 0;
  }
  if (os_path_is_abs(b)) {
    snprintf(out, out_sz, "%s", b);
    return 0;
  }
  size_t al = strlen(a);
  while (al > 0 && (a[al - 1] == '/' || a[al - 1] == '\\'))
    al--;
#ifdef _WIN32
  int n = snprintf(out, out_sz, "%.*s\\%s", (int)al, a, b);
#else
  int n = snprintf(out, out_sz, "%.*s/%s", (int)al, a, b);
#endif
  if (n < 0 || (size_t)n >= out_sz)
    return -1;
  return 0;
}

#ifndef _WIN32
int os_realpath(const char *path, char *out, size_t out_sz) {
  if (!path || !out || out_sz < 2)
    return -1;
  char *r = realpath(path, NULL);
  if (!r)
    return -1;
  if (strlen(r) + 1 > out_sz) {
    free(r);
    return -1;
  }
  memcpy(out, r, strlen(r) + 1);
  free(r);
  return 0;
}

int os_path_under(const char *root, const char *path) {
  if (!root || !path)
    return 0;
  size_t rl = strlen(root);
  if (strncmp(path, root, rl) != 0)
    return 0;
  return path[rl] == '\0' || path[rl] == '/';
}
#endif

int os_mkdir(const char *path, int mode) {
  if (!path)
    return -1;
#ifdef _WIN32
  (void)mode;
  if (_mkdir(path) != 0 && errno != EEXIST)
    return -1;
  return 0;
#else
  if (mkdir(path, (mode_t)mode) != 0 && errno != EEXIST)
    return -1;
  return 0;
#endif
}

int os_mkdir_p(const char *path, int mode) {
  if (!path || !path[0])
    return -1;
  char tmp[OS_PATH_MAX];
  snprintf(tmp, sizeof(tmp), "%s", path);
  for (char *p = tmp + 1; *p; p++) {
    if (*p == '/' || *p == '\\') {
      char c = *p;
      *p = 0;
      os_mkdir(tmp, mode);
      *p = c;
    }
  }
  return os_mkdir(tmp, mode);
}

#ifndef _WIN32
struct os_dir {
  DIR *d;
  char path[OS_PATH_MAX];
  os_dirent_t ent;
};

os_dir_t *os_dir_open(const char *path) {
  if (!path)
    return NULL;
  os_dir_t *d = calloc(1, sizeof(*d));
  if (!d)
    return NULL;
  snprintf(d->path, sizeof(d->path), "%s", path);
  d->d = opendir(path);
  if (!d->d) {
    free(d);
    return NULL;
  }
  return d;
}

const os_dirent_t *os_dir_next(os_dir_t *d) {
  struct dirent *de;
  while (d && (de = readdir(d->d)) != NULL) {
    if (strcmp(de->d_name, ".") == 0 || strcmp(de->d_name, "..") == 0)
      continue;
    d->ent.name = de->d_name;
    d->ent.is_dir = d->ent.is_link = 0;
#ifdef DT_DIR
    if (de->d_type != DT_UNKNOWN) {
      d->ent.is_dir = de->d_type == DT_DIR;
      d->ent.is_link = de->d_type == DT_LNK;
      return &d->ent;
    }
#endif
    char p[OS_PATH_MAX];
    struct stat st;
    if (snprintf(p, sizeof(p), "%s/%s", d->path, de->d_name) <
            (int)sizeof(p) &&
        lstat(p, &st) == 0) {
      d->ent.is_dir = S_ISDIR(st.st_mode);
      d->ent.is_link = S_ISLNK(st.st_mode);
    }
    return &d->ent;
  }
  return NULL;
}

void os_dir_close(os_dir_t *d) {
  if (!d)
    return;
  closedir(d->d);
  free(d);
}

int os_lstat(const char *path, os_stat_t *st) {
  struct stat s;
  memset(st, 0, sizeof(*st));
  if (!path || lstat(path, &s) != 0)
    return -1;
  st->is_dir = S_ISDIR(s.st_mode);
  st->is_reg = S_ISREG(s.st_mode);
  st->is_link = S_ISLNK(s.st_mode);
  st->size = (long long)s.st_size;
  st->mtime = (double)s.st_mtime;
  return 0;
}

int os_rename_replace(const char *from, const char *to) {
  return rename(from, to) == 0 ? 0 : -1;
}
#endif

int os_config_dir(char *out, size_t out_sz) {
  if (!out || out_sz < 8)
    return -1;
#ifdef _WIN32
  const char *base = getenv("XDG_CONFIG_HOME");
  if (!base || !os_path_is_abs(base))
    base = getenv("APPDATA");
  if (!base || !base[0])
    base = getenv("LOCALAPPDATA");
  if (!base || !base[0])
    return -1;
  int n = snprintf(out, out_sz, "%s/cst-agent", base);
  os_path_norm_slashes(out);
#else
  const char *xdg = getenv("XDG_CONFIG_HOME");
  const char *home = getenv("HOME");
  int n;
  if (xdg && xdg[0] == '/')
    n = snprintf(out, out_sz, "%s/cst-agent", xdg);
  else if (home && home[0])
    n = snprintf(out, out_sz, "%s/.config/cst-agent", home);
  else
    return -1;
#endif
  if (n < 0 || (size_t)n >= out_sz)
    return -1;
  return 0;
}

#ifndef _WIN32
/* $TMPDIR is not always usable: Termux has no /tmp unless TMPDIR points at
 * $PREFIX/tmp, and Android may deny /tmp or /data/local/tmp outright. Take
 * the first candidate where a file can actually be created. */
static char g_tmp[OS_PATH_MAX];
static pthread_once_t g_tmp_once = PTHREAD_ONCE_INIT;

static int tmp_writable(const char *dir) {
  char probe[OS_PATH_MAX];
  struct stat st;
  if (!dir || dir[0] != '/' || stat(dir, &st) != 0 || !S_ISDIR(st.st_mode))
    return 0;
  int n = snprintf(probe, sizeof(probe), "%s/.cst-probe-XXXXXX", dir);
  if (n < 0 || (size_t)n >= sizeof(probe))
    return 0;
  int fd = mkstemp(probe);
  if (fd < 0)
    return 0;
  close(fd);
  unlink(probe);
  return 1;
}

static void tmp_trim(char *s) {
  size_t n = strlen(s);
  while (n > 1 && s[n - 1] == '/')
    s[--n] = 0;
}

static void tmp_pick(void) {
  char cand[5][OS_PATH_MAX];
  int nc = 0;
  const char *env = getenv("TMPDIR");
  const char *prefix = getenv("PREFIX");
  const char *home = getenv("HOME");
  const char *cache = getenv("XDG_CACHE_HOME");
  if (env && env[0])
    snprintf(cand[nc++], OS_PATH_MAX, "%s", env);
  if (prefix && prefix[0] == '/')
    snprintf(cand[nc++], OS_PATH_MAX, "%s/tmp", prefix);
  snprintf(cand[nc++], OS_PATH_MAX, "/tmp");
  snprintf(cand[nc++], OS_PATH_MAX, "/var/tmp");
  if (cache && cache[0] == '/')
    snprintf(cand[nc++], OS_PATH_MAX, "%s/cst-agent/tmp", cache);
  else if (home && home[0] == '/')
    snprintf(cand[nc++], OS_PATH_MAX, "%s/.cache/cst-agent/tmp", home);
  for (int i = 0; i < nc; i++) {
    tmp_trim(cand[i]);
    if (i == nc - 1)
      os_mkdir_p(cand[i], 0700);
    if (tmp_writable(cand[i])) {
      memcpy(g_tmp, cand[i], strlen(cand[i]) + 1);
      return;
    }
  }
  /* nothing works: keep the old answer so callers fail as before */
  memcpy(g_tmp, cand[0], strlen(cand[0]) + 1);
}
#endif

int os_temp_dir(char *out, size_t out_sz) {
  if (!out || out_sz < 2)
    return -1;
#ifdef _WIN32
  DWORD n = GetTempPathA((DWORD)out_sz, out);
  if (n == 0 || n >= out_sz)
    return -1;
  os_path_norm_slashes(out);
  size_t L = strlen(out);
  while (L > 0 && out[L - 1] == '/')
    out[--L] = 0;
  return 0;
#else
  pthread_once(&g_tmp_once, tmp_pick);
  int n = snprintf(out, out_sz, "%s", g_tmp);
  return n < 0 || (size_t)n >= out_sz ? -1 : 0;
#endif
}

void os_temp_dir_export(void) {
#ifndef _WIN32
  char d[OS_PATH_MAX];
  const char *t = getenv("TMPDIR");
  if (os_temp_dir(d, sizeof(d)) == 0 && (!t || strcmp(t, d) != 0))
    setenv("TMPDIR", d, 1);
#endif
}

int os_mkstemp(char *out, size_t out_sz, const char *prefix) {
  if (!out || out_sz < 16)
    return -1;
  char dir[OS_PATH_MAX];
  if (os_temp_dir(dir, sizeof(dir)) != 0)
    return -1;
  if (!prefix)
    prefix = "cst";
#ifdef _WIN32
  char name[MAX_PATH];
  if (GetTempFileNameA(dir, prefix, 0, name) == 0)
    return -1;
  os_path_norm_slashes(name);
  if (strlen(name) + 1 > out_sz)
    return -1;
  memcpy(out, name, strlen(name) + 1);
  int fd = _open(out, _O_RDWR | _O_BINARY);
  return fd;
#else
  int n = snprintf(out, out_sz, "%s/%s-XXXXXX", dir, prefix);
  if (n < 0 || (size_t)n >= out_sz)
    return -1;
  int fd = mkstemp(out);
  return fd;
#endif
}

/* Optional: main() may set this for Termux / argv0 fallback when
 * /proc/self/exe is unavailable. */
static char g_argv0_dir[OS_PATH_MAX];

void os_set_prog_path(const char *argv0) {
  g_argv0_dir[0] = 0;
  if (!argv0 || !argv0[0])
    return;
  char buf[OS_PATH_MAX];
  snprintf(buf, sizeof(buf), "%s", argv0);
  os_path_norm_slashes(buf);
  char *slash = strrchr(buf, '/');
  if (!slash)
    return;
  *slash = 0;
  /* Relative "./foo" → keep as-is; caller may pass absolute. */
  snprintf(g_argv0_dir, sizeof(g_argv0_dir), "%s", buf);
}

int os_exe_dir(char *out, size_t out_sz) {
  if (!out || out_sz < 2)
    return -1;
  const char *env = getenv("CST_EXE_DIR");
  if (env && env[0]) {
    snprintf(out, out_sz, "%s", env);
    return 0;
  }
#ifdef _WIN32
  char buf[OS_PATH_MAX];
  DWORD n = GetModuleFileNameA(NULL, buf, (DWORD)sizeof(buf));
  if (n == 0 || n >= sizeof(buf))
    return -1;
  os_path_norm_slashes(buf);
  char *slash = strrchr(buf, '/');
  if (!slash)
    return -1;
  *slash = 0;
  if (strlen(buf) + 1 > out_sz)
    return -1;
  memcpy(out, buf, strlen(buf) + 1);
  return 0;
#else
  char buf[OS_PATH_MAX];
#ifdef __APPLE__
  uint32_t asz = (uint32_t)sizeof(buf);
  ssize_t n = _NSGetExecutablePath(buf, &asz) == 0 ? (ssize_t)strlen(buf) : -1;
#else
  ssize_t n = readlink("/proc/self/exe", buf, sizeof(buf) - 1);
#endif
  if (n >= 0) {
    buf[n] = 0;
    char *slash = strrchr(buf, '/');
    if (slash) {
      *slash = 0;
      if (strlen(buf) + 1 <= out_sz) {
        memcpy(out, buf, strlen(buf) + 1);
        return 0;
      }
    }
  }
  /* Termux / restricted Android: fall back to argv0 dir. */
  if (g_argv0_dir[0]) {
    snprintf(out, out_sz, "%s", g_argv0_dir);
    return 0;
  }
  return -1;
#endif
}

static int file_exists(const char *p) {
#ifdef _WIN32
  DWORD a = GetFileAttributesA(p);
  return a != INVALID_FILE_ATTRIBUTES && !(a & FILE_ATTRIBUTE_DIRECTORY);
#else
  return access(p, X_OK) == 0 || access(p, F_OK) == 0;
#endif
}

int os_resolve_shell(char *out, size_t out_sz) {
  if (!out || out_sz < 2)
    return -1;
  const char *env = getenv("CST_SHELL");
  if (env && env[0]) {
    snprintf(out, out_sz, "%s", env);
    return 0;
  }
  char dir[OS_PATH_MAX];
  if (os_exe_dir(dir, sizeof(dir)) == 0) {
#ifdef _WIN32
    char cand[OS_PATH_MAX];
    if (os_path_join(cand, sizeof(cand), dir, "busybox.exe") == 0 &&
        file_exists(cand)) {
      snprintf(out, out_sz, "%s", cand);
      return 0;
    }
#else
    char cand[OS_PATH_MAX];
    if (os_path_join(cand, sizeof(cand), dir, "busybox") == 0 &&
        file_exists(cand)) {
      snprintf(out, out_sz, "%s", cand);
      return 0;
    }
#endif
  }
#ifdef _WIN32
  snprintf(out, out_sz, "%s", "busybox.exe");
  return 0;
#else
  /* Termux: $PREFIX/bin/sh */
  {
    const char *prefix = getenv("PREFIX");
    if (prefix && prefix[0]) {
      char cand[OS_PATH_MAX];
      if (os_path_join(cand, sizeof(cand), prefix, "bin/sh") == 0 &&
          file_exists(cand)) {
        snprintf(out, out_sz, "%s", cand);
        return 0;
      }
    }
  }
  if (file_exists("/bin/sh")) {
    snprintf(out, out_sz, "%s", "/bin/sh");
    return 0;
  }
  if (file_exists("/system/bin/sh")) {
    snprintf(out, out_sz, "%s", "/system/bin/sh");
    return 0;
  }
  snprintf(out, out_sz, "%s", "sh");
  return 0;
#endif
}

/* Per thread: parallel tool runs and sub-agents each watch their own flag. */
static _Thread_local volatile int *g_run_cancel;
static _Thread_local int g_run_timeout_s;

void os_set_cancel_flag(volatile int *flag) { g_run_cancel = flag; }

void os_set_run_timeout(int seconds) { g_run_timeout_s = seconds; }

int os_get_run_timeout(void) { return g_run_timeout_s; }

int os_run_timeout_effective(void) {
  if (g_run_timeout_s > 0)
    return g_run_timeout_s;
  const char *e = getenv("CST_SHELL_TIMEOUT");
  if (e && atoi(e) > 0)
    return atoi(e);
  return 120;
}

double os_now_ms(void) {
#ifdef _WIN32
  static LARGE_INTEGER freq;
  LARGE_INTEGER now;
  if (!freq.QuadPart)
    QueryPerformanceFrequency(&freq);
  QueryPerformanceCounter(&now);
  return (double)now.QuadPart * 1000.0 / (double)freq.QuadPart;
#else
  struct timespec ts;
  clock_gettime(CLOCK_MONOTONIC, &ts);
  return (double)ts.tv_sec * 1000.0 + (double)ts.tv_nsec / 1e6;
#endif
}

/* Append to capture buffer, keeping at most max_out bytes. */
int os_cap_append(char **buf, size_t *len, size_t *cap, size_t max_out,
                  const char *data, size_t n, int *truncated) {
  if (*len >= max_out) {
    *truncated = 1;
    return 0;
  }
  if (*len + n > max_out) {
    n = max_out - *len;
    *truncated = 1;
  }
  if (*len + n + 1 > *cap) {
    size_t nc = *cap ? *cap * 2 : 4096;
    while (nc < *len + n + 1)
      nc *= 2;
    char *nb = realloc(*buf, nc);
    if (!nb)
      return -1;
    *buf = nb;
    *cap = nc;
  }
  memcpy(*buf + *len, data, n);
  *len += n;
  (*buf)[*len] = 0;
  return 0;
}

void os_cap_note(char **buf, size_t *len, size_t *cap, const char *note) {
  size_t n = strlen(note);
  if (*len + n + 1 > *cap) {
    char *nb = realloc(*buf, *len + n + 1);
    if (!nb)
      return;
    *buf = nb;
    *cap = *len + n + 1;
  }
  memcpy(*buf + *len, note, n + 1);
  *len += n;
}

#ifndef _WIN32
static void cloexec(int fd) {
  int fl = fcntl(fd, F_GETFD);
  if (fl >= 0)
    fcntl(fd, F_SETFD, fl | FD_CLOEXEC);
}

/* Every pipe end is close-on-exec and pipe+fork happen under one lock, so a
 * child forked on one thread never inherits the pipes of a spawn running on
 * another (which would keep that pipe open past its process's exit). */
static pthread_mutex_t g_spawn_mu = PTHREAD_MUTEX_INITIALIZER;

static int pipe_cloexec(int fd[2]) {
  if (pipe(fd) != 0)
    return -1;
  cloexec(fd[0]);
  cloexec(fd[1]);
  return 0;
}

int os_run_capture(const char *cwd, const char *const argv[], size_t max_out,
                   os_run_result_t *r) {
  return os_run_capture_ex(cwd, argv, max_out, r, NULL, NULL);
}

int os_run_capture_ex(const char *cwd, const char *const argv[],
                      size_t max_out, os_run_result_t *r,
                      os_child_hook_fn child_hook, void *ud) {
  if (!argv || !argv[0] || !r)
    return -1;
  if (max_out == 0)
    max_out = 512 * 1024;
  memset(r, 0, sizeof(*r));

  int pipefd[2];
  pthread_mutex_lock(&g_spawn_mu);
  if (pipe_cloexec(pipefd) != 0) {
    pthread_mutex_unlock(&g_spawn_mu);
    return -1;
  }
  pid_t pid = fork();
  if (pid < 0) {
    pthread_mutex_unlock(&g_spawn_mu);
    close(pipefd[0]);
    close(pipefd[1]);
    return -1;
  }
  if (pid == 0) {
    setpgid(0, 0);
    close(pipefd[0]);
    int devnull = open("/dev/null", O_RDONLY);
    if (devnull >= 0) {
      dup2(devnull, STDIN_FILENO);
      close(devnull);
    }
    dup2(pipefd[1], STDOUT_FILENO);
    dup2(pipefd[1], STDERR_FILENO);
    close(pipefd[1]);
    if (cwd && cwd[0] && chdir(cwd) != 0)
      _exit(127);
    if (child_hook && child_hook(ud) != 0) {
      static const char msg[] = "[cst: sandbox setup failed; command not "
                                "run]\n";
      ssize_t w = write(STDERR_FILENO, msg, sizeof(msg) - 1);
      (void)w;
      _exit(126);
    }
    execvp(argv[0], (char *const *)argv);
    _exit(127);
  }
  pthread_mutex_unlock(&g_spawn_mu);
  setpgid(pid, pid); /* also in parent: avoid racing the child */
  close(pipefd[1]);
  size_t cap = 4096, len = 0;
  char *buf = malloc(cap);
  if (!buf) {
    close(pipefd[0]);
    kill(-pid, SIGKILL);
    waitpid(pid, NULL, 0);
    return -1;
  }
  buf[0] = 0;
  int truncated = 0, killed = 0;
  int status = 0, reaped = 0, bg_killed = 0;
  double reaped_at = 0, killed_at = 0;
  double deadline = os_now_ms() + os_run_timeout_effective() * 1000.0;
  for (;;) {
    struct pollfd pfd = {pipefd[0], POLLIN, 0};
    int pr = poll(&pfd, 1, 100);
    if (pr < 0 && errno != EINTR)
      break;
    if (pr > 0) {
      char tmp[4096];
      ssize_t n = read(pipefd[0], tmp, sizeof(tmp));
      if (n == 0)
        break; /* every writer closed */
      if (n > 0)
        os_cap_append(&buf, &len, &cap, max_out, tmp, (size_t)n, &truncated);
      else if (errno != EINTR && errno != EAGAIN)
        break;
    }
    double now = os_now_ms();
    if (!reaped && waitpid(pid, &status, WNOHANG) == pid) {
      reaped = 1;
      reaped_at = now;
    }
    /* The shell exited but a background child still holds the pipe
     * (`server &`): give it a moment, then end the group. */
    if (reaped && !killed && !bg_killed && now - reaped_at > 1000) {
      kill(-pid, SIGKILL);
      bg_killed = 1;
      killed_at = now;
    }
    /* Checked on every pass, so a chatty command still stops promptly. */
    if (!reaped && !killed &&
        ((g_run_cancel && *g_run_cancel) || now > deadline)) {
      killed = (g_run_cancel && *g_run_cancel) ? 2 : 1;
      killed_at = now;
      kill(-pid, SIGTERM);
    }
    if (killed && !reaped && now - killed_at > 1000)
      kill(-pid, SIGKILL);
    /* a writer that left the process group can keep the pipe open */
    if ((killed || bg_killed) && now - killed_at > 3000)
      break;
  }
  close(pipefd[0]);
  if (pid > 0 && !reaped) {
    if (killed)
      kill(-pid, SIGKILL);
    waitpid(pid, &status, 0);
  }
  if (truncated)
    os_cap_note(&buf, &len, &cap, "\n...(output truncated)\n");
  if (bg_killed)
    os_cap_note(&buf, &len, &cap,
             "\n[cst: background processes left running were stopped]\n");
  r->out = buf;
  r->out_len = len;
  r->exit_code = WIFEXITED(status) ? WEXITSTATUS(status) : 1;
  if (killed == 1) {
    char note[96];
    snprintf(note, sizeof(note), "\n[cst: killed after %ds timeout]\n",
             os_run_timeout_effective());
    os_cap_note(&r->out, &r->out_len, &cap, note);
    r->exit_code = 124;
  } else if (killed == 2) {
    os_cap_note(&r->out, &r->out_len, &cap, "\n[cst: cancelled]\n");
    r->exit_code = 130;
  }
  return 0;
}
#endif

int os_run_shell_c(const char *cwd, const char *cmd, size_t max_out,
                   os_run_result_t *r) {
  return os_run_shell_ex(cwd, cmd, max_out, r, NULL, NULL);
}

/* busybox: busybox sh -c cmd ; /bin/sh: sh -c cmd. argv needs 5 slots and
 * points into shell. */
static int shell_argv(char *shell, size_t shell_sz, const char *cmd,
                      const char *argv[5]) {
  if (!cmd || os_resolve_shell(shell, shell_sz) != 0)
    return -1;
  const char *base = shell;
  const char *s = strrchr(shell, '/');
#ifdef _WIN32
  const char *s2 = strrchr(shell, '\\');
  if (s2 && (!s || s2 > s))
    s = s2;
#endif
  if (s)
    base = s + 1;
  int i = 0;
  argv[i++] = shell;
  if (strncmp(base, "busybox", 7) == 0)
    argv[i++] = "sh";
  argv[i++] = "-c";
  argv[i++] = cmd;
  argv[i] = NULL;
  return 0;
}

int os_run_shell_ex(const char *cwd, const char *cmd, size_t max_out,
                    os_run_result_t *r, os_child_hook_fn child_hook,
                    void *ud) {
  char shell[OS_PATH_MAX];
  const char *argv[5];
  if (!r || shell_argv(shell, sizeof(shell), cmd, argv) != 0)
    return -1;
  return os_run_capture_ex(cwd, argv, max_out, r, child_hook, ud);
}

#ifdef _WIN32
int os_run_shell_token(const char *cwd, const char *cmd, size_t max_out,
                       os_run_result_t *r, void *token,
                       const char *const env_add[]) {
  char shell[OS_PATH_MAX];
  const char *argv[5];
  if (!r || shell_argv(shell, sizeof(shell), cmd, argv) != 0)
    return -1;
  return os_run_capture_token(cwd, argv, max_out, r, token, env_add);
}
#endif

#ifndef _WIN32
int os_console_init(void) { return 0; }

char *os_output_to_utf8(const char *s, size_t n, size_t *out_len) {
  (void)s;
  (void)n;
  (void)out_len;
  return NULL;
}
#endif

void os_localtime(const time_t *t, struct tm *out) {
  if (!t || !out)
    return;
#ifdef _WIN32
  localtime_s(out, t);
#else
  localtime_r(t, out);
#endif
}

int os_getpid(void) {
#ifdef _WIN32
  return (int)GetCurrentProcessId();
#else
  return (int)getpid();
#endif
}

#ifndef _WIN32
int os_chmod_private(const char *path) {
  if (!path)
    return -1;
  return chmod(path, 0600);
}
#endif

typedef struct {
  os_task_fn fn;
  void *arg;
} os_task_t;

#ifdef _WIN32
static DWORD WINAPI task_main(LPVOID p) {
  os_task_t *t = p;
  t->fn(t->arg);
  return 0;
}
#else
static void *task_main(void *p) {
  os_task_t *t = p;
  t->fn(t->arg);
  return NULL;
}
#endif

void os_run_parallel(os_task_fn fn, void *const args[], int n) {
  if (n <= 0)
    return;
  if (n == 1) {
    fn(args[0]);
    return;
  }
  os_task_t *tasks = calloc((size_t)n, sizeof(*tasks));
#ifdef _WIN32
  HANDLE *th = calloc((size_t)n, sizeof(*th));
#else
  pthread_t *th = calloc((size_t)n, sizeof(*th));
  char *started = calloc((size_t)n, 1);
#endif
  if (!tasks || !th
#ifndef _WIN32
      || !started
#endif
  ) {
    for (int i = 0; i < n; i++)
      fn(args[i]);
    free(tasks);
    free(th);
#ifndef _WIN32
    free(started);
#endif
    return;
  }
  for (int i = 0; i < n; i++) {
    tasks[i].fn = fn;
    tasks[i].arg = args[i];
#ifdef _WIN32
    th[i] = CreateThread(NULL, 0, task_main, &tasks[i], 0, NULL);
    if (!th[i])
      fn(args[i]);
#else
    if (pthread_create(&th[i], NULL, task_main, &tasks[i]) == 0)
      started[i] = 1;
    else
      fn(args[i]);
#endif
  }
  for (int i = 0; i < n; i++) {
#ifdef _WIN32
    if (th[i]) {
      WaitForSingleObject(th[i], INFINITE);
      CloseHandle(th[i]);
    }
#else
    if (started[i])
      pthread_join(th[i], NULL);
#endif
  }
#ifndef _WIN32
  free(started);
#endif
  free(th);
  free(tasks);
}

int os_cancel_requested(void) { return g_run_cancel && *g_run_cancel; }

volatile int *os_get_cancel_flag(void) { return g_run_cancel; }

#ifndef _WIN32
int os_proc_spawn(const char *cwd, const char *const argv[],
                  const char *const env_add[], const char *stderr_path,
                  os_proc_t *p) {
  memset(p, 0, sizeof(*p));
  p->in_fd = p->out_fd = -1;
  if (!argv || !argv[0])
    return -1;
  signal(SIGPIPE, SIG_IGN);
  int in[2], out[2];
  pthread_mutex_lock(&g_spawn_mu);
  if (pipe_cloexec(in) != 0) {
    pthread_mutex_unlock(&g_spawn_mu);
    return -1;
  }
  if (pipe_cloexec(out) != 0) {
    pthread_mutex_unlock(&g_spawn_mu);
    close(in[0]);
    close(in[1]);
    return -1;
  }
  pid_t pid = fork();
  if (pid < 0) {
    pthread_mutex_unlock(&g_spawn_mu);
    close(in[0]);
    close(in[1]);
    close(out[0]);
    close(out[1]);
    return -1;
  }
  if (pid == 0) {
    setpgid(0, 0);
    dup2(in[0], STDIN_FILENO);
    dup2(out[1], STDOUT_FILENO);
    int err = open(stderr_path ? stderr_path : "/dev/null",
                   O_WRONLY | O_CREAT | O_TRUNC, 0600);
    if (err >= 0) {
      dup2(err, STDERR_FILENO);
      close(err);
    }
    close(in[0]);
    close(in[1]);
    close(out[0]);
    close(out[1]);
    signal(SIGPIPE, SIG_DFL);
    for (int i = 0; env_add && env_add[i]; i++)
      putenv((char *)env_add[i]);
    if (cwd && cwd[0] && chdir(cwd) != 0)
      _exit(127);
    execvp(argv[0], (char *const *)argv);
    _exit(127);
  }
  pthread_mutex_unlock(&g_spawn_mu);
  setpgid(pid, pid);
  close(in[0]);
  close(out[1]);
  p->pid = (int)pid;
  p->in_fd = in[1];
  p->out_fd = out[0];
  return 0;
}

int os_proc_write(os_proc_t *p, const char *data, size_t n) {
  while (n > 0) {
    if (p->in_fd < 0)
      return -1;
    ssize_t w = write(p->in_fd, data, n);
    if (w < 0 && errno == EINTR)
      continue;
    if (w <= 0)
      return -1;
    data += w;
    n -= (size_t)w;
  }
  return 0;
}

long os_proc_read(os_proc_t *p, char *buf, size_t n, int timeout_ms) {
  for (;;) {
    if (p->out_fd < 0)
      return -1;
    struct pollfd pfd = {p->out_fd, POLLIN, 0};
    int pr = poll(&pfd, 1, timeout_ms);
    if (pr < 0 && errno == EINTR)
      continue;
    if (pr == 0)
      return -2;
    ssize_t r = read(p->out_fd, buf, n);
    if (r < 0 && errno == EINTR)
      continue;
    return (long)r;
  }
}

void os_proc_close_stdin(os_proc_t *p) {
  if (p->in_fd >= 0) {
    close(p->in_fd);
    p->in_fd = -1;
  }
}

void os_proc_kill(os_proc_t *p) {
  os_proc_close_stdin(p);
  if (p->pid > 0) {
    int status;
    /* polite first: most servers exit when stdin closes */
    for (int i = 0; i < 10; i++) {
      if (waitpid(p->pid, &status, WNOHANG) == p->pid) {
        p->pid = 0;
        break;
      }
      struct timespec ts = {0, 50 * 1000000L};
      nanosleep(&ts, NULL);
    }
    if (p->pid > 0) {
      kill(-p->pid, SIGTERM);
      for (int i = 0; i < 20; i++) {
        if (waitpid(p->pid, &status, WNOHANG) == p->pid) {
          p->pid = 0;
          break;
        }
        struct timespec ts = {0, 50 * 1000000L};
        nanosleep(&ts, NULL);
      }
    }
    if (p->pid > 0) {
      kill(-p->pid, SIGKILL);
      waitpid(p->pid, &status, 0);
      p->pid = 0;
    }
  }
  if (p->out_fd >= 0) {
    close(p->out_fd);
    p->out_fd = -1;
  }
}
#endif

/* --- UTF-8 ---------------------------------------------------------------
 * See the declaration in os_compat.h for why wcrtomb() is not used. */
int os_utf8_encode(unsigned long cp, char out[4]) {
  if (cp < 0x80) {
    out[0] = (char)cp;
    return 1;
  }
  if (cp < 0x800) {
    out[0] = (char)(0xC0 | (cp >> 6));
    out[1] = (char)(0x80 | (cp & 0x3F));
    return 2;
  }
  if (cp >= 0xD800 && cp <= 0xDFFF)
    return 0; /* lone surrogate half from a 16-bit wchar_t */
  if (cp < 0x10000) {
    out[0] = (char)(0xE0 | (cp >> 12));
    out[1] = (char)(0x80 | ((cp >> 6) & 0x3F));
    out[2] = (char)(0x80 | (cp & 0x3F));
    return 3;
  }
  if (cp <= 0x10FFFF) {
    out[0] = (char)(0xF0 | (cp >> 18));
    out[1] = (char)(0x80 | ((cp >> 12) & 0x3F));
    out[2] = (char)(0x80 | ((cp >> 6) & 0x3F));
    out[3] = (char)(0x80 | (cp & 0x3F));
    return 4;
  }
  return 0;
}

/* See the declaration in os_compat.h for why mbrtowc() is not used. */
int os_utf8_decode(const char *s, size_t avail, unsigned long *cp) {
  const unsigned char *p = (const unsigned char *)s;
  int need, i;
  unsigned long v;
  static const unsigned long MINV[4] = {0, 0x80, 0x800, 0x10000};

  if (!s || !cp || avail == 0)
    return 0;
  if (p[0] < 0x80) {
    *cp = p[0];
    return 1;
  }
  if ((p[0] & 0xE0) == 0xC0) {
    need = 1;
    v = p[0] & 0x1Fu;
  } else if ((p[0] & 0xF0) == 0xE0) {
    need = 2;
    v = p[0] & 0x0Fu;
  } else if ((p[0] & 0xF8) == 0xF0) {
    need = 3;
    v = p[0] & 0x07u;
  } else {
    return 0; /* not a UTF-8 lead byte */
  }
  if (avail < (size_t)need + 1)
    return 0; /* truncated */
  for (i = 1; i <= need; i++) {
    if ((p[i] & 0xC0) != 0x80)
      return 0; /* bad continuation byte */
    v = (v << 6) | (p[i] & 0x3Fu);
  }
  if (v < MINV[need] || (v >= 0xD800 && v <= 0xDFFF) || v > 0x10FFFF)
    return 0; /* overlong, surrogate, or out of range */
  *cp = v;
  return need + 1;
}

/* --- libc gaps on Windows -----------------------------------------------
 * strcasestr() is a GNU extension and setenv()/unsetenv() are POSIX; glibc
 * has all three, MinGW-w64 has none of them. src/tui.c needs them (command
 * filtering and ESCDELAY), so the Windows build supplies its own.
 *
 * The case folding here is ASCII-only, unlike glibc's locale-aware version.
 * That is deliberate: these are used to match command and setting names,
 * which are ASCII.
 */
#if defined(_WIN32)

static int ascii_lower(int c) {
  return (c >= 'A' && c <= 'Z') ? c + ('a' - 'A') : c;
}

char *strcasestr(const char *haystack, const char *needle) {
  if (!haystack || !needle)
    return NULL;
  if (!*needle)
    return (char *)haystack;
  for (; *haystack; haystack++) {
    const char *h = haystack;
    const char *n = needle;
    while (*h && *n && ascii_lower((unsigned char)*h) == ascii_lower((unsigned char)*n)) {
      h++;
      n++;
    }
    if (!*n)
      return (char *)haystack;
  }
  return NULL;
}

int setenv(const char *name, const char *value, int overwrite) {
  if (!name || !*name || strchr(name, '='))
    return -1;
  if (!overwrite && getenv(name))
    return 0;
  return _putenv_s(name, value ? value : "");
}

int unsetenv(const char *name) {
  if (!name || !*name || strchr(name, '='))
    return -1;
  return _putenv_s(name, "");
}

#endif /* _WIN32 */