#define _DEFAULT_SOURCE
#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif

#include "os_compat.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 <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.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;
}

int os_realpath(const char *path, char *out, size_t out_sz) {
  if (!path || !out || out_sz < 2)
    return -1;
#ifdef _WIN32
  char buf[OS_PATH_MAX];
  DWORD n = GetFullPathNameA(path, (DWORD)sizeof(buf), buf, NULL);
  if (n == 0 || n >= sizeof(buf))
    return -1;
  /* Prefer forward slashes internally for sandbox compares. */
  os_path_norm_slashes(buf);
  if (strlen(buf) + 1 > out_sz)
    return -1;
  memcpy(out, buf, strlen(buf) + 1);
  /* Lowercase drive letter for stable compares */
  if (out[0] && out[1] == ':') {
    if (out[0] >= 'A' && out[0] <= 'Z')
      out[0] = (char)(out[0] - 'A' + 'a');
  }
  return 0;
#else
  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;
#endif
}

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;
  if (path[rl] == '\0')
    return 1;
#ifdef _WIN32
  return path[rl] == '/' || path[rl] == '\\';
#else
  return 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_config_dir(char *out, size_t out_sz) {
  if (!out || out_sz < 8)
    return -1;
#ifdef _WIN32
  const char *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);
#else
  const char *home = getenv("HOME");
  if (!home || !home[0])
    return -1;
  int n = snprintf(out, out_sz, "%s/.config/cst-agent", home);
#endif
  if (n < 0 || (size_t)n >= out_sz)
    return -1;
  return 0;
}

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
  const char *t = getenv("TMPDIR");
  if (!t || !t[0])
    t = "/tmp";
  snprintf(out, out_sz, "%s", t);
  return 0;
#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];
  ssize_t n = readlink("/proc/self/exe", buf, sizeof(buf) - 1);
  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
}

#ifdef _WIN32
int os_run_capture(const char *cwd, const char *const argv[], size_t max_out,
                   os_run_result_t *r) {
  if (!argv || !argv[0] || !r)
    return -1;
  if (max_out == 0)
    max_out = 512 * 1024;
  memset(r, 0, sizeof(*r));

  char cmdline[8192];
  size_t pos = 0;
  cmdline[0] = 0;
  for (int i = 0; argv[i]; i++) {
    const char *a = argv[i];
    int need_q = strchr(a, ' ') || strchr(a, '\t') || strchr(a, '"');
    if (i && pos + 1 < sizeof(cmdline))
      cmdline[pos++] = ' ';
    if (need_q) {
      if (pos + 1 < sizeof(cmdline))
        cmdline[pos++] = '"';
      for (const char *p = a; *p && pos + 2 < sizeof(cmdline); p++) {
        if (*p == '"') {
          cmdline[pos++] = '\\';
          cmdline[pos++] = '"';
        } else {
          cmdline[pos++] = *p;
        }
      }
      if (pos + 1 < sizeof(cmdline))
        cmdline[pos++] = '"';
    } else {
      size_t L = strlen(a);
      if (pos + L >= sizeof(cmdline))
        break;
      memcpy(cmdline + pos, a, L);
      pos += L;
    }
    cmdline[pos] = 0;
  }

  SECURITY_ATTRIBUTES sa = {0};
  sa.nLength = sizeof(sa);
  sa.bInheritHandle = TRUE;
  HANDLE rd = NULL, wr = NULL;
  if (!CreatePipe(&rd, &wr, &sa, 0))
    return -1;
  SetHandleInformation(rd, HANDLE_FLAG_INHERIT, 0);

  STARTUPINFOA si = {0};
  si.cb = sizeof(si);
  si.dwFlags = STARTF_USESTDHANDLES;
  si.hStdOutput = wr;
  si.hStdError = wr;
  si.hStdInput = GetStdHandle(STD_INPUT_HANDLE);
  PROCESS_INFORMATION pi = {0};

  char *cmd_mut = _strdup(cmdline);
  if (!cmd_mut) {
    CloseHandle(rd);
    CloseHandle(wr);
    return -1;
  }
  BOOL ok = CreateProcessA(NULL, cmd_mut, NULL, NULL, TRUE, 0, NULL,
                           cwd && cwd[0] ? cwd : NULL, &si, &pi);
  free(cmd_mut);
  CloseHandle(wr);
  if (!ok) {
    CloseHandle(rd);
    return -1;
  }

  size_t cap = 4096, len = 0;
  char *buf = malloc(cap);
  if (!buf) {
    CloseHandle(rd);
    CloseHandle(pi.hProcess);
    CloseHandle(pi.hThread);
    return -1;
  }
  for (;;) {
    char tmp[1024];
    DWORD n = 0;
    if (!ReadFile(rd, tmp, sizeof(tmp), &n, NULL) || n == 0)
      break;
    if (len + n + 1 > cap) {
      size_t nc = cap * 2;
      if (nc < len + n + 1)
        nc = len + n + 1;
      char *nb = realloc(buf, nc);
      if (!nb)
        break;
      buf = nb;
      cap = nc;
    }
    memcpy(buf + len, tmp, n);
    len += n;
    if (len >= max_out)
      break;
  }
  CloseHandle(rd);
  WaitForSingleObject(pi.hProcess, INFINITE);
  DWORD code = 1;
  GetExitCodeProcess(pi.hProcess, &code);
  CloseHandle(pi.hProcess);
  CloseHandle(pi.hThread);
  buf[len] = 0;
  r->out = buf;
  r->out_len = len;
  r->exit_code = (int)code;
  return 0;
}
#else
int os_run_capture(const char *cwd, const char *const argv[], size_t max_out,
                   os_run_result_t *r) {
  if (!argv || !argv[0] || !r)
    return -1;
  if (max_out == 0)
    max_out = 512 * 1024;
  memset(r, 0, sizeof(*r));

  int pipefd[2];
  if (pipe(pipefd) != 0)
    return -1;
  pid_t pid = fork();
  if (pid < 0) {
    close(pipefd[0]);
    close(pipefd[1]);
    return -1;
  }
  if (pid == 0) {
    close(pipefd[0]);
    dup2(pipefd[1], STDOUT_FILENO);
    dup2(pipefd[1], STDERR_FILENO);
    close(pipefd[1]);
    if (cwd && cwd[0] && chdir(cwd) != 0)
      _exit(127);
    execvp(argv[0], (char *const *)argv);
    _exit(127);
  }
  close(pipefd[1]);
  size_t cap = 4096, len = 0;
  char *buf = malloc(cap);
  if (!buf) {
    close(pipefd[0]);
    waitpid(pid, NULL, 0);
    return -1;
  }
  for (;;) {
    if (len + 1024 > cap) {
      cap *= 2;
      char *nb = realloc(buf, cap);
      if (!nb)
        break;
      buf = nb;
    }
    ssize_t n = read(pipefd[0], buf + len, 1024);
    if (n < 0) {
      if (errno == EINTR)
        continue;
      break;
    }
    if (n == 0)
      break;
    len += (size_t)n;
    if (len >= max_out)
      break;
  }
  close(pipefd[0]);
  int status = 0;
  waitpid(pid, &status, 0);
  buf[len] = 0;
  r->out = buf;
  r->out_len = len;
  r->exit_code = WIFEXITED(status) ? WEXITSTATUS(status) : 1;
  return 0;
}
#endif

int os_run_shell_c(const char *cwd, const char *cmd, size_t max_out,
                   os_run_result_t *r) {
  if (!cmd || !r)
    return -1;
  char shell[OS_PATH_MAX];
  if (os_resolve_shell(shell, sizeof(shell)) != 0)
    return -1;

  /* busybox: busybox sh -c cmd ; /bin/sh: sh -c cmd */
  int is_busybox = 0;
  {
    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;
    if (strncmp(base, "busybox", 7) == 0)
      is_busybox = 1;
  }

  if (is_busybox) {
    const char *argv[] = {shell, "sh", "-c", cmd, NULL};
    return os_run_capture(cwd, argv, max_out, r);
  } else {
    const char *argv[] = {shell, "-c", cmd, NULL};
    return os_run_capture(cwd, argv, max_out, r);
  }
}

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
}

int os_chmod_private(const char *path) {
  if (!path)
    return -1;
#ifdef _WIN32
  (void)path;
  return 0;
#else
  return chmod(path, 0600);
#endif
}