// Copyright 2017-2018 ccls Authors
// SPDX-License-Identifier: Apache-2.0

#if defined(__unix__) || defined(__APPLE__)
#include "platform.h"

#include "utils.h"

#include <assert.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <sys/stat.h>
#include <sys/types.h> // required for stat.h
#include <sys/wait.h>
#include <unistd.h>
#ifdef __GLIBC__
#include <malloc.h>
#endif

#include <string>

namespace {

// Returns the canonicalized absolute pathname, without expanding symbolic
// links. This is a variant of realpath(2), C++ rewrite of
// https://github.com/freebsd/freebsd/blob/master/lib/libc/stdlib/realpath.c
std::optional<std::string> RealPathNotExpandSymlink(std::string path) {
  if (path.empty()) {
    errno = EINVAL;
    return std::nullopt;
  }
  if (path[0] == '\0') {
    errno = ENOENT;
    return std::nullopt;
  }

  // Do not use PATH_MAX because it is tricky on Linux.
  // See https://eklitzke.org/path-max-is-tricky
  char tmp[1024];
  std::string resolved;
  size_t i = 0;
  struct stat sb;
  if (path[0] == '/') {
    resolved = "/";
    i = 1;
  } else {
    if (!getcwd(tmp, sizeof tmp))
      return std::nullopt;
    resolved = tmp;
  }

  while (i < path.size()) {
    auto j = path.find('/', i);
    if (j == std::string::npos)
      j = path.size();
    auto next_token = path.substr(i, j - i);
    i = j + 1;
    if (resolved.back() != '/')
      resolved += '/';
    if (next_token.empty() || next_token == ".") {
      // Handle consequential slashes and "."
      continue;
    } else if (next_token == "..") {
      // Strip the last path component except when it is single "/"
      if (resolved.size() > 1)
        resolved.resize(resolved.rfind('/', resolved.size() - 2) + 1);
      continue;
    }
    // Append the next path component.
    // Here we differ from realpath(3), we use stat(2) instead of
    // lstat(2) because we do not want to resolve symlinks.
    resolved += next_token;
    if (stat(resolved.c_str(), &sb) != 0)
      return std::nullopt;
    if (!S_ISDIR(sb.st_mode) && j < path.size()) {
      errno = ENOTDIR;
      return std::nullopt;
    }
  }

  // Remove trailing slash except when a single "/".
  if (resolved.size() > 1 && resolved.back() == '/')
    resolved.pop_back();
  return resolved;
}

} // namespace

std::string NormalizePath(const std::string &path) {
  std::optional<std::string> resolved = RealPathNotExpandSymlink(path);
  return resolved ? *resolved : path;
}

void FreeUnusedMemory() {
#ifdef __GLIBC__
  malloc_trim(4 * 1024 * 1024);
#endif
}

void TraceMe() {
  // If the environment variable is defined, wait for a debugger.
  // In gdb, you need to invoke `signal SIGCONT` if you want ccls to continue
  // after detaching.
  const char *traceme = getenv("CCLS_TRACEME");
  if (traceme)
    raise(traceme[0] == 's' ? SIGSTOP : SIGTSTP);
}

std::string GetExternalCommandOutput(const std::vector<std::string> &command,
                                     std::string_view input) {
  int pin[2], pout[2];
  if (pipe(pin) < 0) {
    perror("pipe(stdin)");
    return "";
  }
  if (pipe(pout) < 0) {
    perror("pipe(stdout)");
    close(pin[0]);
    close(pin[1]);
    return "";
  }
  pid_t child = fork();
  if (child == 0) {
    dup2(pout[0], 0);
    dup2(pin[1], 1);
    close(pin[0]);
    close(pin[1]);
    close(pout[0]);
    close(pout[1]);
    auto argv = new char *[command.size() + 1];
    for (size_t i = 0; i < command.size(); i++)
      argv[i] = const_cast<char *>(command[i].c_str());
    argv[command.size()] = nullptr;
    execvp(argv[0], argv);
    _Exit(127);
  }
  close(pin[1]);
  close(pout[0]);
  // O_NONBLOCK is disabled, write(2) blocks until all bytes are written.
  (void)write(pout[1], input.data(), input.size());
  close(pout[1]);
  std::string ret;
  char buf[4096];
  ssize_t n;
  while ((n = read(pin[0], buf, sizeof buf)) > 0)
    ret.append(buf, n);
  close(pin[0]);
  waitpid(child, NULL, 0);
  return ret;
}

#endif