/*
  ISC License

  Copyright (c) 2026, Antonio SJ Musumeci <trapexit@spawn.link>

  Permission to use, copy, modify, and/or distribute this software for any
  purpose with or without fee is hereby granted, provided that the above
  copyright notice and this permission notice appear in all copies.

  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/

#include "mergerfs.hpp"
#include "mergerfs_fsck.hpp"
#include "mergerfs_collect_info.hpp"

#include "caps.hpp"
#include "config.hpp"
#include "fs_path.hpp"
#include "fs_readahead.hpp"
#include "fs_umount2.hpp"
#include "fs_wait_for_mount.hpp"
#include "maintenance_thread.hpp"
#include "oom.hpp"
#include "option_parser.hpp"
#include "procfs.hpp"
#include "resources.hpp"
#include "strvec.hpp"
#include "syslog.hpp"
#include "version.hpp"

#include "fuse_access.hpp"
#include "fuse_bmap.hpp"
#include "fuse_chmod.hpp"
#include "fuse_chown.hpp"
#include "fuse_copy_file_range.hpp"
#include "fuse_create.hpp"
#include "fuse_destroy.hpp"
#include "fuse_fallocate.hpp"
#include "fuse_fchmod.hpp"
#include "fuse_fchown.hpp"
#include "fuse_fgetattr.hpp"
#include "fuse_flush.hpp"
#include "fuse_fsync.hpp"
#include "fuse_fsyncdir.hpp"
#include "fuse_ftruncate.hpp"
#include "fuse_futimens.hpp"
#include "fuse_getattr.hpp"
#include "fuse_getxattr.hpp"
#include "fuse_init.hpp"
#include "fuse_ioctl.hpp"
#include "fuse_link.hpp"
#include "fuse_listxattr.hpp"
#include "fuse_mkdir.hpp"
#include "fuse_mknod.hpp"
#include "fuse_open.hpp"
#include "fuse_opendir.hpp"
#include "fuse_poll.hpp"
#include "fuse_read.hpp"
#include "fuse_readdir.hpp"
#include "fuse_readdir_plus.hpp"
#include "fuse_readlink.hpp"
#include "fuse_release.hpp"
#include "fuse_releasedir.hpp"
#include "fuse_removemapping.hpp"
#include "fuse_removexattr.hpp"
#include "fuse_rename.hpp"
#include "fuse_rmdir.hpp"
#include "fuse_setupmapping.hpp"
#include "fuse_setxattr.hpp"
#include "fuse_statfs.hpp"
#include "fuse_statx.hpp"
#include "fuse_symlink.hpp"
#include "fuse_syncfs.hpp"
#include "fuse_tmpfile.hpp"
#include "fuse_truncate.hpp"
#include "fuse_unlink.hpp"
#include "fuse_utimens.hpp"
#include "fuse_write.hpp"

#include "fuse.h"

#include <csignal>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <unordered_set>


static
void
_get_fuse_operations(struct fuse_operations &ops_,
                     const bool              nullrw_)
{
  ops_.access          = FUSE::access;
  ops_.bmap            = FUSE::bmap;
  ops_.chmod           = FUSE::chmod;
  ops_.chown           = FUSE::chown;
  ops_.copy_file_range = FUSE::copy_file_range;
  ops_.create          = FUSE::create;
  ops_.destroy         = FUSE::destroy;
  ops_.fallocate       = FUSE::fallocate;
  ops_.fchmod          = FUSE::fchmod;
  ops_.fchown          = FUSE::fchown;
  ops_.fgetattr        = FUSE::fgetattr;
  ops_.flush           = FUSE::flush;
  ops_.fsync           = FUSE::fsync;
  ops_.fsyncdir        = FUSE::fsyncdir;
  ops_.ftruncate       = FUSE::ftruncate;
  ops_.futimens        = FUSE::futimens;
  ops_.getattr         = FUSE::getattr;
  ops_.getxattr        = FUSE::getxattr;
  ops_.init            = FUSE::init;
  ops_.ioctl           = FUSE::ioctl;
  ops_.link            = FUSE::link;
  ops_.listxattr       = FUSE::listxattr;
  ops_.mkdir           = FUSE::mkdir;
  ops_.mknod           = FUSE::mknod;
  ops_.open            = FUSE::open;
  ops_.opendir         = FUSE::opendir;
  ops_.poll            = FUSE::poll;
  ops_.read            = (nullrw_ ? FUSE::read_null : FUSE::read);
  ops_.readdir         = FUSE::readdir;
  ops_.readdir_plus    = FUSE::readdir_plus;
  ops_.readlink        = FUSE::readlink;
  ops_.release         = FUSE::release;
  ops_.releasedir      = FUSE::releasedir;
  ops_.removemapping   = FUSE::removemapping;
  ops_.removexattr     = FUSE::removexattr;
  ops_.rename          = FUSE::rename;
  ops_.rmdir           = FUSE::rmdir;
  ops_.setupmapping    = FUSE::setupmapping;
  ops_.setxattr        = FUSE::setxattr;
  ops_.statfs          = FUSE::statfs;
  ops_.statx           = FUSE::statx;
  ops_.statx_fh        = FUSE::statx_fh;
  ops_.symlink         = FUSE::symlink;
  ops_.syncfs          = FUSE::syncfs;
  ops_.tmpfile         = FUSE::tmpfile;
  ops_.truncate        = FUSE::truncate;
  ops_.unlink          = FUSE::unlink;
  ops_.utimens         = FUSE::utimens;
  ops_.write           = (nullrw_ ? FUSE::write_null : FUSE::write);

  return;
}

static
void
_setup_resources(const int scheduling_priority_)
{
  std::srand(time(NULL));
  resources::reset_umask();
  resources::maxout_rlimit_nofile();
  resources::maxout_rlimit_fsize();
  resources::setpriority(scheduling_priority_);
}

static
void
_set_oom_score_adj()
{
  int rv;
  int orig;
  int score;

  if(!oom::has_oom_score_adj())
    return;

  score = -990;

  orig = oom::get_oom_score_adj();
  rv   = oom::set_oom_score_adj(score);

  (void)rv;
  SysLog::info("set oom_score_adj to {}, originally {}",
               score,
               orig);
}

static
bool
_wait_for_mount()
{
  int failures;
  std::vector<fs::path> paths;
  std::chrono::milliseconds timeout;

  paths = cfg.branches->to_paths();

  SysLog::info("Waiting {} seconds for {} branches to mount",
               (u64)cfg.branches_mount_timeout,
               paths.size());

  timeout = std::chrono::milliseconds(cfg.branches_mount_timeout * 1000);
  failures = fs::wait_for_mount(cfg.mountpoint,
                                paths,
                                timeout);
  if(failures)
    {
      if(cfg.branches_mount_timeout_fail)
        {
          SysLog::error("{} of {} branches were not mounted"
                        " within the timeout of {}s. Exiting",
                        failures,
                        paths.size(),
                        (u64)cfg.branches_mount_timeout);
          return true;
        }

      SysLog::warning("Continuing to mount mergerfs despite {} branches not "
                      "being different from the mountpoint filesystem",
                      failures);
    }
  else
    {
      SysLog::info("All {} branches are mounted",
                   paths.size());
    }

  return false;
}

static
void
_lazy_umount(const fs::path &target_)
{
  int rv;

  rv = fs::umount_lazy(target_);
  switch(rv)
    {
    case 0:
      SysLog::notice("{} has been successfully lazily unmounted",
                     target_.string());
      break;
    case -EINVAL:
      SysLog::notice("{} was not a mount point needing to be unmounted",
                     target_.string());
      break;
    default:
      SysLog::error("Error unmounting {}: {} - {}",
                    target_.string(),
                    -rv,
                    strerror(-rv));
      break;
    }
}

static
void
_usr1_signal_handler(int signal_)
{
  (void)signal_;
  // SysLog::info("Received SIGUSR1 - invalidating all nodes");
  // fuse_invalidate_all_nodes();
}

static
void
_usr2_signal_handler(int signal_)
{
  (void)signal_;
  // SysLog::info("Received SIGUSR2 - triggering thorough gc");
  // fuse_gc();
}

static
void
_hup_signal_handler(int signal_)
{
  (void)signal_;
}

static
void
_setup_signal_handlers()
{
  std::signal(SIGUSR1,::_usr1_signal_handler);
  std::signal(SIGUSR2,::_usr2_signal_handler);
  std::signal(SIGHUP,::_hup_signal_handler);
}

static
void
_warn_if_not_root()
{
  uid_t uid;

  uid = geteuid();
  if(uid == 0)
    return;

  constexpr const char *s =
    "mergerfs is not running as root"
    " and may not work correctly";
  fmt::println(stderr,"* WARNING: {}",s);
  SysLog::warning(s);
}

int
_main(int    argc_,
      char **argv_)
{
  int rv;
  fuse_args       args;
  fuse_operations ops;

  SysLog::open();

  memset(&ops,0,sizeof(fuse_operations));

  args.argc      = argc_;
  args.argv      = argv_;
  args.allocated = false;

  SysLog::info("mergerfs v{} started",MERGERFS_VERSION);
  SysLog::info("Go to https://trapexit.github.io/mergerfs/latest/support for support");

  for(int i = 0; i < argc_; i++)
    SysLog::info("argv[{}]: {}",i,argv_[i]);

  options::parse(&args);

  if(!cfg.errs.empty())
    {
      for(auto &err : cfg.errs)
        {
          const std::string s = err.to_string();

          SysLog::error("error: {}",s);
          fmt::println(stderr,"mergerfs: ERROR - {}",s);
        }

      return EXIT_FAILURE;
    }

  if(cfg.branches_mount_timeout > 0)
    {
      bool failure;

      failure = ::_wait_for_mount();
      if(failure)
        return EXIT_FAILURE;
    }

  ::_warn_if_not_root();
  ::_setup_resources(cfg.scheduling_priority);
  ::_setup_signal_handlers();
  ::_set_oom_score_adj();
  ::_get_fuse_operations(ops,cfg.nullrw);

  if(cfg.lazy_umount_mountpoint)
    ::_lazy_umount(cfg.mountpoint);

  caps::setup();

  rv = fuse_main(args.argc,
                 args.argv,
                 &ops);

  SysLog::info("exiting main loop with return code {}",rv);

  SysLog::close();

  return rv;
}

static
int
_pick_app_and_run(int    argc_,
                  char **argv_)
{
  fs::path appname;

  appname = argv_[0];
  appname = appname.filename();

  if(appname == "fsck.mergerfs")
    return mergerfs::fsck::main(argc_,argv_);
  if(appname == "mergerfs.collect-info")
    return mergerfs::collect_info::main(argc_,argv_);

  return ::_main(argc_,argv_);
}

int
main(int    argc_,
     char **argv_)
{
  return ::_pick_app_and_run(argc_,argv_);
}
