/*
  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_fsck.hpp"

#include "fs_close.hpp"
#include "fs_copyfile.hpp"
#include "fs_lchmod.hpp"
#include "fs_lchown.hpp"
#include "fs_lgetxattr.hpp"
#include "fs_lstat.hpp"
#include "fs_open.hpp"
#include "mergerfs_api.hpp"
#include "str.hpp"

#include "fmt/core.h"
#include "fmt/chrono.h"
#include "CLI11/CLI11.hpp"

#include "base_types.h"

#include <filesystem>

namespace FS = std::filesystem;

struct PathStat
{
  PathStat(const std::string &path_)
    : path(path_),
      st{}
  {
  }

  std::string path;
  struct stat st;
};

using PathStatVec = std::vector<PathStat>;
using FixFunc = std::function<void(const PathStatVec&,const bool)>;

static
bool
_files_differ(const PathStatVec &paths_,
              const bool         check_size_)
{
  if(paths_.size() <= 1)
    return false;

  const struct stat &st0 = paths_[0].st;
  for(u64 i = 1; i < paths_.size(); i++)
    {
      const struct stat &st = paths_[i].st;

      if(st.st_mode != st0.st_mode)
        return true;
      if(st.st_uid != st0.st_uid)
        return true;
      if(st.st_gid != st0.st_gid)
        return true;
      if(check_size_ &&
         S_ISREG(st0.st_mode) &&
         (st.st_size != st0.st_size))
        return true;
    }

  return false;
}

static
bool
_files_same_type(const PathStatVec &paths_)
{
  mode_t type;

  if(paths_.size() <= 1)
    return true;

  type = (paths_[0].st.st_mode & S_IFMT);
  for(u64 i = 1; i < paths_.size(); i++)
    {
      if((paths_[i].st.st_mode & S_IFMT) != type)
        return false;
    }

  return true;
}

static
const char*
_file_type(const mode_t mode_)
{
  switch(mode_ & S_IFMT)
    {
    case S_IFBLK:
      return "block dev";
    case S_IFCHR:
      return "char dev";
    case S_IFDIR:
      return "directory";
    case S_IFIFO:
      return "fifo";
    case S_IFLNK:
      return "symlink";
    case S_IFSOCK:
      return "socket";
    case S_IFREG:
      return "regular";
    }

  return "unknown";
}

static
void
_compare_files(const std::string &mergerfs_path_,
               PathStatVec       &pathstats_,
               const FixFunc      fix_func_,
               const bool         check_size_,
               const bool         copy_file_)
{
  int rv;

  if(pathstats_.size() <= 1)
    return;

  for(auto &pathstat : pathstats_)
    {
      rv = fs::lstat(pathstat.path,&pathstat.st);
      if(rv < 0)
        pathstat.st.st_size = rv;
    }

  if(!::_files_differ(pathstats_,check_size_))
    return;

  fmt::println("* {}",mergerfs_path_);
  for(u64 i = 0; i < pathstats_.size(); i++)
    {
      const auto &path = pathstats_[i].path;
      const auto &st   = pathstats_[i].st;

      fmt::println("  {}: {}",i,path);
      if(st.st_size < 0)
        fmt::println("    - err: {}",strerror(-st.st_size));

      time_t   mtime    = st.st_mtime;
      std::tm *mtime_tm = std::localtime(&mtime);
      fmt::println("    -"
                   " uid: {};"
                   " gid: {};"
                   " mode: {:05o};"
                   " type: {};"
                   " size: {};"
                   " mtime: {:%Y-%m-%dT%H:%M:%S%z}",
                   st.st_uid,
                   st.st_gid,
                   st.st_mode,
                   ::_file_type(st.st_mode),
                   st.st_size,
                   *mtime_tm);
    }

  if(!fix_func_)
    return;

  if(::_files_same_type(pathstats_))
    fix_func_(pathstats_,copy_file_);
  else
    fmt::println("  X: WARNING - files are of different types."
                 " Requires manual intervention.");
}

static
int
_get_allpaths(const std::string &mergerfs_path_,
              PathStatVec       &pathstats_)
{
  int rv;
  std::vector<std::string> allpaths;

  rv = mergerfs::api::allpaths(mergerfs_path_,allpaths);
  if(rv < 0)
    return rv;

  for(const auto &path : allpaths)
    pathstats_.emplace_back(path);

  return 0;
}

static
u64
_read_u64(const u64 min_,
          const u64 max_)
{
  u64 rv;
  while(true)
    {
      fmt::print("Select correct file: ");
      std::cin >> rv;
      if((rv >= min_) && (rv <= max_))
        return rv;
      std::cin.clear();
      std::cin.ignore(100, '\n');
    }
}

static
void
_setattr(const struct stat &st_,
         const PathStatVec &pathstats_)
{
  int rv;

  for(const auto &path : pathstats_)
    {
      rv  = fs::lchmod(path.path,st_.st_mode);
      rv |= fs::lchown(path.path,st_.st_uid,st_.st_gid);
      if(rv)
        fmt::println("ERROR: problem setting mode or owner - {}",
                     strerror(errno));
    }
}

static
void
_copy_files(const std::string &src_,
            const PathStatVec &dsts_)
{
  for(const auto &dst : dsts_)
    {
      int rv;

      // TODO: Additional protection to confirm not the literal same
      // file. fs::is_same_file(src,dst);
      if(src_ == dst.path)
        continue;

      rv = fs::copyfile(src_,dst.path,{.cleanup_failure=false});
      if(rv < 0)
        fmt::print(stderr,
                   "ERROR: failed copying to {} - {}",
                   dst.path,
                   strerror(errno));
    }
}

static
bool
_mtime_cmp(const struct stat &a_,
           const struct stat &b_)
{
  if(a_.st_mtim.tv_sec == b_.st_mtim.tv_sec)
    return (a_.st_mtim.tv_nsec < b_.st_mtim.tv_nsec);
  return (a_.st_mtim.tv_sec < b_.st_mtim.tv_sec);
}

static
bool
_pathstat_cmp(const PathStatVec::value_type &a_,
              const PathStatVec::value_type &b_)
{
  return ::_mtime_cmp(a_.st,b_.st);
}

static
const
PathStatVec::value_type*
_find_latest_mtime(const PathStatVec &pathstats_)
{
  PathStatVec::const_iterator i;

  i = std::max_element(pathstats_.begin(),
                       pathstats_.end(),
                       ::_pathstat_cmp);

  return &(*i);
}

static
const
PathStatVec::value_type*
_find_largest(const PathStatVec &pathstats_)
{
  PathStatVec::const_iterator i;

  i = std::max_element(pathstats_.begin(),
                       pathstats_.end(),
                       [](const PathStatVec::value_type &a_,
                          const PathStatVec::value_type &b_)
                       {
                         return (a_.st.st_size < b_.st.st_size);
                       });

  return &(*i);
}

static
void
_fix_func_manual(const PathStatVec &pathstats_,
                 const bool         copy_file_)
{
  u64 idx;

  idx = ::_read_u64(0ULL,pathstats_.size()-1);

  if(copy_file_ && S_ISREG(pathstats_[idx].st.st_mode))
    ::_copy_files(pathstats_[idx].path,pathstats_);
  else
    ::_setattr(pathstats_[idx].st,pathstats_);
}

static
void
_fix_func_newest(const PathStatVec &pathstats_,
                 const bool         copy_file_)
{
  const PathStatVec::value_type *pathst;

  pathst = _find_latest_mtime(pathstats_);
  if(!pathst)
    return;

  if(copy_file_ && S_ISREG(pathst->st.st_mode))
    ::_copy_files(pathst->path,pathstats_);
  else
    ::_setattr(pathst->st,pathstats_);
};

static
void
_fix_func_largest(const PathStatVec &pathstats_,
                  const bool         copy_file_)
{
  const PathStatVec::value_type *pathst;

  pathst = ::_find_largest(pathstats_);
  if(!pathst)
    return;

  if(copy_file_ && S_ISREG(pathst->st.st_mode))
    ::_copy_files(pathst->path,pathstats_);
  else
    ::_setattr(pathst->st,pathstats_);
}

static
FixFunc
_select_fix_func(const std::string &fix_)
{
  if(fix_ == "none")
    return {};
  else if(fix_ == "manual")
    return ::_fix_func_manual;
  else if(fix_ == "newest")
    return ::_fix_func_newest;
  else if(fix_ == "largest")
    return ::_fix_func_largest;
  else
    abort();

  return {};
}

static
void
_fsck(const FS::path &path_,
      const FixFunc   fix_func_,
      const bool      check_size_,
      const bool      copy_file_)
{
  int rv;
  PathStatVec paths;

  ::_get_allpaths(path_,paths);
  ::_compare_files(path_,paths,fix_func_,check_size_,copy_file_);

  auto opts = FS::directory_options::skip_permission_denied;
  auto rdi = FS::recursive_directory_iterator(path_,opts);
  for(const auto &de : rdi)
    {
      paths.clear();
      rv = ::_get_allpaths(de.path(),paths);
      if(rv < 0)
        continue;

      ::_compare_files(de.path(),
                       paths,
                       fix_func_,
                       check_size_,
                       copy_file_);
    }
}

int
mergerfs::fsck::main(int    argc_,
                     char **argv_)
{
  CLI::App app;
  FS::path path;
  std::string fix;
  bool check_size;
  bool copy_file;
  FixFunc fix_func;

  app.description("fsck.mergerfs:"
                  " A tool to help diagnose and solve mergerfs pool issues");
  app.name("USAGE: fsck.mergerfs");

  app.add_option("path",path)
    ->description("mergerfs path")
    ->check(CLI::ExistingDirectory)
    ->required();
  app.add_option("--fix",fix)
    ->description("Will attempt to 'fix' the problem by chown+chmod or copying files based on a selected file.\n"
                  " * none: Do nothing. Just print details.\n"
                  " * manual: User selects source file.\n"
                  " * newest: Use file with most recent mtime.\n"
                  " * largest: Use file with largest size.")
    ->check(CLI::IsMember({"none","manual","newest","largest"}))
    ->default_val("none");
  app.add_option("--check-size",check_size)
    ->description("Considers file size in calculating differences")
    ->default_val(false)
    ->default_str("false");
  app.add_option("--copy-file",copy_file)
    ->description("Copy file rather than chown/chmod to fix")
    ->default_val(false)
    ->default_str("false");

  try
    {
      app.parse(argc_,argv_);
    }
  catch(const CLI::ParseError &e)
    {
      return app.exit(e);
    }

  if((geteuid() != 0) && (fix != "none"))
    fmt::println(stderr,"WARNING: fsck.mergerfs should be run as root to apply fixes");

  fix_func = ::_select_fix_func(fix);

  ::_fsck(path,
          fix_func,
          check_size,
          copy_file);

  return 0;
}