// Copyright (C) 2019-2026 Joel Rosdahl and other contributors
//
// See doc/authors.adoc for a complete list of contributors.
//
// This program is free software; you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by the Free
// Software Foundation; either version 3 of the License, or (at your option)
// any later version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
// more details.
//
// You should have received a copy of the GNU General Public License along with
// this program; if not, write to the Free Software Foundation, Inc., 51
// Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

#include "atomicfile.hpp"

#include <ccache/core/exceptions.hpp>
#include <ccache/util/assertions.hpp>
#include <ccache/util/expected.hpp>
#include <ccache/util/file.hpp>
#include <ccache/util/filesystem.hpp>
#include <ccache/util/format.hpp>
#include <ccache/util/temporaryfile.hpp>

namespace fs = util::filesystem;

namespace core {

AtomicFile::AtomicFile(const fs::path& path, Mode mode)
  : m_path(path)
{
  auto tmp_file =
    util::value_or_throw<core::Error>(util::TemporaryFile::create(path));
  m_stream = fdopen(*tmp_file.fd, mode == Mode::binary ? "w+b" : "w+");
  if (!m_stream) {
    const std::string error = strerror(errno);
    std::ignore = util::remove(tmp_file.path);
    throw core::Error(
      FMT("failed to open stream for {}: {}", tmp_file.path, error));
  }
  tmp_file.fd.release(); // Ownership transferred to m_stream
  m_tmp_path = std::move(tmp_file.path);
}

AtomicFile::~AtomicFile()
{
  if (m_stream) {
    // commit() was not called so remove the lingering temporary file.
    std::ignore = fclose(m_stream);         // Not much to do if this fails
    std::ignore = util::remove(m_tmp_path); // Or this
  }
}

void
AtomicFile::write(std::string_view data)
{
  if (data.empty()) {
    return;
  }
  if (fwrite(data.data(), data.size(), 1, m_stream) != 1) {
    throw core::Error(
      FMT("failed to write data to {}: {}", m_path, strerror(errno)));
  }
}

void
AtomicFile::write(std::span<const uint8_t> data)
{
  if (data.empty()) {
    return;
  }
  if (fwrite(data.data(), data.size(), 1, m_stream) != 1) {
    throw core::Error(
      FMT("failed to write data to {}: {}", m_path, strerror(errno)));
  }
}

void
AtomicFile::flush()
{
  if (fflush(m_stream) != 0) {
    throw core::Error(
      FMT("failed to flush data to {}: {}", m_path, strerror(errno)));
  }
}

void
AtomicFile::commit()
{
  ASSERT(m_stream);
  int retcode = fclose(m_stream);
  m_stream = nullptr;
  if (retcode == EOF) {
    std::ignore = util::remove(m_tmp_path);
    throw core::Error(
      FMT("failed to write data to {}: {}", m_path, strerror(errno)));
  }
  const auto result = fs::rename(m_tmp_path, m_path);
  if (!result) {
    throw core::Error(FMT("failed to rename {} to {}: {}",
                          m_tmp_path,
                          m_path,
                          result.error().message()));
  }
}

} // namespace core
