// Copyright 2005-2024 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the 'License');
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an 'AS IS' BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// See www.openfst.org for extensive documentation on this weighted
// finite-state transducer library.
//
// FST utility definitions.

#include <fst/util.h>

#include <cctype>
#include <charconv>
#include <cstddef>
#include <cstdint>
#include <istream>
#include <optional>
#include <ostream>
#include <sstream>
#include <string>
#include <system_error>

#include <fst/flags.h>
#include <fst/log.h>
#include <string_view>

// Utility flag definitions

DEFINE_bool(fst_error_fatal, true,
          "FST errors are fatal; o.w. return objects flagged as bad: "
          "e.g., FSTs: kError property set, FST weights: not a Member()");

namespace fst {

std::optional<int64_t> ParseInt64(std::string_view s, int base) {
  // Portability note: std::from_chars does not play nicely with string_view
  // using Microsoft Visual Studio Compiler. The string_view's begin() and end()
  // do not return implicit char pointers on this platforms. Using data()
  // and size() instead should be more portable.
  //
  // See:
  // https://stackoverflow.com/questions/61203317/stdfrom-chars-doenst-compile-under-msvc
  int64_t n;
  if (const auto [p, ec] =
          std::from_chars(s.data(), s.data() + s.size(), n, /*base=*/base);
      ec != std::errc() || p != (s.data() + s.size())) {
    return std::nullopt;
  }
  return n;
}

int64_t StrToInt64(std::string_view s, std::string_view source, size_t nline,
                   bool*  error) {
  if (error) *error = false;
  const std::optional<int64_t> maybe_n = ParseInt64(s);
  if (!maybe_n.has_value()) {
    FSTERROR() << "StrToInt64: Bad integer = " << s << "\", source = " << source
               << ", line = " << nline;
    if (error) *error = true;
    return 0;
  }
  return *maybe_n;
}

void ConvertToLegalCSymbol(std::string* s) {
  for (auto it = s->begin(); it != s->end(); ++it) {
    if (!isalnum(*it)) {
      *it = '_';
    }
  }
}

// Skips over input characters to align to 'align' bytes. Returns false if can't
// align.
bool AlignInput(std::istream& strm, size_t align) {
  char c;
  for (size_t i = 0; i < align; ++i) {
    int64_t pos = strm.tellg();
    if (pos < 0) {
      LOG(ERROR) << "AlignInput: Can't determine stream position";
      return false;
    }
    if (pos % align == 0) break;
    strm.read(&c, 1);
  }
  return true;
}

// Write null output characters to align to 'align' bytes. Returns false if
// can't align.
bool AlignOutput(std::ostream& strm, size_t align) {
  for (size_t i = 0; i < align; ++i) {
    int64_t pos = strm.tellp();
    if (pos < 0) {
      LOG(ERROR) << "AlignOutput: Can't determine stream position";
      return false;
    }
    if (pos % align == 0) break;
    strm.write("", 1);
  }
  return true;
}

int AlignBufferWithOutputStream(std::ostream& strm, std::ostringstream& buffer,
                                size_t align) {
  const auto strm_pos = strm.tellp();
  if (strm_pos == -1) {
    LOG(ERROR) << "Cannot determine stream position";
    return -1;
  }
  const int stream_offset = strm_pos % align;
  for (int i = 0; i < stream_offset; ++i) buffer.write("", 1);
  return stream_offset;
}

}  // namespace fst
