/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * 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.
 */

#include <folly/logging/LogMessage.h>

#include <folly/logging/LogCategory.h>
#include <folly/logging/LoggerDB.h>
#include <folly/system/ThreadId.h>

using std::chrono::system_clock;

namespace {
std::string getContextStringFromCategory(const folly::LogCategory* category) {
  return category->getDB()->getContextString();
}
} // namespace

namespace folly {

LogMessage::LogMessage(
    const LogCategory* category,
    LogLevel level,
    StringPiece filename,
    unsigned int lineNumber,
    StringPiece functionName,
    std::string&& msg)
    : category_{category},
      level_{level},
      threadID_{getOSThreadID()},
      timestamp_{system_clock::now()},
      filename_{filename},
      lineNumber_{lineNumber},
      functionName_{functionName},
      contextString_{getContextStringFromCategory(category_)},
      rawMessage_{std::move(msg)} {
  sanitizeMessage();
}

LogMessage::LogMessage(
    const LogCategory* category,
    LogLevel level,
    system_clock::time_point timestamp,
    StringPiece filename,
    unsigned int lineNumber,
    StringPiece functionName,
    std::string&& msg)
    : category_{category},
      level_{level},
      threadID_{getOSThreadID()},
      timestamp_{timestamp},
      filename_{filename},
      lineNumber_{lineNumber},
      functionName_{functionName},
      contextString_{getContextStringFromCategory(category_)},
      rawMessage_{std::move(msg)} {
  sanitizeMessage();
}

StringPiece LogMessage::getFileBaseName() const {
#ifdef _WIN32
  // Windows allows either backwards or forwards slash as path separator
  auto idx1 = filename_.rfind('\\');
  auto idx2 = filename_.rfind('/');
  StringPiece::size_type idx;
  if (idx1 == StringPiece::npos) {
    idx = idx2;
  } else if (idx2 == StringPiece::npos) {
    idx = idx1;
  } else {
    idx = std::max(idx1, idx2);
  }
#else
  auto idx = filename_.rfind('/');
#endif
  if (idx == StringPiece::npos) {
    return filename_;
  }
  return filename_.subpiece(idx + 1);
}

void LogMessage::sanitizeMessage() {
  // Compute how long the sanitized string will be.
  size_t sanitizedLength = 0;
  size_t numNewlines = 0;
  for (const char c : rawMessage_) {
    if (c == '\\') {
      // Backslashes are escaped as two backslashes
      sanitizedLength += 2;
    } else if (static_cast<unsigned char>(c) < 0x20) {
      // Newlines and tabs are emitted directly with no escaping.
      // All other control characters are emitted as \xNN (4 characters)
      if (c == '\n') {
        sanitizedLength += 1;
        ++numNewlines;
      } else if (c == '\t') {
        sanitizedLength += 1;
      } else {
        sanitizedLength += 4;
      }
    } else if (c == 0x7f) {
      // Bytes above the ASCII range are emitted as \xNN (4 characters)
      sanitizedLength += 4;
    } else {
      // This character will be emitted as-is, with no escaping.
      ++sanitizedLength;
    }
  }
  numNewlines_ = numNewlines;
  // If nothing is different, just use rawMessage_ directly,
  // and don't populate message_.
  if (sanitizedLength == rawMessage_.size()) {
    return;
  }

  message_.reserve(sanitizedLength);
  for (const char c : rawMessage_) {
    if (c == '\\') {
      message_.push_back('\\');
      message_.push_back('\\');
    } else if (static_cast<unsigned char>(c) < 0x20) {
      if (c == '\n' || c == '\t') {
        message_.push_back(c);
      } else {
        static constexpr StringPiece hexdigits{"0123456789abcdef"};
        std::array<char, 4> data{
            {'\\', 'x', hexdigits[(c >> 4) & 0xf], hexdigits[c & 0xf]}};
        message_.append(data.data(), data.size());
      }
    } else if (c == 0x7f) {
      constexpr std::array<char, 4> data{{'\\', 'x', '7', 'f'}};
      message_.append(data.data(), data.size());
    } else {
      message_.push_back(c);
    }
  }
}
} // namespace folly
