#include "sedpp/Regex.h"

#include <stdexcept>

namespace sedpp {

Regex::Regex(const std::string &pattern, const Options &options,
             bool ignoreCase, bool multiline) {
  int flags = 0;
  // Keep regex flavor decisions here so compiler-normalized patterns can be
  // reused by addresses and substitutions without duplicating regcomp flags.
  if (options.extendedRegex) {
    flags |= REG_EXTENDED;
  }
  if (ignoreCase) {
    flags |= REG_ICASE;
  }
  if (multiline) {
    flags |= REG_NEWLINE;
  }

  const int rc = ::regcomp(&regex_, pattern.c_str(), flags);
  if (rc != 0) {
    char message[256];
    ::regerror(rc, &regex_, message, sizeof(message));
    throw std::runtime_error(message);
  }
  compiled_ = true;
}

Regex::Regex(Regex &&other) noexcept {
  // regex_t is a C resource; moving transfers the compiled object and prevents
  // the source wrapper from freeing it.
  regex_ = other.regex_;
  compiled_ = other.compiled_;
  other.compiled_ = false;
}

Regex &Regex::operator=(Regex &&other) noexcept {
  if (this != &other) {
    if (compiled_) {
      ::regfree(&regex_);
    }
    regex_ = other.regex_;
    compiled_ = other.compiled_;
    other.compiled_ = false;
  }
  return *this;
}

Regex::~Regex() {
  if (compiled_) {
    ::regfree(&regex_);
  }
}

std::optional<Match> Regex::search(const std::string &text,
                                   std::size_t start) const {
  constexpr std::size_t kMaxGroups = 10;
  Match match;
  match.groups.resize(kMaxGroups);

  const char *base = text.c_str();
  // Searches after byte 0 should not let ^ match the original beginning again.
  const int eflags = start == 0 ? 0 : REG_NOTBOL;
  const int rc = ::regexec(&regex_, base + start, match.groups.size(),
                           match.groups.data(), eflags);
  if (rc == REG_NOMATCH) {
    return std::nullopt;
  }
  if (rc != 0) {
    char message[256];
    ::regerror(rc, &regex_, message, sizeof(message));
    throw std::runtime_error(message);
  }

  for (regmatch_t &group : match.groups) {
    if (group.rm_so >= 0) {
      // regexec saw base + start, so convert offsets back into the full string.
      group.rm_so += static_cast<regoff_t>(start);
      group.rm_eo += static_cast<regoff_t>(start);
    }
  }
  return match;
}

} // namespace sedpp