#include <ATen/core/Dimname.h>
#include <c10/util/Exception.h>
#include <cctype>

namespace at {

static Symbol kWildcard = Symbol::dimname("*");

std::ostream& operator<<(std::ostream& out, const Dimname& dimname) {
  if (dimname.type() == NameType::WILDCARD) {
    out << "None";
  } else {
    out << "'" << dimname.symbol().toUnqualString() << "'";
  }
  return out;
}

bool Dimname::isValidName(const std::string& name) {
  // allow valid ASCII python identifiers: "uppercase and lowercase
  // letters A through Z, the underscore _ and, except for the first
  // character, the digits 0 through 9" (at least length 1)
  // https://docs.python.org/3/reference/lexical_analysis.html#identifiers
  if (name.empty()) {
    return false;
  }
  for (auto it = name.begin(); it != name.end(); ++it) {
    // NOLINTNEXTLINE(bugprone-branch-clone)
    const unsigned char ch = static_cast<unsigned char>(*it);
    if (std::isalpha(ch) || ch == '_') {
      continue;
    } else if (it != name.begin() && std::isdigit(ch)) {
      continue;
    }
    return false;
  }
  return true;
}

static void check_valid_identifier(const std::string& name) {
  TORCH_CHECK(
      Dimname::isValidName(name),
      "Invalid name: a valid identifier contains only digits, alphabetical "
      "characters, and/or underscore and starts with a non-digit. got: '",
      name, "'.");
}

Dimname Dimname::fromSymbol(Symbol name) {
  TORCH_INTERNAL_ASSERT(name.is_dimname());
  if (name == kWildcard) {
    return Dimname::wildcard();
  }
  check_valid_identifier(name.toUnqualString());
  return Dimname(name);
}

Dimname Dimname::wildcard() {
  static Dimname result(kWildcard, NameType::WILDCARD);
  return result;
}

std::optional<Dimname> Dimname::unify(Dimname other) const {
  if (other.type() == NameType::WILDCARD) {
    return *this;
  }
  if (type_ == NameType::WILDCARD) {
    return other;
  }
  if (name_ == other.symbol()) {
    return *this;
  }
  return std::nullopt;
}

bool Dimname::matches(Dimname other) const {
  return unify(other).has_value();
}

} // namespace at
