//===-- runtime/io-stmt.cpp -----------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#include "io-stmt.h"
#include "connection.h"
#include "format.h"
#include "tools.h"
#include "unit.h"
#include "flang/Runtime/memory.h"
#include <algorithm>
#include <cstdio>
#include <cstring>
#include <limits>

namespace Fortran::runtime::io {

int IoStatementBase::EndIoStatement() { return GetIoStat(); }

bool IoStatementBase::Emit(const char *, std::size_t, std::size_t) {
  return false;
}

bool IoStatementBase::Emit(const char *, std::size_t) {
  return false;
}

bool IoStatementBase::Emit(const char16_t *, std::size_t) {
  return false;
}

bool IoStatementBase::Emit(const char32_t *, std::size_t) {
  return false;
}

std::optional<char32_t> IoStatementBase::GetCurrentChar() {
  return std::nullopt;
}

bool IoStatementBase::AdvanceRecord(int) { return false; }

void IoStatementBase::BackspaceRecord() {}

bool IoStatementBase::Receive(char *, std::size_t, std::size_t) {
  return false;
}

std::optional<DataEdit> IoStatementBase::GetNextDataEdit(
    IoStatementState &, int) {
  return std::nullopt;
}

ExternalFileUnit *IoStatementBase::GetExternalFileUnit() const {
  return nullptr;
}

bool IoStatementBase::BeginReadingRecord() { return true; }

void IoStatementBase::FinishReadingRecord() {}

void IoStatementBase::HandleAbsolutePosition(std::int64_t) {}

void IoStatementBase::HandleRelativePosition(std::int64_t) {}

bool IoStatementBase::Inquire(InquiryKeywordHash, char *, std::size_t) {
  return false;
}

bool IoStatementBase::Inquire(InquiryKeywordHash, bool &) {
  return false;
}

bool IoStatementBase::Inquire(InquiryKeywordHash, std::int64_t, bool &) {
  return false;
}

bool IoStatementBase::Inquire(InquiryKeywordHash, std::int64_t &) {
  return false;
}

void IoStatementBase::BadInquiryKeywordHashCrash(InquiryKeywordHash inquiry) {
  char buffer[16];
  const char *decode{InquiryKeywordHashDecode(buffer, sizeof buffer, inquiry)};
  Crash("bad InquiryKeywordHash 0x%x (%s)", inquiry,
      decode ? decode : "(cannot decode)");
}

template <Direction DIR, typename CHAR>
InternalIoStatementState<DIR, CHAR>::InternalIoStatementState(
    Buffer scalar, std::size_t length, const char *sourceFile, int sourceLine)
    : IoStatementBase{sourceFile, sourceLine}, unit_{scalar, length} {}

template <Direction DIR, typename CHAR>
InternalIoStatementState<DIR, CHAR>::InternalIoStatementState(
    const Descriptor &d, const char *sourceFile, int sourceLine)
    : IoStatementBase{sourceFile, sourceLine}, unit_{d, *this} {}

template <Direction DIR, typename CHAR>
bool InternalIoStatementState<DIR, CHAR>::Emit(
    const CharType *data, std::size_t chars) {
  if constexpr (DIR == Direction::Input) {
    Crash("InternalIoStatementState<Direction::Input>::Emit() called");
    return false;
  }
  return unit_.Emit(data, chars * sizeof(CharType), *this);
}

template <Direction DIR, typename CHAR>
std::optional<char32_t> InternalIoStatementState<DIR, CHAR>::GetCurrentChar() {
  if constexpr (DIR == Direction::Output) {
    Crash(
        "InternalIoStatementState<Direction::Output>::GetCurrentChar() called");
    return std::nullopt;
  }
  return unit_.GetCurrentChar(*this);
}

template <Direction DIR, typename CHAR>
bool InternalIoStatementState<DIR, CHAR>::AdvanceRecord(int n) {
  while (n-- > 0) {
    if (!unit_.AdvanceRecord(*this)) {
      return false;
    }
  }
  return true;
}

template <Direction DIR, typename CHAR>
void InternalIoStatementState<DIR, CHAR>::BackspaceRecord() {
  unit_.BackspaceRecord(*this);
}

template <Direction DIR, typename CHAR>
int InternalIoStatementState<DIR, CHAR>::EndIoStatement() {
  if constexpr (DIR == Direction::Output) {
    unit_.EndIoStatement(); // fill
  }
  auto result{IoStatementBase::EndIoStatement()};
  if (free_) {
    FreeMemory(this);
  }
  return result;
}

template <Direction DIR, typename CHAR>
void InternalIoStatementState<DIR, CHAR>::HandleAbsolutePosition(
    std::int64_t n) {
  return unit_.HandleAbsolutePosition(n);
}

template <Direction DIR, typename CHAR>
void InternalIoStatementState<DIR, CHAR>::HandleRelativePosition(
    std::int64_t n) {
  return unit_.HandleRelativePosition(n);
}

template <Direction DIR, typename CHAR>
InternalFormattedIoStatementState<DIR, CHAR>::InternalFormattedIoStatementState(
    Buffer buffer, std::size_t length, const CHAR *format,
    std::size_t formatLength, const char *sourceFile, int sourceLine)
    : InternalIoStatementState<DIR, CHAR>{buffer, length, sourceFile,
          sourceLine},
      ioStatementState_{*this}, format_{*this, format, formatLength} {}

template <Direction DIR, typename CHAR>
InternalFormattedIoStatementState<DIR, CHAR>::InternalFormattedIoStatementState(
    const Descriptor &d, const CHAR *format, std::size_t formatLength,
    const char *sourceFile, int sourceLine)
    : InternalIoStatementState<DIR, CHAR>{d, sourceFile, sourceLine},
      ioStatementState_{*this}, format_{*this, format, formatLength} {}

template <Direction DIR, typename CHAR>
int InternalFormattedIoStatementState<DIR, CHAR>::EndIoStatement() {
  if constexpr (DIR == Direction::Output) {
    format_.Finish(*this); // ignore any remaining input positioning actions
  }
  return InternalIoStatementState<DIR, CHAR>::EndIoStatement();
}

template <Direction DIR, typename CHAR>
InternalListIoStatementState<DIR, CHAR>::InternalListIoStatementState(
    Buffer buffer, std::size_t length, const char *sourceFile, int sourceLine)
    : InternalIoStatementState<DIR, CharType>{buffer, length, sourceFile,
          sourceLine},
      ioStatementState_{*this} {}

template <Direction DIR, typename CHAR>
InternalListIoStatementState<DIR, CHAR>::InternalListIoStatementState(
    const Descriptor &d, const char *sourceFile, int sourceLine)
    : InternalIoStatementState<DIR, CharType>{d, sourceFile, sourceLine},
      ioStatementState_{*this} {}

ExternalIoStatementBase::ExternalIoStatementBase(
    ExternalFileUnit &unit, const char *sourceFile, int sourceLine)
    : IoStatementBase{sourceFile, sourceLine}, unit_{unit} {}

MutableModes &ExternalIoStatementBase::mutableModes() { return unit_.modes; }

ConnectionState &ExternalIoStatementBase::GetConnectionState() { return unit_; }

int ExternalIoStatementBase::EndIoStatement() {
  if (mutableModes().nonAdvancing) {
    unit_.leftTabLimit = unit_.furthestPositionInRecord;
  } else {
    unit_.leftTabLimit.reset();
  }
  auto result{IoStatementBase::EndIoStatement()};
  unit_.EndIoStatement(); // annihilates *this in unit_.u_
  return result;
}

void OpenStatementState::set_path(const char *path, std::size_t length) {
  pathLength_ = TrimTrailingSpaces(path, length);
  path_ = SaveDefaultCharacter(path, pathLength_, *this);
}

int OpenStatementState::EndIoStatement() {
  if (path_.get() || wasExtant_ ||
      (status_ && *status_ == OpenStatus::Scratch)) {
    unit().OpenUnit(status_, action_, position_, std::move(path_), pathLength_,
        convert_, *this);
  } else {
    unit().OpenAnonymousUnit(status_, action_, position_, convert_, *this);
  }
  if (access_) {
    if (*access_ != unit().access) {
      if (wasExtant_) {
        SignalError("ACCESS= may not be changed on an open unit");
      }
    }
    unit().access = *access_;
  }
  if (!unit().isUnformatted) {
    unit().isUnformatted = isUnformatted_;
  }
  if (isUnformatted_ && *isUnformatted_ != *unit().isUnformatted) {
    if (wasExtant_) {
      SignalError("FORM= may not be changed on an open unit");
    }
    unit().isUnformatted = *isUnformatted_;
  }
  if (!unit().isUnformatted) {
    // Set default format (C.7.4 point 2).
    unit().isUnformatted = unit().access != Access::Sequential;
  }
  return ExternalIoStatementBase::EndIoStatement();
}

int CloseStatementState::EndIoStatement() {
  int result{ExternalIoStatementBase::EndIoStatement()};
  unit().CloseUnit(status_, *this);
  unit().DestroyClosed();
  return result;
}

int NoUnitIoStatementState::EndIoStatement() {
  auto result{IoStatementBase::EndIoStatement()};
  FreeMemory(this);
  return result;
}

template <Direction DIR>
ExternalIoStatementState<DIR>::ExternalIoStatementState(
    ExternalFileUnit &unit, const char *sourceFile, int sourceLine)
    : ExternalIoStatementBase{unit, sourceFile, sourceLine}, mutableModes_{
                                                                 unit.modes} {}

template <Direction DIR> int ExternalIoStatementState<DIR>::EndIoStatement() {
  if constexpr (DIR == Direction::Input) {
    BeginReadingRecord(); // in case there were no I/O items
    if (!mutableModes().nonAdvancing) {
      FinishReadingRecord();
    }
  } else {
    if (!mutableModes().nonAdvancing) {
      unit().AdvanceRecord(*this);
    }
    unit().FlushIfTerminal(*this);
  }
  return ExternalIoStatementBase::EndIoStatement();
}

template <Direction DIR>
bool ExternalIoStatementState<DIR>::Emit(
    const char *data, std::size_t bytes, std::size_t elementBytes) {
  if constexpr (DIR == Direction::Input) {
    Crash("ExternalIoStatementState::Emit(char) called for input statement");
  }
  return unit().Emit(data, bytes, elementBytes, *this);
}

template <Direction DIR>
bool ExternalIoStatementState<DIR>::Emit(const char *data, std::size_t bytes) {
  if constexpr (DIR == Direction::Input) {
    Crash("ExternalIoStatementState::Emit(char) called for input statement");
  }
  return unit().Emit(data, bytes, 0, *this);
}

template <Direction DIR>
bool ExternalIoStatementState<DIR>::Emit(
    const char16_t *data, std::size_t chars) {
  if constexpr (DIR == Direction::Input) {
    Crash(
        "ExternalIoStatementState::Emit(char16_t) called for input statement");
  }
  // TODO: UTF-8 encoding
  return unit().Emit(reinterpret_cast<const char *>(data), chars * sizeof *data,
      sizeof *data, *this);
}

template <Direction DIR>
bool ExternalIoStatementState<DIR>::Emit(
    const char32_t *data, std::size_t chars) {
  if constexpr (DIR == Direction::Input) {
    Crash(
        "ExternalIoStatementState::Emit(char32_t) called for input statement");
  }
  // TODO: UTF-8 encoding
  return unit().Emit(reinterpret_cast<const char *>(data), chars * sizeof *data,
      sizeof *data, *this);
}

template <Direction DIR>
std::optional<char32_t> ExternalIoStatementState<DIR>::GetCurrentChar() {
  if constexpr (DIR == Direction::Output) {
    Crash(
        "ExternalIoStatementState<Direction::Output>::GetCurrentChar() called");
  }
  return unit().GetCurrentChar(*this);
}

template <Direction DIR>
bool ExternalIoStatementState<DIR>::AdvanceRecord(int n) {
  while (n-- > 0) {
    if (!unit().AdvanceRecord(*this)) {
      return false;
    }
  }
  return true;
}

template <Direction DIR> void ExternalIoStatementState<DIR>::BackspaceRecord() {
  unit().BackspaceRecord(*this);
}

template <Direction DIR>
void ExternalIoStatementState<DIR>::HandleAbsolutePosition(std::int64_t n) {
  return unit().HandleAbsolutePosition(n);
}

template <Direction DIR>
void ExternalIoStatementState<DIR>::HandleRelativePosition(std::int64_t n) {
  return unit().HandleRelativePosition(n);
}

template <Direction DIR>
bool ExternalIoStatementState<DIR>::BeginReadingRecord() {
  if constexpr (DIR == Direction::Input) {
    return unit().BeginReadingRecord(*this);
  } else {
    Crash("ExternalIoStatementState<Direction::Output>::BeginReadingRecord() "
          "called");
    return false;
  }
}

template <Direction DIR>
void ExternalIoStatementState<DIR>::FinishReadingRecord() {
  if constexpr (DIR == Direction::Input) {
    unit().FinishReadingRecord(*this);
  } else {
    Crash("ExternalIoStatementState<Direction::Output>::FinishReadingRecord() "
          "called");
  }
}

template <Direction DIR, typename CHAR>
ExternalFormattedIoStatementState<DIR, CHAR>::ExternalFormattedIoStatementState(
    ExternalFileUnit &unit, const CHAR *format, std::size_t formatLength,
    const char *sourceFile, int sourceLine)
    : ExternalIoStatementState<DIR>{unit, sourceFile, sourceLine},
      format_{*this, format, formatLength} {}

template <Direction DIR, typename CHAR>
int ExternalFormattedIoStatementState<DIR, CHAR>::EndIoStatement() {
  format_.Finish(*this);
  return ExternalIoStatementState<DIR>::EndIoStatement();
}

std::optional<DataEdit> IoStatementState::GetNextDataEdit(int n) {
  return std::visit(
      [&](auto &x) { return x.get().GetNextDataEdit(*this, n); }, u_);
}

bool IoStatementState::Emit(
    const char *data, std::size_t n, std::size_t elementBytes) {
  return std::visit(
      [=](auto &x) { return x.get().Emit(data, n, elementBytes); }, u_);
}

bool IoStatementState::Emit(const char *data, std::size_t n) {
  return std::visit([=](auto &x) { return x.get().Emit(data, n); }, u_);
}

bool IoStatementState::Emit(const char16_t *data, std::size_t chars) {
  return std::visit([=](auto &x) { return x.get().Emit(data, chars); }, u_);
}

bool IoStatementState::Emit(const char32_t *data, std::size_t chars) {
  return std::visit([=](auto &x) { return x.get().Emit(data, chars); }, u_);
}

bool IoStatementState::Receive(
    char *data, std::size_t n, std::size_t elementBytes) {
  return std::visit(
      [=](auto &x) { return x.get().Receive(data, n, elementBytes); }, u_);
}

std::optional<char32_t> IoStatementState::GetCurrentChar() {
  return std::visit([&](auto &x) { return x.get().GetCurrentChar(); }, u_);
}

bool IoStatementState::AdvanceRecord(int n) {
  return std::visit([=](auto &x) { return x.get().AdvanceRecord(n); }, u_);
}

void IoStatementState::BackspaceRecord() {
  std::visit([](auto &x) { x.get().BackspaceRecord(); }, u_);
}

void IoStatementState::HandleRelativePosition(std::int64_t n) {
  std::visit([=](auto &x) { x.get().HandleRelativePosition(n); }, u_);
}

void IoStatementState::HandleAbsolutePosition(std::int64_t n) {
  std::visit([=](auto &x) { x.get().HandleAbsolutePosition(n); }, u_);
}

int IoStatementState::EndIoStatement() {
  return std::visit([](auto &x) { return x.get().EndIoStatement(); }, u_);
}

ConnectionState &IoStatementState::GetConnectionState() {
  return std::visit(
      [](auto &x) -> ConnectionState & { return x.get().GetConnectionState(); },
      u_);
}

MutableModes &IoStatementState::mutableModes() {
  return std::visit(
      [](auto &x) -> MutableModes & { return x.get().mutableModes(); }, u_);
}

bool IoStatementState::BeginReadingRecord() {
  return std::visit([](auto &x) { return x.get().BeginReadingRecord(); }, u_);
}

IoErrorHandler &IoStatementState::GetIoErrorHandler() const {
  return std::visit(
      [](auto &x) -> IoErrorHandler & {
        return static_cast<IoErrorHandler &>(x.get());
      },
      u_);
}

ExternalFileUnit *IoStatementState::GetExternalFileUnit() const {
  return std::visit([](auto &x) { return x.get().GetExternalFileUnit(); }, u_);
}

bool IoStatementState::EmitRepeated(char ch, std::size_t n) {
  return std::visit(
      [=](auto &x) {
        for (std::size_t j{0}; j < n; ++j) {
          if (!x.get().Emit(&ch, 1)) {
            return false;
          }
        }
        return true;
      },
      u_);
}

bool IoStatementState::EmitField(
    const char *p, std::size_t length, std::size_t width) {
  if (width <= 0) {
    width = static_cast<int>(length);
  }
  if (length > static_cast<std::size_t>(width)) {
    return EmitRepeated('*', width);
  } else {
    return EmitRepeated(' ', static_cast<int>(width - length)) &&
        Emit(p, length);
  }
}

std::optional<char32_t> IoStatementState::PrepareInput(
    const DataEdit &edit, std::optional<int> &remaining) {
  remaining.reset();
  if (edit.descriptor == DataEdit::ListDirected) {
    GetNextNonBlank();
  } else {
    if (edit.width.value_or(0) > 0) {
      remaining = *edit.width;
    }
    SkipSpaces(remaining);
  }
  return NextInField(remaining);
}

std::optional<char32_t> IoStatementState::SkipSpaces(
    std::optional<int> &remaining) {
  while (!remaining || *remaining > 0) {
    if (auto ch{GetCurrentChar()}) {
      if (*ch != ' ' && *ch != '\t') {
        return ch;
      }
      HandleRelativePosition(1);
      if (remaining) {
        --*remaining;
      }
    } else {
      break;
    }
  }
  return std::nullopt;
}

std::optional<char32_t> IoStatementState::NextInField(
    std::optional<int> &remaining) {
  if (!remaining) { // list-directed or NAMELIST: check for separators
    if (auto next{GetCurrentChar()}) {
      switch (*next) {
      case ' ':
      case '\t':
      case ',':
      case ';':
      case '/':
      case '(':
      case ')':
      case '\'':
      case '"':
      case '*':
      case '\n': // for stream access
        break;
      default:
        HandleRelativePosition(1);
        return next;
      }
    }
  } else if (*remaining > 0) {
    if (auto next{GetCurrentChar()}) {
      --*remaining;
      HandleRelativePosition(1);
      return next;
    }
    const ConnectionState &connection{GetConnectionState()};
    if (!connection.IsAtEOF() && connection.isFixedRecordLength &&
        connection.recordLength &&
        connection.positionInRecord >= *connection.recordLength) {
      if (connection.modes.pad) { // PAD='YES'
        --*remaining;
        return std::optional<char32_t>{' '};
      }
      IoErrorHandler &handler{GetIoErrorHandler()};
      if (mutableModes().nonAdvancing) {
        handler.SignalEor();
      } else {
        handler.SignalError(IostatRecordReadOverrun);
      }
    }
  }
  return std::nullopt;
}

std::optional<char32_t> IoStatementState::GetNextNonBlank() {
  auto ch{GetCurrentChar()};
  bool inNamelist{GetConnectionState().modes.inNamelist};
  while (!ch || *ch == ' ' || *ch == '\t' || (inNamelist && *ch == '!')) {
    if (ch && (*ch == ' ' || *ch == '\t')) {
      HandleRelativePosition(1);
    } else if (!AdvanceRecord()) {
      return std::nullopt;
    }
    ch = GetCurrentChar();
  }
  return ch;
}

bool IoStatementState::Inquire(
    InquiryKeywordHash inquiry, char *out, std::size_t chars) {
  return std::visit(
      [&](auto &x) { return x.get().Inquire(inquiry, out, chars); }, u_);
}

bool IoStatementState::Inquire(InquiryKeywordHash inquiry, bool &out) {
  return std::visit([&](auto &x) { return x.get().Inquire(inquiry, out); }, u_);
}

bool IoStatementState::Inquire(
    InquiryKeywordHash inquiry, std::int64_t id, bool &out) {
  return std::visit(
      [&](auto &x) { return x.get().Inquire(inquiry, id, out); }, u_);
}

bool IoStatementState::Inquire(InquiryKeywordHash inquiry, std::int64_t &n) {
  return std::visit([&](auto &x) { return x.get().Inquire(inquiry, n); }, u_);
}

bool ListDirectedStatementState<Direction::Output>::EmitLeadingSpaceOrAdvance(
    IoStatementState &io, std::size_t length, bool isCharacter) {
  if (length == 0) {
    return true;
  }
  const ConnectionState &connection{io.GetConnectionState()};
  int space{connection.positionInRecord == 0 ||
      !(isCharacter && lastWasUndelimitedCharacter())};
  set_lastWasUndelimitedCharacter(false);
  if (connection.NeedAdvance(space + length)) {
    return io.AdvanceRecord();
  }
  if (space) {
    return io.Emit(" ", 1);
  }
  return true;
}

std::optional<DataEdit>
ListDirectedStatementState<Direction::Output>::GetNextDataEdit(
    IoStatementState &io, int maxRepeat) {
  DataEdit edit;
  edit.descriptor = DataEdit::ListDirected;
  edit.repeat = maxRepeat;
  edit.modes = io.mutableModes();
  return edit;
}

std::optional<DataEdit>
ListDirectedStatementState<Direction::Input>::GetNextDataEdit(
    IoStatementState &io, int maxRepeat) {
  // N.B. list-directed transfers cannot be nonadvancing (C1221)
  ConnectionState &connection{io.GetConnectionState()};
  DataEdit edit;
  edit.descriptor = DataEdit::ListDirected;
  edit.repeat = 1; // may be overridden below
  edit.modes = connection.modes;
  if (hitSlash_) { // everything after '/' is nullified
    edit.descriptor = DataEdit::ListDirectedNullValue;
    return edit;
  }
  char32_t comma{','};
  if (io.mutableModes().editingFlags & decimalComma) {
    comma = ';';
  }
  if (remaining_ > 0 && !realPart_) { // "r*c" repetition in progress
    RUNTIME_CHECK(
        io.GetIoErrorHandler(), connection.resumptionRecordNumber.has_value());
    while (connection.currentRecordNumber >
        connection.resumptionRecordNumber.value_or(
            connection.currentRecordNumber)) {
      io.BackspaceRecord();
    }
    connection.HandleAbsolutePosition(repeatPositionInRecord_);
    if (!imaginaryPart_) {
      edit.repeat = std::min<int>(remaining_, maxRepeat);
      auto ch{io.GetCurrentChar()};
      if (!ch || *ch == ' ' || *ch == '\t' || *ch == comma) {
        // "r*" repeated null
        edit.descriptor = DataEdit::ListDirectedNullValue;
      }
    }
    remaining_ -= edit.repeat;
    if (remaining_ <= 0) {
      connection.resumptionRecordNumber.reset();
    }
    return edit;
  }
  // Skip separators, handle a "r*c" repeat count; see 13.10.2 in Fortran 2018
  if (imaginaryPart_) {
    imaginaryPart_ = false;
  } else if (realPart_) {
    realPart_ = false;
    imaginaryPart_ = true;
    edit.descriptor = DataEdit::ListDirectedImaginaryPart;
  }
  auto ch{io.GetNextNonBlank()};
  if (ch && *ch == comma && eatComma_) {
    // Consume comma & whitespace after previous item.
    // This includes the comma between real and imaginary components
    // in list-directed/NAMELIST complex input.
    io.HandleRelativePosition(1);
    ch = io.GetNextNonBlank();
  }
  eatComma_ = true;
  if (!ch) {
    return std::nullopt;
  }
  if (*ch == '/') {
    hitSlash_ = true;
    edit.descriptor = DataEdit::ListDirectedNullValue;
    return edit;
  }
  if (*ch == comma) { // separator: null value
    edit.descriptor = DataEdit::ListDirectedNullValue;
    return edit;
  }
  if (imaginaryPart_) { // can't repeat components
    return edit;
  }
  if (*ch >= '0' && *ch <= '9') { // look for "r*" repetition count
    auto start{connection.positionInRecord};
    int r{0};
    do {
      static auto constexpr clamp{(std::numeric_limits<int>::max() - '9') / 10};
      if (r >= clamp) {
        r = 0;
        break;
      }
      r = 10 * r + (*ch - '0');
      io.HandleRelativePosition(1);
      ch = io.GetCurrentChar();
    } while (ch && *ch >= '0' && *ch <= '9');
    if (r > 0 && ch && *ch == '*') { // subtle: r must be nonzero
      io.HandleRelativePosition(1);
      ch = io.GetCurrentChar();
      if (ch && *ch == '/') { // r*/
        hitSlash_ = true;
        edit.descriptor = DataEdit::ListDirectedNullValue;
        return edit;
      }
      if (!ch || *ch == ' ' || *ch == '\t' || *ch == comma) { // "r*" null
        edit.descriptor = DataEdit::ListDirectedNullValue;
      }
      edit.repeat = std::min<int>(r, maxRepeat);
      remaining_ = r - edit.repeat;
      if (remaining_ > 0) {
        connection.resumptionRecordNumber = connection.currentRecordNumber;
      } else {
        connection.resumptionRecordNumber.reset();
      }
      repeatPositionInRecord_ = connection.positionInRecord;
    } else { // not a repetition count, just an integer value; rewind
      connection.positionInRecord = start;
    }
  }
  if (!imaginaryPart_ && ch && *ch == '(') {
    realPart_ = true;
    io.HandleRelativePosition(1);
    edit.descriptor = DataEdit::ListDirectedRealPart;
  }
  return edit;
}

template <Direction DIR>
bool ExternalUnformattedIoStatementState<DIR>::Receive(
    char *data, std::size_t bytes, std::size_t elementBytes) {
  if constexpr (DIR == Direction::Output) {
    this->Crash("ExternalUnformattedIoStatementState::Receive() called for "
                "output statement");
  }
  return this->unit().Receive(data, bytes, elementBytes, *this);
}

template <Direction DIR>
ChildIoStatementState<DIR>::ChildIoStatementState(
    ChildIo &child, const char *sourceFile, int sourceLine)
    : IoStatementBase{sourceFile, sourceLine}, child_{child} {}

template <Direction DIR>
MutableModes &ChildIoStatementState<DIR>::mutableModes() {
  return child_.parent().mutableModes();
}

template <Direction DIR>
ConnectionState &ChildIoStatementState<DIR>::GetConnectionState() {
  return child_.parent().GetConnectionState();
}

template <Direction DIR>
ExternalFileUnit *ChildIoStatementState<DIR>::GetExternalFileUnit() const {
  return child_.parent().GetExternalFileUnit();
}

template <Direction DIR> int ChildIoStatementState<DIR>::EndIoStatement() {
  auto result{IoStatementBase::EndIoStatement()};
  child_.EndIoStatement(); // annihilates *this in child_.u_
  return result;
}

template <Direction DIR>
bool ChildIoStatementState<DIR>::Emit(
    const char *data, std::size_t bytes, std::size_t elementBytes) {
  return child_.parent().Emit(data, bytes, elementBytes);
}

template <Direction DIR>
bool ChildIoStatementState<DIR>::Emit(const char *data, std::size_t bytes) {
  return child_.parent().Emit(data, bytes);
}

template <Direction DIR>
bool ChildIoStatementState<DIR>::Emit(const char16_t *data, std::size_t chars) {
  return child_.parent().Emit(data, chars);
}

template <Direction DIR>
bool ChildIoStatementState<DIR>::Emit(const char32_t *data, std::size_t chars) {
  return child_.parent().Emit(data, chars);
}

template <Direction DIR>
std::optional<char32_t> ChildIoStatementState<DIR>::GetCurrentChar() {
  return child_.parent().GetCurrentChar();
}

template <Direction DIR>
void ChildIoStatementState<DIR>::HandleAbsolutePosition(std::int64_t n) {
  return child_.parent().HandleAbsolutePosition(n);
}

template <Direction DIR>
void ChildIoStatementState<DIR>::HandleRelativePosition(std::int64_t n) {
  return child_.parent().HandleRelativePosition(n);
}

template <Direction DIR, typename CHAR>
ChildFormattedIoStatementState<DIR, CHAR>::ChildFormattedIoStatementState(
    ChildIo &child, const CHAR *format, std::size_t formatLength,
    const char *sourceFile, int sourceLine)
    : ChildIoStatementState<DIR>{child, sourceFile, sourceLine},
      mutableModes_{child.parent().mutableModes()}, format_{*this, format,
                                                        formatLength} {}

template <Direction DIR, typename CHAR>
int ChildFormattedIoStatementState<DIR, CHAR>::EndIoStatement() {
  format_.Finish(*this);
  return ChildIoStatementState<DIR>::EndIoStatement();
}

template <Direction DIR, typename CHAR>
bool ChildFormattedIoStatementState<DIR, CHAR>::AdvanceRecord(int) {
  return false; // no can do in a child I/O
}

template <Direction DIR>
bool ChildUnformattedIoStatementState<DIR>::Receive(
    char *data, std::size_t bytes, std::size_t elementBytes) {
  return this->child().parent().Receive(data, bytes, elementBytes);
}

template class InternalIoStatementState<Direction::Output>;
template class InternalIoStatementState<Direction::Input>;
template class InternalFormattedIoStatementState<Direction::Output>;
template class InternalFormattedIoStatementState<Direction::Input>;
template class InternalListIoStatementState<Direction::Output>;
template class InternalListIoStatementState<Direction::Input>;
template class ExternalIoStatementState<Direction::Output>;
template class ExternalIoStatementState<Direction::Input>;
template class ExternalFormattedIoStatementState<Direction::Output>;
template class ExternalFormattedIoStatementState<Direction::Input>;
template class ExternalListIoStatementState<Direction::Output>;
template class ExternalListIoStatementState<Direction::Input>;
template class ExternalUnformattedIoStatementState<Direction::Output>;
template class ExternalUnformattedIoStatementState<Direction::Input>;
template class ChildIoStatementState<Direction::Output>;
template class ChildIoStatementState<Direction::Input>;
template class ChildFormattedIoStatementState<Direction::Output>;
template class ChildFormattedIoStatementState<Direction::Input>;
template class ChildListIoStatementState<Direction::Output>;
template class ChildListIoStatementState<Direction::Input>;
template class ChildUnformattedIoStatementState<Direction::Output>;
template class ChildUnformattedIoStatementState<Direction::Input>;

int ExternalMiscIoStatementState::EndIoStatement() {
  ExternalFileUnit &ext{unit()};
  switch (which_) {
  case Flush:
    ext.FlushOutput(*this);
    std::fflush(nullptr); // flushes C stdio output streams (12.9(2))
    break;
  case Backspace:
    ext.BackspaceRecord(*this);
    break;
  case Endfile:
    ext.Endfile(*this);
    break;
  case Rewind:
    ext.Rewind(*this);
    break;
  }
  return ExternalIoStatementBase::EndIoStatement();
}

InquireUnitState::InquireUnitState(
    ExternalFileUnit &unit, const char *sourceFile, int sourceLine)
    : ExternalIoStatementBase{unit, sourceFile, sourceLine} {}

bool InquireUnitState::Inquire(
    InquiryKeywordHash inquiry, char *result, std::size_t length) {
  if (unit().createdForInternalChildIo()) {
    SignalError(IostatInquireInternalUnit,
        "INQUIRE of unit created for defined derived type I/O of an internal "
        "unit");
    return false;
  }
  const char *str{nullptr};
  switch (inquiry) {
  case HashInquiryKeyword("ACCESS"):
    switch (unit().access) {
    case Access::Sequential:
      str = "SEQUENTIAL";
      break;
    case Access::Direct:
      str = "DIRECT";
      break;
    case Access::Stream:
      str = "STREAM";
      break;
    }
    break;
  case HashInquiryKeyword("ACTION"):
    str = unit().mayWrite() ? unit().mayRead() ? "READWRITE" : "WRITE" : "READ";
    break;
  case HashInquiryKeyword("ASYNCHRONOUS"):
    str = unit().mayAsynchronous() ? "YES" : "NO";
    break;
  case HashInquiryKeyword("BLANK"):
    str = unit().isUnformatted.value_or(true)   ? "UNDEFINED"
        : unit().modes.editingFlags & blankZero ? "ZERO"
                                                : "NULL";
    break;
  case HashInquiryKeyword("CARRIAGECONTROL"):
    str = "LIST";
    break;
  case HashInquiryKeyword("CONVERT"):
    str = unit().swapEndianness() ? "SWAP" : "NATIVE";
    break;
  case HashInquiryKeyword("DECIMAL"):
    str = unit().isUnformatted.value_or(true)      ? "UNDEFINED"
        : unit().modes.editingFlags & decimalComma ? "COMMA"
                                                   : "POINT";
    break;
  case HashInquiryKeyword("DELIM"):
    if (unit().isUnformatted.value_or(true)) {
      str = "UNDEFINED";
    } else {
      switch (unit().modes.delim) {
      case '\'':
        str = "APOSTROPHE";
        break;
      case '"':
        str = "QUOTE";
        break;
      default:
        str = "NONE";
        break;
      }
    }
    break;
  case HashInquiryKeyword("DIRECT"):
    str = unit().access == Access::Direct ||
            (unit().mayPosition() && unit().isFixedRecordLength)
        ? "YES"
        : "NO";
    break;
  case HashInquiryKeyword("ENCODING"):
    str = unit().isUnformatted.value_or(true) ? "UNDEFINED"
        : unit().isUTF8                       ? "UTF-8"
                                              : "ASCII";
    break;
  case HashInquiryKeyword("FORM"):
    str = !unit().isUnformatted ? "UNDEFINED"
        : *unit().isUnformatted ? "UNFORMATTED"
                                : "FORMATTED";
    break;
  case HashInquiryKeyword("FORMATTED"):
    str = !unit().isUnformatted ? "UNKNOWN"
        : *unit().isUnformatted ? "NO"
                                : "YES";
    break;
  case HashInquiryKeyword("NAME"):
    str = unit().path();
    if (!str) {
      return true; // result is undefined
    }
    break;
  case HashInquiryKeyword("PAD"):
    str = unit().isUnformatted.value_or(true) ? "UNDEFINED"
        : unit().modes.pad                    ? "YES"
                                              : "NO";
    break;
  case HashInquiryKeyword("POSITION"):
    if (unit().access == Access::Direct) {
      str = "UNDEFINED";
    } else {
      auto size{unit().knownSize()};
      auto pos{unit().position()};
      if (pos == size.value_or(pos + 1)) {
        str = "APPEND";
      } else if (pos == 0) {
        str = "REWIND";
      } else {
        str = "ASIS"; // processor-dependent & no common behavior
      }
    }
    break;
  case HashInquiryKeyword("READ"):
    str = unit().mayRead() ? "YES" : "NO";
    break;
  case HashInquiryKeyword("READWRITE"):
    str = unit().mayRead() && unit().mayWrite() ? "YES" : "NO";
    break;
  case HashInquiryKeyword("ROUND"):
    if (unit().isUnformatted.value_or(true)) {
      str = "UNDEFINED";
    } else {
      switch (unit().modes.round) {
      case decimal::FortranRounding::RoundNearest:
        str = "NEAREST";
        break;
      case decimal::FortranRounding::RoundUp:
        str = "UP";
        break;
      case decimal::FortranRounding::RoundDown:
        str = "DOWN";
        break;
      case decimal::FortranRounding::RoundToZero:
        str = "ZERO";
        break;
      case decimal::FortranRounding::RoundCompatible:
        str = "COMPATIBLE";
        break;
      }
    }
    break;
  case HashInquiryKeyword("SEQUENTIAL"):
    // "NO" for Direct, since Sequential would not work if
    // the unit were reopened without RECL=.
    str = unit().access == Access::Sequential ? "YES" : "NO";
    break;
  case HashInquiryKeyword("SIGN"):
    str = unit().isUnformatted.value_or(true)  ? "UNDEFINED"
        : unit().modes.editingFlags & signPlus ? "PLUS"
                                               : "SUPPRESS";
    break;
  case HashInquiryKeyword("STREAM"):
    str = unit().access == Access::Stream ? "YES" : "NO";
    break;
  case HashInquiryKeyword("WRITE"):
    str = unit().mayWrite() ? "YES" : "NO";
    break;
  case HashInquiryKeyword("UNFORMATTED"):
    str = !unit().isUnformatted ? "UNKNOWN"
        : *unit().isUnformatted ? "YES"
                                : "NO";
    break;
  }
  if (str) {
    ToFortranDefaultCharacter(result, length, str);
    return true;
  } else {
    BadInquiryKeywordHashCrash(inquiry);
    return false;
  }
}

bool InquireUnitState::Inquire(InquiryKeywordHash inquiry, bool &result) {
  switch (inquiry) {
  case HashInquiryKeyword("EXIST"):
    result = true;
    return true;
  case HashInquiryKeyword("NAMED"):
    result = unit().path() != nullptr;
    return true;
  case HashInquiryKeyword("OPENED"):
    result = true;
    return true;
  case HashInquiryKeyword("PENDING"):
    result = false; // asynchronous I/O is not implemented
    return true;
  default:
    BadInquiryKeywordHashCrash(inquiry);
    return false;
  }
}

bool InquireUnitState::Inquire(
    InquiryKeywordHash inquiry, std::int64_t, bool &result) {
  switch (inquiry) {
  case HashInquiryKeyword("PENDING"):
    result = false; // asynchronous I/O is not implemented
    return true;
  default:
    BadInquiryKeywordHashCrash(inquiry);
    return false;
  }
}

bool InquireUnitState::Inquire(
    InquiryKeywordHash inquiry, std::int64_t &result) {
  switch (inquiry) {
  case HashInquiryKeyword("NEXTREC"):
    if (unit().access == Access::Direct) {
      result = unit().currentRecordNumber;
    }
    return true;
  case HashInquiryKeyword("NUMBER"):
    result = unit().unitNumber();
    return true;
  case HashInquiryKeyword("POS"):
    result = unit().position();
    return true;
  case HashInquiryKeyword("RECL"):
    if (unit().access == Access::Stream) {
      result = -2;
    } else if (unit().isFixedRecordLength && unit().recordLength) {
      result = *unit().recordLength;
    } else {
      result = std::numeric_limits<std::uint32_t>::max();
    }
    return true;
  case HashInquiryKeyword("SIZE"):
    if (auto size{unit().knownSize()}) {
      result = *size;
    } else {
      result = -1;
    }
    return true;
  default:
    BadInquiryKeywordHashCrash(inquiry);
    return false;
  }
}

InquireNoUnitState::InquireNoUnitState(const char *sourceFile, int sourceLine)
    : NoUnitIoStatementState{sourceFile, sourceLine, *this} {}

bool InquireNoUnitState::Inquire(
    InquiryKeywordHash inquiry, char *result, std::size_t length) {
  switch (inquiry) {
  case HashInquiryKeyword("ACCESS"):
  case HashInquiryKeyword("ACTION"):
  case HashInquiryKeyword("ASYNCHRONOUS"):
  case HashInquiryKeyword("BLANK"):
  case HashInquiryKeyword("CARRIAGECONTROL"):
  case HashInquiryKeyword("CONVERT"):
  case HashInquiryKeyword("DECIMAL"):
  case HashInquiryKeyword("DELIM"):
  case HashInquiryKeyword("FORM"):
  case HashInquiryKeyword("NAME"):
  case HashInquiryKeyword("PAD"):
  case HashInquiryKeyword("POSITION"):
  case HashInquiryKeyword("ROUND"):
  case HashInquiryKeyword("SIGN"):
    ToFortranDefaultCharacter(result, length, "UNDEFINED");
    return true;
  case HashInquiryKeyword("DIRECT"):
  case HashInquiryKeyword("ENCODING"):
  case HashInquiryKeyword("FORMATTED"):
  case HashInquiryKeyword("READ"):
  case HashInquiryKeyword("READWRITE"):
  case HashInquiryKeyword("SEQUENTIAL"):
  case HashInquiryKeyword("STREAM"):
  case HashInquiryKeyword("WRITE"):
  case HashInquiryKeyword("UNFORMATTED"):
    ToFortranDefaultCharacter(result, length, "UNKNONN");
    return true;
  default:
    BadInquiryKeywordHashCrash(inquiry);
    return false;
  }
}

bool InquireNoUnitState::Inquire(InquiryKeywordHash inquiry, bool &result) {
  switch (inquiry) {
  case HashInquiryKeyword("EXIST"):
    result = true;
    return true;
  case HashInquiryKeyword("NAMED"):
  case HashInquiryKeyword("OPENED"):
  case HashInquiryKeyword("PENDING"):
    result = false;
    return true;
  default:
    BadInquiryKeywordHashCrash(inquiry);
    return false;
  }
}

bool InquireNoUnitState::Inquire(
    InquiryKeywordHash inquiry, std::int64_t, bool &result) {
  switch (inquiry) {
  case HashInquiryKeyword("PENDING"):
    result = false;
    return true;
  default:
    BadInquiryKeywordHashCrash(inquiry);
    return false;
  }
}

bool InquireNoUnitState::Inquire(
    InquiryKeywordHash inquiry, std::int64_t &result) {
  switch (inquiry) {
  case HashInquiryKeyword("NEXTREC"):
  case HashInquiryKeyword("NUMBER"):
  case HashInquiryKeyword("POS"):
  case HashInquiryKeyword("RECL"):
  case HashInquiryKeyword("SIZE"):
    result = -1;
    return true;
  default:
    BadInquiryKeywordHashCrash(inquiry);
    return false;
  }
}

InquireUnconnectedFileState::InquireUnconnectedFileState(
    OwningPtr<char> &&path, const char *sourceFile, int sourceLine)
    : NoUnitIoStatementState{sourceFile, sourceLine, *this}, path_{std::move(
                                                                 path)} {}

bool InquireUnconnectedFileState::Inquire(
    InquiryKeywordHash inquiry, char *result, std::size_t length) {
  const char *str{nullptr};
  switch (inquiry) {
  case HashInquiryKeyword("ACCESS"):
  case HashInquiryKeyword("ACTION"):
  case HashInquiryKeyword("ASYNCHRONOUS"):
  case HashInquiryKeyword("BLANK"):
  case HashInquiryKeyword("CARRIAGECONTROL"):
  case HashInquiryKeyword("CONVERT"):
  case HashInquiryKeyword("DECIMAL"):
  case HashInquiryKeyword("DELIM"):
  case HashInquiryKeyword("FORM"):
  case HashInquiryKeyword("PAD"):
  case HashInquiryKeyword("POSITION"):
  case HashInquiryKeyword("ROUND"):
  case HashInquiryKeyword("SIGN"):
    str = "UNDEFINED";
    break;
  case HashInquiryKeyword("DIRECT"):
  case HashInquiryKeyword("ENCODING"):
  case HashInquiryKeyword("FORMATTED"):
  case HashInquiryKeyword("SEQUENTIAL"):
  case HashInquiryKeyword("STREAM"):
  case HashInquiryKeyword("UNFORMATTED"):
    str = "UNKNONN";
    break;
  case HashInquiryKeyword("READ"):
    str = MayRead(path_.get()) ? "YES" : "NO";
    break;
  case HashInquiryKeyword("READWRITE"):
    str = MayReadAndWrite(path_.get()) ? "YES" : "NO";
    break;
  case HashInquiryKeyword("WRITE"):
    str = MayWrite(path_.get()) ? "YES" : "NO";
    break;
  case HashInquiryKeyword("NAME"):
    str = path_.get();
    return true;
  }
  if (str) {
    ToFortranDefaultCharacter(result, length, str);
    return true;
  } else {
    BadInquiryKeywordHashCrash(inquiry);
    return false;
  }
}

bool InquireUnconnectedFileState::Inquire(
    InquiryKeywordHash inquiry, bool &result) {
  switch (inquiry) {
  case HashInquiryKeyword("EXIST"):
    result = IsExtant(path_.get());
    return true;
  case HashInquiryKeyword("NAMED"):
    result = true;
    return true;
  case HashInquiryKeyword("OPENED"):
    result = false;
    return true;
  case HashInquiryKeyword("PENDING"):
    result = false;
    return true;
  default:
    BadInquiryKeywordHashCrash(inquiry);
    return false;
  }
}

bool InquireUnconnectedFileState::Inquire(
    InquiryKeywordHash inquiry, std::int64_t, bool &result) {
  switch (inquiry) {
  case HashInquiryKeyword("PENDING"):
    result = false;
    return true;
  default:
    BadInquiryKeywordHashCrash(inquiry);
    return false;
  }
}

bool InquireUnconnectedFileState::Inquire(
    InquiryKeywordHash inquiry, std::int64_t &result) {
  switch (inquiry) {
  case HashInquiryKeyword("NEXTREC"):
  case HashInquiryKeyword("NUMBER"):
  case HashInquiryKeyword("POS"):
  case HashInquiryKeyword("RECL"):
  case HashInquiryKeyword("SIZE"):
    result = -1;
    return true;
  default:
    BadInquiryKeywordHashCrash(inquiry);
    return false;
  }
}

InquireIOLengthState::InquireIOLengthState(
    const char *sourceFile, int sourceLine)
    : NoUnitIoStatementState{sourceFile, sourceLine, *this} {}

} // namespace Fortran::runtime::io