//===-- rosa/support/csv/CSVReader.hpp --------------------------*- C++ -*-===//
//
//                                 The RoSA Framework
//
//===----------------------------------------------------------------------===//
///
/// \file rosa/support/csv/CSVReader.hpp
///
/// \author David Juhasz (david.juhasz@tuwien.ac.at)
///
/// \date 2017-2019
///
/// \brief Facitilities to read CSV files.
///
/// \note The implementation is based on the solution at
/// https://stackoverflow.com/a/1120224
///
//===----------------------------------------------------------------------===//

#ifndef ROSA_SUPPORT_CSV_CSVREADER_HPP
#define ROSA_SUPPORT_CSV_CSVREADER_HPP

#include "rosa/support/debug.hpp"

#include <istream>
#include <sstream>
#include <vector>

namespace rosa {
namespace csv {

/// Anonymous namespace providing implementation details for
/// \c rosa::csv::CSVIterator, consider it private.
namespace {

/// Provides facility for parsing values from one row CSV data.
///
/// \tparam T type of values to parse from the line
/// \tparam IsSignedInt if \p T is a signed integral type, always use default
/// \tparam IsUnsignedInt if \p T is an unsigned integral type, always use
/// default
/// \tparam IsFloat if \p T is a floating-point type, always use default
/// \tparam IsString if \p T is \c std::string, always use default
///
/// \note Specializations of this `struct` are provided for arithmentic types
/// and \c std::string.
template <typename T, bool IsSignedInt = (std::is_integral<T>::value &&
                                          std::is_signed<T>::value),
          bool IsUnsignedInt =
              (std::is_integral<T>::value && std::is_unsigned<T>::value),
          bool IsFloat = std::is_floating_point<T>::value,
          bool IsString = std::is_same<T, std::string>::value>
struct CSVRowParser;

/// Specialization for signed integral types.
///
/// \tparam T type of values to parse from the line
///
/// \pre \p T is a signed integral type:\code
/// std::is_integral<T>::value && std::is_signed<T>::value
/// \endcode
template <typename T> struct CSVRowParser<T, true, false, false, false> {
  STATIC_ASSERT((std::is_integral<T>::value && std::is_signed<T>::value),
                "wrong type"); // Sanity check.

  /// Parses a given row of CSV data into a given container.
  ///
  /// \p Data is cleared and then filled with values parsed from \p LineStream.
  /// Entries in the line are to be separated by commas, the character `,`. A
  /// trailing comma results in an empty entry at the end of the line. No empty
  /// entry should be present otherwise.
  ///
  /// \note Parsed values are silently converted to type \p T.
  ///
  /// \param [in,out] LineStream the line to parse
  /// \param [in,out] Data the container to store the parsed values
  static void parse(std::stringstream &LineStream, std::vector<T> &Data) {
    std::string Cell;
    Data.clear();
    while (std::getline(LineStream, Cell, ',')) {
      Data.push_back(static_cast<T>(std::stoll(Cell)));
    }
    // This checks for a trailing comma with no data after it.
    if (!LineStream && Cell.empty()) {
      // If there was a trailing comma then add an empty element.
      Data.push_back(0);
    }
  }
};

/// Specialization for unsigned integral types.
///
/// \tparam T type of values to parse from the line
///
/// \pre \p T is an unsigned integral type:\code
/// std::is_integral<T>::value && std::is_unsigned<T>::value
/// \endcode
template <typename T> struct CSVRowParser<T, false, true, false, false> {
  STATIC_ASSERT((std::is_integral<T>::value && std::is_unsigned<T>::value),
                "wrong type"); // Sanity check.

  /// Parses a given row of CSV data into a given container.
  ///
  /// \p Data is cleared and then filled with values parsed from \p LineStream.
  /// Entries in the line are to be separated by commas, the character `,`. A
  /// trailing comma results in an empty entry at the end of the line. No empty
  /// entry should be present otherwise.
  ///
  /// \note Parsed values are silently converted to type \p T.
  ///
  /// \param [in,out] LineStream the line to parse
  /// \param [in,out] Data the container to store the parsed values
  static void parse(std::stringstream &LineStream, std::vector<T> &Data) {
    std::string Cell;
    Data.clear();
    while (std::getline(LineStream, Cell, ',')) {
      Data.push_back(static_cast<T>(std::stoull(Cell)));
    }
    // This checks for a trailing comma with no data after it.
    if (!LineStream && Cell.empty()) {
      // If there was a trailing comma then add an empty element.
      Data.push_back(0);
    }
  }
};

/// Specialization for floating-point types.
///
/// \tparam T type of values to parse from the line
///
/// \pre \p T is a floating-point type:\code
/// std::is_floating_point<T>::value
/// \endcode
template <typename T> struct CSVRowParser<T, false, false, true, false> {
  STATIC_ASSERT((std::is_floating_point<T>::value),
                "wrong type"); // Sanity check.

  /// Parses a given row of CSV data into a given container.
  ///
  /// \p Data is cleared and then filled with values parsed from \p LineStream.
  /// Entries in the line are to be separated by commas, the character `,`. A
  /// trailing comma results in an empty entry at the end of the line. No empty
  /// entry should be present otherwise.
  ///
  /// \note Parsed values are silently converted to type \p T.
  ///
  /// \param [in,out] LineStream the line to parse
  /// \param [in,out] Data the container to store the parsed values
  static void parse(std::stringstream &LineStream, std::vector<T> &Data) {
    std::string Cell;
    Data.clear();
    while (std::getline(LineStream, Cell, ',')) {
      Data.push_back(static_cast<T>(std::stold(Cell)));
    }
    // This checks for a trailing comma with no data after it.
    if (!LineStream && Cell.empty()) {
      // If there was a trailing comma then add an empty element.
      Data.push_back(0);
    }
  }
};

/// Specialization for \c std::string.
///
/// \tparam T type of values to parse from the line
///
/// \pre \p T is \c std::string:\code
/// std::is_same<T, std::string>::value
/// \endcode
template <typename T> struct CSVRowParser<T, false, false, false, true> {
  STATIC_ASSERT((std::is_same<T, std::string>::value),
                "wrong type"); // Sanity check.

  /// Parses a given row of CSV data into a given container.
  ///
  /// \p Data is cleared and then filled with values parsed from \p LineStream.
  /// Entries in the line are to be separated by commas, the character `,`. A
  /// trailing comma results in an empty entry at the end of the line. No empty
  /// entry should be present otherwise.
  ///
  /// \param [in,out] LineStream the line to parse
  /// \param [in,out] Data the container to store the parsed values
  static void parse(std::stringstream &LineStream, std::vector<T> &Data) {
    std::string Cell;
    Data.clear();
    while (std::getline(LineStream, Cell, ',')) {
      Data.push_back(Cell);
    }
    // This checks for a trailing comma with no data after it.
    if (!LineStream && Cell.empty()) {
      // If there was a trailing comma then add an empty element.
      Data.push_back("");
    }
  }
};

/// Parses and stores entries from a row of CSV data.
///
/// \tparam T type of values to parse and store, i.e. entries in the row
///
/// \note The implementation relies on \c rosa::csv::CSVRowParser, which is
/// implemented only for `arithmetic` types -- signed and unsigned integral and
/// floating-point types -- and for \c std::string. Those are the valid values
/// for \p T.
template <typename T>
class CSVRow {
public:
  /// Gives a constant reference for an entry at a given position of the row.
  ///
  /// \note No bounds checking is performed.
  ///
  /// \param Index the position of the entry
  ///
  /// \return constant reference for the stored entry at position \p Index
  const T &operator[](const size_t Index) const noexcept { return Data[Index]; }

  /// Tells the number of entries stored in the row.
  ///
  /// \return number of stored entries.
  size_t size(void) const noexcept { return Data.size(); }

  /// Parses and stores one row of CSV data.
  ///
  /// The function reads one line from \p Str and parses it into
  /// \c rosa::csv::CSVRow::Data using \c rosa::csv::CSVRowParser.
  ///
  /// \param [in,out] Str input stream of a CSV file
  void readNextRow(std::istream &Str) {
    std::string Line;
    std::getline(Str, Line);
    std::stringstream LineStream(Line);
    CSVRowParser<T>::parse(LineStream, Data);
  }

private:
  std::vector<T> Data; ///< Stores parsed entries
};

/// Reads a row of CSV data into \c rosa::csv::CSVRow.
///
/// The next line is read from \p Str by calling
/// \c rosa::csv::CSVRow::readNextRow on \p Data.
///
/// \note A CSV file should contain no empty lines.
///
/// \param [in,out] Str input stream of a CSV file
/// \param [in,out] Data object to read the next line into
///
/// \return \p Str after reading one line from it
template <typename T>
std::istream &operator>>(std::istream &Str, CSVRow<T> &Data) {
  Data.readNextRow(Str);
  return Str;
}

} // End namespace

/// Provides `InputIterator` features for iterating over a CSV file in a
/// flat way.
///
/// The iterator hides rows of the CSV file, and iterates over the entries
/// row-by-row.
///
/// \note A CSV file should contain no empty lines.
///
/// \tparam T type of values to iterate over, i.e. entries in the CSV file.
///
/// \note The implementation relies on \c rosa::csv::CSVRow, which in turn
/// relies on \c rosa::csv::CSVRowParser, which is implemented only for
/// `arithmetic` types -- signed and unsigned integral types and floating-point
/// types -- and for \c std::string. Those are the valid values for \p T.
template <typename T>
class CSVFlatIterator {
public:
  /// \defgroup CSVFlatIteratorTypedefs Typedefs of rosa::csv::CSVFlatIterator
  ///
  /// Standard `typedef`s for iterators.
  ///
  ///@{
  typedef std::input_iterator_tag
      iterator_category;               ///< Category of the iterator.
  typedef T value_type;                ///< Type of values iterated over.
  typedef std::size_t difference_type; ///< Type to identify distance.
  typedef T *pointer;                  ///< Pointer to the type iterated over.
  typedef T &reference;                ///< Reference to the type iterated over.
  ///@}

  /// Creates a new instance.
  ///
  /// \param [in,out] S input stream to iterate over
  CSVFlatIterator(std::istream &S)
      : Str(S.good() ? &S : nullptr), Pos((size_t)(-1)) {
    // \c rosa::csv::CSVFlatIterator::Pos is initialized to `-1` so the first
    // incrementation here will set it properly.
    ++(*this);
  }

  /// Creates an empty new instance.
  CSVFlatIterator(void) noexcept : Str(nullptr) {}

  /// Pre-increment operator.
  ///
  /// The implementation moves over the entries in the current row and advances
  /// to the next row when the end of the current row is reached. If the end of
  /// the input stream is reached, the operator becomes empty and has no
  /// further effect.
  ///
  /// \return \p this object after incrementing it.
  CSVFlatIterator &operator++() {
    if (Str) {
      ++Pos;
      if (Pos == Row.size()) {
        if (!((*Str) >> Row)) {
          Str = nullptr;
          --Pos; // Stay on the last entry forever.
        } else {
          Pos = 0;
        }
      }
    }
    return *this;
  }

  /// Post-increment operator.
  ///
  /// The implementation uses the pre-increment operator and returns a copy of
  /// the original state of \p this object.
  ///
  /// \return \p this object before incrementing it.
  CSVFlatIterator operator++(int) {
    CSVFlatIterator Tmp(*this);
    ++(*this);
    return Tmp;
  }

  /// Returns a constant reference to the current entry.
  ///
  /// \note Should not dereference the iterator when it is empty.
  ///
  /// \return constant reference to the current entry.
  const T &operator*(void)const noexcept { return Row[Pos]; }

  /// Returns a constant pointer to the current entry.
  ///
  /// \note Should not dereference the iterator when it is empty.
  ///
  /// \return constant pointer to the current entry.
  const T *operator->(void)const noexcept { return &Row[Pos]; }

  /// Tells if \p this object is equal to another one.
  ///
  /// Two \c rosa::csv::CSVReader instances are equal if and only if they are
  /// the same or both are empty.
  ///
  /// \param RHS other object to compare to
  ///
  /// \return whether \p this object is equal with \p RHS
  bool operator==(const CSVFlatIterator &RHS) const noexcept {
    return ((this == &RHS) || ((this->Str == nullptr) && (RHS.Str == nullptr)));
  }

  /// Tells if \p this object is not equal to another one.
  ///
  /// \see rosa::csv::CSVReader::operator==
  ///
  /// \param RHS other object to compare to
  ///
  /// \return whether \p this object is not equal with \p RHS.
  bool operator!=(const CSVFlatIterator &RHS) const noexcept {
    return !((*this) == RHS);
  }

private:
  std::istream *Str; ///< Input stream of a CSV file to iterate over.
  CSVRow<T> Row;     ///< Content of the current row iterating over.
  size_t Pos;        ///< Current position within the current row.
};

} // End namespace csv
} // End namespace rosa

#endif // ROSA_SUPPORT_CSV_CSVREADER_HPP