/** Implementation of libpqxx STL-style cursor classes.
 *
 * These classes wrap SQL cursors in STL-like interfaces.
 *
 * Copyright (c) 2000-2022, Jeroen T. Vermeulen.
 *
 * See COPYING for copyright license.  If you did not receive a file called
 * COPYING with this source code, please notify the distributor of this
 * mistake, or contact the author.
 */
#include "pqxx-source.hxx"

#include <iterator>

#include "pqxx/internal/header-pre.hxx"

#include "pqxx/cursor.hxx"
#include "pqxx/internal/gates/icursor_iterator-icursorstream.hxx"
#include "pqxx/internal/gates/icursorstream-icursor_iterator.hxx"
#include "pqxx/result.hxx"
#include "pqxx/strconv.hxx"
#include "pqxx/transaction.hxx"

#include "pqxx/internal/header-post.hxx"


pqxx::cursor_base::difference_type pqxx::cursor_base::all() noexcept
{
  // Implemented out-of-line so we don't fall afoul of Visual Studio defining
  // min() and max() macros, which turn this expression into malformed code:
  return std::numeric_limits<int>::max() - 1;
}


pqxx::cursor_base::difference_type pqxx::cursor_base::backward_all() noexcept
{
  // Implemented out-of-line so we don't fall afoul of Visual Studio defining
  // min() and max() macros, which turn this expression into malformed code:
  return std::numeric_limits<int>::min() + 1;
}


pqxx::cursor_base::cursor_base(
  connection &context, std::string_view Name, bool embellish_name) :
        m_name{embellish_name ? context.adorn_name(Name) : Name}
{}


pqxx::result::size_type
pqxx::internal::obtain_stateless_cursor_size(sql_cursor &cur)
{
  if (cur.endpos() == -1)
    cur.move(cursor_base::all());
  return result::size_type(cur.endpos() - 1);
}


pqxx::result pqxx::internal::stateless_cursor_retrieve(
  sql_cursor &cur, result::difference_type size,
  result::difference_type begin_pos, result::difference_type end_pos)
{
  if (begin_pos < 0 or begin_pos > size)
    throw range_error{"Starting position out of range"};

  if (end_pos < -1)
    end_pos = -1;
  else if (end_pos > size)
    end_pos = size;

  if (begin_pos == end_pos)
    return cur.empty_result();

  int const direction{((begin_pos < end_pos) ? 1 : -1)};
  cur.move((begin_pos - direction) - (cur.pos() - 1));
  return cur.fetch(end_pos - begin_pos);
}


pqxx::icursorstream::icursorstream(
  transaction_base &context, std::string_view query, std::string_view basename,
  difference_type sstride) :
        m_cur{
          context,
          query,
          basename,
          cursor_base::forward_only,
          cursor_base::read_only,
          cursor_base::owned,
          false},
        m_stride{sstride},
        m_realpos{0},
        m_reqpos{0},
        m_iterators{nullptr},
        m_done{false}
{
  set_stride(sstride);
}


pqxx::icursorstream::icursorstream(
  transaction_base &context, field const &cname, difference_type sstride,
  cursor_base::ownership_policy op) :
        m_cur{context, cname.c_str(), op},
        m_stride{sstride},
        m_realpos{0},
        m_reqpos{0},
        m_iterators{nullptr},
        m_done{false}
{
  set_stride(sstride);
}


void pqxx::icursorstream::set_stride(difference_type stride) &
{
  if (stride < 1)
    throw argument_error{
      internal::concat("Attempt to set cursor stride to ", stride)};
  m_stride = stride;
}


pqxx::result pqxx::icursorstream::fetchblock()
{
  result const r{m_cur.fetch(m_stride)};
  m_realpos += std::size(r);
  if (std::empty(r))
    m_done = true;
  return r;
}


pqxx::icursorstream &pqxx::icursorstream::ignore(std::streamsize n) &
{
  auto offset{m_cur.move(difference_type(n))};
  m_realpos += offset;
  if (offset < n)
    m_done = true;
  return *this;
}


pqxx::icursorstream::size_type pqxx::icursorstream::forward(size_type n)
{
  m_reqpos += difference_type(n) * m_stride;
  return icursorstream::size_type(m_reqpos);
}


void pqxx::icursorstream::insert_iterator(icursor_iterator *i) noexcept
{
  pqxx::internal::gate::icursor_iterator_icursorstream{*i}.set_next(
    m_iterators);
  if (m_iterators != nullptr)
    pqxx::internal::gate::icursor_iterator_icursorstream{*m_iterators}
      .set_prev(i);
  m_iterators = i;
}


void pqxx::icursorstream::remove_iterator(icursor_iterator *i) const noexcept
{
  pqxx::internal::gate::icursor_iterator_icursorstream igate{*i};
  if (i == m_iterators)
  {
    m_iterators = igate.get_next();
    if (m_iterators != nullptr)
      pqxx::internal::gate::icursor_iterator_icursorstream{*m_iterators}
        .set_prev(nullptr);
  }
  else
  {
    auto prev{igate.get_prev()}, next{igate.get_next()};
    pqxx::internal::gate::icursor_iterator_icursorstream{*prev}.set_next(next);
    if (next != nullptr)
      pqxx::internal::gate::icursor_iterator_icursorstream{*next}.set_prev(
        prev);
  }
  igate.set_prev(nullptr);
  igate.set_next(nullptr);
}


void pqxx::icursorstream::service_iterators(difference_type topos)
{
  if (topos < m_realpos)
    return;

  using todolist = std::multimap<difference_type, icursor_iterator *>;
  todolist todo;
  for (icursor_iterator *i{m_iterators}, *next; i != nullptr; i = next)
  {
    pqxx::internal::gate::icursor_iterator_icursorstream gate{*i};
    auto const ipos{gate.pos()};
    if (ipos >= m_realpos and ipos <= topos)
      todo.insert(todolist::value_type(ipos, i));
    next = gate.get_next();
  }
  auto const todo_end = std::end(todo);
  for (auto i{std::begin(todo)}; i != todo_end;)
  {
    auto const readpos{i->first};
    if (readpos > m_realpos)
      ignore(readpos - m_realpos);
    result const r{fetchblock()};
    for (; i != todo_end and i->first == readpos; ++i)
      pqxx::internal::gate::icursor_iterator_icursorstream{*i->second}.fill(r);
  }
}


pqxx::icursor_iterator::icursor_iterator() noexcept : m_pos{0} {}


pqxx::icursor_iterator::icursor_iterator(istream_type &s) noexcept :
        m_stream{&s},
        m_pos{difference_type(
          pqxx::internal::gate::icursorstream_icursor_iterator(s).forward(0))}
{
  pqxx::internal::gate::icursorstream_icursor_iterator{*m_stream}
    .insert_iterator(this);
}


pqxx::icursor_iterator::icursor_iterator(icursor_iterator const &rhs) noexcept
        :
        m_stream{rhs.m_stream}, m_here{rhs.m_here}, m_pos{rhs.m_pos}
{
  if (m_stream != nullptr)
    pqxx::internal::gate::icursorstream_icursor_iterator{*m_stream}
      .insert_iterator(this);
}


pqxx::icursor_iterator::~icursor_iterator() noexcept
{
  if (m_stream != nullptr)
    pqxx::internal::gate::icursorstream_icursor_iterator{*m_stream}
      .remove_iterator(this);
}


pqxx::icursor_iterator pqxx::icursor_iterator::operator++(int)
{
  icursor_iterator old{*this};
  m_pos = difference_type(
    pqxx::internal::gate::icursorstream_icursor_iterator{*m_stream}.forward());
  m_here.clear();
  return old;
}


pqxx::icursor_iterator &pqxx::icursor_iterator::operator++()
{
  m_pos = difference_type(
    pqxx::internal::gate::icursorstream_icursor_iterator{*m_stream}.forward());
  m_here.clear();
  return *this;
}


pqxx::icursor_iterator &pqxx::icursor_iterator::operator+=(difference_type n)
{
  if (n <= 0)
  {
    PQXX_UNLIKELY
    if (n == 0)
      return *this;
    throw argument_error{"Advancing icursor_iterator by negative offset."};
  }
  PQXX_LIKELY
  m_pos = difference_type(
    pqxx::internal::gate::icursorstream_icursor_iterator{*m_stream}.forward(
      icursorstream::size_type(n)));
  m_here.clear();
  return *this;
}


pqxx::icursor_iterator &
pqxx::icursor_iterator::operator=(icursor_iterator const &rhs) noexcept
{
  if (rhs.m_stream == m_stream)
  {
    PQXX_UNLIKELY
    m_here = rhs.m_here;
    m_pos = rhs.m_pos;
  }
  else
  {
    PQXX_LIKELY
    if (m_stream != nullptr)
      pqxx::internal::gate::icursorstream_icursor_iterator{*m_stream}
        .remove_iterator(this);
    m_here = rhs.m_here;
    m_pos = rhs.m_pos;
    m_stream = rhs.m_stream;
    if (m_stream != nullptr)
      pqxx::internal::gate::icursorstream_icursor_iterator{*m_stream}
        .insert_iterator(this);
  }
  return *this;
}


bool pqxx::icursor_iterator::operator==(icursor_iterator const &rhs) const
{
  if (m_stream == rhs.m_stream)
    return pos() == rhs.pos();
  if (m_stream != nullptr and rhs.m_stream != nullptr)
    return false;
  refresh();
  rhs.refresh();
  return std::empty(m_here) and std::empty(rhs.m_here);
}


bool pqxx::icursor_iterator::operator<(icursor_iterator const &rhs) const
{
  if (m_stream == rhs.m_stream)
    return pos() < rhs.pos();
  refresh();
  rhs.refresh();
  return not std::empty(m_here);
}


void pqxx::icursor_iterator::refresh() const
{
  if (m_stream != nullptr)
    pqxx::internal::gate::icursorstream_icursor_iterator{*m_stream}
      .service_iterators(pos());
}


void pqxx::icursor_iterator::fill(result const &r)
{
  m_here = r;
}