/* Copyright(C) 2011 Brazil

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License version 2.1 as published by the Free Software Foundation.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include "key-cursor.hpp"

#include <algorithm>
#include <cstring>

#include "trie.hpp"

namespace grn {
namespace dat {

KeyCursor::KeyCursor()
    : trie_(NULL),
      offset_(0),
      limit_(MAX_UINT32),
      flags_(KEY_RANGE_CURSOR),
      buf_(),
      count_(0),
      max_count_(0),
      finished_(false),
      end_buf_(NULL),
      end_str_() {}

KeyCursor::~KeyCursor() {
  if (end_buf_ != NULL) {
    delete [] end_buf_;
  }
}

void KeyCursor::open(const Trie &trie,
                     const String &min_str,
                     const String &max_str,
                     UInt32 offset,
                     UInt32 limit,
                     UInt32 flags) {
  GRN_DAT_THROW_IF(PARAM_ERROR,
                   (min_str.ptr() == NULL) && (min_str.length() != 0));
  GRN_DAT_THROW_IF(PARAM_ERROR,
                   (max_str.ptr() == NULL) && (max_str.length() != 0));

  flags = fix_flags(flags);
  KeyCursor new_cursor(trie, offset, limit, flags);
  new_cursor.init(min_str, max_str);
  new_cursor.swap(this);
}

void KeyCursor::close() {
  KeyCursor new_cursor;
  new_cursor.swap(this);
}

const Key &KeyCursor::next() {
  if (finished_ || (count_ >= max_count_)) {
    return Key::invalid_key();
  }

  if ((flags_ & ASCENDING_CURSOR) == ASCENDING_CURSOR) {
    return ascending_next();
  } else {
    return descending_next();
  }
}

KeyCursor::KeyCursor(const Trie &trie,
                     UInt32 offset, UInt32 limit, UInt32 flags)
    : trie_(&trie),
      offset_(offset),
      limit_(limit),
      flags_(flags),
      buf_(),
      count_(0),
      max_count_(0),
      finished_(false),
      end_buf_(NULL),
      end_str_() {}

UInt32 KeyCursor::fix_flags(UInt32 flags) const {
  const UInt32 cursor_type = flags & CURSOR_TYPE_MASK;
  GRN_DAT_THROW_IF(PARAM_ERROR, (cursor_type != 0) &&
                                (cursor_type != KEY_RANGE_CURSOR));
  flags |= KEY_RANGE_CURSOR;

  const UInt32 cursor_order = flags & CURSOR_ORDER_MASK;
  GRN_DAT_THROW_IF(PARAM_ERROR, (cursor_order != 0) &&
                                (cursor_order != ASCENDING_CURSOR) &&
                                (cursor_order != DESCENDING_CURSOR));
  if (cursor_order == 0) {
    flags |= ASCENDING_CURSOR;
  }

  const UInt32 cursor_options = flags & CURSOR_OPTIONS_MASK;
  GRN_DAT_THROW_IF(PARAM_ERROR,
      cursor_options & ~(EXCEPT_LOWER_BOUND | EXCEPT_UPPER_BOUND));

  return flags;
}

void KeyCursor::init(const String &min_str, const String &max_str) {
  if (offset_ > (MAX_UINT32 - limit_)) {
    max_count_ = MAX_UINT32;
  } else {
    max_count_ = offset_ + limit_;
  }

  if (limit_ == 0) {
    return;
  }

  if ((flags_ & ASCENDING_CURSOR) == ASCENDING_CURSOR) {
    ascending_init(min_str, max_str);
  } else {
    descending_init(min_str, max_str);
  }
}

void KeyCursor::ascending_init(const String &min_str, const String &max_str) {
  if (max_str.ptr() != NULL) {
    if (max_str.length() != 0) {
      end_buf_ = new UInt8[max_str.length()];
      grn_memcpy(end_buf_, max_str.ptr(), max_str.length());
      end_str_.assign(end_buf_, max_str.length());
    }
  }

  if ((min_str.ptr() == NULL) || (min_str.length() == 0)) {
    buf_.push_back(ROOT_NODE_ID);
    return;
  }

  UInt32 node_id = ROOT_NODE_ID;
  Node node;
  for (UInt32 i = 0; i < min_str.length(); ++i) {
    node = trie_->ith_node(node_id);
    if (node.is_linker()) {
      const Key &key = trie_->get_key(node.key_pos());
      const int result = key.str().compare(min_str, i);
      if ((result > 0) || ((result == 0) &&
          ((flags_ & EXCEPT_LOWER_BOUND) != EXCEPT_LOWER_BOUND))) {
        buf_.push_back(node_id);
      } else if (node.sibling() != INVALID_LABEL) {
        buf_.push_back(node_id ^ node.label() ^ node.sibling());
      }
      return;
    } else if (node.sibling() != INVALID_LABEL) {
      buf_.push_back(node_id ^ node.label() ^ node.sibling());
    }

    node_id = node.offset() ^ min_str[i];
    if (trie_->ith_node(node_id).label() != min_str[i]) {
      UInt16 label = node.child();
      if (label == TERMINAL_LABEL) {
        label = trie_->ith_node(node.offset() ^ label).sibling();
      }
      while (label != INVALID_LABEL) {
        if (label > min_str[i]) {
          buf_.push_back(node.offset() ^ label);
          break;
        }
        label = trie_->ith_node(node.offset() ^ label).sibling();
      }
      return;
    }
  }

  node = trie_->ith_node(node_id);
  if (node.is_linker()) {
    const Key &key = trie_->get_key(node.key_pos());
    if ((key.length() != min_str.length()) ||
        ((flags_ & EXCEPT_LOWER_BOUND) != EXCEPT_LOWER_BOUND)) {
      buf_.push_back(node_id);
    } else if (node.sibling() != INVALID_LABEL) {
      buf_.push_back(node_id ^ node.label() ^ node.sibling());
    }
    return;
  } else if (node.sibling() != INVALID_LABEL) {
    buf_.push_back(node_id ^ node.label() ^ node.sibling());
  }

  UInt16 label = node.child();
  if ((label == TERMINAL_LABEL) &&
      ((flags_ & EXCEPT_LOWER_BOUND) == EXCEPT_LOWER_BOUND)) {
    label = trie_->ith_node(node.offset() ^ label).sibling();
  }
  if (label != INVALID_LABEL) {
    buf_.push_back(node.offset() ^ label);
  }
}

void KeyCursor::descending_init(const String &min_str, const String &max_str) {
  if (min_str.ptr() != NULL) {
    if (min_str.length() != 0) {
      end_buf_ = new UInt8[min_str.length()];
      grn_memcpy(end_buf_, min_str.ptr(), min_str.length());
      end_str_.assign(end_buf_, min_str.length());
    }
  }

  if ((max_str.ptr() == NULL) || (max_str.length() == 0)) {
    buf_.push_back(ROOT_NODE_ID);
    return;
  }

  UInt32 node_id = ROOT_NODE_ID;
  for (UInt32 i = 0; i < max_str.length(); ++i) {
    const Base base = trie_->ith_node(node_id).base();
    if (base.is_linker()) {
      const Key &key = trie_->get_key(base.key_pos());
      const int result = key.str().compare(max_str, i);
      if ((result < 0) || ((result == 0) &&
          ((flags_ & EXCEPT_UPPER_BOUND) != EXCEPT_UPPER_BOUND))) {
        buf_.push_back(node_id | POST_ORDER_FLAG);
      }
      return;
    }

    UInt32 label = trie_->ith_node(node_id).child();
    if (label == TERMINAL_LABEL) {
      node_id = base.offset() ^ label;
      buf_.push_back(node_id | POST_ORDER_FLAG);
      label = trie_->ith_node(node_id).sibling();
    }
    while (label != INVALID_LABEL) {
      node_id = base.offset() ^ label;
      if (label < max_str[i]) {
        buf_.push_back(node_id);
      } else if (label > max_str[i]) {
        return;
      } else {
        break;
      }
      label = trie_->ith_node(node_id).sibling();
    }
    if (label == INVALID_LABEL) {
      return;
    }
  }

  const Base base = trie_->ith_node(node_id).base();
  if (base.is_linker()) {
    const Key &key = trie_->get_key(base.key_pos());
    if ((key.length() == max_str.length()) &&
        ((flags_ & EXCEPT_UPPER_BOUND) != EXCEPT_UPPER_BOUND)) {
      buf_.push_back(node_id | POST_ORDER_FLAG);
    }
    return;
  }

  UInt16 label = trie_->ith_node(node_id).child();
  if ((label == TERMINAL_LABEL) &&
      ((flags_ & EXCEPT_UPPER_BOUND) != EXCEPT_UPPER_BOUND)) {
    buf_.push_back((base.offset() ^ label) | POST_ORDER_FLAG);
  }
}

void KeyCursor::swap(KeyCursor *cursor) {
  std::swap(trie_, cursor->trie_);
  std::swap(offset_, cursor->offset_);
  std::swap(limit_, cursor->limit_);
  std::swap(flags_, cursor->flags_);
  buf_.swap(&cursor->buf_);
  std::swap(count_, cursor->count_);
  std::swap(max_count_, cursor->max_count_);
  std::swap(finished_, cursor->finished_);
  std::swap(end_buf_, cursor->end_buf_);
  end_str_.swap(&cursor->end_str_);
}

const Key &KeyCursor::ascending_next() {
  while (!buf_.empty()) {
    const UInt32 node_id = buf_.back();
    buf_.pop_back();

    const Node node = trie_->ith_node(node_id);
    if (node.sibling() != INVALID_LABEL) {
      buf_.push_back(node_id ^ node.label() ^ node.sibling());
    }

    if (node.is_linker()) {
      const Key &key = trie_->get_key(node.key_pos());
      if (end_buf_ != NULL) {
        const int result = key.str().compare(end_str_);
        if ((result > 0) || ((result == 0) &&
            ((flags_ & EXCEPT_UPPER_BOUND) == EXCEPT_UPPER_BOUND))) {
          finished_ = true;
          return Key::invalid_key();
        }
      }
      if (count_++ >= offset_) {
        return key;
      }
    } else if (node.child() != INVALID_LABEL) {
      buf_.push_back(node.offset() ^ node.child());
    }
  }
  return Key::invalid_key();
}

const Key &KeyCursor::descending_next() {
  while (!buf_.empty()) {
    const bool post_order = (buf_.back() & POST_ORDER_FLAG) == POST_ORDER_FLAG;
    const UInt32 node_id = buf_.back() & ~POST_ORDER_FLAG;

    const Base base = trie_->ith_node(node_id).base();
    if (post_order) {
      buf_.pop_back();
      if (base.is_linker()) {
        const Key &key = trie_->get_key(base.key_pos());
        if (end_buf_ != NULL) {
          const int result = key.str().compare(end_str_);
          if ((result < 0) || ((result == 0) &&
              ((flags_ & EXCEPT_LOWER_BOUND) == EXCEPT_LOWER_BOUND))) {
            finished_ = true;
            return Key::invalid_key();
          }
        }
        if (count_++ >= offset_) {
          return key;
        }
      }
    } else {
      buf_.back() |= POST_ORDER_FLAG;
      UInt16 label = trie_->ith_node(node_id).child();
      while (label != INVALID_LABEL) {
        buf_.push_back(base.offset() ^ label);
        label = trie_->ith_node(base.offset() ^ label).sibling();
      }
    }
  }
  return Key::invalid_key();
}

}  // namespace dat
}  // namespace grn
