/*
 * Strawberry Music Player
 * This file was part of Clementine.
 * Copyright 2012, David Sansome <me@davidsansome.com>
 *
 * Strawberry is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Strawberry 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Strawberry.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#include "config.h"

#include <QList>
#include <QMap>
#include <QSet>
#include <QChar>
#include <QScopedPointer>
#include <QVariant>
#include <QString>
#include <QtAlgorithms>
#include <QAbstractItemModel>

#include "playlist.h"
#include "playlistfilterparser.h"

class SearchTermComparator {
 public:
  virtual ~SearchTermComparator() {}
  virtual bool Matches(const QString &element) const = 0;
};

// "compares" by checking if the field contains the search term
class DefaultComparator : public SearchTermComparator {
 public:
  explicit DefaultComparator(const QString &value) : search_term_(value) {}
  bool Matches(const QString &element) const override {
    return element.contains(search_term_);
  }
 private:
  QString search_term_;
};

class EqComparator : public SearchTermComparator {
 public:
  explicit EqComparator(const QString &value) : search_term_(value) {}
  bool Matches(const QString &element) const override {
    return search_term_ == element;
  }
 private:
  QString search_term_;
};

class NeComparator : public SearchTermComparator {
 public:
  explicit NeComparator(const QString &value) : search_term_(value) {}
  bool Matches(const QString &element) const override {
    return search_term_ != element;
  }
 private:
  QString search_term_;
};

class LexicalGtComparator : public SearchTermComparator {
 public:
  explicit LexicalGtComparator(const QString &value) : search_term_(value) {}
  bool Matches(const QString &element) const override {
    return element > search_term_;
  }
 private:
  QString search_term_;
};

class LexicalGeComparator : public SearchTermComparator {
 public:
  explicit LexicalGeComparator(const QString &value) : search_term_(value) {}
  bool Matches(const QString &element) const override {
    return element >= search_term_;
  }
 private:
  QString search_term_;
};

class LexicalLtComparator : public SearchTermComparator {
 public:
  explicit LexicalLtComparator(const QString &value) : search_term_(value) {}
  bool Matches(const QString &element) const override {
    return element < search_term_;
  }
 private:
  QString search_term_;
};

class LexicalLeComparator : public SearchTermComparator {
 public:
  explicit LexicalLeComparator(const QString &value) : search_term_(value) {}
  bool Matches(const QString &element) const override {
    return element <= search_term_;
  }
 private:
  QString search_term_;
};

class GtComparator : public SearchTermComparator {
 public:
  explicit GtComparator(int value) : search_term_(value) {}
  bool Matches(const QString &element) const override {
    return element.toInt() > search_term_;
  }
 private:
  int search_term_;
};

class GeComparator : public SearchTermComparator {
 public:
  explicit GeComparator(int value) : search_term_(value) {}
  bool Matches(const QString &element) const override {
    return element.toInt() >= search_term_;
  }
 private:
  int search_term_;
};

class LtComparator : public SearchTermComparator {
 public:
  explicit LtComparator(int value) : search_term_(value) {}
  bool Matches(const QString &element) const override {
    return element.toInt() < search_term_;
  }
 private:
  int search_term_;
};

class LeComparator : public SearchTermComparator {
 public:
  explicit LeComparator(int value) : search_term_(value) {}
  bool Matches(const QString &element) const override {
    return element.toInt() <= search_term_;
  }
 private:
  int search_term_;
};

// The length field of the playlist (entries) contains a song's running time in nano seconds.
// However, We don't really care about nano seconds, just seconds.
// Thus, with this decorator we drop the last 9 digits, if that many are present.
class DropTailComparatorDecorator : public SearchTermComparator {
 public:
  explicit DropTailComparatorDecorator(SearchTermComparator *cmp) : cmp_(cmp) {}

  bool Matches(const QString &element) const override {
    if (element.length() > 9)
      return cmp_->Matches(element.left(element.length() - 9));
    else
      return cmp_->Matches(element);
  }
 private:
  QScopedPointer<SearchTermComparator> cmp_;
};

class RatingComparatorDecorator : public SearchTermComparator {
 public:
  explicit RatingComparatorDecorator(SearchTermComparator *cmp) : cmp_(cmp) {}
  bool Matches(const QString &element) const override {
    return cmp_->Matches(QString::number(static_cast<int>(element.toDouble() * 10.0 + 0.5)));
  }
 private:
  QScopedPointer<SearchTermComparator> cmp_;
};

// filter that applies a SearchTermComparator to all fields of a playlist entry
class FilterTerm : public FilterTree {
 public:
  explicit FilterTerm(SearchTermComparator *comparator, const QList<int> &columns) : cmp_(comparator), columns_(columns) {}

  bool accept(int row, const QModelIndex &parent, const QAbstractItemModel *const model) const override {
    for (int i : columns_) {
      QModelIndex idx(model->index(row, i, parent));
      if (cmp_->Matches(idx.data().toString().toLower())) return true;
    }
    return false;
  }
  FilterType type() override { return Term; }
 private:
  QScopedPointer<SearchTermComparator> cmp_;
  QList<int> columns_;
};

// filter that applies a SearchTermComparator to one specific field of a playlist entry
class FilterColumnTerm : public FilterTree {
 public:
  FilterColumnTerm(int column, SearchTermComparator *comparator) : col(column), cmp_(comparator) {}

  bool accept(int row, const QModelIndex &parent, const QAbstractItemModel *const model) const override {
    QModelIndex idx(model->index(row, col, parent));
    return cmp_->Matches(idx.data().toString().toLower());
  }
  FilterType type() override { return Column; }
 private:
  int col;
  QScopedPointer<SearchTermComparator> cmp_;
};

class NotFilter : public FilterTree {
 public:
  explicit NotFilter(const FilterTree *inv) : child_(inv) {}

  bool accept(int row, const QModelIndex &parent, const QAbstractItemModel *const model) const override {
    return !child_->accept(row, parent, model);
  }
  FilterType type() override { return Not; }
 private:
  QScopedPointer<const FilterTree> child_;
};

class OrFilter : public FilterTree {
 public:
  ~OrFilter() override { qDeleteAll(children_); }
  virtual void add(FilterTree *child) { children_.append(child); }
  bool accept(int row, const QModelIndex &parent, const QAbstractItemModel *const model) const override {
    for (FilterTree *child : children_) {
      if (child->accept(row, parent, model)) return true;
    }
    return false;
  }
  FilterType type() override { return Or; }
 private:
  QList<FilterTree*> children_;
};

class AndFilter : public FilterTree {
 public:
  ~AndFilter() override { qDeleteAll(children_); }
  virtual void add(FilterTree *child) { children_.append(child); }
  bool accept(int row, const QModelIndex &parent, const QAbstractItemModel *const model) const override {
    for (FilterTree *child : children_) {
      if (!child->accept(row, parent, model)) return false;
    }
    return true;
  }
  FilterType type() override { return And; }
 private:
  QList<FilterTree*> children_;
};

FilterParser::FilterParser(const QString &filter, const QMap<QString, int> &columns, const QSet<int> &numerical_cols) : filterstring_(filter), columns_(columns), numerical_columns_(numerical_cols) {}

FilterTree *FilterParser::parse() {
  iter_ = filterstring_.constBegin();
  end_ = filterstring_.constEnd();
  return parseOrGroup();
}

void FilterParser::advance() {
  while (iter_ != end_ && iter_->isSpace()) {
    ++iter_;
  }
}

FilterTree *FilterParser::parseOrGroup() {
  advance();
  if (iter_ == end_) return new NopFilter;

  OrFilter *group = new OrFilter;
  group->add(parseAndGroup());
  advance();
  while (checkOr()) {
    group->add(parseAndGroup());
    advance();
  }
  return group;
}

FilterTree *FilterParser::parseAndGroup() {
  advance();
  if (iter_ == end_) return new NopFilter;

  AndFilter *group = new AndFilter();
  do {
    group->add(parseSearchExpression());
    advance();
    if (iter_ != end_ && *iter_ == QChar(')')) break;
    if (checkOr(false)) {
      break;
    }
    checkAnd();  // if there's no 'AND', we'll add the term anyway...
  }
  while (iter_ != end_);
  return group;
}

bool FilterParser::checkAnd() {
  if (iter_ != end_) {
    if (*iter_ == QChar('A')) {
      buf_ += *iter_;
      ++iter_;
      if (iter_ != end_ && *iter_ == QChar('N')) {
        buf_ += *iter_;
        ++iter_;
        if (iter_ != end_ && *iter_ == QChar('D')) {
          buf_ += *iter_;
          ++iter_;
          if (iter_ != end_ && (iter_->isSpace() || *iter_ == QChar('-') || *iter_ == '(')) {
            advance();
            buf_.clear();
            return true;
          }
        }
      }
    }
  }
  return false;
}

bool FilterParser::checkOr(bool step_over) {
  if (!buf_.isEmpty()) {
    if (buf_ == "OR") {
      if (step_over) {
        buf_.clear();
        advance();
      }
      return true;
    }
  }
  else {
    if (iter_ != end_) {
      if (*iter_ == 'O') {
        buf_ += *iter_;
        ++iter_;
        if (iter_ != end_ && *iter_ == 'R') {
          buf_ += *iter_;
          ++iter_;
          if (iter_ != end_ && (iter_->isSpace() || *iter_ == '-' || *iter_ == '(')) {
            if (step_over) {
              buf_.clear();
              advance();
            }
            return true;
          }
        }
      }
    }
  }
  return false;
}

FilterTree *FilterParser::parseSearchExpression() {
  advance();
  if (iter_ == end_) return new NopFilter;
  if (*iter_ == '(') {
    ++iter_;
    advance();
    FilterTree *tree = parseOrGroup();
    advance();
    if (iter_ != end_) {
      if (*iter_ == ')') {
        ++iter_;
      }
    }
    return tree;
  }
  else if (*iter_ == '-') {
    ++iter_;
    FilterTree *tree = parseSearchExpression();
    if (tree->type() != FilterTree::Nop) return new NotFilter(tree);
    return tree;
  }
  else {
    return parseSearchTerm();
  }
}

FilterTree *FilterParser::parseSearchTerm() {
  QString col;
  QString search;
  QString prefix;
  bool inQuotes = false;
  for (; iter_ != end_; ++iter_) {
    if (inQuotes) {
      if (*iter_ == '"')
        inQuotes = false;
      else
        buf_ += *iter_;
    }
    else {
      if (*iter_ == '"') {
        inQuotes = true;
      }
      else if (col.isEmpty() && *iter_ == ':') {
        col = buf_.toLower();
        buf_.clear();
        prefix.clear();  // prefix isn't allowed here - let's ignore it
      }
      else if (iter_->isSpace() || *iter_ == '(' || *iter_ == ')' || *iter_ == '-') {
        break;
      }
      else if (buf_.isEmpty()) {
        // we don't know whether there is a column part in this search term thus we assume the latter and just try and read a prefix
        if (prefix.isEmpty() && (*iter_ == '>' || *iter_ == '<' || *iter_ == '=' || *iter_ == '!')) {
          prefix += *iter_;
        }
        else if (prefix != "=" && *iter_ == '=') {
          prefix += *iter_;
        }
        else {
          buf_ += *iter_;
        }
      }
      else {
        buf_ += *iter_;
      }
    }
  }

  search = buf_.toLower();
  buf_.clear();

  return createSearchTermTreeNode(col, prefix, search);
}

FilterTree *FilterParser::createSearchTermTreeNode(const QString &col, const QString &prefix, const QString &search) const {

  if (search.isEmpty() && prefix != "=") {
    return new NopFilter;
  }
  // here comes a mess :/
  // well, not that much of a mess, but so many options -_-
  SearchTermComparator *cmp = nullptr;
  if (prefix == "!=" || prefix == "<>") {
    cmp = new NeComparator(search);
  }
  else if (!col.isEmpty() && columns_.contains(col) && numerical_columns_.contains(columns_[col])) {
    // the length column contains the time in seconds (nano seconds, actually - the "nano" part is handled by the DropTailComparatorDecorator,  though).
    int search_value = 0;
    if (columns_[col] == Playlist::Column_Length) {
      search_value = parseTime(search);
    }
    else {
      search_value = search.toInt();
    }
    // alright, back to deciding which comparator we'll use
    if (prefix == ">") {
      cmp = new GtComparator(search_value);
    }
    else if (prefix == ">=") {
      cmp = new GeComparator(search_value);
    }
    else if (prefix == "<") {
      cmp = new LtComparator(search_value);
    }
    else if (prefix == "<=") {
      cmp = new LeComparator(search_value);
    }
    else {
      // convert back because for time/rating
      cmp = new EqComparator(QString::number(search_value));
    }
  }
  else {
    if (prefix == "=") {
      cmp = new EqComparator(search);
    }
    else if (prefix == ">") {
      cmp = new LexicalGtComparator(search);
    }
    else if (prefix == ">=") {
      cmp = new LexicalGeComparator(search);
    }
    else if (prefix == "<") {
      cmp = new LexicalLtComparator(search);
    }
    else if (prefix == "<=") {
      cmp = new LexicalLeComparator(search);
    }
    else {
      cmp = new DefaultComparator(search);
    }
  }
  if (columns_.contains(col)) {
    if (columns_[col] == Playlist::Column_Length) {
      cmp = new DropTailComparatorDecorator(cmp);
    }
    return new FilterColumnTerm(columns_[col], cmp);
  }
  else {
    return new FilterTerm(cmp, columns_.values());
  }
}

// Try and parse the string as '[[h:]m:]s' (ignoring all spaces),
// and return the number of seconds if it parses correctly.
// If not, the original string is returned.
// The 'h', 'm' and 's' components can have any length (including 0).
//
// A few examples:
//  "::"       is parsed to "0"
//  "1::"      is parsed to "3600"
//  "3:45"     is parsed to "225"
//  "1:165"    is parsed to "225"
//  "225"      is parsed to "225" (srsly! ^.^)
//  "2:3:4:5"  is parsed to "2:3:4:5"
//  "25m"      is parsed to "25m"
int FilterParser::parseTime(const QString &time_str) const {

  int seconds = 0;
  int accum = 0;
  int colon_count = 0;
  for (const QChar &c : time_str) {
    if (c.isDigit()) {
      accum = accum * 10 + c.digitValue();
    }
    else if (c == ':') {
      seconds = seconds * 60 + accum;
      accum = 0;
      ++colon_count;
      if (colon_count > 2) {
        return 0;
      }
    }
    else if (!c.isSpace()) {
      return 0;
    }
  }
  seconds = seconds * 60 + accum;
  return seconds;
}