/*
 * Copyright (C) 2008 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.common.base.Supplier;
import java.io.Serializable;
import java.util.Comparator;
import java.util.Iterator;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import org.checkerframework.checker.nullness.qual.Nullable;

Implementation of Table whose row keys and column keys are ordered by their natural ordering or by supplied comparators. When constructing a TreeBasedTable, you may provide comparators for the row keys and the column keys, or you may use natural ordering for both. 
The rowKeySet method returns a SortedSet and the rowMap method returns a SortedMap, instead of the Set and Map specified by the Table interface. 
The views returned by StandardTable.column, StandardTable.columnKeySet(), and StandardTable.columnMap() have iterators that don't support remove(). Otherwise, all optional operations are supported. Null row keys, columns keys, and values are not supported. 
Lookups by row key are often faster than lookups by column key, because the data is stored in a Map<R, Map<C, V>>. A method call like column(columnKey).get(rowKey) still runs quickly, since the row key is provided. However, column(columnKey).size() takes longer, since an iteration across all row keys occurs. 
Because a TreeBasedTable has unique sorted values for a given row, both 
row(rowKey) and rowMap().get(rowKey) are SortedMap instances, instead of the Map specified in the Table interface. 
Note that this implementation is not synchronized. If multiple threads access this table
concurrently and one of the threads modifies the table, it must be synchronized externally.
See the Guava User Guide article on  Table.
Author:
Jared Levy, Louis Wasserman
Since:
7.0/**
 * Implementation of {@code Table} whose row keys and column keys are ordered by their natural
 * ordering or by supplied comparators. When constructing a {@code TreeBasedTable}, you may provide
 * comparators for the row keys and the column keys, or you may use natural ordering for both.
 *
 * <p>The {@link #rowKeySet} method returns a {@link SortedSet} and the {@link #rowMap} method
 * returns a {@link SortedMap}, instead of the {@link Set} and {@link Map} specified by the {@link
 * Table} interface.
 *
 * <p>The views returned by {@link #column}, {@link #columnKeySet()}, and {@link #columnMap()} have
 * iterators that don't support {@code remove()}. Otherwise, all optional operations are supported.
 * Null row keys, columns keys, and values are not supported.
 *
 * <p>Lookups by row key are often faster than lookups by column key, because the data is stored in
 * a {@code Map<R, Map<C, V>>}. A method call like {@code column(columnKey).get(rowKey)} still runs
 * quickly, since the row key is provided. However, {@code column(columnKey).size()} takes longer,
 * since an iteration across all row keys occurs.
 *
 * <p>Because a {@code TreeBasedTable} has unique sorted values for a given row, both {@code
 * row(rowKey)} and {@code rowMap().get(rowKey)} are {@link SortedMap} instances, instead of the
 * {@link Map} specified in the {@link Table} interface.
 *
 * <p>Note that this implementation is not synchronized. If multiple threads access this table
 * concurrently and one of the threads modifies the table, it must be synchronized externally.
 *
 * <p>See the Guava User Guide article on <a href=
 * "https://github.com/google/guava/wiki/NewCollectionTypesExplained#table"> {@code Table}</a>.
 *
 * @author Jared Levy
 * @author Louis Wasserman
 * @since 7.0
 */
@GwtCompatible(serializable = true)
public class TreeBasedTable<R, C, V> extends StandardRowSortedTable<R, C, V> {
  private final Comparator<? super C> columnComparator;

  private static class Factory<C, V> implements Supplier<TreeMap<C, V>>, Serializable {
    final Comparator<? super C> comparator;

    Factory(Comparator<? super C> comparator) {
      this.comparator = comparator;
    }

    @Override
    public TreeMap<C, V> get() {
      return new TreeMap<>(comparator);
    }

    private static final long serialVersionUID = 0;
  }

  
Creates an empty TreeBasedTable that uses the natural orderings of both row and column keys. 
The method signature specifies R extends Comparable with a raw Comparable, instead of R extends Comparable<? super R>, and the same for C. That's necessary to support classes defined without generics. /**
   * Creates an empty {@code TreeBasedTable} that uses the natural orderings of both row and column
   * keys.
   *
   * <p>The method signature specifies {@code R extends Comparable} with a raw {@link Comparable},
   * instead of {@code R extends Comparable<? super R>}, and the same for {@code C}. That's
   * necessary to support classes defined without generics.
   */
  public static <R extends Comparable, C extends Comparable, V> TreeBasedTable<R, C, V> create() {
    return new TreeBasedTable<>(Ordering.natural(), Ordering.natural());
  }

  
Creates an empty TreeBasedTable that is ordered by the specified comparators. 
Params:
rowComparator – the comparator that orders the row keys
columnComparator – the comparator that orders the column keys/**
   * Creates an empty {@code TreeBasedTable} that is ordered by the specified comparators.
   *
   * @param rowComparator the comparator that orders the row keys
   * @param columnComparator the comparator that orders the column keys
   */
  public static <R, C, V> TreeBasedTable<R, C, V> create(
      Comparator<? super R> rowComparator, Comparator<? super C> columnComparator) {
    checkNotNull(rowComparator);
    checkNotNull(columnComparator);
    return new TreeBasedTable<>(rowComparator, columnComparator);
  }

  
Creates a TreeBasedTable with the same mappings and sort order as the specified 
TreeBasedTable. /**
   * Creates a {@code TreeBasedTable} with the same mappings and sort order as the specified {@code
   * TreeBasedTable}.
   */
  public static <R, C, V> TreeBasedTable<R, C, V> create(TreeBasedTable<R, C, ? extends V> table) {
    TreeBasedTable<R, C, V> result =
        new TreeBasedTable<>(table.rowComparator(), table.columnComparator());
    result.putAll(table);
    return result;
  }

  TreeBasedTable(Comparator<? super R> rowComparator, Comparator<? super C> columnComparator) {
    super(new TreeMap<R, Map<C, V>>(rowComparator), new Factory<C, V>(columnComparator));
    this.columnComparator = columnComparator;
  }

  // TODO(jlevy): Move to StandardRowSortedTable?

  
Returns the comparator that orders the rows. With natural ordering, Ordering.natural() is returned. 
Deprecated:
Use table.rowKeySet().comparator() instead./**
   * Returns the comparator that orders the rows. With natural ordering, {@link Ordering#natural()}
   * is returned.
   *
   * @deprecated Use {@code table.rowKeySet().comparator()} instead.
   */
  @Deprecated
  public Comparator<? super R> rowComparator() {
    return rowKeySet().comparator();
  }

  
Returns the comparator that orders the columns. With natural ordering, Ordering.natural() is returned. 
Deprecated:
Store the Comparator alongside the Table. Or, if you know that the Table contains at least one value, you can retrieve the Comparator with: ((SortedMap<C, V>) table.rowMap().values().iterator().next()).comparator();./**
   * Returns the comparator that orders the columns. With natural ordering, {@link
   * Ordering#natural()} is returned.
   *
   * @deprecated Store the {@link Comparator} alongside the {@link Table}. Or, if you know that the
   *     {@link Table} contains at least one value, you can retrieve the {@link Comparator} with:
   *     {@code ((SortedMap<C, V>) table.rowMap().values().iterator().next()).comparator();}.
   */
  @Deprecated
  public Comparator<? super C> columnComparator() {
    return columnComparator;
  }

  // TODO(lowasser): make column return a SortedMap

  
{@inheritDoc}
Because a TreeBasedTable has unique sorted values for a given row, this method returns a SortedMap, instead of the Map specified in the Table interface. 
Since:
10.0 (mostly
    source-compatible since 7.0)/**
   * {@inheritDoc}
   *
   * <p>Because a {@code TreeBasedTable} has unique sorted values for a given row, this method
   * returns a {@link SortedMap}, instead of the {@link Map} specified in the {@link Table}
   * interface.
   *
   * @since 10.0 (<a href="https://github.com/google/guava/wiki/Compatibility" >mostly
   *     source-compatible</a> since 7.0)
   */
  @Override
  public SortedMap<C, V> row(R rowKey) {
    return new TreeRow(rowKey);
  }

  private class TreeRow extends Row implements SortedMap<C, V> {
    final @Nullable C lowerBound;
    final @Nullable C upperBound;

    TreeRow(R rowKey) {
      this(rowKey, null, null);
    }

    TreeRow(R rowKey, @Nullable C lowerBound, @Nullable C upperBound) {
      super(rowKey);
      this.lowerBound = lowerBound;
      this.upperBound = upperBound;
      checkArgument(
          lowerBound == null || upperBound == null || compare(lowerBound, upperBound) <= 0);
    }

    @Override
    public SortedSet<C> keySet() {
      return new Maps.SortedKeySet<>(this);
    }

    @Override
    public Comparator<? super C> comparator() {
      return columnComparator();
    }

    int compare(Object a, Object b) {
      // pretend we can compare anything
      @SuppressWarnings({"rawtypes", "unchecked"})
      Comparator<Object> cmp = (Comparator) comparator();
      return cmp.compare(a, b);
    }

    boolean rangeContains(@Nullable Object o) {
      return o != null
          && (lowerBound == null || compare(lowerBound, o) <= 0)
          && (upperBound == null || compare(upperBound, o) > 0);
    }

    @Override
    public SortedMap<C, V> subMap(C fromKey, C toKey) {
      checkArgument(rangeContains(checkNotNull(fromKey)) && rangeContains(checkNotNull(toKey)));
      return new TreeRow(rowKey, fromKey, toKey);
    }

    @Override
    public SortedMap<C, V> headMap(C toKey) {
      checkArgument(rangeContains(checkNotNull(toKey)));
      return new TreeRow(rowKey, lowerBound, toKey);
    }

    @Override
    public SortedMap<C, V> tailMap(C fromKey) {
      checkArgument(rangeContains(checkNotNull(fromKey)));
      return new TreeRow(rowKey, fromKey, upperBound);
    }

    @Override
    public C firstKey() {
      SortedMap<C, V> backing = backingRowMap();
      if (backing == null) {
        throw new NoSuchElementException();
      }
      return backingRowMap().firstKey();
    }

    @Override
    public C lastKey() {
      SortedMap<C, V> backing = backingRowMap();
      if (backing == null) {
        throw new NoSuchElementException();
      }
      return backingRowMap().lastKey();
    }

    transient @Nullable SortedMap<C, V> wholeRow;

    /*
     * If the row was previously empty, we check if there's a new row here every
     * time we're queried.
     */
    SortedMap<C, V> wholeRow() {
      if (wholeRow == null || (wholeRow.isEmpty() && backingMap.containsKey(rowKey))) {
        wholeRow = (SortedMap<C, V>) backingMap.get(rowKey);
      }
      return wholeRow;
    }

    @Override
    SortedMap<C, V> backingRowMap() {
      return (SortedMap<C, V>) super.backingRowMap();
    }

    @Override
    SortedMap<C, V> computeBackingRowMap() {
      SortedMap<C, V> map = wholeRow();
      if (map != null) {
        if (lowerBound != null) {
          map = map.tailMap(lowerBound);
        }
        if (upperBound != null) {
          map = map.headMap(upperBound);
        }
        return map;
      }
      return null;
    }

    @Override
    void maintainEmptyInvariant() {
      if (wholeRow() != null && wholeRow.isEmpty()) {
        backingMap.remove(rowKey);
        wholeRow = null;
        backingRowMap = null;
      }
    }

    @Override
    public boolean containsKey(Object key) {
      return rangeContains(key) && super.containsKey(key);
    }

    @Override
    public V put(C key, V value) {
      checkArgument(rangeContains(checkNotNull(key)));
      return super.put(key, value);
    }
  }

  // rowKeySet() and rowMap() are defined here so they appear in the Javadoc.

  @Override
  public SortedSet<R> rowKeySet() {
    return super.rowKeySet();
  }

  @Override
  public SortedMap<R, Map<C, V>> rowMap() {
    return super.rowMap();
  }

  
Overridden column iterator to return columns values in globally sorted order. /** Overridden column iterator to return columns values in globally sorted order. */
  @Override
  Iterator<C> createColumnKeyIterator() {
    final Comparator<? super C> comparator = columnComparator();

    final Iterator<C> merged =
        Iterators.mergeSorted(
            Iterables.transform(
                backingMap.values(),
                new Function<Map<C, V>, Iterator<C>>() {
                  @Override
                  public Iterator<C> apply(Map<C, V> input) {
                    return input.keySet().iterator();
                  }
                }),
            comparator);

    return new AbstractIterator<C>() {
      @Nullable C lastValue;

      @Override
      protected C computeNext() {
        while (merged.hasNext()) {
          C next = merged.next();
          boolean duplicate = lastValue != null && comparator.compare(next, lastValue) == 0;

          // Keep looping till we find a non-duplicate value.
          if (!duplicate) {
            lastValue = next;
            return lastValue;
          }
        }

        lastValue = null; // clear reference to unused data
        return endOfData();
      }
    };
  }

  private static final long serialVersionUID = 0;
}