/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.cassandra.db.lifecycle;

import java.util.*;

import com.google.common.base.Predicate;
import com.google.common.collect.*;

import org.apache.cassandra.io.sstable.SSTable;
import org.apache.cassandra.io.sstable.format.SSTableReader;
import org.apache.cassandra.utils.Throwables;

import static com.google.common.base.Predicates.*;
import static com.google.common.collect.Iterables.any;
import static com.google.common.collect.Iterables.concat;
import static com.google.common.collect.Iterables.filter;
import static com.google.common.collect.Iterables.getFirst;
import static org.apache.cassandra.utils.Throwables.merge;

class Helpers
{
    
update the contents of a set with the provided sets, ensuring that the items to remove are
really present, and that the items to add are not (unless we're also removing them)
Returns:
a new set with the contents of the provided one modified/**
     * update the contents of a set with the provided sets, ensuring that the items to remove are
     * really present, and that the items to add are not (unless we're also removing them)
     * @return a new set with the contents of the provided one modified
     */
    static <T> Set<T> replace(Set<T> original, Set<T> remove, Iterable<T> add)
    {
        return ImmutableSet.copyOf(replace(identityMap(original), remove, add).keySet());
    }

    
update the contents of an "identity map" with the provided sets, ensuring that the items to remove are
really present, and that the items to add are not (unless we're also removing them)
Returns:
a new identity map with the contents of the provided one modified/**
     * update the contents of an "identity map" with the provided sets, ensuring that the items to remove are
     * really present, and that the items to add are not (unless we're also removing them)
     * @return a new identity map with the contents of the provided one modified
     */
    static <T> Map<T, T> replace(Map<T, T> original, Set<T> remove, Iterable<T> add)
    {
        // ensure the ones being removed are the exact same ones present
        for (T reader : remove)
            assert original.get(reader) == reader;

        // ensure we don't already contain any we're adding, that we aren't also removing
        assert !any(add, and(not(in(remove)), in(original.keySet()))) : String.format("original:%s remove:%s add:%s", original.keySet(), remove, add);

        Map<T, T> result =
            identityMap(concat(add, filter(original.keySet(), not(in(remove)))));

        assert result.size() == original.size() - remove.size() + Iterables.size(add) :
        String.format("Expecting new size of %d, got %d while replacing %s by %s in %s",
                      original.size() - remove.size() + Iterables.size(add), result.size(), remove, add, original.keySet());
        return result;
    }

    
A convenience method for encapsulating this action over multiple SSTableReader with exception-safety
Returns:
accumulate if not null (with any thrown exception attached), or any thrown exception otherwise/**
     * A convenience method for encapsulating this action over multiple SSTableReader with exception-safety
     * @return accumulate if not null (with any thrown exception attached), or any thrown exception otherwise
     */
    static void setupOnline(Iterable<SSTableReader> readers)
    {
        for (SSTableReader reader : readers)
            reader.setupOnline();
    }

    
A convenience method for encapsulating this action over multiple SSTableReader with exception-safety
Returns:
accumulate if not null (with any thrown exception attached), or any thrown exception otherwise/**
     * A convenience method for encapsulating this action over multiple SSTableReader with exception-safety
     * @return accumulate if not null (with any thrown exception attached), or any thrown exception otherwise
     */
    static Throwable setReplaced(Iterable<SSTableReader> readers, Throwable accumulate)
    {
        for (SSTableReader reader : readers)
        {
            try
            {
                reader.setReplaced();
            }
            catch (Throwable t)
            {
                accumulate = merge(accumulate, t);
            }
        }
        return accumulate;
    }

    
assert that none of these readers have been replaced
/**
     * assert that none of these readers have been replaced
     */
    static void checkNotReplaced(Iterable<SSTableReader> readers)
    {
        for (SSTableReader reader : readers)
            assert !reader.isReplaced();
    }

    static Throwable markObsolete(List<LogTransaction.Obsoletion> obsoletions, Throwable accumulate)
    {
        if (obsoletions == null || obsoletions.isEmpty())
            return accumulate;

        for (LogTransaction.Obsoletion obsoletion : obsoletions)
        {
            try
            {
                obsoletion.reader.markObsolete(obsoletion.tidier);
            }
            catch (Throwable t)
            {
                accumulate = merge(accumulate, t);
            }
        }
        return accumulate;
    }

    static Throwable prepareForObsoletion(Iterable<SSTableReader> readers, LogTransaction txnLogs, List<LogTransaction.Obsoletion> obsoletions, Throwable accumulate)
    {
        Map<SSTable, LogRecord> logRecords = txnLogs.makeRemoveRecords(readers);
        for (SSTableReader reader : readers)
        {
            try
            {
                obsoletions.add(new LogTransaction.Obsoletion(reader, txnLogs.obsoleted(reader, logRecords.get(reader))));
            }
            catch (Throwable t)
            {
                accumulate = Throwables.merge(accumulate, t);
            }
        }
        return accumulate;
    }

    static Throwable abortObsoletion(List<LogTransaction.Obsoletion> obsoletions, Throwable accumulate)
    {
        if (obsoletions == null || obsoletions.isEmpty())
            return accumulate;

        for (LogTransaction.Obsoletion obsoletion : obsoletions)
        {
            try
            {
                obsoletion.tidier.abort();
            }
            catch (Throwable t)
            {
                accumulate = merge(accumulate, t);
            }
        }
        return accumulate;
    }

    
Returns:
the identity function, as a Map, with domain of the provided values/**
     * @return the identity function, as a Map, with domain of the provided values
     */
    static <T> Map<T, T> identityMap(Iterable<T> values)
    {
        ImmutableMap.Builder<T, T> builder = ImmutableMap.<T, T>builder();
        for (T t : values)
            builder.put(t, t);
        return builder.build();
    }

    
Returns:
an Iterable of the union if the sets, with duplicates being represented by their first encountered instance
(as defined by the order of set provision)/**
     * @return an Iterable of the union if the sets, with duplicates being represented by their first encountered instance
     * (as defined by the order of set provision)
     */
    static <T> Iterable<T> concatUniq(Set<T>... sets)
    {
        List<Predicate<T>> notIn = new ArrayList<>(sets.length);
        for (Set<T> set : sets)
            notIn.add(not(in(set)));
        List<Iterable<T>> results = new ArrayList<>(sets.length);
        for (int i = 0 ; i < sets.length ; i++)
            results.add(filter(sets[i], and(notIn.subList(0, i))));
        return concat(results);
    }

    
Returns:
a Predicate yielding true for an item present in NONE of the provided sets/**
     * @return a Predicate yielding true for an item present in NONE of the provided sets
     */
    static <T> Predicate<T> notIn(Set<T>... sets)
    {
        return not(orIn(sets));
    }

    
Returns:
a Predicate yielding true for an item present in ANY of the provided sets/**
     * @return a Predicate yielding true for an item present in ANY of the provided sets
     */
    static <T> Predicate<T> orIn(Collection<T>... sets)
    {
        Predicate<T>[] orIn = new Predicate[sets.length];
        for (int i = 0 ; i < orIn.length ; i++)
            orIn[i] = in(sets[i]);
        return or(orIn);
    }

    
filter out (i.e. remove) matching elements
Returns:
filter, filtered to only those elements that *are not* present in *any* of the provided sets (are present in none)/**
     * filter out (i.e. remove) matching elements
     * @return filter, filtered to only those elements that *are not* present in *any* of the provided sets (are present in none)
     */
    static <T> Iterable<T> filterOut(Iterable<T> filter, Set<T>... inNone)
    {
        return filter(filter, notIn(inNone));
    }

    
filter in (i.e. retain)
Returns:
filter, filtered to only those elements that *are* present in *any* of the provided sets/**
     * filter in (i.e. retain)
     *
     * @return filter, filtered to only those elements that *are* present in *any* of the provided sets
     */
    static <T> Iterable<T> filterIn(Iterable<T> filter, Set<T>... inAny)
    {
        return filter(filter, orIn(inAny));
    }

    static Set<SSTableReader> emptySet()
    {
        return Collections.emptySet();
    }

    static <T> T select(T t, Collection<T> col)
    {
        if (col instanceof Set && !col.contains(t))
            return null;
        return getFirst(filter(col, equalTo(t)), null);
    }

    static <T> T selectFirst(T t, Collection<T> ... sets)
    {
        for (Collection<T> set : sets)
        {
            T select = select(t, set);
            if (select != null)
                return select;
        }
        return null;
    }

    static <T> Predicate<T> idIn(Set<T> set)
    {
        return idIn(identityMap(set));
    }

    static <T> Predicate<T> idIn(final Map<T, T> identityMap)
    {
        return new Predicate<T>()
        {
            public boolean apply(T t)
            {
                return identityMap.get(t) == t;
            }
        };
    }

}