/*
 * 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.facebook.presto.operator.scalar;

import com.facebook.presto.common.block.Block;
import com.facebook.presto.common.block.BlockBuilder;
import com.facebook.presto.common.function.SqlFunctionProperties;
import com.facebook.presto.common.type.MapType;
import com.facebook.presto.common.type.RowType;
import com.facebook.presto.common.type.Type;
import com.facebook.presto.operator.aggregation.TypedSet;
import com.facebook.presto.spi.PrestoException;
import com.facebook.presto.spi.function.Description;
import com.facebook.presto.spi.function.ScalarFunction;
import com.facebook.presto.spi.function.SqlNullable;
import com.facebook.presto.spi.function.SqlType;
import com.facebook.presto.spi.function.TypeParameter;
import com.google.common.collect.ImmutableList;

import static com.facebook.presto.spi.StandardErrorCode.INVALID_FUNCTION_ARGUMENT;
import static java.lang.String.format;

@ScalarFunction("map_from_entries")
@Description("construct a map from an array of entries")
public final class MapFromEntriesFunction
{
    @TypeParameter("K")
    @TypeParameter("V")
    public MapFromEntriesFunction(@TypeParameter("map(K,V)") Type mapType) {}

    @TypeParameter("K")
    @TypeParameter("V")
    @SqlType("map(K,V)")
    @SqlNullable
    public Block mapFromEntries(
            @TypeParameter("map(K,V)") MapType mapType,
            SqlFunctionProperties properties,
            @SqlType("array(row(K,V))") Block block)
    {
        Type keyType = mapType.getKeyType();
        Type valueType = mapType.getValueType();
        RowType rowType = RowType.anonymous(ImmutableList.of(keyType, valueType));
        int entryCount = block.getPositionCount();

        BlockBuilder mapBlockBuilder = mapType.createBlockBuilder(null, block.getPositionCount());
        BlockBuilder resultBuilder = mapBlockBuilder.beginBlockEntry();
        TypedSet uniqueKeys = new TypedSet(keyType, entryCount, "map_from_entries");

        for (int i = 0; i < entryCount; i++) {
            if (block.isNull(i)) {
                throw new PrestoException(INVALID_FUNCTION_ARGUMENT, "map entry cannot be null");
            }
            Block rowBlock = rowType.getObject(block, i);

            if (rowBlock.isNull(0)) {
                throw new PrestoException(INVALID_FUNCTION_ARGUMENT, "map key cannot be null");
            }

            if (!uniqueKeys.add(rowBlock, 0)) {
                throw new PrestoException(INVALID_FUNCTION_ARGUMENT, format("Duplicate keys (%s) are not allowed", keyType.getObjectValue(properties, rowBlock, 0)));
            }

            keyType.appendTo(rowBlock, 0, resultBuilder);
            valueType.appendTo(rowBlock, 1, resultBuilder);
        }

        mapBlockBuilder.closeEntry();
        return mapType.getObject(mapBlockBuilder, mapBlockBuilder.getPositionCount() - 1);
    }
}
