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/*
 * Copyright 2018-2019 the original author or 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
 *
 *      https://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.springframework.data.cassandra.core;

import java.util.List;
import java.util.stream.Stream;

import lombok.AccessLevel;
import lombok.NonNull;
import lombok.RequiredArgsConstructor;
import lombok.experimental.FieldDefaults;

import org.springframework.dao.IncorrectResultSizeDataAccessException;
import org.springframework.data.cassandra.core.cql.CqlIdentifier;
import org.springframework.data.cassandra.core.query.Query;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ObjectUtils;

/**
 * Implementation of {@link ExecutableSelectOperation}.
 *
 * @author Mark Paluch
 * @see org.springframework.data.cassandra.core.ExecutableSelectOperation
 * @see org.springframework.data.cassandra.core.query.Query
 * @since 2.1
 */
@RequiredArgsConstructor
class ExecutableSelectOperationSupport implements ExecutableSelectOperation {

	private final @NonNull CassandraTemplate template;

	/* (non-Javadoc)
	 * @see org.springframework.data.cassandra.core.ExecutableSelectOperation#query(java.lang.Class)
	 */
	@Override
	public  ExecutableSelect query(Class domainType) {

		Assert.notNull(domainType, "DomainType must not be null");

		return new ExecutableSelectSupport<>(this.template, domainType, domainType, Query.empty(), null);
	}

	// TODO: rethink the implementation
	// While the use of final fields and construction on mutation effectively makes this class Thread-safe,
	// it is possible this implementation could generate a high-level of young-gen garbage on the JVM heap,
	// particularly if the template query(..) (and this class) are used inside of a loop for a large number
	// of domain types.  Of course, this assumption is highly contingent on the user's `Query`
	// in addition to his/her application design.

	@RequiredArgsConstructor
	@FieldDefaults(level = AccessLevel.PRIVATE, makeFinal = true)
	static class ExecutableSelectSupport implements ExecutableSelect {

		@NonNull CassandraTemplate template;

		@NonNull Class domainType;

		@NonNull Class returnType;

		@NonNull Query query;

		@Nullable CqlIdentifier tableName;

		/* (non-Javadoc)
		 * @see org.springframework.data.cassandra.core.ExecutableSelectOperation.SelectWithTable#inTable(org.springframework.data.cassandra.core.cql.CqlIdentifier)
		 */
		@Override
		public SelectWithProjection inTable(CqlIdentifier tableName) {

			Assert.notNull(tableName, "Table name must not be null");

			return new ExecutableSelectSupport<>(this.template, this.domainType, this.returnType,
					this.query, tableName);
		}

		/* (non-Javadoc)
		 * @see org.springframework.data.cassandra.core.ExecutableSelectOperation.SelectWithProjection#as(java.lang.Class)
		 */
		@Override
		public  SelectWithQuery as(Class returnType) {

			Assert.notNull(returnType, "ReturnType must not be null");

			return new ExecutableSelectSupport<>(this.template, this.domainType, returnType,
					this.query, this.tableName);
		}

		/* (non-Javadoc)
		 * @see org.springframework.data.cassandra.core.ExecutableSelectOperation.SelectWithQuery#matching(org.springframework.data.cassandra.core.query.Query)
		 */
		@Override
		public TerminatingSelect matching(Query query) {

			Assert.notNull(query, "Query must not be null");

			return new ExecutableSelectSupport<>(this.template, this.domainType, this.returnType,
					query, this.tableName);
		}

		/* (non-Javadoc)
		 * @see org.springframework.data.cassandra.core.ExecutableSelectOperation.TerminatingSelect#count()
		 */
		@Override
		public long count() {
			return this.template.doCount(this.query, this.domainType, getTableName());
		}

		/* (non-Javadoc)
		 * @see org.springframework.data.cassandra.core.ExecutableSelectOperation.TerminatingSelect#exists()
		 */
		@Override
		public boolean exists() {
			return this.template.doExists(this.query, this.domainType, getTableName());
		}

		/* (non-Javadoc)
		 * @see org.springframework.data.cassandra.core.ExecutableSelectOperation.TerminatingSelect#firstValue()
		 */
		@Override
		public T firstValue() {

			List result =
					this.template.doSelect(this.query.limit(1), this.domainType, getTableName(), this.returnType);

			return ObjectUtils.isEmpty(result) ? null : result.iterator().next();
		}

		/* (non-Javadoc)
		 * @see org.springframework.data.cassandra.core.ExecutableSelectOperation.TerminatingSelect#oneValue()
		 */
		@Override
		public T oneValue() {

			List result =
					this.template.doSelect(this.query.limit(2), this.domainType, getTableName(), this.returnType);

			if (ObjectUtils.isEmpty(result)) {
				return null;
			}

			if (result.size() > 1) {
				throw new IncorrectResultSizeDataAccessException(
						String.format("Query [%s] returned non unique result.", this.query), 1);
			}

			return result.iterator().next();
		}

		/* (non-Javadoc)
		 * @see org.springframework.data.cassandra.core.ExecutableSelectOperation.TerminatingSelect#all()
		 */
		@Override
		public List all() {
			return this.template.doSelect(this.query, this.domainType, getTableName(), this.returnType);
		}

		/* (non-Javadoc)
		 * @see org.springframework.data.cassandra.core.ExecutableSelectOperation.TerminatingSelect#stream()
		 */
		@Override
		public Stream stream() {
			return this.template.doStream(this.query, this.domainType, getTableName(), this.returnType);
		}

		private CqlIdentifier getTableName() {
			return this.tableName != null ? this.tableName : this.template.getTableName(this.domainType);
		}
	}
}