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/*
 * Copyright 2019-2023 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.relational.core.sql.render;

import java.util.OptionalLong;
import java.util.function.Function;

import org.springframework.data.domain.Sort;
import org.springframework.data.relational.core.dialect.OrderByNullPrecedence;
import org.springframework.data.relational.core.sql.LockMode;
import org.springframework.data.relational.core.sql.Select;

/**
 * Render context specifically for {@code SELECT} statements. This interface declares rendering hooks that are called
 * before/after/during a specific {@code SELECT} clause part. The rendering content is appended directly after/before an
 * element without further whitespace processing. Hooks are responsible for adding required surrounding whitespaces.
 *
 * @author Mark Paluch
 * @author Myeonghyeon Lee
 * @author Jens Schauder
 * @author Chirag Tailor
 * @since 1.1
 */
public interface SelectRenderContext {

	/**
	 * Customization hook: Rendition of a part after the {@code SELECT} list and before any {@code FROM} renderings.
	 * Renders an empty string by default.
	 *
	 * @return render {@link Function} invoked after rendering {@code SELECT} list.
	 */
	default Function afterSelectList() {
		return select -> "";
	}

	/**
	 * Customization hook: Rendition of a part after {@code FROM} table. Renders an empty string by default.
	 *
	 * @return render {@link Function} invoked after rendering {@code FROM} table.
	 */
	default Function afterFromTable() {
		return select -> "";
	}

	/**
	 * Customization hook: Rendition of a part after {@code ORDER BY}. The rendering function is called always, regardless
	 * whether {@code ORDER BY} exists or not.
	 * 
	 * Renders lock, limit and offset clause as appropriate.
	 * 
	 *
	 * @param hasOrderBy the actual value whether the {@link Select} statement has a {@code ORDER BY} clause.
	 * @return render {@link Function} invoked after rendering {@code ORDER BY}.
	 */
	default Function afterOrderBy(boolean hasOrderBy) {

		return select -> {

			OptionalLong limit = select.getLimit();
			OptionalLong offset = select.getOffset();
			LockMode lockMode = select.getLockMode();

			String lockPrefix = (lockMode == null) ? "" : " FOR UPDATE";

			if (limit.isPresent() && offset.isPresent()) {
				return String.format("%s OFFSET %d ROWS FETCH FIRST %d ROWS ONLY", lockPrefix, offset.getAsLong(),
						limit.getAsLong());
			}
			if (limit.isPresent()) {
				return String.format("%s FETCH FIRST %d ROWS ONLY", lockPrefix, limit.getAsLong());
			}
			if (offset.isPresent()) {
				return String.format("%s OFFSET %d ROWS", lockPrefix, offset.getAsLong());
			}

			return lockPrefix;
		};
	}

	/**
	 * Customization hook: Rendition of the null handling option for an {@code ORDER BY} sort expression.
	 *
	 * @param nullHandling the {@link Sort.NullHandling} for the {@code ORDER BY} sort expression. Must not be {@literal null}.
	 * @return render {@link String} SQL text to be included in an {@code ORDER BY} sort expression.
	 * @since 2.4
	 */
	default String evaluateOrderByNullHandling(Sort.NullHandling nullHandling) {
		return OrderByNullPrecedence.NONE.evaluate(nullHandling);
	}
}