/*
 * Copyright 2015-2022 Transmogrify LLC, 2022-2025 Revetware LLC.
 *
 * 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.pyranid;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.ThreadSafe;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.Optional;

/**
 * Enables per-column {@link ResultSet} mapping customization via {@link ResultSetMapper}.
 *
 * @author <a href="https://www.revetkn.com">Mark Allen</a>
 * @since 3.0.0
 */
public interface CustomColumnMapper {
        /**
         * Perform custom mapping of a {@link ResultSet} column: given a {@code resultSetValue}, optionally return an instance of {@code targetType} instead.
         * <p>
         * This method is only invoked when {@code resultSetValue} is non-null.
         *
         * @param statementContext current SQL context
         * @param resultSet        the {@link ResultSet} from which data was read
         * @param resultSetValue   the already-read value from the {@link ResultSet}, to be optionally converted to an instance of {@code targetType}
         * @param targetType       the type to which the {@code resultSetValue} should be converted
         * @param columnIndex      1-based column index
         * @param columnLabel      normalized column label, if available
         * @param instanceProvider instance-creation factory, may be used to instantiate values
         * @return the result of the custom column mapping operation - either {@link MappingResult#of(Object)} to indicate a successfully-mapped value or {@link MappingResult#fallback()} if Pyranid should fall back to the registered {@link ResultSetMapper} mapping behavior.
         * @throws SQLException if an error occurs during mapping
         */
        @Nonnull
        MappingResult map(@Nonnull StatementContext<?> statementContext,
                                                                                @Nonnull ResultSet resultSet,
                                                                                @Nonnull Object resultSetValue,
                                                                                @Nonnull TargetType targetType,
                                                                                @Nonnull Integer columnIndex,
                                                                                @Nullable String columnLabel,
                                                                                @Nonnull InstanceProvider instanceProvider) throws SQLException;

        /**
         * Specifies which types this mapper should handle.
         * <p>
         * For example, if this mapper should apply when marshaling to {@code MyCustomType}, this method could return {@code targetType.matchesClass(MyCustomType.class)}.
         * <p>
         * For parameterized types like {@code List<UUID>}, this method could return {@code targetType.matchesParameterizedType(List.class, UUID.class)}.
         *
         * @param targetType the target type to evaluate - should this mapper handle it or not?
         * @return {@code true} if this mapper should handle the type, {@code false} otherwise.
         */
        @Nonnull
        Boolean appliesTo(@Nonnull TargetType targetType);

        /**
         * Result of a custom column mapping attempt.
         * <p>
         * Use {@link #of(Object)} to indicate a successfully mapped value or {@link #fallback()} to indicate "didn't map; fall back to the registered {@link ResultSetMapper} behavior".</p>
         */
        @ThreadSafe
        sealed abstract class MappingResult permits MappingResult.CustomMapping, MappingResult.Fallback {
                private MappingResult() {}

                /**
                 * Indicates a successfully-mapped custom value.
                 *
                 * @param value the custom value, may be {@code null}
                 * @return a result which indicates a successfully-mapped custom value
                 */
                @Nonnull
                public static MappingResult of(@Nullable Object value) {
                        return new CustomMapping(value);
                }

                /**
                 * Indicates that this mapper did not map a custom value and prefers to fall back to the behavior of the registered {@link ResultSetMapper}.
                 *
                 * @return a result which indicates that this mapper did not map a custom value
                 */
                @Nonnull
                public static MappingResult fallback() {
                        return Fallback.INSTANCE;
                }

                @ThreadSafe
                static final class CustomMapping extends MappingResult {
                        @Nullable
                        private final Object value;

                        private CustomMapping(@Nullable Object value) {
                                this.value = value;
                        }

                        @Nonnull
                        public Optional<Object> getValue() {
                                return Optional.ofNullable(value);
                        }
                }

                @ThreadSafe
                static final class Fallback extends MappingResult {
                        static final Fallback INSTANCE = new Fallback();

                        private Fallback() {}
                }
        }
}