/*
 * Copyright 2021 Red Hat, Inc. and/or its affiliates
 * and other contributors as indicated by the @author tags.
 * 
 * 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 org.keycloak.models.map.storage;

import org.keycloak.storage.SearchableModelField;

/**
 * Builder for criteria that can be used to limit results obtained from the store.
 * This class is used for similar purpose as e.g. JPA's {@code CriteriaBuilder},
 * however it is much simpler version as it is tailored to very specific needs
 * of future Keycloak store.
 * <p>
 * Implementations are expected to be immutable. The expected use is like this:
 * <pre>
 * cb = storage.getCriteriaBuilder();
 * storage.read(
 *   cb.or(
 *     cb.compare(FIELD1, EQ, 1).compare(FIELD2, EQ, 2),
 *     cb.compare(FIELD1, EQ, 3).compare(FIELD2, EQ, 4)
 *   )
 * );
 * </pre>
 * The above code should read items where
 * {@code (FIELD1 == 1 && FIELD2 == 2) || (FIELD1 == 3 && FIELD2 == 4)}.
 *
 * <p>
 * It is equivalent to this:
 * <pre>
 * cb = storage.getCriteriaBuilder();
 * storage.read(
 *   cb.or(
 *     cb.and(cb.compare(FIELD1, EQ, 1), cb.compare(FIELD2, EQ, 2)),
 *     cb.and(cb.compare(FIELD1, EQ, 3), cb.compare(FIELD2, EQ, 4))
 *   )
 * );
 * </pre>
 *
 * @author hmlnarik
 */
public interface ModelCriteriaBuilder<M> {

    /**
     * The operators are very basic ones for this use case. In the real scenario,
     * new operators can be added, possibly with different arity, e.g. {@code IN}.
     * The {@link ModelCriteriaBuilder#compare} method would need an adjustment
     * then, likely to taky vararg {@code value} instead of single value as it
     * is now.
     */
    public enum Operator {
        /** Equals to */
        EQ,
        /** Not equals to */
        NE,
        /** Less than */
        LT,
        /** Less than or equal */
        LE,
        /** Greater than */
        GT,
        /** Greater than or equal */
        GE,
        /** Similar to SQL case-sensitive LIKE Whole string is matched.
         * Percent sign means "any characters", question mark means "any single character":
         * <ul>
         *   <li>{@code field LIKE "abc"} means <i>value of the field {@code field} must match exactly {@code abc}</i></li>
         *   <li>{@code field LIKE "abc%"} means <i>value of the field {@code field} must start with {@code abc}</i></li>
         *   <li>{@code field LIKE "%abc"} means <i>value of the field {@code field} must end with {@code abc}</i></li>
         *   <li>{@code field LIKE "%abc%"} means <i>value of the field {@code field} must contain {@code abc}</i></li>
         * </ul>
         */
        LIKE,
        /**
         * Similar to SQL case-insensitive LIKE. Whole string is matched.
         * Percent sign means "any characters", question mark means "any single character":
         * <ul>
         *   <li>{@code field ILIKE "abc"} means <i>value of the field {@code field} must match exactly {@code abc}, {@code ABC}, {@code aBc} etc.</i></li>
         *   <li>{@code field ILIKE "abc%"} means <i>value of the field {@code field} must start with {@code abc}, {@code ABC}, {@code aBc} etc.</i></li>
         *   <li>{@code field ILIKE "%abc"} means <i>value of the field {@code field} must end with {@code abc}, {@code ABC}, {@code aBc} etc.</i></li>
         *   <li>{@code field ILIKE "%abc%"} means <i>value of the field {@code field} must contain {@code abc}, {@code ABC}, {@code aBc} etc.</i></li>
         * </ul>
         */
        ILIKE,
        /**
         * Operator for belonging into a collection of values. Operand in {@code value}
         * can be an array (via an implicit conversion of the vararg), a {@link Collection} or a {@link Stream}.
         */
        IN,
        /** Is not null */
        EXISTS,
        /** Is null */
        NOT_EXISTS,
    }

    /**
     * Adds a constraint for the given model field to this criteria builder
     * and returns a criteria builder that is combined with the the new constraint.
     * The resulting constraint is a logical conjunction (i.e. AND) of the original
     * constraint present in this {@link ModelCriteriaBuilder} and the given operator.
     *
     * @param modelField Field on the logical <i>model</i> to be constrained
     * @param op Operator
     * @param value Additional operands of the operator.
     * @return
     * @throws CriterionNotSupported If the operator is not supported for the given field.
     */
    ModelCriteriaBuilder<M> compare(SearchableModelField<M> modelField, Operator op, Object... value);

    /**
     * Creates and returns a new instance of {@code ModelCriteriaBuilder} that
     * combines the given builders with the Boolean AND operator.
     * <p>
     * Predicate coming out of {@code and} on an empty array of {@code builders}
     * (i.e. empty conjunction) is always {@code true}.
     *
     * <pre>
     *   cb = storage.getCriteriaBuilder();
     *   storage.read(cb.or(
     *     cb.and(cb.compare(FIELD1, EQ, 1), cb.compare(FIELD2, EQ, 2)),
     *     cb.and(cb.compare(FIELD1, EQ, 3), cb.compare(FIELD2, EQ, 4))
     *   );
     * </pre>
     *
     * @throws CriterionNotSupported If the operator is not supported for the given field.
     */
    ModelCriteriaBuilder<M> and(ModelCriteriaBuilder<M>... builders);

    /**
     * Creates and returns a new instance of {@code ModelCriteriaBuilder} that
     * combines the given builders with the Boolean OR operator.
     * <p>
     * Predicate coming out of {@code or} on an empty array of {@code builders}
     * (i.e. empty disjunction) is always {@code false}.
     *
     * <pre>
     *   cb = storage.getCriteriaBuilder();
     *   storage.read(cb.or(
     *     cb.compare(FIELD1, EQ, 1).compare(FIELD2, EQ, 2),
     *     cb.compare(FIELD1, EQ, 3).compare(FIELD2, EQ, 4)
     *   );
     * </pre>
     *
     * @throws CriterionNotSupported If the operator is not supported for the given field.
     */
    ModelCriteriaBuilder<M> or(ModelCriteriaBuilder<M>... builders);

    /**
     * Creates and returns a new instance of {@code ModelCriteriaBuilder} that
     * negates the given builder.
     * <p>
     * Note that if the {@code builder} has no condition yet, there is nothing
     * to negate: empty negation is always {@code true}.
     *
     * @param builder
     * @return
     * @throws CriterionNotSupported If the operator is not supported for the given field.
     */
    ModelCriteriaBuilder<M> not(ModelCriteriaBuilder<M> builder);

    /**
     * Returns this object cast to the given class, or {@code null} if the class cannot be cast to that {@code clazz}.
     * @param <T>
     * @param clazz
     * @return
     */
    default <T extends ModelCriteriaBuilder> T unwrap(Class<T> clazz) {
        if (clazz.isInstance(this)) {
            return clazz.cast(this);
        } else {
            return null;
        }
    }

}
