/*
 * Copyright 2018 Confluent Inc.
 * Portions Copyright 2020 Amazon.com, Inc. or its affiliates.
 * All Rights Reserved.
 * 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.amazonaws.services.schemaregistry.kafkaconnect.avrodata;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

/**
 * <p>
 * A Builder for creating SchemaValidators.
 * </p>
 */
public final class SchemaValidatorBuilder {
    private SchemaValidationStrategy strategy;

    /**
     * Use a strategy that validates that a schema can be used to read existing
     * schema(s) according to the JSON default schema resolution.
     */
    public SchemaValidatorBuilder canReadStrategy() {
        this.strategy = (toValidate, existing) -> toValidate.isBackwardCompatible(existing);
        return this;
    }

    /**
     * Use a strategy that validates that a schema can be read by existing
     * schema(s) according to the JSON default schema resolution.
     */
    public SchemaValidatorBuilder canBeReadStrategy() {
        this.strategy = (toValidate, existing) -> existing.isBackwardCompatible(toValidate);
        return this;
    }

    /**
     * Use a strategy that validates that a schema can read existing schema(s),
     * and vice-versa, according to the JSON default schema resolution.
     */
    public SchemaValidatorBuilder mutualReadStrategy() {

        this.strategy = (toValidate, existing) -> {
            List<String> result = new ArrayList<>();
            result.addAll(existing.isBackwardCompatible(toValidate));
            result.addAll(toValidate.isBackwardCompatible(existing));
            return result;
        };
        return this;
    }

    public SchemaValidator validateLatest() {
        valid();
        return (toValidate, schemasInOrder) -> {
            Iterator<? extends ParsedSchema> schemas = schemasInOrder.iterator();
            if (schemas.hasNext()) {
                ParsedSchema existing = schemas.next();
                return strategy.validate(toValidate, existing);
            }
            return Collections.emptyList();
        };
    }

    public SchemaValidator validateAll() {
        valid();
        return (toValidate, schemasInOrder) -> {
            for (ParsedSchema existing : schemasInOrder) {
                List<String> errorMessages = strategy.validate(toValidate, existing);
                if (!errorMessages.isEmpty()) {
                    return errorMessages;
                }
            }
            return Collections.emptyList();
        };
    }

    private void valid() {
        if (null == strategy) {
            throw new RuntimeException("SchemaValidationStrategy not specified in builder");
        }
    }
}
