/*-
 * ============LICENSE_START=======================================================
 * policy-yaml
 * ================================================================================
 * Copyright (C) 2017-2018 AT&T Intellectual Property. All rights reserved.
 * Modifications Copyright (C) 2019 Nordix Foundation.
 * ================================================================================
 * 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.
 * ============LICENSE_END=========================================================
 */

package org.onap.policy.controlloop.guard.compiler;

import java.io.InputStream;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import org.onap.policy.controlloop.compiler.CompilerException;
import org.onap.policy.controlloop.compiler.ControlLoopCompilerCallback;
import org.onap.policy.controlloop.policy.guard.Constraint;
import org.onap.policy.controlloop.policy.guard.ControlLoopGuard;
import org.onap.policy.controlloop.policy.guard.GuardPolicy;
import org.yaml.snakeyaml.Yaml;
import org.yaml.snakeyaml.constructor.Constructor;

public class ControlLoopGuardCompiler {
    
    private static final String GUARD_POLICIES_SHOULD_NOT_BE_NULL = "Guard policies should not be null";
    private static final String GUARD_POLICY = "Guard policy ";

    private ControlLoopGuardCompiler(){
        // Private Constructor 
    }
    
    /**
     * Compile the control loop guard.
     * 
     * @param clGuard the guard
     * @param callback callback routine
     * @return the guard object
     * @throws CompilerException compilation exception
     */
    public static ControlLoopGuard compile(ControlLoopGuard clGuard, 
                    ControlLoopCompilerCallback callback) throws CompilerException {
        //
        // Ensure ControlLoopGuard has at least one guard policies
        //
        validateControlLoopGuard(clGuard, callback);
        //
        // Ensure each guard policy has at least one constraints and all guard policies are unique
        //
        validateGuardPolicies(clGuard.getGuards(), callback);
        //
        // Ensure constraints for each guard policy are unique
        //
        validateConstraints(clGuard.getGuards(), callback);
        
        return clGuard;
    }
    
    /**
     * Compile the control loop guard.
     * 
     * @param yamlSpecification yaml specification as a stream
     * @param callback callback method
     * @return guard object
     * @throws CompilerException throws compile exception
     */
    public static ControlLoopGuard  compile(InputStream yamlSpecification, 
                    ControlLoopCompilerCallback callback) throws CompilerException {
        Yaml yaml = new Yaml(new Constructor(ControlLoopGuard.class));
        Object obj = yaml.load(yamlSpecification);
        if (obj == null) {
            throw new CompilerException("Could not parse yaml specification.");
        }
        if (! (obj instanceof ControlLoopGuard)) {
            throw new CompilerException("Yaml could not parse specification into required ControlLoopGuard object");
        }
        return ControlLoopGuardCompiler.compile((ControlLoopGuard) obj, callback);
    }
    
    private static void validateControlLoopGuard(ControlLoopGuard clGuard, 
                    ControlLoopCompilerCallback callback) throws CompilerException {
        if (clGuard == null) {
            if (callback != null) {
                callback.onError("ControlLoop Guard cannot be null");
            }
            throw new CompilerException("ControlLoop Guard cannot be null");
        }
        if (clGuard.getGuard() == null && callback != null) {
            callback.onError("Guard version cannot be null");
        }
        if (clGuard.getGuards() == null) {
            if (callback != null) {
                callback.onError("ControlLoop Guard should have at least one guard policies");
            }
        } else if (clGuard.getGuards().isEmpty() && callback != null) {
            callback.onError("ControlLoop Guard should have at least one guard policies");
        }
    }
    
    private static void validateGuardPolicies(List<GuardPolicy> policies, 
                    ControlLoopCompilerCallback callback) throws CompilerException {
        if (policies == null) {
            if (callback != null) {
                callback.onError(GUARD_POLICIES_SHOULD_NOT_BE_NULL);
            }
            throw new CompilerException(GUARD_POLICIES_SHOULD_NOT_BE_NULL);
        }
        //
        // Ensure all guard policies are unique
        //
        Set<GuardPolicy> newSet = new HashSet<>(policies);
        if (newSet.size() != policies.size() && callback != null) {
            callback.onWarning("There are duplicate guard policies");
        }
        //
        // Ensure each guard policy has at least one constraints
        //
        for (GuardPolicy policy : policies) {
            if (policy.getLimit_constraints() == null || policy.getLimit_constraints().isEmpty()) {
                if (callback != null) {
                    callback.onError(GUARD_POLICY + policy.getName() + " does not have any limit constraint");
                }
                throw new CompilerException(GUARD_POLICY + policy.getName() + " does not have any limit constraint");
            }
        }
    }
    
    private static void validateConstraints(List<GuardPolicy> policies, 
                    ControlLoopCompilerCallback callback) throws CompilerException {
        if (policies == null) {
            if (callback != null) {
                callback.onError(GUARD_POLICIES_SHOULD_NOT_BE_NULL);
            }
            throw new CompilerException(GUARD_POLICIES_SHOULD_NOT_BE_NULL);
        }
        for (GuardPolicy policy : policies) {
            Set<Constraint> newSet = new HashSet<>(policy.getLimit_constraints());
            if (newSet.size() != policy.getLimit_constraints().size() && callback != null) {
                callback.onWarning(GUARD_POLICY + policy.getName() + " has duplicate limit constraints");
            }
        }
    }
    
}