software.amazon.awssdk.services.autoscaling.endpoints.internal.RuleEvaluator Maven / Gradle / Ivy

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The AWS Java SDK for Auto Scaling module holds the client classes that are used for communicating with Auto Scaling Service
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/*
 * Copyright 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. A copy of the License is located at
 * 
 * http://aws.amazon.com/apache2.0
 * 
 * or in the "license" file accompanying this file. This file 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 software.amazon.awssdk.services.autoscaling.endpoints.internal;

import java.util.List;
import java.util.Map;
import software.amazon.awssdk.annotations.SdkInternalApi;

@SdkInternalApi
public class RuleEvaluator implements FnVisitor, ExprVisitor {
    private final Scope scope = new Scope<>();

    public Value evaluateRuleset(EndpointRuleset ruleset, Map input) {
        return scope.inScope(() -> {
            ruleset.getParameters().toList().forEach(param -> {
                param.getDefault().ifPresent(value -> scope.insert(param.getName(), value));
            });
            input.forEach(scope::insert);
            for (Rule rule : ruleset.getRules()) {
                Value result = handleRule(rule);
                if (!result.isNone()) {
                    return result;
                }
            }
            throw new RuntimeException("No rules in ruleset matched");
        });
    }

    @Override
    public Value visitLiteral(Literal literal) {
        return literal.eval(scope);
    }

    @Override
    public Value visitRef(Ref ref) {
        return scope.getValue(ref.getName()).orElseThrow(
                () -> new RuntimeException(String.format("Invalid ruleset: %s was not in scope", ref)));
    }

    @Override
    public Value visitFn(Fn fn) {
        return fn.acceptFnVisitor(this);
    }

    @Override
    public Value visitPartition(PartitionFn fn) {
        return fn.eval(scope);
    }

    @Override
    public Value visitParseArn(ParseArn fn) {
        return fn.eval(scope);
    }

    @Override
    public Value visitIsValidHostLabel(IsValidHostLabel fn) {
        return fn.eval(scope);
    }

    @Override
    public Value visitBoolEquals(BooleanEqualsFn fn) {
        return fn.eval(scope);
    }

    @Override
    public Value visitStringEquals(StringEqualsFn fn) {
        return fn.eval(scope);
    }

    @Override
    public Value visitIsSet(IsSet fn) {
        return fn.eval(scope);
    }

    @Override
    public Value visitNot(Not not) {
        return Value.fromBool(!not.target().accept(this).expectBool());
    }

    @Override
    public Value visitGetAttr(GetAttr getAttr) {
        return getAttr.eval(scope);
    }

    @Override
    public Value visitParseUrl(ParseUrl parseUrl) {
        return parseUrl.eval(scope);
    }

    @Override
    public Value visitSubstring(Substring fn) {
        return fn.eval(scope);
    }

    @Override
    public Value visitUriEncode(UriEncodeFn fn) {
        return fn.eval(scope);
    }

    @Override
    public Value visitIsVirtualHostLabelsS3Bucket(IsVirtualHostableS3Bucket fn) {
        return fn.eval(scope);
    }

    private Value handleRule(Rule rule) {
        RuleEvaluator self = this;
        return scope.inScope(() -> {
            for (Condition condition : rule.getConditions()) {
                Value value = evaluateCondition(condition);
                if (value.isNone() || value.equals(Value.fromBool(false))) {
                    return Value.none();
                }
            }
            return rule.accept(new RuleValueVisitor() {
                @Override
                public Value visitTreeRule(List rules) {
                    for (Rule subrule : rules) {
                        Value result = handleRule(subrule);
                        if (!result.isNone()) {
                            return result;
                        }
                    }
                    throw new RuntimeException(String.format("no rules inside of tree rule matched—invalid rules (%s)", this));
                }

                @Override
                public Value visitErrorRule(Expr error) {
                    return error.accept(self);
                }

                @Override
                public Value visitEndpointRule(EndpointResult endpoint) {
                    return generateEndpoint(endpoint);
                }
            });
        });
    }

    public Value evaluateCondition(Condition condition) {
        Value value = condition.getFn().accept(this);
        if (!value.isNone()) {
            condition.getResult().ifPresent(res -> scope.insert(res, value));
        }
        return value;
    }

    public Value generateEndpoint(EndpointResult endpoint) {
        Value.Endpoint.Builder builder = Value.Endpoint.builder().url(endpoint.getUrl().accept(this).expectString());
        endpoint.getProperties().forEach((key, value) -> {
            builder.property(key.toString(), value.accept(this));
        });
        endpoint.getHeaders().forEach((name, exprs) -> {
            exprs.forEach(expr -> builder.addHeader(name, expr.accept(this).expectString()));
        });

        return builder.build();
    }
}