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Camel REST component
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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.camel.component.rest;

import java.util.Map;
import java.util.Set;

import org.apache.camel.Component;
import org.apache.camel.Consumer;
import org.apache.camel.ExchangePattern;
import org.apache.camel.NoFactoryAvailableException;
import org.apache.camel.NoSuchBeanException;
import org.apache.camel.Processor;
import org.apache.camel.Producer;
import org.apache.camel.spi.FactoryFinder;
import org.apache.camel.spi.Metadata;
import org.apache.camel.spi.RestApiConsumerFactory;
import org.apache.camel.spi.RestApiProcessorFactory;
import org.apache.camel.spi.RestConfiguration;
import org.apache.camel.spi.UriEndpoint;
import org.apache.camel.spi.UriParam;
import org.apache.camel.spi.UriPath;
import org.apache.camel.support.DefaultEndpoint;
import org.apache.camel.util.HostUtils;
import org.apache.camel.util.ObjectHelper;

/**
 * The rest-api component is used for providing Swagger API of the REST services which has been defined using the rest-dsl in Camel.
 */
@UriEndpoint(firstVersion = "2.16.0", scheme = "rest-api", title = "REST API", syntax = "rest-api:path/contextIdPattern",
    consumerOnly = true, label = "core,rest", lenientProperties = true)
public class RestApiEndpoint extends DefaultEndpoint {

    public static final String DEFAULT_API_COMPONENT_NAME = "swagger";
    public static final String RESOURCE_PATH = "META-INF/services/org/apache/camel/restapi/";

    @UriPath
    @Metadata(required = true)
    private String path;
    @UriPath
    private String contextIdPattern;
    @UriParam
    private String componentName;
    @UriParam
    private String apiComponentName;

    private Map parameters;

    public RestApiEndpoint(String endpointUri, RestApiComponent component) {
        super(endpointUri, component);
        setExchangePattern(ExchangePattern.InOut);
    }

    @Override
    public RestApiComponent getComponent() {
        return (RestApiComponent) super.getComponent();
    }

    public String getPath() {
        return path;
    }

    /**
     * The base path
     */
    public void setPath(String path) {
        this.path = path;
    }

    public String getContextIdPattern() {
        return contextIdPattern;
    }

    /**
     * Optional CamelContext id pattern to only allow Rest APIs from rest services within CamelContext's which name matches the pattern.
     */
    public void setContextIdPattern(String contextIdPattern) {
        this.contextIdPattern = contextIdPattern;
    }

    public String getComponentName() {
        return componentName;
    }

    /**
     * The Camel Rest component to use for the REST transport, such as restlet, spark-rest.
     * If no component has been explicit configured, then Camel will lookup if there is a Camel component
     * that integrates with the Rest DSL, or if a org.apache.camel.spi.RestConsumerFactory is registered in the registry.
     * If either one is found, then that is being used.
     */
    public void setComponentName(String componentName) {
        this.componentName = componentName;
    }

    public String getApiComponentName() {
        return apiComponentName;
    }

    /**
     * The Camel Rest API component to use for generating the API of the REST services, such as swagger.
     */
    public void setApiComponentName(String apiComponentName) {
        this.apiComponentName = apiComponentName;
    }

    public Map getParameters() {
        return parameters;
    }

    /**
     * Additional parameters to configure the consumer of the REST transport for this REST service
     */
    public void setParameters(Map parameters) {
        this.parameters = parameters;
    }

    @Override
    public Producer createProducer() throws Exception {
        RestApiProcessorFactory factory = null;

        RestConfiguration config = getCamelContext().getRestConfiguration(componentName, true);

        // lookup in registry
        Set factories = getCamelContext().getRegistry().findByType(RestApiProcessorFactory.class);
        if (factories != null && factories.size() == 1) {
            factory = factories.iterator().next();
        }

        // lookup on classpath using factory finder to automatic find it (just add camel-swagger-java to classpath etc)
        if (factory == null) {
            String name = apiComponentName != null ? apiComponentName : config.getApiComponent();
            if (name == null) {
                name = DEFAULT_API_COMPONENT_NAME;
            }
            try {
                FactoryFinder finder = getCamelContext().getFactoryFinder(RESOURCE_PATH);
                Object instance = finder.newInstance(name);
                if (instance instanceof RestApiProcessorFactory) {
                    factory = (RestApiProcessorFactory) instance;
                }
            } catch (NoFactoryAvailableException e) {
                // ignore
            }
        }

        if (factory != null) {

            // if no explicit port/host configured, then use port from rest configuration
            String host = "";
            int port = 80;

            if (config.getApiHost() != null) {
                host = config.getApiHost();
            } else if (config.getHost() != null) {
                host = config.getHost();
            }
            int num = config.getPort();
            if (num > 0) {
                port = num;
            }

            // if no explicit hostname set then resolve the hostname
            if (ObjectHelper.isEmpty(host)) {
                if (config.getHostNameResolver() == RestConfiguration.RestHostNameResolver.allLocalIp) {
                    host = "0.0.0.0";
                } else if (config.getHostNameResolver() == RestConfiguration.RestHostNameResolver.localHostName) {
                    host = HostUtils.getLocalHostName();
                } else if (config.getHostNameResolver() == RestConfiguration.RestHostNameResolver.localIp) {
                    host = HostUtils.getLocalIp();
                }

                // no host was configured so calculate a host to use
                // there should be no schema in the host (but only port)
                String targetHost = host + (port != 80 ? ":" + port : "");
                getParameters().put("host", targetHost);
            }

            // the base path should start with a leading slash
            String path = getPath();
            if (path != null && !path.startsWith("/")) {
                path = "/" + path;
            }

            // whether listing of the context id's is enabled or not
            boolean contextIdListing = config.isApiContextListing();

            Processor processor = factory.createApiProcessor(getCamelContext(), path, getContextIdPattern(), contextIdListing, config, getParameters());
            return new RestApiProducer(this, processor);
        } else {
            throw new IllegalStateException("Cannot find RestApiProcessorFactory in Registry or classpath (such as the camel-swagger-java component)");
        }
    }

    @Override
    public Consumer createConsumer(Processor processor) throws Exception {
        RestApiConsumerFactory factory = null;
        String cname = null;

        // we use the rest component as the HTTP consumer to service the API
        // the API then uses the api component (eg usually camel-swagger-java) to build the API
        if (getComponentName() != null) {
            Object comp = getCamelContext().getRegistry().lookupByName(getComponentName());
            if (comp instanceof RestApiConsumerFactory) {
                factory = (RestApiConsumerFactory) comp;
            } else {
                comp = getCamelContext().getComponent(getComponentName());
                if (comp instanceof RestApiConsumerFactory) {
                    factory = (RestApiConsumerFactory) comp;
                }
            }

            if (factory == null) {
                if (comp != null) {
                    throw new IllegalArgumentException("Component " + getComponentName() + " is not a RestApiConsumerFactory");
                } else {
                    throw new NoSuchBeanException(getComponentName(), RestApiConsumerFactory.class.getName());
                }
            }
            cname = getComponentName();
        }

        // try all components
        if (factory == null) {
            for (String name : getCamelContext().getComponentNames()) {
                Component comp = getCamelContext().getComponent(name);
                if (comp instanceof RestApiConsumerFactory) {
                    factory = (RestApiConsumerFactory) comp;
                    cname = name;
                    break;
                }
            }
        }

        // lookup in registry
        if (factory == null) {
            Set factories = getCamelContext().getRegistry().findByType(RestApiConsumerFactory.class);
            if (factories != null && factories.size() == 1) {
                factory = factories.iterator().next();
            }
        }

        if (factory != null) {
            // calculate the url to the rest API service
            RestConfiguration config = getCamelContext().getRestConfiguration(cname, true);

            // calculate the url to the rest API service
            String path = getPath();
            if (path != null && !path.startsWith("/")) {
                path = "/" + path;
            }

            Consumer consumer = factory.createApiConsumer(getCamelContext(), processor, path, config, getParameters());
            configureConsumer(consumer);

            return consumer;
        } else {
            throw new IllegalStateException("Cannot find RestApiConsumerFactory in Registry or as a Component to use");
        }
    }

    @Override
    public boolean isSingleton() {
        return true;
    }

    @Override
    public boolean isLenientProperties() {
        return true;
    }
}