HrefVarsGenerator.java

/*
 * Copyright 2012 Guido Steinacker
 *
 * 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 de.otto.jsonhome.generator;

import de.otto.jsonhome.annotation.HrefTemplate;
import de.otto.jsonhome.model.Documentation;
import de.otto.jsonhome.model.HrefVar;

import java.lang.reflect.Method;
import java.net.URI;
import java.util.ArrayList;
import java.util.List;

import static de.otto.jsonhome.generator.MethodHelper.getParameterInfos;
import static de.otto.jsonhome.generator.UriTemplateHelper.variableNamesFrom;
import static de.otto.jsonhome.model.Documentation.emptyDocs;
import static de.otto.jsonhome.model.HrefVar.hrefVar;
import static java.net.URI.create;
import static org.springframework.core.annotation.AnnotationUtils.findAnnotation;

/**
 * Abstract generator used to generate {@link de.otto.jsonhome.model.HrefVar}s for a templated resource.
 *
 * @author Guido Steinacker
 */
public abstract class HrefVarsGenerator {

    private final DocsGenerator docsGenerator;

    /**
     * Creates a HrefVarsGenerator.
     *
     * @param relationTypeBaseUri the base URI used to create absolute relation-type URIs.
     * @param docRootDir the root classpath directory containing Markdown documents. May be null.
     */
    protected HrefVarsGenerator(final URI relationTypeBaseUri, final String docRootDir) {
        docsGenerator = new DocsGenerator(relationTypeBaseUri, docRootDir);
    }

    /**
     * Analyzes the method and returns a list of HrefVar instances, describing the variables of a templated resource.
     *
     * @param varTypeBaseUri the base URI used to construct var-type URIs.
     * @param varTypeUrisAsFragment if true, the varType URI is created as a fragment of the varTypeBaseUri,
     *                              otherwise as a sub-resource.
     * @param method the method to analyse.
     * @return list of href-vars.
     */
    public final List<HrefVar> hrefVarsFor(final URI varTypeBaseUri, final boolean varTypeUrisAsFragment, final Method method) {
        final List<HrefVar> hrefVars;
        final HrefTemplate hrefTemplateAnnotation = findAnnotation(method, HrefTemplate.class);
        if (hrefTemplateAnnotation != null) {
            hrefVars = new ArrayList<>();
            final String template = hrefTemplateAnnotation.value();
            for (String varName : variableNamesFrom(template)) {
                hrefVars.add(hrefVar(varName, varTypeUriFrom(varTypeBaseUri, varName, varTypeUrisAsFragment), emptyDocs()));
            }
            if(hrefVars.isEmpty()) {
                throw new IllegalArgumentException("no variables found");
            }
        } else {
            hrefVars = new ArrayList<>();
            for (final ParameterInfo parameterInfo : getParameterInfos(method)) {
                final String varName = parameterInfo.getName();
                final Documentation docs = docsGenerator.documentationFor(parameterInfo);
                if (hasPathVariable(parameterInfo) || hasRequestParam(parameterInfo)) {
                    hrefVars.add(hrefVar(varName, varTypeUriFrom(varTypeBaseUri, varName, varTypeUrisAsFragment), docs));
                }
            }
        }
        return hrefVars;
    }

    /**
     * @param parameterInfo information about a method parameter.
     * @return true if the parameterInfo is describing a request parameter, false otherwise.
     */
    protected abstract boolean hasRequestParam(final ParameterInfo parameterInfo);

    /**
     * @param parameterInfo information about a method parameter.
     * @return true if the parameterInfo is describing a path variable, false otherwise.
     */
    protected abstract boolean hasPathVariable(final ParameterInfo parameterInfo);

    /**
     * Constructs the URI of a var-type as a fragment or sub-resource of a base URI.
     * @param varTypeBaseUri the base URI used to construct the URI of the var type.
     * @param varName the name of the variable
     * @param asFragment create resultung URI as a fragment (#varName) or sub-resource (/varName)
     * @return URI of the varType
     */
    private URI varTypeUriFrom(final URI varTypeBaseUri, final String varName, final boolean asFragment) {
        final String s = varTypeBaseUri.toString();
        if (asFragment) {
            return s.endsWith("/")
                    ? create(s.substring(0, s.length() - 1) + "#" + varName)
                    : create(s + "#" + varName);
        } else {
            return varTypeBaseUri.toString().endsWith("/")
                    ? create(s + varName)
                    : create(s + "/" + varName);
        }
    }

}