/*
 * Copyright © 2017 the original authors (http://cereebro.io)
 *
 * 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 io.cereebro.server;

import java.io.IOException;
import java.net.URI;
import java.util.Objects;

import org.springframework.core.io.Resource;

import com.fasterxml.jackson.databind.ObjectMapper;

import io.cereebro.core.Snitch;
import io.cereebro.core.SnitchingException;
import io.cereebro.core.SystemFragment;

/**
 * Snitch backed by a static Spring {@link Resource}. The resource must contain
 * a valid JSON representation of a {@link SystemFragment}.
 * 
 * @author michaeltecourt
 */
public class ResourceSnitch implements Snitch {

    private final ObjectMapper objectMapper;
    private final Resource resource;

    /**
     * Snitch backed by a static Spring {@link Resource}. The resource must
     * contain a valid JSON representation of a {@link SystemFragment}.
     * 
     * @param mapper
     *            Jackson object mapper
     * @param resource
     *            Resource containing a JSON SystemFragment.
     */
    public ResourceSnitch(ObjectMapper mapper, Resource resource) {
        this.resource = Objects.requireNonNull(resource, "Resource required");
        this.objectMapper = Objects.requireNonNull(mapper, "ObjectMapper required");
    }

    /**
     * Snitch backed by a static Spring {@link Resource}. The resource must
     * contain a valid JSON representation of a {@link SystemFragment}.
     * 
     * @param mapper
     *            Jackson object mapper
     * @param resource
     *            Resource containing a JSON SystemFragment.
     * @return ResourceSnitch
     */
    public static ResourceSnitch of(ObjectMapper mapper, Resource resource) {
        return new ResourceSnitch(mapper, resource);
    }

    @Override
    public URI getUri() {
        try {
            return resource.getURI();
        } catch (IOException e) {
            throw new IllegalStateException("Error reading Snitch Resource URI : " + resource.getDescription(), e);
        }
    }

    @Override
    public SystemFragment snitch() {
        try {
            return objectMapper.readValue(resource.getInputStream(), SystemFragment.class);
        } catch (IOException e) {
            throw new SnitchingException(getUri(), "Error while reading resource content", e);
        }
    }

}