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/*
 * Copyright (C) 2015 Stefan Niederhauser ([email protected])
 *
 * 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 guru.nidi.graphviz.engine;

import java.io.IOException;
import java.io.InputStream;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.TimeUnit;

/**
 *
 */
public abstract class AbstractGraphvizEngine implements GraphvizEngine {
    private final CountDownLatch state;
    private final EngineInitListener engineInitListener;
    private Exception initException;

    public AbstractGraphvizEngine(boolean sync, EngineInitListener engineInitListener) {
        state = new CountDownLatch(1);
        this.engineInitListener = engineInitListener;
        if (sync) {
            init();
        } else {
            final Thread starter = new Thread(this::init);
            starter.setDaemon(true);
            starter.start();
        }
    }

    public String execute(String dot) {
        if (initException != null) {
            throw new GraphvizException("Could not start graphviz engine", initException);
        }
        try {
            if (!state.await(60, TimeUnit.SECONDS)) {
                throw new GraphvizException("Initializing graphviz engine took too long");
            }
        } catch (InterruptedException e) {
            //ignore
        }
        return doExecute(dot);
    }

    private void init() {
        try {
            doInit();
            state.countDown();
        } catch (Exception e) {
            initException = e;
            if (engineInitListener != null) {
                engineInitListener.engineInitException(e);
            }
        }
    }

    protected abstract void doInit() throws Exception;

    protected abstract String doExecute(String dot);

    protected String vizCode() throws IOException {
        final InputStream in = getClass().getResourceAsStream("/viz-1.0.1.js");
        final byte[] buf = new byte[in.available()];
        int read, total = 0;
        while ((read = in.read(buf, total, Math.min(100000, buf.length - total))) > 0) {
            total += read;
        }
        return new String(buf, "utf-8");
    }

    protected String jsEscape(String js) {
        return js.replace("\n", " ").replace("\\", "\\\\").replace("'", "\\'");
    }
}