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Copyright 2011, Google Inc.
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    * Redistributions of source code must retain the above copyright
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    * Redistributions in binary form must reproduce the above
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*/

package com.google.refine.importing;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

import org.apache.commons.io.FileUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.google.refine.RefineServlet;

import edu.mit.simile.butterfly.ButterflyModule;

public class ImportingManager {
    static public class Format {
        @JsonProperty("id")
        final public String id;
        @JsonProperty("label")
        final public String label;
        @JsonProperty("download")
        final public boolean download;
        @JsonProperty("uiClass")
        final public String uiClass;
        @JsonIgnore
        final public ImportingParser parser;
        
        private Format(
            String id,
            String label,
            boolean download,
            String uiClass,
            ImportingParser parser
        ) {
            this.id = id;
            this.label = label;
            this.download = download;
            this.uiClass = uiClass;
            this.parser = parser;
        }
    }
    
    final static Logger logger = LoggerFactory.getLogger("importing");
    
    static private RefineServlet servlet;
    static private File importDir;
    
    final static private Map<Long, ImportingJob> jobs = Collections.synchronizedMap(new HashMap<Long, ImportingJob>());
    static private long jobIdCounter = 0;
    final static private Object jobIdLock = new Object();
    
    // Mapping from format to label, e.g., "text" to "Text files", "text/xml" to "XML files"
    final static public Map<String, Format> formatToRecord = new HashMap<String, Format>();
    
    // Mapping from format to guessers
    final static public Map<String, List<FormatGuesser>> formatToGuessers = new HashMap<String, List<FormatGuesser>>();
    
    // Mapping from file extension to format, e.g., ".xml" to "text/xml"
    final static public Map<String, String> extensionToFormat = new HashMap<String, String>();
    
    // Mapping from mime type to format, e.g., "application/json" to "text/json"
    final static public Map<String, String> mimeTypeToFormat = new HashMap<String, String>();
    
    // URL rewriters
    final static public Set<UrlRewriter> urlRewriters = new HashSet<UrlRewriter>();
    
    // Mapping from controller name to controller
    final static public Map<String, ImportingController> controllers = new HashMap<String, ImportingController>();
    
    // timer for periodically deleting stale importing jobs
    static private ScheduledExecutorService service;

    final static private long TIMER_PERIOD = 10; // 10 minutes
    final static private long STALE_PERIOD = 60 * 60 * 1000; // 60 minutes in milliseconds
    
    static private class CleaningTimerTask implements Runnable {
        @Override
        public void run() {
            // An exception here will keep future runs of this task from happening, 
            // but won't affect other timer tasks
            cleanUpStaleJobs();
        }
    }
    
    static public void initialize(RefineServlet servlet) {
        ImportingManager.servlet = servlet;
        
        service =  Executors.newSingleThreadScheduledExecutor();
        service.scheduleWithFixedDelay(new CleaningTimerTask(), TIMER_PERIOD, TIMER_PERIOD, TimeUnit.MINUTES);
    }
    
    static public void registerFormat(String format, String label) {
        registerFormat(format, label, null, null);
    }
    
    static public void registerFormat(String format, String label, String uiClass, ImportingParser parser) {
        formatToRecord.put(format, new Format(format, label, true, uiClass, parser));
    }
    
    static public void registerFormat(
            String format, String label, boolean download, String uiClass, ImportingParser parser) {
        formatToRecord.put(format, new Format(format, label, download, uiClass, parser));
    }
    
    static public void registerFormatGuesser(String format, FormatGuesser guesser) {
        List<FormatGuesser> guessers = formatToGuessers.get(format);
        if (guessers == null) {
            guessers = new LinkedList<FormatGuesser>();
            formatToGuessers.put(format, guessers);
        }
        guessers.add(0, guesser); // prepend so that newer guessers take priority
    }
    
    static public void registerExtension(String extension, String format) {
        extensionToFormat.put(extension.startsWith(".") ? extension : ("." + extension), format);
    }
    
    static public void registerMimeType(String mimeType, String format) {
        mimeTypeToFormat.put(mimeType, format);
    }
    
    static public void registerUrlRewriter(UrlRewriter urlRewriter) {
        urlRewriters.add(urlRewriter);
    }
    
    static public void registerController(ButterflyModule module, String name, ImportingController controller) {
        String key = module.getName() + "/" + name;
        controllers.put(key, controller);
        
        controller.init(servlet);
    }

    static synchronized public File getImportDir() {
        if (importDir == null) {
            File tempDir = servlet.getTempDir();
            importDir = tempDir == null ? new File(".import-temp") : new File(tempDir, "import");
            
            if (importDir.exists()) {
                try {
                    // start fresh
                    FileUtils.deleteDirectory(importDir);
                } catch (IOException e) {
                }
            }
            importDir.mkdirs();
        }
        return importDir;
    }
    
    static public ImportingJob createJob() {
        long id;
        
        synchronized(jobIdLock) {
            ++jobIdCounter;
            
            // Avoid negative job id's when the counter wraps around.
            if (jobIdCounter < 0) {
                jobIdCounter = 1;
            }
            
            id = jobIdCounter;
        }
        
        File jobDir = new File(getImportDir(), Long.toString(id));
        
        ImportingJob job = new ImportingJob(id, jobDir);
        jobs.put(id, job);
        
        return job;
    }
    
    static public ImportingJob getJob(long id) {
        return jobs.get(id);
    }
    
    static public void disposeJob(long id) {
        ImportingJob job = getJob(id);
        if (job != null) {
            job.dispose();
            jobs.remove(id);
        }
    }
    
    static public class ImportingConfiguration {
        @JsonProperty("formats")
        public Map<String, Format> getFormats() { return formatToRecord; }
        @JsonProperty("mimeTypeToFormat")
        public Map<String, String> getMimeTypeToFormat() { return mimeTypeToFormat; }
        @JsonProperty("extensionToFormat")
        public Map<String, String> getExtensionToFormat() { return extensionToFormat; }
    }
    
    static public String getFormatFromFileName(String fileName) {
        int start = 0;
        while (true) {
            int dot = fileName.indexOf('.', start);
            if (dot < 0) {
                break;
            }
            
            String extension = fileName.substring(dot);
            String format = extensionToFormat.get(extension);
            if (format != null) {
                return format;
            } else {
                start = dot + 1;
            }
        }
        return null;
    }
    
    static public String getFormatFromMimeType(String mimeType) {
        String format = mimeTypeToFormat.get(mimeType);
        if (format == null) {
            // Try Structured Name Syntax Suffix
            // https://tools.ietf.org/html/rfc6838#section-4.2.8
            if (mimeType.contains("+")) {
                // These are registered with a leading plus sign (+) to show they're suffixes
                mimeType = "+" + mimeType.split("\\+")[1];
                format = mimeTypeToFormat.get(mimeType);
            }
        }
        return format;
    }
    
    static public String getFormat(String fileName, String mimeType) {
        String fileNameFormat = getFormatFromFileName(fileName);
        String mimeTypeFormat = mimeType == null ? null : getFormatFromMimeType(mimeType);
        if (mimeTypeFormat == null) {
            return fileNameFormat;
        } else if (fileNameFormat == null) {
            return mimeTypeFormat;
        } else if (mimeTypeFormat.startsWith(fileNameFormat)) {
            // mime type-base format is more specific
            return mimeTypeFormat;
        } else {
            return fileNameFormat;
        }
    }
    
    static private void cleanUpStaleJobs() {
        long now = System.currentTimeMillis();
        Collection<Long> keys;
        synchronized(jobs) {
            keys = new ArrayList<Long>(jobs.keySet());
        }
        for (Long id : keys) {
            ImportingJob job = jobs.get(id);
            if (job != null && !job.updating && now - job.lastTouched > STALE_PERIOD) {
                job.dispose();
                jobs.remove(id);
                logger.info("Removed Stale Import Job ID " + id);
            }
        }
    }
}
