package com.aurea.maven.plugins.util;
   
   import java.io.BufferedWriter;
   import java.io.File;
   import java.io.FileInputStream;
   import java.io.FileWriter;
   import java.io.IOException;
   import java.util.Properties;
   
  import org.apache.maven.project.MavenProject;
  import org.apache.velocity.Template;
  import org.apache.velocity.VelocityContext;
  import org.apache.velocity.app.Velocity;
  
  public class VelocityRunner {
  
    private static VelocityRunner instance = null; 
    private VelocityContext context = null;
    private MavenProject project = null;
    private File outputDirectory = null;
    
    private VelocityRunner(MavenProject project) {
      try {
        Velocity.init();
        context = new VelocityContext();
        this.project = project;
        Velocity.setProperty(Velocity.FILE_RESOURCE_LOADER_PATH, project.getBasedir());
      } catch (Exception e) {
        // do nothing 
      }
    }
    
    public static VelocityRunner getInstance(MavenProject project) {
      if (instance == null) {
        instance = new VelocityRunner(project);
      }
      return instance;
    }
  
    public static VelocityRunner getInstance() throws Exception {
      if (instance == null) 
        throw new Exception("VelocityRunner not initialized.");
      
      return instance;
    }
  
    public void setOutputDirectory(String outputDirName) {
      outputDirectory = new File(project.getBuild().getDirectory(), outputDirName);
    }
    
    public void addProperties(String prefix, String propFileName) {
      
      Properties props = new Properties();
      
      if (propFileName != null) {
        File propFile = new File(project.getBasedir() + "/" + propFileName);
        if (propFile.exists() && propFile.canRead()) {
          try {
            props.load(new FileInputStream(propFile));
          } catch (Exception e) {
            // do nothing 
          }
        }
      }
      addProperty(prefix, props);
    }
    
    public void addProperty(String key, Object value) {
      context.put(key, value);
    }
  
    public void run(String tplFile, String outFileName) throws Exception {
      if (!outputDirectory.exists()) {
        outputDirectory.mkdirs();
      }
      
      BufferedWriter out = null;
      try {
        Template template = Velocity.getTemplate(tplFile);
        File outFile = new File(outputDirectory.getAbsoluteFile(),  outFileName);
        outFile.getParentFile().mkdirs();
        out = new BufferedWriter(new FileWriter(outFile));
        template.merge(context, out);
      } catch (Exception e) {
        throw new Exception("Template generation failed ...");
      } finally {
        try {
          if (out != null) {
            out.flush();
            out.close();
          }
        } catch (IOException ioe) {
          // do nothing 
        }
      }
    }
  }