package com.atlassian.plugin.loaders;
   
   import com.atlassian.plugin.PluginException;
   import com.atlassian.plugin.loaders.classloading.DeploymentUnit;
   import com.atlassian.plugin.loaders.classloading.Scanner;
   
   import java.io.File;
   import java.util.ArrayList;
   import java.util.Collection;
  import java.util.Collections;
  
  /**
   * A scanner that simply scans a given set of input files.
   * This scanner will always return the units in the order supplied in the constructor.
   */
  public class FileListScanner implements Scanner {
      private final Collection<File> files;
      private transient Collection<DeploymentUnit> units;
  
      public FileListScanner(final Collection<File> files) {
          this.files = new ArrayList<>(files);
      }
  
      public Collection<DeploymentUnit> scan() {
          if (units != null) {
              return Collections.emptyList();
          }
  
          units = new ArrayList<>();
          for (final File file : files) {
              units.add(new DeploymentUnit(file));
          }
  
          return units;
      }
  
      public Collection<DeploymentUnit> getDeploymentUnits() {
          return Collections.unmodifiableCollection(units);
      }
  
      public void reset() {
          units = null;
      }
  
      public void remove(final DeploymentUnit unit) throws PluginException {
          throw new PluginException("Cannot remove files in a file-list scanner: " + unit.getPath());
      }
  }