import java.io.*;
import java.util.*;

public abstract class AbstractHandler implements Handler {

  private static List<String> list(String s) {
    List<String> lst = new ArrayList<String>();
    lst.add(s);
    return lst;
  }

  /** The extensions for the files about which we know. */
  private final List<String> exts = new ArrayList<String>();

  /** The hash of key-value pairs for current file (not multi-threaded). */
  private Map<String,String> hash;

  /** The keys of key-value pairs for current file (not multi-threaded). */
  private List<String> keys;

  public AbstractHandler() {
    this((String[])null);
  }

  public AbstractHandler(String... exts) {
    if (exts != null) {
      for (String ext : exts) {
        this.exts.add(ext);
      }
    }
  }
  public final List<String> extensions() {return this.exts;}

  public final Map<String,String> explain(File f) {

    // Create the new values for member state
    hash = new HashMap<String,String>();
    keys = new ArrayList<String>();

    // Use some default key-value pairs
    add("name", f.getName());
    add("size", Util.getInstance().niceSize(f));
    add("modified", new Date(f.lastModified()));

    explainRest(f);
    return hash;
  }

  public final List<String> keys() {
    return keys;
  }

  /**
   * Subclasses use {@see #add(String,String)} to add relevant
   * key-value pairs for the {@see File} <code>f</code>.
   *
   * @param f File in question
   */
  abstract void explainRest(File f);

  /**
   * Adds a key-value pair to the current file's hash.
   *
   * @param key new key
   * @param val new value
   */
  protected final void add(String key,Object val) {
    if (val == null || val.equals("")) return;
    key = capitalize(key);
    hash.put(key,String.valueOf(val));
    keys.add(key);
  }

  /**
   * Capitalizes <code>s</code>.
   *
   * @param s string to capitalize
   */
  protected final String capitalize(String s) {
    if (s == null) return s;
    char first = Character.toUpperCase(s.charAt(0));
    return first + s.substring(1);
  }
}