FacebookParam.java

/*
  +---------------------------------------------------------------------------+
  | Facebook Development Platform Java Client                                 |
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  | Copyright (c) 2007-2008 Facebook, Inc.                                    |
  | All rights reserved.                                                      |
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  | 1. Redistributions of source code must retain the above copyright         |
  |    notice, this list of conditions and the following disclaimer.          |
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  | THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR      |
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  | OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.   |
  | IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,          |
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 */
package com.facebook.api;

import java.util.HashMap;
import java.util.Map;

public enum FacebookParam
  implements CharSequence {
  SIGNATURE,
  USER("user"),
  SESSION_KEY("session_key"),
  EXPIRES("expires"),
  IN_CANVAS("in_canvas"),
  IN_IFRAME("in_iframe"),
  IN_PROFILE("profile"),
  TIME("time"),
  FRIENDS("friends"),
  ADDED("added"),
  PROFILE_UPDATE_TIME("profile_update_time"),
  API_KEY("api_key")
  ;

  private static Map<String, FacebookParam> _lookupTable =
    new HashMap<String, FacebookParam>(FacebookParam.values().length);
  static {
    for (FacebookParam param: FacebookParam.values()) {
      _lookupTable.put(param.toString(), param);
    }
  }

  /**
   * Retrieves the FacebookParam corresponding to the supplied String key.
   * @param key a possible FacebookParam
   * @return the matching FacebookParam or null if there's no match
   */
  public static FacebookParam get(String key) {
    return isInNamespace(key) ? _lookupTable.get(key) : null;
  }

  /**
   * Indicates whether a given key is in the FacebookParam namespace
   * @param key the parameter name to check
   * @return true if key is in the FacebookParam namespace, false otherwise 
   */
  public static boolean isInNamespace(String key) {
    return null != key && key.startsWith(FacebookParam.SIGNATURE.toString());
  }

  /**
   * @param key
   * @return 
   */
  public static boolean isSignature(String key) {
    return SIGNATURE.equals(get(key));
  }

  private String _paramName;
  private String _signatureName;

  private FacebookParam() {
    this._paramName = "fb_sig";
  }

  private FacebookParam(String name) {
    this._signatureName = name;
    this._paramName = "fb_sig_" + name;
  }

  /* Implementing CharSequence */
  public char charAt(int index) {
    return this._paramName.charAt(index);
  }

  public int length() {
    return this._paramName.length();
  }

  public CharSequence subSequence(int start, int end) {
    return this._paramName.subSequence(start, end);
  }

  public String toString() {
    return this._paramName;
  }
  
  public String getSignatureName() {
    return this._signatureName;
  }

  /**
   * Strips the signature prefix, if present, from <code>paramName</code>,
   * and returns the result.
   * @param paramName
   * @return the paramName, minus the signature prefix
   */
  public static String stripSignaturePrefix(String paramName) {
    if (paramName != null && paramName.startsWith("fb_sig_")) {
      return paramName.substring(7);
    }
    return paramName;
  }
}