package org.tinyjee.maven.dim.sources;
   
   import org.tinyjee.maven.dim.spi.Globals;
   
   import java.util.HashMap;
   import java.util.Map;
   
   /**
    * Is an abstract base for tools that
   *
   * @author Juergen_Kellerer, 2011-10-17
   */
  public class AbstractParametricVelocityTool<E extends AbstractParametricVelocityTool> {
  
  	// Thread-safe parameter store
  	private final ThreadLocal<Map<String, String>> parameters = new ThreadLocal<Map<String, String>>() {
  		@Override
  		protected Map<String, String> initialValue() {
  			return new HashMap<String, String>();
  		}
  	};
  
  	/**
  	 * Returns the current value of the internally stored parameter for the given key.
  	 * <p/>
  	 * If a parameter is not internally stored, the method retrieves the default value for the given key from the request parameters.
  	 * If there's no default value, 'null' will be returned.
  	 *
  	 * @param key the name of the parameter to get.
  	 * @return the value of the parameter, may be 'null' if the parameter does not exist.
  	 */
  	public String get(String key) {
  		String value = parameters.get().get(key);
  		if (value == null) {
  			Object rawValue = Globals.getInstance().getRequest().getParameter(key);
  			if (rawValue != null) value = String.valueOf(rawValue);
  		}
  		return value;
  	}
  
  	/**
  	 * Sets a parameter that will be used with the next invocation.
  	 *
  	 * @param key   the name of the parameter to set.
  	 * @param value the value to set.
  	 * @return an instance of this tool to allow invocation chaining.
  	 */
  	@SuppressWarnings("unchecked")
  	public E put(String key, String value) {
  		parameters.get().put(key, value);
  		return (E) this;
  	}
  
  	/**
  	 * Removes a parameter form the internally maintained parameter list.
  	 *
  	 * @param key the name of the parameter to unset.
  	 * @return an instance of this tool to allow invocation chaining.
  	 */
  	@SuppressWarnings("unchecked")
  	public E remove(String key) {
  		parameters.get().remove(key);
  		return (E) this;
  	}
  
  	/**
  	 * Clears all parameters form the internally maintained parameter list.
  	 *
  	 * @return an instance of this tool to allow invocation chaining.
  	 */
  	@SuppressWarnings("unchecked")
  	public E clear() {
  		parameters.get().clear();
  		return (E) this;
  	}
  
  	/**
  	 * Creates the next parameters to be used to invoke a command inside this tool.
  	 *
  	 * @return the next parameters to be used to invoke a command inside this tool.
  	 */
  	protected Map<String, String> nextInvocationParameters() {
  		@SuppressWarnings("unchecked")
  		Map<String, String> params = new HashMap<String, String>(Globals.getInstance().getRequest().getParameters());
  		params.putAll(parameters.get());
  
  		return params;
  	}
  
  	@Override
  	public String toString() {
  		return getClass().getSimpleName() + '{' +
  				"parameters=" + parameters +
  				'}';
  	}
  }