package com.corejsf;

import java.io.IOException;
import java.util.Map;

import javax.faces.component.FacesComponent;
import javax.faces.component.UIInput;
import javax.faces.context.FacesContext;
import javax.faces.context.ResponseWriter;
import javax.faces.convert.IntegerConverter;

@FacesComponent("com.corejsf.Spinner")
public class UISpinner extends UIInput {
   private static final String MORE = ".more";
   private static final String LESS = ".less";

   public UISpinner() {
      setConverter(new IntegerConverter()); // to convert the submitted value
      setRendererType(null); // this component renders itself
   }

   public void encodeBegin(FacesContext context) throws IOException {
      ResponseWriter writer = context.getResponseWriter();
      String clientId = getClientId(context);

      encodeInputField(writer, clientId);
      encodeDecrementButton(writer, clientId);
      encodeIncrementButton(writer, clientId);
   }

   public void decode(FacesContext context) {
      Map<String, String> requestMap 
         = context.getExternalContext().getRequestParameterMap();
      String clientId = getClientId(context);

      int increment;
      if (requestMap.containsKey(clientId + MORE)) increment = 1;
      else if (requestMap.containsKey(clientId + LESS)) increment = -1;
      else increment = 0;

      try {
         int submittedValue 
            = Integer.parseInt((String) requestMap.get(clientId));

         int newValue = getIncrementedValue(submittedValue, increment);
         setSubmittedValue("" + newValue);
      }
      catch(NumberFormatException ex) {
         // let the converter take care of bad input, but we still have 
         // to set the submitted value, or the converter won't have 
         // any input to deal with
         setSubmittedValue((String) requestMap.get(clientId));
      }
   }

   private void encodeInputField(ResponseWriter writer, String clientId) 
         throws IOException {
      writer.startElement("input", this);
      writer.writeAttribute("name", clientId, null);

      Object v = getValue();
      if (v != null) writer.writeAttribute("value", v, "value");

      Object size = getAttributes().get("size");
      if (size != null) writer.writeAttribute("size", size, "size");

      writer.endElement("input");
   }

   private void encodeDecrementButton(ResponseWriter writer, String clientId) 
         throws IOException {
      writer.startElement("input", this);
      writer.writeAttribute("type", "submit", null);
      writer.writeAttribute("name", clientId + LESS, null);
      writer.writeAttribute("value", "<", "value");
      writer.endElement("input");
   }

   private void encodeIncrementButton(ResponseWriter writer, String clientId) 
         throws IOException {
      writer.startElement("input", this);
      writer.writeAttribute("type", "submit", null);
      writer.writeAttribute("name", clientId + MORE, null);
      writer.writeAttribute("value", ">", "value");
      writer.endElement("input");
   }

   private int getIncrementedValue(int submittedValue, int increment) {
      Integer minimum = toInteger(getAttributes().get("minimum"));
      Integer maximum = toInteger(getAttributes().get("maximum"));
      int newValue = submittedValue + increment;

      if ((minimum == null || newValue >= minimum.intValue()) &&
         (maximum == null || newValue <= maximum.intValue()))
         return newValue;
      else
         return submittedValue;
   }   
   
   private static Integer toInteger(Object value) {      
      if (value == null) return null;
      if (value instanceof Number) return ((Number) value).intValue();
      if (value instanceof String) return Integer.parseInt((String) value);
      throw new IllegalArgumentException("Cannot convert " + value);
   }
}
