/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2011, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
package ch.qos.logback.core.joran.spi;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Stack;
import java.util.Vector;

import org.xml.sax.Attributes;
import org.xml.sax.Locator;

import ch.qos.logback.core.Context;
import ch.qos.logback.core.joran.action.Action;
import ch.qos.logback.core.joran.action.ImplicitAction;
import ch.qos.logback.core.joran.event.BodyEvent;
import ch.qos.logback.core.joran.event.EndEvent;
import ch.qos.logback.core.joran.event.SaxEvent;
import ch.qos.logback.core.joran.event.StartEvent;
import ch.qos.logback.core.spi.ContextAwareImpl;

/**
 * <id>Interpreter</id> is Joran's main driving class. It extends SAX
 * {@link org.xml.sax.helpers.DefaultHandler DefaultHandler} which invokes
 * various {@link Action actions} according to predefined patterns.
 * 
 * <p>
 * Patterns are kept in a {@link RuleStore} which is programmed to store and
 * then later produce the applicable actions for a given pattern.
 * 
 * <p>
 * The pattern corresponding to a top level &lt;a&gt; element is the string
 * <id>"a"</id>.
 * 
 * <p>
 * The pattern corresponding to an element &lt;b&gt; embedded within a top level
 * &lt;a&gt; element is the string <id>"a/b"</id>.
 * 
 * <p>
 * The pattern corresponding to an &lt;b&gt; and any level of nesting is
 * "&#42;/b. Thus, the &#42; character placed at the beginning of a pattern
 * serves as a wildcard for the level of nesting.
 * 
 * Conceptually, this is very similar to the API of commons-digester. Joran
 * offers several small advantages. First and foremost, it offers support for
 * implicit actions which result in a significant leap in flexibility. Second,
 * in our opinion better error reporting capability. Third, it is self-reliant.
 * It does not depend on other APIs, in particular commons-logging which is too
 * unreliable. Last but not least, Joran is quite tiny and is expected to remain
 * so.
 * 
 * @author Ceki G&uuml;lcu&uuml;
 * 
 */
public class Interpreter {
  private static List EMPTY_LIST = new Vector(0);

  final private RuleStore ruleStore;
  final private InterpretationContext interpretationContext;
  final private ArrayList<ImplicitAction> implicitActions;
  final private CAI_WithLocatorSupport cai;
  private Pattern pattern;
  Locator locator;
  EventPlayer player;

  /**
   * The <id>actionListStack</id> contains a list of actions that are executing
   * for the given XML element.
   * 
   * A list of actions is pushed by the {link #startElement} and popped by
   * {@link #endElement}.
   * 
   */
  Stack<List> actionListStack;

  /**
   * If the skip nested is set, then we skip all its nested elements until it is
   * set back to null at when the element's end is reached.
   */
  Pattern skip = null;

  public Interpreter(Context context, RuleStore rs, Pattern initialPattern) {
    this.cai = new CAI_WithLocatorSupport(this);
    this.cai.setContext(context);
    ruleStore = rs;
    interpretationContext = new InterpretationContext(context, this);
    implicitActions = new ArrayList<ImplicitAction>(3);
    this.pattern = initialPattern;
    actionListStack = new Stack<List>();
    player = new EventPlayer(this);
  }

  public void setInterpretationContextPropertiesMap(
      Map<String, String> propertiesMap) {
    interpretationContext.setPropertiesMap(propertiesMap);
  }

  /**
   * @deprecated replaced by {@link #getInterpretationContext()}
   */
  public InterpretationContext getExecutionContext() {
    return getInterpretationContext();
  }

  public InterpretationContext getInterpretationContext() {
    return interpretationContext;
  }

  public void startDocument() {
  }

  public void startElement(StartEvent se) {
    setDocumentLocator(se.getLocator());
    startElement(se.namespaceURI, se.localName, se.qName, se.attributes);
  }

  private void startElement(String namespaceURI, String localName,
      String qName, Attributes atts) {

    String tagName = getTagName(localName, qName);
    pattern.push(tagName);

    if (skip != null) {
      // every startElement pushes an action list
      pushEmptyActionList();
      return;
    }

    List applicableActionList = getApplicableActionList(pattern, atts);
    if (applicableActionList != null) {
      actionListStack.add(applicableActionList);
      callBeginAction(applicableActionList, tagName, atts);
    } else {
      // every startElement pushes an action list
      pushEmptyActionList();
      String errMsg = "no applicable action for [" + tagName
          + "], current pattern is [" + pattern + "]";
      cai.addError(errMsg);
    }
  }

  /**
   * This method is used to
   */
  private void pushEmptyActionList() {
    actionListStack.add(EMPTY_LIST);
  }

  public void characters(BodyEvent be) {

    setDocumentLocator(be.locator);

    String body = be.getText();
    List applicableActionList = (List) actionListStack.peek();

    if (body != null) {
      body = body.trim();
    }
    if (body.length() > 0) {
      // System.out.println("calling body method with ["+body+ "]");
      callBodyAction(applicableActionList, body);
    }
  }

  public void endElement(EndEvent endEvent) {
    setDocumentLocator(endEvent.locator);
    endElement(endEvent.namespaceURI, endEvent.localName, endEvent.qName);
  }

  private void endElement(String namespaceURI, String localName, String qName) {
    // given that an action list is always pushed for every startElement, we
    // need
    // to always pop for every endElement
    List applicableActionList = (List) actionListStack.pop();

    if (skip != null) {
      if (skip.equals(pattern)) {
        skip = null;
      }
    } else if (applicableActionList != EMPTY_LIST) {
      callEndAction(applicableActionList, getTagName(localName, qName));
    }

    // given that we always push, we must also pop the pattern
    pattern.pop();
  }

  public Locator getLocator() {
    return locator;
  }

  public void setDocumentLocator(Locator l) {
    locator = l;
  }

  String getTagName(String localName, String qName) {
    String tagName = localName;

    if ((tagName == null) || (tagName.length() < 1)) {
      tagName = qName;
    }

    return tagName;
  }

  public void addImplicitAction(ImplicitAction ia) {
    implicitActions.add(ia);
  }

  /**
   * Check if any implicit actions are applicable. As soon as an applicable
   * action is found, it is returned. Thus, the returned list will have at most
   * one element.
   */
  List lookupImplicitAction(Pattern pattern, Attributes attributes,
      InterpretationContext ec) {
    int len = implicitActions.size();

    for (int i = 0; i < len; i++) {
      ImplicitAction ia = (ImplicitAction) implicitActions.get(i);

      if (ia.isApplicable(pattern, attributes, ec)) {
        List<Action> actionList = new ArrayList<Action>(1);
        actionList.add(ia);

        return actionList;
      }
    }

    return null;
  }

  /**
   * Return the list of applicable patterns for this
   */
  List getApplicableActionList(Pattern pattern, Attributes attributes) {
    List applicableActionList = ruleStore.matchActions(pattern);

    // logger.debug("set of applicable patterns: " + applicableActionList);
    if (applicableActionList == null) {
      applicableActionList = lookupImplicitAction(pattern, attributes,
          interpretationContext);
    }

    return applicableActionList;
  }

  void callBeginAction(List applicableActionList, String tagName,
      Attributes atts) {
    if (applicableActionList == null) {
      return;
    }

    Iterator i = applicableActionList.iterator();
    while (i.hasNext()) {
      Action action = (Action) i.next();
      // now let us invoke the action. We catch and report any eventual
      // exceptions
      try {
        action.begin(interpretationContext, tagName, atts);
      } catch (ActionException e) {
        skip = (Pattern) pattern.clone();
        cai.addError("ActionException in Action for tag [" + tagName + "]", e);
      } catch (RuntimeException e) {
        skip = (Pattern) pattern.clone();
        cai.addError("RuntimeException in Action for tag [" + tagName + "]", e);
      }
    }
  }

  private void callBodyAction(List applicableActionList, String body) {
    if (applicableActionList == null) {
      return;
    }
    Iterator i = applicableActionList.iterator();

    while (i.hasNext()) {
      Action action = (Action) i.next();
      try {
        action.body(interpretationContext, body);
      } catch (ActionException ae) {
        cai
            .addError("Exception in end() methd for action [" + action + "]",
                ae);
      }
    }
  }

  private void callEndAction(List applicableActionList, String tagName) {
    if (applicableActionList == null) {
      return;
    }

    // logger.debug("About to call end actions on node: [" + localName + "]");
    Iterator i = applicableActionList.iterator();

    while (i.hasNext()) {
      Action action = (Action) i.next();
      // now let us invoke the end method of the action. We catch and report
      // any eventual exceptions
      try {
        action.end(interpretationContext, tagName);
      } catch (ActionException ae) {
        // at this point endAction, there is no point in skipping children as
        // they have been already processed
        cai.addError("ActionException in Action for tag [" + tagName + "]", ae);
      } catch (RuntimeException e) {
        // no point in setting skip
        cai.addError("RuntimeException in Action for tag [" + tagName + "]", e);
      }
    }
  }

  public RuleStore getRuleStore() {
    return ruleStore;
  }

  public void play(List<SaxEvent> eventList) {
    player.play(eventList);
  }

  public void addEventsDynamically(List<SaxEvent> eventList, int offset) {
    if (player != null) {
      player.addEventsDynamically(eventList, offset);
    }
  }
}

/**
 * When {@link Interpreter} class is used as the origin of an
 * {@link ContextAwareImpl} instance, then XML locator information is lost. This
 * class preserves locator information (as a string).
 * 
 * @author ceki
 */
class CAI_WithLocatorSupport extends ContextAwareImpl {

  CAI_WithLocatorSupport(Interpreter interpreter) {
    super(interpreter);
  }

  @Override
  protected Object getOrigin() {
    Interpreter i = (Interpreter) super.getOrigin();
    Locator locator = i.locator;
    if (locator != null) {
      return Interpreter.class.getName() + "@" + locator.getLineNumber() + ":"
          + locator.getColumnNumber();
    } else {
      return Interpreter.class.getName() + "@NA:NA";
    }
  }
}
