package io.jawk.backend;
   
   /*-
    * ╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲
    * Jawk
    * ჻჻჻჻჻჻
    * Copyright (C) 2006 - 2026 MetricsHub
    * ჻჻჻჻჻჻
    * This program is free software: you can redistribute it and/or modify
   * it under the terms of the GNU Lesser General Public License as
   * published by the Free Software Foundation, either version 3 of the
   * License, or (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Lesser Public License for more details.
   *
   * You should have received a copy of the GNU General Lesser Public
   * License along with this program.  If not, see
   * <http://www.gnu.org/licenses/lgpl-3.0.html>.
   * ╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱╲╱
   */
  
  import java.util.ArrayDeque;
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.Deque;
  import java.util.LinkedHashMap;
  import java.util.List;
  import java.util.Map;
  import io.jawk.intermediate.UninitializedObject;
  
  /**
   * Runtime stack used by the AVM interpreter.
   */
  class RuntimeStack {
  
  	static final UninitializedObject BLANK = new UninitializedObject();
  	private static final Object[] NULL_LOCALS_SENTINEL = new Object[0];
  
  	private Object[] globals = null;
  	private List<String> globalNamesByOffset = Collections.emptyList();
  	private Map<String, Integer> globalOffsetsByName = Collections.emptyMap();
  	private Object[] locals = null;
  	private Deque<Object[]> localsStack = new ArrayDeque<Object[]>();
  	private Deque<Integer> returnIndexes = new ArrayDeque<Integer>();
  
  	@SuppressWarnings("unused")
  	public void dump() {
  		System.out.println("globals = " + Arrays.toString(globals));
  		System.out.println("globalNamesByOffset = " + globalNamesByOffset);
  		System.out.println("locals = " + Arrays.toString(locals));
  		System.out.println("localsStack = " + localsStack);
  		System.out.println("returnIndexes = " + returnIndexes);
  	}
  
  	Object[] getNumGlobals() {
  		return globals;
  	}
  
  	void reset() {
  		clearGlobals();
  		resetTransientState();
  	}
  
  	void clearGlobals() {
  		globals = null;
  		globalNamesByOffset = Collections.emptyList();
  		globalOffsetsByName = Collections.emptyMap();
  	}
  
  	void resetTransientState() {
  		locals = null;
  		localsStack.clear();
  		returnIndexes.clear();
  		returnValue = null;
  	}
  
  	/** Must be one of the first methods executed. */
  	void setNumGlobals(long l, Map<String, Integer> offsetsByName) {
  		globals = new Object[(int) l];
  		for (int i = 0; i < l; i++) {
  			globals[i] = null;
  		}
  		setGlobalLayoutMetadata((int) l, offsetsByName);
  		// must accept multiple executions
  		// expandFrameIfNecessary(num_globals);
  	}
  
  	/*
  	 * // this assumes globals = Object[0] upon initialization
  	 * private void expandFrameIfNecessary(int num_globals) {
  	 * if (num_globals == globals.length)
  	 * // no need for expansion;
  	 * // do nothing
  	 * return;
  	 * Object[] new_frame = new Object[num_globals];
 	 * for (int i=0;i<globals.length;++i)
 	 * new_frame[i] = globals[i];
 	 * globals = new_frame;
 	 * }
 	 */
 
 	void rebindGlobals(List<String> namesByOffset) {
 		globals = new Object[namesByOffset.size()];
 		for (int i = 0; i < globals.length; i++) {
 			globals[i] = null;
 		}
 		setGlobalLayoutMetadata(namesByOffset);
 	}
 
 	Map<String, Object> snapshotGlobalVariables() {
 		Map<String, Object> snapshot = new LinkedHashMap<String, Object>();
 		if (globals == null) {
 			return snapshot;
 		}
 		for (int i = 0; i < globals.length && i < globalNamesByOffset.size(); i++) {
 			String name = globalNamesByOffset.get(i);
 			if (name != null) {
 				snapshot.put(name, globals[i]);
 			}
 		}
 		return snapshot;
 	}
 
 	boolean hasGlobalVariable(String name) {
 		return globalOffsetsByName.containsKey(name);
 	}
 
 	Object getGlobalVariable(String name) {
 		Integer offset = globalOffsetsByName.get(name);
 		return offset == null ? null : globals[offset.intValue()];
 	}
 
 	void setGlobalVariable(String name, Object value) {
 		Integer offset = globalOffsetsByName.get(name);
 		if (offset != null) {
 			globals[offset.intValue()] = value;
 		}
 	}
 
 	String getGlobalName(int offset) {
 		return offset >= 0 && offset < globalNamesByOffset.size() ? globalNamesByOffset.get(offset) : null;
 	}
 
 	Object getVariable(long offset, boolean isGlobal) {
 		if (isGlobal) {
 			return globals[(int) offset];
 		} else {
 			return locals[(int) offset];
 		}
 	}
 
 	Object[] getVariableFrame(boolean isGlobal) {
 		return isGlobal ? globals : locals;
 	}
 
 	int frameCount() {
 		return localsStack.size();
 	}
 
 	Object setVariable(long offset, Object val, boolean isGlobal) {
 		if (isGlobal) {
 			globals[(int) offset] = val;
 			return val;
 		} else {
 			locals[(int) offset] = val;
 			return val;
 		}
 	}
 
 	// for _DELETE_ARRAY_
 	void removeVariable(long offset, boolean isGlobal) {
 		if (isGlobal) {
 			globals[(int) offset] = null;
 		} else {
 			locals[(int) offset] = null;
 		}
 	}
 
 	void setFilelistVariable(int offset, Object value) {
 		globals[offset] = value;
 	}
 
 	void pushFrame(long numFormalParams, int positionIdx) {
 		localsStack.push(locals == null ? NULL_LOCALS_SENTINEL : locals);
 		locals = new Object[(int) numFormalParams];
 		returnIndexes.push(positionIdx);
 	}
 
 	/** returns the position index */
 	int popFrame() {
 		Object[] restoredLocals = localsStack.pop();
 		locals = restoredLocals == NULL_LOCALS_SENTINEL ? null : restoredLocals;
 		return returnIndexes.pop();
 	}
 
 	void popAllFrames() {
 		for (int i = localsStack.size(); i > 0; i--) {
 			Object[] restoredLocals = localsStack.pop();
 			locals = restoredLocals == NULL_LOCALS_SENTINEL ? null : restoredLocals;
 			returnIndexes.pop();
 		}
 	}
 
 	private Object returnValue;
 
 	void setReturnValue(Object obj) {
 		returnValue = obj;
 	}
 
 	Object getReturnValue() {
 		Object retval;
 		if (returnValue == null) {
 			retval = BLANK;
 		} else {
 			retval = returnValue;
 		}
 		returnValue = null;
 		return retval;
 	}
 
 	private void setGlobalLayoutMetadata(int numGlobals, Map<String, Integer> offsetsByName) {
 		List<String> namesByOffset = new ArrayList<String>(Collections.nCopies(numGlobals, (String) null));
 		if (offsetsByName != null) {
 			for (Map.Entry<String, Integer> entry : offsetsByName.entrySet()) {
 				int offset = entry.getValue().intValue();
 				if (offset >= 0 && offset < numGlobals) {
 					namesByOffset.set(offset, entry.getKey());
 				}
 			}
 		}
 		setGlobalLayoutMetadata(namesByOffset);
 	}
 
 	private void setGlobalLayoutMetadata(List<String> namesByOffset) {
 		globalNamesByOffset = new ArrayList<String>(namesByOffset);
 		Map<String, Integer> offsetsByName = new LinkedHashMap<String, Integer>();
 		for (int i = 0; i < namesByOffset.size(); i++) {
 			String name = namesByOffset.get(i);
 			if (name != null) {
 				offsetsByName.put(name, Integer.valueOf(i));
 			}
 		}
 		globalOffsetsByName = offsetsByName;
 	}
 }