poi/src/java/org/apache/poi/ss/formula/OperandClassTransformer.java

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   this work for additional information regarding copyright ownership.
   The ASF licenses this file to You under the Apache License, Version 2.0
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package org.apache.poi.ss.formula;

import org.apache.poi.ss.formula.ptg.AbstractFunctionPtg;
import org.apache.poi.ss.formula.ptg.AttrPtg;
import org.apache.poi.ss.formula.ptg.ControlPtg;
import org.apache.poi.ss.formula.ptg.FuncVarPtg;
import org.apache.poi.ss.formula.ptg.IntersectionPtg;
import org.apache.poi.ss.formula.ptg.MemAreaPtg;
import org.apache.poi.ss.formula.ptg.MemFuncPtg;
import org.apache.poi.ss.formula.ptg.Ptg;
import org.apache.poi.ss.formula.ptg.RangePtg;
import org.apache.poi.ss.formula.ptg.UnionPtg;
import org.apache.poi.ss.formula.ptg.ValueOperatorPtg;

/**
 * This class performs 'operand class' transformation. Non-base tokens are classified into three
 * operand classes:
 * <ul>
 * <li>reference</li>
 * <li>value</li>
 * <li>array</li>
 * </ul>
 * <p/>
 *
 * The final operand class chosen for each token depends on the formula type and the token's place
 * in the formula. If POI gets the operand class wrong, Excel <em>may</em> interpret the formula
 * incorrectly.  This condition is typically manifested as a formula cell that displays as '#VALUE!',
 * but resolves correctly when the user presses F2, enter.<p/>
 *
 * The logic implemented here was partially inspired by the description in
 * "OpenOffice.org's Documentation of the Microsoft Excel File Format".  The model presented there
 * seems to be inconsistent with observed Excel behaviour (These differences have not been fully
 * investigated). The implementation in this class has been heavily modified in order to satisfy
 * concrete examples of how Excel performs the same logic (see TestRVA).<p/>
 *
 * Hopefully, as additional important test cases are identified and added to the test suite,
 * patterns might become more obvious in this code and allow for simplification.
 *
 * @author Josh Micich
 */
final class OperandClassTransformer {

	private final int _formulaType;

	public OperandClassTransformer(int formulaType) {
		_formulaType = formulaType;
	}

	/**
	 * Traverses the supplied formula parse tree, calling <tt>Ptg.setClass()</tt> for each non-base
	 * token to set its operand class.
	 */
	public void transformFormula(ParseNode rootNode) {
		byte rootNodeOperandClass;
		switch (_formulaType) {
			case FormulaType.CELL:
				rootNodeOperandClass = Ptg.CLASS_VALUE;
				break;
			case FormulaType.ARRAY:
				rootNodeOperandClass = Ptg.CLASS_ARRAY;
				break;
			case FormulaType.NAMEDRANGE:
			case FormulaType.DATAVALIDATION_LIST:
				rootNodeOperandClass = Ptg.CLASS_REF;
				break;
			default:
				throw new RuntimeException("Incomplete code - formula type ("
						+ _formulaType + ") not supported yet");

		}
		transformNode(rootNode, rootNodeOperandClass, false);
	}

	/**
	 * @param callerForceArrayFlag <code>true</code> if one of the current node's parents is a
	 * function Ptg which has been changed from default 'V' to 'A' type (due to requirements on
	 * the function return value).
	 */
	private void transformNode(ParseNode node, byte desiredOperandClass,
			boolean callerForceArrayFlag) {
		Ptg token = node.getToken();
		ParseNode[] children = node.getChildren();
		boolean isSimpleValueFunc = isSimpleValueFunction(token);

		if (isSimpleValueFunc) {
			boolean localForceArray = desiredOperandClass == Ptg.CLASS_ARRAY;
			for (int i = 0; i < children.length; i++) {
				transformNode(children[i], desiredOperandClass, localForceArray);
			}
			setSimpleValueFuncClass((AbstractFunctionPtg) token, desiredOperandClass, callerForceArrayFlag);
			return;
		}

		if (isSingleArgSum(token)) {
			// Need to process the argument of SUM with transformFunctionNode below
			// so make a dummy FuncVarPtg for that call.
			token = FuncVarPtg.SUM;
			// Note - the tAttrSum token (node.getToken()) is a base
			// token so does not need to have its operand class set
		}
		if (token instanceof ValueOperatorPtg || token instanceof ControlPtg
				|| token instanceof MemFuncPtg
				|| token instanceof MemAreaPtg
				|| token instanceof UnionPtg
				|| token instanceof IntersectionPtg) {
			// Value Operator Ptgs and Control are base tokens, so token will be unchanged
			// but any child nodes are processed according to desiredOperandClass and callerForceArrayFlag

			// As per OOO documentation Sec 3.2.4 "Token Class Transformation", "Step 1"
			// All direct operands of value operators that are initially 'R' type will
			// be converted to 'V' type.
			byte localDesiredOperandClass = desiredOperandClass == Ptg.CLASS_REF ? Ptg.CLASS_VALUE : desiredOperandClass;
			for (int i = 0; i < children.length; i++) {
				transformNode(children[i], localDesiredOperandClass, callerForceArrayFlag);
			}
			return;
		}
		if (token instanceof AbstractFunctionPtg) {
			transformFunctionNode((AbstractFunctionPtg) token, children, desiredOperandClass, callerForceArrayFlag);
			return;
		}
		if (children.length > 0) {
			if (token == RangePtg.instance) {
				// TODO is any token transformation required under the various ref operators?
				return;
			}
			throw new IllegalStateException("Node should not have any children");
		}

		if (token.isBaseToken()) {
			// nothing to do
			return;
		}
		token.setClass(transformClass(token.getPtgClass(), desiredOperandClass, callerForceArrayFlag));
	}

	private static boolean isSingleArgSum(Ptg token) {
		if (token instanceof AttrPtg) {
			AttrPtg attrPtg = (AttrPtg) token;
			return attrPtg.isSum();
		}
		return false;
	}

	private static boolean isSimpleValueFunction(Ptg token) {
		if (token instanceof AbstractFunctionPtg) {
			AbstractFunctionPtg aptg = (AbstractFunctionPtg) token;
			if (aptg.getDefaultOperandClass() != Ptg.CLASS_VALUE) {
				return false;
			}
			int numberOfOperands = aptg.getNumberOfOperands();
			for (int i=numberOfOperands-1; i>=0; i--) {
				if (aptg.getParameterClass(i) != Ptg.CLASS_VALUE) {
					return false;
				}
			}
			return true;
		}
		return false;
	}

	private byte transformClass(byte currentOperandClass, byte desiredOperandClass,
			boolean callerForceArrayFlag) {
		switch (desiredOperandClass) {
			case Ptg.CLASS_VALUE:
				if (!callerForceArrayFlag) {
					return Ptg.CLASS_VALUE;
				}
				// else fall through
			case Ptg.CLASS_ARRAY:
				return Ptg.CLASS_ARRAY;
			case Ptg.CLASS_REF:
				if (!callerForceArrayFlag) {
					return currentOperandClass;
				}
				return Ptg.CLASS_REF;
		}
		throw new IllegalStateException("Unexpected operand class (" + desiredOperandClass + ")");
	}

	private void transformFunctionNode(AbstractFunctionPtg afp, ParseNode[] children,
			byte desiredOperandClass, boolean callerForceArrayFlag) {

		boolean localForceArrayFlag;
		byte defaultReturnOperandClass = afp.getDefaultOperandClass();

		if (callerForceArrayFlag) {
			switch (defaultReturnOperandClass) {
				case Ptg.CLASS_REF:
					if (desiredOperandClass == Ptg.CLASS_REF) {
						afp.setClass(Ptg.CLASS_REF);
					} else {
						afp.setClass(Ptg.CLASS_ARRAY);
					}
					localForceArrayFlag = false;
					break;
				case Ptg.CLASS_ARRAY:
					afp.setClass(Ptg.CLASS_ARRAY);
					localForceArrayFlag = false;
					break;
				case Ptg.CLASS_VALUE:
					afp.setClass(Ptg.CLASS_ARRAY);
					localForceArrayFlag = true;
					break;
				default:
					throw new IllegalStateException("Unexpected operand class ("
							+ defaultReturnOperandClass + ")");
			}
		} else {
			if (defaultReturnOperandClass == desiredOperandClass) {
				localForceArrayFlag = false;
				// an alternative would have been to for non-base Ptgs to set their operand class
				// from their default, but this would require the call in many subclasses because
				// the default OC is not known until the end of the constructor
				afp.setClass(defaultReturnOperandClass);
			} else {
				switch (desiredOperandClass) {
					case Ptg.CLASS_VALUE:
						// always OK to set functions to return 'value'
						afp.setClass(Ptg.CLASS_VALUE);
						localForceArrayFlag = false;
						break;
					case Ptg.CLASS_ARRAY:
						switch (defaultReturnOperandClass) {
							case Ptg.CLASS_REF:
								afp.setClass(Ptg.CLASS_REF);
//								afp.setClass(Ptg.CLASS_ARRAY);
								break;
							case Ptg.CLASS_VALUE:
								afp.setClass(Ptg.CLASS_ARRAY);
								break;
							default:
								throw new IllegalStateException("Unexpected operand class ("
										+ defaultReturnOperandClass + ")");
						}
						localForceArrayFlag = (defaultReturnOperandClass == Ptg.CLASS_VALUE);
						break;
					case Ptg.CLASS_REF:
						switch (defaultReturnOperandClass) {
							case Ptg.CLASS_ARRAY:
								afp.setClass(Ptg.CLASS_ARRAY);
								break;
							case Ptg.CLASS_VALUE:
								afp.setClass(Ptg.CLASS_VALUE);
								break;
							default:
								throw new IllegalStateException("Unexpected operand class ("
										+ defaultReturnOperandClass + ")");
						}
						localForceArrayFlag = false;
						break;
					default:
						throw new IllegalStateException("Unexpected operand class ("
								+ desiredOperandClass + ")");
				}

			}
		}

		for (int i = 0; i < children.length; i++) {
			ParseNode child = children[i];
			byte paramOperandClass = afp.getParameterClass(i);
			transformNode(child, paramOperandClass, localForceArrayFlag);
		}
	}

	private void setSimpleValueFuncClass(AbstractFunctionPtg afp,
			byte desiredOperandClass, boolean callerForceArrayFlag) {

		if (callerForceArrayFlag  || desiredOperandClass == Ptg.CLASS_ARRAY) {
			afp.setClass(Ptg.CLASS_ARRAY);
		} else {
			afp.setClass(Ptg.CLASS_VALUE);
		}
	}
}