/* ====================================================================
   Licensed to the Apache Software Foundation (ASF) under one or more
   contributor license agreements.  See the NOTICE file distributed with
   this work for additional information regarding copyright ownership.
   The ASF licenses this file to You under the Apache License, Version 2.0
   (the "License"); you may not use this file except in compliance with
   the License.  You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
==================================================================== */

package org.apache.poi.ss.formula.ptg;

import java.util.Locale;
import java.util.Map;
import java.util.function.Supplier;

import org.apache.poi.ss.formula.function.FunctionMetadata;
import org.apache.poi.ss.formula.function.FunctionMetadataRegistry;
import org.apache.poi.util.GenericRecordUtil;

/**
 * This class provides the base functionality for Excel sheet functions
 * There are two kinds of function Ptgs - tFunc and tFuncVar
 * Therefore, this class will have ONLY two subclasses
 */
public abstract class AbstractFunctionPtg extends OperationPtg {

    /**
     * The name of the IF function (i.e. "IF").  Extracted as a constant for clarity.
     */
    public static final String FUNCTION_NAME_IF = "IF";
    /** All external functions have function index 255 */
    private static final short FUNCTION_INDEX_EXTERNAL = 255;

    private final byte returnClass;
    private final byte[] paramClass;

    private final int _numberOfArgs;
    private final short _functionIndex;

    protected AbstractFunctionPtg(int functionIndex, int pReturnClass, byte[] paramTypes, int nParams) {
        _numberOfArgs = nParams;
        if (functionIndex < Short.MIN_VALUE || functionIndex > Short.MAX_VALUE)
            throw new IllegalStateException("functionIndex " + functionIndex + " cannot be cast to short");
        _functionIndex = (short) functionIndex;
        if (pReturnClass < Byte.MIN_VALUE || pReturnClass > Byte.MAX_VALUE)
            throw new IllegalStateException("pReturnClass " + pReturnClass + " cannot be cast to byte");
        returnClass = (byte) pReturnClass;
        paramClass = paramTypes;
    }
    @Override
    public final boolean isBaseToken() {
        return false;
    }

    public final short getFunctionIndex() {
        return _functionIndex;
    }
    @Override
    public final int getNumberOfOperands() {
        return _numberOfArgs;
    }

    public final String getName() {
        return lookupName(_functionIndex);
    }
    /**
     * external functions get some special processing
     * @return {@code true} if this is an external function
     */
    public final boolean isExternalFunction() {
        return _functionIndex == FUNCTION_INDEX_EXTERNAL;
    }

    @Override
    public final String toFormulaString() {
        return getName();
    }

    @Override
    public String toFormulaString(String[] operands) {
        StringBuilder buf = new StringBuilder();

        if(isExternalFunction()) {
            buf.append(operands[0]); // first operand is actually the function name
            appendArgs(buf, 1, operands);
        } else {
            buf.append(getName());
            appendArgs(buf, 0, operands);
        }
        return buf.toString();
    }

    private static void appendArgs(StringBuilder buf, int firstArgIx, String[] operands) {
        buf.append('(');
        for (int i=firstArgIx;i<operands.length;i++) {
            if (i>firstArgIx) {
                buf.append(',');
            }
            buf.append(operands[i]);
        }
        buf.append(")");
    }

    @Override
    public abstract int getSize();


    /**
     * Used to detect whether a function name found in a formula is one of the standard excel functions
     * <p>
     * The name matching is case insensitive.
     * @return {@code true} if the name specifies a standard worksheet function,
     *  {@code false} if the name should be assumed to be an external function.
     */
    public static boolean isBuiltInFunctionName(String name) {
        short ix = FunctionMetadataRegistry.lookupIndexByName(name.toUpperCase(Locale.ROOT));
        return ix >= 0;
    }

    protected String lookupName(short index) {
        return lookupName(index, false);
    }

    protected final String lookupName(short index, boolean isCetab) {
        if(index == FunctionMetadataRegistry.FUNCTION_INDEX_EXTERNAL) {
            return "#external#";
        }
        final FunctionMetadata fm;
        if(isCetab) {
            fm = FunctionMetadataRegistry.getCetabFunctionByIndex(index);
        } else {
            fm = FunctionMetadataRegistry.getFunctionByIndex(index);
        }
        if(fm == null) {
            throw new IllegalStateException("bad function index (" + index + ", " + isCetab + ")");
        }
        return fm.getName();
    }

    /**
     * Resolves internal function names into function indexes.
     * <p>
     * The name matching is case insensitive.
     * @return the standard worksheet function index if found, otherwise {@code FUNCTION_INDEX_EXTERNAL}
     */
    protected static short lookupIndex(String name) {
        short ix = FunctionMetadataRegistry.lookupIndexByName(name.toUpperCase(Locale.ROOT));
        if (ix < 0) {
            return FUNCTION_INDEX_EXTERNAL;
        }
        return ix;
    }

    @Override
    public byte getDefaultOperandClass() {
        return returnClass;
    }

    public final byte getParameterClass(int index) {
        if (index >= paramClass.length) {
            // For var-arg (and other?) functions, the metadata does not list all the parameter
            // operand classes.  In these cases, all extra parameters are assumed to have the
            // same operand class as the last one specified.
            return paramClass[paramClass.length - 1];
        }
        return paramClass[index];
    }

    @Override
    public Map<String, Supplier<?>> getGenericProperties() {
        return GenericRecordUtil.getGenericProperties(
            "functionIndex", this::getFunctionIndex,
            "functionName", this::getName,
            "numberOfOperands", this::getNumberOfOperands,
            "externalFunction", this::isExternalFunction,
            "defaultOperandClass", this::getDefaultOperandClass
        );
    }
}
