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/**
 * (c) Copyright 2018, 2019 IBM Corporation
 * 1 New Orchard Road, 
 * Armonk, New York, 10504-1722
 * United States
 * +1 914 499 1900
 * support: Nathaniel Mills [email protected]
 *
 * Licensed 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 com.api.jsonata4java.expressions.functions;

import java.util.ArrayList;
import java.util.List;

import org.antlr.v4.runtime.ParserRuleContext;
import org.antlr.v4.runtime.tree.TerminalNode;

import com.api.jsonata4java.expressions.EvaluateRuntimeException;
import com.api.jsonata4java.expressions.ExpressionsVisitor;
import com.api.jsonata4java.expressions.generated.MappingExpressionParser;
import com.api.jsonata4java.expressions.generated.MappingExpressionParser.ExprContext;
import com.api.jsonata4java.expressions.generated.MappingExpressionParser.ExprListContext;
import com.api.jsonata4java.expressions.generated.MappingExpressionParser.ExprValuesContext;
import com.api.jsonata4java.expressions.generated.MappingExpressionParser.Function_callContext;
import com.api.jsonata4java.expressions.generated.MappingExpressionParser.VarListContext;
import com.api.jsonata4java.expressions.generated.MappingExpressionParser.Var_recallContext;
import com.api.jsonata4java.expressions.utils.Constants;
import com.fasterxml.jackson.databind.JsonNode;

public class DeclaredFunction {

	VarListContext _varList;
	ExprListContext _exprList;

	public DeclaredFunction(VarListContext varList, ExprListContext exprList) {
		if (varList == null) {
			throw new EvaluateRuntimeException("VarListContext passed is null.");
		}
		if (exprList == null) {
			throw new EvaluateRuntimeException("ExprListContext passed is null.");
		}
		_varList = varList;
		_exprList = exprList;
	}

	public ExprListContext getExpressionList() {
	   return _exprList;
	}
	
	public List getVariables() {
		List variables = _varList.getTokens(MappingExpressionParser.VAR_ID);
		if (variables == null) {
			variables = new ArrayList();
		}
		return variables;
	}

	public int getVariableCount() {
		return getVariables().size();
	}
	
	public int getMaxArgs() {
		return getVariableCount();
	}

	public int getMinArgs() {
		return getVariableCount();
	}

	public JsonNode invoke(ExpressionsVisitor expressionVisitor, ParserRuleContext ruleValues) {
		JsonNode result = null;
		ExprValuesContext exprValues = null;
		Function_callContext fctCallValues = null;
		if (ruleValues instanceof ExprValuesContext) {
		   exprValues = (ExprValuesContext)ruleValues;
   		List varListCtx = _varList.VAR_ID();
         List exprValuesCtx = new ArrayList();
         if (exprValues != null) {
         	exprValuesCtx = exprValues.exprList().expr();
         }
   		int varListCount = varListCtx.size();
   		int exprListCount = exprValuesCtx.size();
   		// ensure a direct mapping is possible
   		if (varListCount != exprListCount) {
//   			throw new EvaluateRuntimeException(
//   					"Expected equal counts for varibles (" + varListCount + ") and values (" + exprListCount + ")");
   		}
   		for (int i = 0; i < varListCount; i++) {
   			String varID = varListCtx.get(i).getText();
   			JsonNode value = expressionVisitor.visit(exprValuesCtx.get(i));
   			expressionVisitor.setVariable(varID, value);
   		}
		} else if (ruleValues instanceof Function_callContext) {
		   fctCallValues = (Function_callContext)ruleValues;
         List varListCtx = _varList.VAR_ID();
         exprValues = (ExprValuesContext)fctCallValues.exprValues();
         List exprValuesCtx = new ArrayList();
         if (exprValues != null) {
         	exprValuesCtx = exprValues.exprList().expr();
         }
         int varListCount = varListCtx.size();
         int exprListCount = exprValuesCtx.size();
         // ensure a direct mapping is possible
         if (varListCount != exprListCount) {
            throw new EvaluateRuntimeException(
                  "Expected equal counts for varibles (" + varListCount + ") and values (" + exprListCount + ")");
         }
         for (int i = 0; i < varListCount; i++) {
            String varID = varListCtx.get(i).getText();
            JsonNode value = expressionVisitor.visit(exprValuesCtx.get(i));
            expressionVisitor.setVariable(varID, value);
         }
		} else if (ruleValues instanceof Var_recallContext) {
			String fctName = ((Var_recallContext) ruleValues).VAR_ID().getText();
			// assume this is a variable pointing to a function
			DeclaredFunction declFct = expressionVisitor.getDeclaredFunction(fctName);
			if (declFct == null) {
				Function function = expressionVisitor.getJsonataFunction(fctName);
				if (function == null) {
					function = Constants.FUNCTIONS.get(fctName);
				}
				if (function != null) {
					result = function.invoke(expressionVisitor, (Function_callContext)ruleValues.getRuleContext());
				} else {
					throw new EvaluateRuntimeException("Unknown function: " + fctName);
				}
			} else {
	         for (int i = 0; i < declFct.getVariableCount(); i++) {
	            String varID = declFct._varList.VAR_ID().get(i).getText();
	            JsonNode value = expressionVisitor.visit(_exprList.expr().get(i));
	            expressionVisitor.setVariable(varID, value);
	         }
				result = expressionVisitor.visit(declFct._exprList);
			}
		}// else EmptyValuesContext
      result = expressionVisitor.visit(_exprList);
		return result;
	}
}