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A collection of general utilities.
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/*
 * Copyright (c) 2013-2018, João Vitor Verona Biazibetti - All Rights Reserved
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see .
 *
 * https://www.github.com/BloodShura
 */

package com.github.bloodshura.x.utilities.eval.compiler;

import com.github.bloodshura.x.utilities.eval.enumeration.Operator;
import com.github.bloodshura.x.utilities.eval.exception.EvaluationException;
import com.github.bloodshura.x.utilities.eval.operation.Operation;
import com.github.bloodshura.x.utilities.eval.operation.OperationFactory;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;

public class Compiler {
	@Nonnull
	public static Operation compile(@Nonnull Tokenizer tokenizer) throws EvaluationException {
		Object expression = compile(tokenizer, null, null, 0, (char) 0, -1);

		if (expression instanceof Operation) {
			return (Operation) expression;
		}

		return OperationFactory.createNop(expression);
	}

	@Nonnull
	protected static Object compile(@Nonnull Tokenizer tokenizer, @Nullable Object preReadOperand, @Nullable Operator preReadOperator, int nestingLevel, char endOfExpressionChar, int terminatePrecedence) throws EvaluationException {
		Object operand = preReadOperand != null ? preReadOperand : getOperand(tokenizer, nestingLevel);
		Operator operator = preReadOperator != null ? preReadOperator : tokenizer.getOperator(endOfExpressionChar);

		while (operator != Operator.END) {
			if (operator == Operator.TERNARY) {
				Object operand2 = compile(tokenizer, null, null, nestingLevel, ':', -1);
				Object operand3 = compile(tokenizer, null, null, nestingLevel, endOfExpressionChar, -1);

				operand = OperationFactory.createTernaryValue(operator, operand, operand2, operand3);
				operator = Operator.END;
			}
			else {
				Object nextOperand = getOperand(tokenizer, nestingLevel);
				Operator nextOperator = tokenizer.getOperator(endOfExpressionChar);

				if (nextOperator == Operator.END) {
					operand = OperationFactory.createBinaryValue(operator, operand, nextOperand);
					operator = Operator.END;

					if (preReadOperator != null && endOfExpressionChar != 0) {
						tokenizer.pushBack(Operator.END);
					}
				}
				else if (nextOperator.getPrecedence() <= terminatePrecedence) {
					operand = OperationFactory.createBinaryValue(operator, operand, nextOperand);
					tokenizer.pushBack(nextOperator);
					operator = Operator.END;
				}
				else if (operator.getPrecedence() >= nextOperator.getPrecedence()) {
					operand = OperationFactory.createBinaryValue(operator, operand, nextOperand);
					operator = nextOperator;
				}
				else {
					operand = OperationFactory.createBinaryValue(operator, operand, compile(tokenizer, nextOperand, nextOperator, nestingLevel, endOfExpressionChar, operator.getPrecedence()));
					operator = tokenizer.getOperator(endOfExpressionChar);

					if (operator == Operator.END && preReadOperator != null && endOfExpressionChar != 0) {
						tokenizer.pushBack(Operator.END);
					}
				}
			}
		}

		return operand;
	}

	@Nonnull
	protected static Object getOperand(@Nonnull Tokenizer tokenizer, int nestingLevel) throws EvaluationException {
		Object operand = tokenizer.getOperand();

		if (operand.equals(Tokenizer.START_EXPRESSION)) {
			return compile(tokenizer, null, null, nestingLevel + 1, Tokenizer.END_EXPRESSION, -1);
		}

		if (operand instanceof Operator) {
			return OperationFactory.createUnaryValue((Operator) operand, getOperand(tokenizer, nestingLevel));
		}

		return operand;
	}
}