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package de.hysky.skyblocker.utils;
import net.minecraft.util.Util;
import java.util.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Calculator {
public enum TokenType {
NUMBER, OPERATOR, L_PARENTHESIS, R_PARENTHESIS
}
public static class Token {
public TokenType type;
String value;
int tokenLength;
}
private static final Pattern NUMBER_PATTERN = Pattern.compile("(\\d+\\.?\\d*)([kmbs]?)");
private static final HashMap<String, Integer> magnitudeValues = Util.make(new HashMap<>(), map -> {
map.put("s", 64);
map.put("k", 1000);
map.put("m", 1000000);
map.put("b", 1000000000);
});
private static List<Token> lex(String input) {
List<Token> tokens = new ArrayList<>();
input = input.replace(" ", "").toLowerCase().replace("x", "*");
int i = 0;
while (i < input.length()) {
Token token = new Token();
switch (input.charAt(i)) {
case '+', '-', '*', '/' -> {
token.type = TokenType.OPERATOR;
token.value = String.valueOf(input.charAt(i));
token.tokenLength = 1;
}
case '(' -> {
token.type = TokenType.L_PARENTHESIS;
token.value = String.valueOf(input.charAt(i));
token.tokenLength = 1;
//add implicit multiplication when there is a number before brackets
if (!tokens.isEmpty()) {
TokenType lastType = tokens.get(tokens.size() - 1).type;
if (lastType == TokenType.R_PARENTHESIS || lastType == TokenType.NUMBER) {
Token mutliplyToken = new Token();
mutliplyToken.type = TokenType.OPERATOR;
mutliplyToken.value = "*";
tokens.add(mutliplyToken);
}
}
}
case ')' -> {
token.type = TokenType.R_PARENTHESIS;
token.value = String.valueOf(input.charAt(i));
token.tokenLength = 1;
}
default -> {
token.type = TokenType.NUMBER;
Matcher numberMatcher = NUMBER_PATTERN.matcher(input.substring(i));
if (!numberMatcher.find()) {//invalid value to lex
throw new UnsupportedOperationException("invalid character");
}
int end = numberMatcher.end();
token.value = input.substring(i, i + end);
token.tokenLength = end;
}
}
tokens.add(token);
i += token.tokenLength;
}
return tokens;
}
/**
* This is an implementation of the shunting yard algorithm to convert the equation to reverse polish notation
*
* @param tokens equation in infix notation order
* @return equation in RPN order
*/
private static List<Token> shunt(List<Token> tokens) {
Deque<Token> operatorStack = new ArrayDeque<>();
List<Token> outputQueue = new ArrayList<>();
for (Token shuntingToken : tokens)
switch (shuntingToken.type) {
case NUMBER -> {
outputQueue.add(shuntingToken);
}
case OPERATOR -> {
int precedence = getPrecedence(shuntingToken.value);
while (!operatorStack.isEmpty()) {
Token leftToken = operatorStack.peek();
if (leftToken.type == TokenType.L_PARENTHESIS) {
break;
}
assert (leftToken.type == TokenType.OPERATOR);
int leftPrecedence = getPrecedence(leftToken.value);
if (leftPrecedence >= precedence) {
outputQueue.add(operatorStack.pop());
continue;
}
break;
}
operatorStack.push(shuntingToken);
}
case L_PARENTHESIS -> {
operatorStack.push(shuntingToken);
}
case R_PARENTHESIS -> {
while (true) {
if (operatorStack.isEmpty()) {
throw new UnsupportedOperationException("Unbalanced left parenthesis");
}
Token leftToken = operatorStack.pop();
if (leftToken.type == TokenType.L_PARENTHESIS) {
break;
}
outputQueue.add(leftToken);
}
}
}
//empty the operator stack
while (!operatorStack.isEmpty()) {
Token leftToken = operatorStack.pop();
if (leftToken.type == TokenType.L_PARENTHESIS) {
//technically unbalanced left parenthesis error but just assume they are close after the equation and ignore them from here
continue;
}
outputQueue.add(leftToken);
}
return outputQueue.stream().toList();
}
private static int getPrecedence(String operator) {
switch (operator) {
case "+", "-" -> {
return 0;
}
case "*", "/" -> {
return 1;
}
default -> throw new UnsupportedOperationException("Invalid operator");
}
}
/**
* @param tokens list of Tokens in reverse polish notation
* @return answer to equation
*/
private static double evaluate(List<Token> tokens) {
Deque<Double> values = new ArrayDeque<>();
for (Token token : tokens) {
switch (token.type) {
case NUMBER -> {
values.push(calculateValue(token.value));
}
case OPERATOR -> {
double right = values.pop();
double left = values.pop();
switch (token.value) {
case "+" -> {
values.push(left + right);
}
case "-" -> {
values.push(left - right);
}
case "/" -> {
if (right == 0) {
throw new UnsupportedOperationException("Can not divide by 0");
}
values.push(left / right);
}
case "*" -> {
values.push(left * right);
}
}
}
case L_PARENTHESIS, R_PARENTHESIS -> {
throw new UnsupportedOperationException("Equation is not in RPN");
}
}
}
if (values.isEmpty()) {
throw new UnsupportedOperationException("Equation is empty");
}
return values.pop();
}
private static double calculateValue(String value) {
Matcher numberMatcher = NUMBER_PATTERN.matcher(value.toLowerCase());
if (!numberMatcher.matches()) {
throw new UnsupportedOperationException("Invalid number");
}
double number = Double.parseDouble(numberMatcher.group(1));
String magnitude = numberMatcher.group(2);
if (!magnitude.isEmpty()) {
if (!magnitudeValues.containsKey(magnitude)) {//its invalid if its another letter
throw new UnsupportedOperationException("Invalid magnitude");
}
number *= magnitudeValues.get(magnitude);
}
return number;
}
public static double calculate(String equation) {
return evaluate(shunt(lex(equation)));
}
}
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