Allow for math expressions in GuiCraftAmount textbox (#353)

src/main/java/appeng/client/gui/MathExpressionParser.java

@@ -0,0 +1,208 @@
+package appeng.client.gui;
+
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+import java.util.Collections;
+import java.util.Stack;
+
+public class MathExpressionParser {
+
+    private final Stack<String> postfixStack = new Stack<>();
+    private final Stack<Character> opStack = new Stack<>();
+    private static final int[] OPERATOR_PRIORITY = new int[] { 0, 3, 2, 1, -1, 1, 0, 2 };
+
+    public static double parse(String expression) {
+        double result;
+
+        if (expression == null) return Double.NaN;
+
+        expression = expression.replace(" ", "");
+
+        if (expression.length() == 1 && Character.isDigit(expression.charAt(0))) {
+            return expression.charAt(0) - '0';
+        }
+        try {
+            expression = transform(expression);
+            result = new MathExpressionParser().calculate(expression);
+        } catch (Exception e) {
+            return Double.NaN;
+        }
+        return result;
+    }
+
+    /**
+     * replace '-' with '~'
+     * e.g.-2+-1*(-3E-2)-(-1) -> ~2+~1*(~3E~2)-(~1)
+     */
+    private static String transform(String expression) {
+        char[] arr = expression.toCharArray();
+        for (int i = 0; i < arr.length; i++) {
+            if (arr[i] == '-') {
+                if (i == 0) {
+                    arr[i] = '~';
+                } else {
+                    char c = arr[i - 1];
+                    if (c == '+' || c == '-' || c == '*' || c == '/' || c == '(' || c == 'E' || c == 'e') {
+                        arr[i] = '~';
+                    }
+                }
+            }
+        }
+        if (arr[0] == '~' || arr[1] == '(') {
+            arr[0] = '-';
+            return "0" + new String(arr);
+        } else {
+            return new String(arr);
+        }
+    }
+
+    public double calculate(String expression) {
+        Stack<String> resultStack = new Stack<>();
+        prepare(expression);
+        Collections.reverse(postfixStack);
+        String firstValue, secondValue, currentValue;
+        while (!postfixStack.isEmpty()) {
+            currentValue = postfixStack.pop();
+            if (!isOperator(currentValue.charAt(0))) {
+                currentValue = currentValue.replace("~", "-");
+                resultStack.push(currentValue);
+            } else {
+                secondValue = resultStack.pop();
+                firstValue = resultStack.pop();
+
+                firstValue = firstValue.replace("~", "-");
+                secondValue = secondValue.replace("~", "-");
+
+                String tempResult = calculate(firstValue, secondValue, currentValue.charAt(0));
+                resultStack.push(String.valueOf(tempResult));
+            }
+        }
+        return Double.parseDouble(resultStack.pop());
+    }
+
+    private void prepare(String expression) {
+        opStack.push(',');
+        char[] arr = expression.toCharArray();
+        int currentIndex = 0;
+        int count = 0;
+        char currentOp, peekOp;
+        for (int i = 0; i < arr.length; i++) {
+            currentOp = arr[i];
+            if (isOperator(currentOp)) {
+                if (count > 0) {
+                    postfixStack.push(new String(arr, currentIndex, count));
+                }
+                peekOp = opStack.peek();
+                if (currentOp == ')') {
+                    while (opStack.peek() != '(') {
+                        postfixStack.push(String.valueOf(opStack.pop()));
+                    }
+                    opStack.pop();
+                } else {
+                    while (currentOp != '(' && peekOp != ',' && compare(currentOp, peekOp)) {
+                        postfixStack.push(String.valueOf(opStack.pop()));
+                        peekOp = opStack.peek();
+                    }
+                    opStack.push(currentOp);
+                }
+                count = 0;
+                currentIndex = i + 1;
+            } else {
+                count++;
+            }
+        }
+        if (count > 1 || (count == 1 && !isOperator(arr[currentIndex]))) {
+            postfixStack.push(new String(arr, currentIndex, count));
+        }
+
+        while (opStack.peek() != ',') {
+            postfixStack.push(String.valueOf(opStack.pop()));
+        }
+    }
+
+    private static boolean isOperator(char c) {
+        return c == '+' || c == '-' || c == '*' || c == '/' || c == '(' || c == ')';
+    }
+
+    private static boolean compare(char cur, char peek) {
+        return OPERATOR_PRIORITY[(peek) - 40] >= OPERATOR_PRIORITY[(cur) - 40];
+    }
+
+    private String calculate(String firstValue, String secondValue, char currentOp) {
+        return switch (currentOp) {
+            case '+' -> add(firstValue, secondValue);
+            case '-' -> sub(firstValue, secondValue);
+            case '*' -> mul(firstValue, secondValue);
+            case '/' -> div(firstValue, secondValue);
+            default -> "";
+        };
+    }
+
+    public static String add(String v1, String v2) {
+        BigDecimal b1 = new BigDecimal(v1);
+        BigDecimal b2 = new BigDecimal(v2);
+        return String.valueOf(b1.add(b2));
+    }
+
+    /**
+     * subtraction
+     *
+     * @param v1 p1
+     * @param v2 p2
+     * @return sub
+     */
+    public static String sub(String v1, String v2) {
+        BigDecimal b1 = new BigDecimal(v1);
+        BigDecimal b2 = new BigDecimal(v2);
+        return String.valueOf(b1.subtract(b2));
+    }
+
+    /**
+     * multiplication
+     *
+     * @param v1 p1
+     * @param v2 p2
+     * @return mul
+     */
+    public static String mul(String v1, String v2) {
+        BigDecimal b1 = new BigDecimal(v1);
+        BigDecimal b2 = new BigDecimal(v2);
+        return String.valueOf(b1.multiply(b2));
+    }
+
+    /**
+     * division. e = 10^-10
+     *
+     * @param v1 p1
+     * @param v2 p2
+     * @return div
+     */
+    public static String div(String v1, String v2) {
+        BigDecimal b1 = new BigDecimal(v1);
+        BigDecimal b2 = new BigDecimal(v2);
+        return String.valueOf(b1.divide(b2, 16, RoundingMode.HALF_UP));
+    }
+
+    /**
+     * rounding
+     *
+     * @param v     p
+     * @param scale scale
+     * @return result
+     */
+    public static double round(double v, int scale) {
+        if (scale < 0) {
+            throw new IllegalArgumentException("The scale must be a positive integer or zero");
+        }
+        BigDecimal b = new BigDecimal(Double.toString(v));
+        return b.divide(BigDecimal.ONE, scale, RoundingMode.HALF_UP).doubleValue();
+    }
+
+    public static String round(String v, int scale) {
+        if (scale < 0) {
+            throw new IllegalArgumentException("The scale must be a positive integer or zero");
+        }
+        BigDecimal b = new BigDecimal(v);
+        return String.valueOf(b.divide(BigDecimal.ONE, scale, RoundingMode.HALF_UP));
+    }
+}