Implement ExpressionConfigEntry that implements shunting yard and postfix notation to compute values based on strings
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179
Projects/BanquetForFools/BanquetForCyka/ExpressionConfigEntry.cs
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179
Projects/BanquetForFools/BanquetForCyka/ExpressionConfigEntry.cs
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using System;
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using System.Collections.Generic;
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using BepInEx.Configuration;
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using UnityEngine;
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namespace BanquetForCyka {
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public class ExpressionConfigEntry {
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private readonly ConfigEntry<string> _configEntry;
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private Func<float, float> _compiledExpression;
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private string _lastValidExpression;
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private bool _isValid = true;
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public string Value {
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get => _configEntry.Value;
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set {
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if (value == _configEntry.Value)
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return;
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// Try to compile the expression
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try {
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var newExpr = ParseExpression(value);
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_compiledExpression = newExpr;
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_lastValidExpression = value;
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_isValid = true;
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_configEntry.Value = value;
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} catch (Exception) {
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_isValid = false;
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// Don't update the config value if invalid
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}
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}
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}
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public bool IsValid => _isValid;
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public string LastValidExpression => _lastValidExpression;
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public ExpressionConfigEntry(ConfigFile config, string section, string key, string defaultValue,
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string description) {
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_configEntry = config.Bind(
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section, key, defaultValue,
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new ConfigDescription(description +
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"\nUse 'v' to represent the input value. Examples: 'v*4', 'v+13', '(v+5)*2'"));
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// Initial compilation
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_compiledExpression = ParseExpression(_configEntry.Value);
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_lastValidExpression = _configEntry.Value;
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// Recompile when config changes
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_configEntry.SettingChanged += (sender, args) => {
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try {
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_compiledExpression = ParseExpression(_configEntry.Value);
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_lastValidExpression = _configEntry.Value;
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_isValid = true;
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} catch (Exception) {
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_isValid = false;
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}
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};
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}
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public float Evaluate(float input) {
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if (!_isValid) {
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return input; // Return original value if expression is invalid
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}
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return _compiledExpression(input);
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}
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// Copy of the expression parser from Main
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private static Func<float, float> ParseExpression(string expr) {
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try {
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// Remove all whitespace
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expr = expr.Replace(" ", "");
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var tokens = new List<string>();
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var current = "";
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// Tokenize the expression
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for (int i = 0; i < expr.Length; i++) {
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char c = expr[i];
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if (c == 'v') {
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if (current != "") {
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tokens.Add(current);
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current = "";
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}
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tokens.Add("v");
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} else if (c == '+' || c == '-' || c == '*' || c == '/' || c == '(' || c == ')') {
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if (current != "") {
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tokens.Add(current);
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current = "";
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}
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tokens.Add(c.ToString());
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} else {
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current += c;
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}
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}
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if (current != "") {
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tokens.Add(current);
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}
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// Convert to postfix notation using shunting yard
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var output = new List<string>();
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var operators = new Stack<string>();
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foreach (var token in tokens) {
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if (token == "v" || float.TryParse(token, out _)) {
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output.Add(token);
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} else if (token == "(") {
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operators.Push(token);
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} else if (token == ")") {
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while (operators.Count > 0 && operators.Peek() != "(") {
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output.Add(operators.Pop());
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}
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if (operators.Count > 0)
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operators.Pop(); // Remove "("
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} else {
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while (operators.Count > 0 && operators.Peek() != "(" &&
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GetPrecedence(operators.Peek()) >= GetPrecedence(token)) {
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output.Add(operators.Pop());
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}
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operators.Push(token);
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}
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}
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while (operators.Count > 0) {
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output.Add(operators.Pop());
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}
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// Build the expression tree
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var stack = new Stack<Func<float, float>>();
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foreach (var token in output) {
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if (token == "v") {
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stack.Push(v => v);
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} else if (float.TryParse(token, out float num)) {
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stack.Push(v => num);
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} else {
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var right = stack.Pop();
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var left = stack.Pop();
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switch (token) {
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case "+":
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stack.Push(v => left(v) + right(v));
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break;
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case "-":
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stack.Push(v => left(v) - right(v));
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break;
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case "*":
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stack.Push(v => left(v) * right(v));
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break;
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case "/":
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stack.Push(v => {
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var r = right(v);
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return r != 0 ? left(v) / r : left(v);
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});
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break;
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}
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}
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}
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return stack.Pop();
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} catch (Exception e) {
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throw new FormatException($"Failed to parse expression '{expr}': {e.Message}");
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}
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}
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private static int GetPrecedence(string op) {
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switch (op) {
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case "+":
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return 1;
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case "-":
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return 1;
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case "*":
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return 2;
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case "/":
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return 2;
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default:
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return 0;
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}
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}
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}
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}
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