feat: Added support for unlimited arithmetic operations

NOTE: These are not true PEMDOS operations - it is simply FIFO operations

placeholder-.ts

@@ -6,6 +6,7 @@ interface RollResult {
   rolls: number[];     // Kept dice
   discarded: number[]; // Discarded dice
   summary: string;     // Formatted string of all dice
+  steps?: string[];    // Arithmetic operations performed
 }
 
 function rollDie(diceType: DiceType): number {
@@ -32,7 +33,6 @@ function getDieRange(diceType: DiceType): { min: number; max: number } {
 
 function formatSummary(rolls: number[], discarded: number[], diceType: DiceType): string {
   const { min, max } = getDieRange(diceType);
-
   const all = rolls.map(r => ({ value: r, kept: true }))
     .concat(discarded.map(r => ({ value: r, kept: false })));
 
@@ -60,15 +60,16 @@ function parseExpression(input: string): RollResult | RollResult[] {
 }
 
 function parseSingleExpression(expr: string): RollResult {
-  const match = expr.match(/^(\d+)?([frt])(?:(kh|kl)(\d+))?(?:([+\-*])(\d+))?$/);
-  if (!match) throw new Error(`Invalid expression: ${expr}`);
+  const baseMatch = expr.match(/^(\d+)?([frt])(?:(kh|kl)(\d+))?/);
+  if (!baseMatch) throw new Error(`Invalid expression: ${expr}`);
+
+  const [, countStr, diceType, keepType, keepCountStr] = baseMatch;
+  const diceExprLength = baseMatch[0].length;
+  const arithmeticExpr = expr.slice(diceExprLength);
 
-  const [, countStr, diceType, keepType, keepCountStr, op, modStr] = match;
   const count = parseInt(countStr || '1', 10);
   const dice = diceType as DiceType;
   const keepCount = keepCountStr ? parseInt(keepCountStr, 10) : null;
-  const modifier = modStr ? parseInt(modStr, 10) : 0;
-  const operator = op || '+';
 
   const allRolls = rollDice(count, dice);
   let rolls = [...allRolls];
@@ -80,38 +81,39 @@ function parseSingleExpression(expr: string): RollResult {
     discarded = sorted.slice(keepCount);
   }
 
-  const baseSum = rolls.reduce((acc, val) => acc + val, 0);
-  let finalValue: number;
+  const steps: string[] = [];
+  let result = rolls.reduce((acc, val) => acc + val, 0);
+  steps.push(`Initial sum: ${result}`);
 
-  switch (operator) {
-    case '+':
-      finalValue = baseSum + modifier;
-      break;
-    case '-':
-      finalValue = baseSum - modifier;
-      break;
-    case '*':
-      finalValue = baseSum * modifier;
-      break;
-    default:
-      finalValue = baseSum;
+  const opRegex = /([+\-*/])\s*(-?\d+(?:\.\d+)?)/g;
+  let match;
+  while ((match = opRegex.exec(arithmeticExpr)) !== null) {
+    const [, op, valStr] = match;
+    const val = parseFloat(valStr);
+    const prev = result;
+    switch (op) {
+      case '+': result += val; break;
+      case '-': result -= val; break;
+      case '*': result *= val; break;
+      case '/': result /= val; break;
+    }
+    steps.push(`${prev} ${op} ${val} = ${result}`);
   }
 
   return {
     input: expr,
-    value: finalValue,
+    value: result,
     rolls,
     discarded,
-    summary: formatSummary(rolls, discarded, dice)
+    summary: formatSummary(rolls, discarded, dice),
+    steps
   };
 }
 
 function safeParseInput(message: string): RollResult | RollResult[] | null {
   const trimmed = message.trim();
-
   const isSingleWord = !trimmed.includes(' ');
 
-  // CASE 1: Single word without brackets
   if (isSingleWord && !trimmed.startsWith('[') && !trimmed.endsWith(']')) {
     try {
       return parseExpression(trimmed);
@@ -120,7 +122,6 @@ function safeParseInput(message: string): RollResult | RollResult[] | null {
     }
   }
 
-  // CASE 2: Single word WITH brackets like "[3f]"
   if (isSingleWord && trimmed.startsWith('[') && trimmed.endsWith(']')) {
     const inside = trimmed.slice(1, -1).trim();
     try {
@@ -130,7 +131,6 @@ function safeParseInput(message: string): RollResult | RollResult[] | null {
     }
   }
 
-  // CASE 3: Multi-word input — check each word
   const words = trimmed.split(/\s+/);
   const expressions = words
     .filter(word => word.startsWith('[') && word.endsWith(']'))