From 857a252feaf9da3ac371d5dcd1ed3337bbad1049 Mon Sep 17 00:00:00 2001
From: Loosetooth <loosetooth@protonmail.com>
Date: Mon, 3 Feb 2025 18:22:26 +0100
Subject: [PATCH] WIP: math parser

---
 .../solution.ts                               | 130 ++++++++++++++++--
 1 file changed, 118 insertions(+), 12 deletions(-)

diff --git a/2kyu/evaluate-mathematical-expression/solution.ts b/2kyu/evaluate-mathematical-expression/solution.ts
index 9c4fc80..05a06d8 100644
--- a/2kyu/evaluate-mathematical-expression/solution.ts
+++ b/2kyu/evaluate-mathematical-expression/solution.ts
@@ -1,27 +1,133 @@
 
-type Token = number | '+' | '-' | '*' | '/' | '(' | ')';
-
 
+type TokenType = 'number' | 'operator' | 'parenthesis';
+type TokenValue = number | '+' | '-' | '*' | '/' | '(' | ')';
 
-type ASTNode = {
-  type: string,
+type Token = {
+  type: TokenType,
+  value: TokenValue,
 }
 
-type OperatorNode = {
+type OperatorChars = '+' | '-' | '*' | '/';
+type OperatorToken = Token & {
   type: 'operator',
-  value: '+' | '-' | '*' | '/',
-  left: ASTNode,
-  right: ASTNode,
+  value: OperatorChars,
 }
 
-type NumberNode = {
+const isOperatorChar = (char: string): char is OperatorChars => {
+  return char === '+' || char === '-' || char === '*' || char === '/';
+}
+
+type NumberToken = Token & {
   type: 'number',
   value: number,
 }
 
-type GroupNode = {
-  type: 'group',
-  value: ASTNode,
+type ParenthesisChars = '(' | ')';
+type ParenthesisToken = Token & {
+  type: 'parenthesis',
+  value: ParenthesisChars,
+}
+
+const isParenthesisChar = (char: string): char is ParenthesisChars => {
+  return char === '(' || char === ')';
+}
+
+const tokenize = (expression: string): Token[] => {
+  const tokens: Token[] = [];
+  const chars = expression.split('');
+  let done = false;
+  let i = 0;
+  while (!done) {
+    if (i >= chars.length) {
+      done = true;
+      continue;
+    }
+
+    const char = chars[i];
+    if (char === ' ') {
+      i++;
+      continue;
+    }
+    // parenthesis
+    if (isParenthesisChar(char)) {
+      tokens.push({ type: 'parenthesis', value: char });
+      i++;
+      continue;
+    }
+    // operator
+    if (isOperatorChar(char)) {
+      tokens.push({ type: 'operator', value: char });
+      i++;
+      continue;
+    }
+    // number
+    if (char.match(/\d/)) {
+      let number = '';
+      while (chars[i].match(/\d/)) {
+        number += chars[i];
+        i++;
+      }
+      tokens.push({ type: 'number', value: parseInt(number) });
+    } else {
+      throw new Error('Invalid character');
+    }
+  }
+  return tokens;
+}
+
+abstract class ASTNodeCommon {
+  abstract readonly type: string;
+  abstract get value(): number;
+}
+
+type ASTNode = NumberNode | OperatorNode | GroupNode | NegationNode;
+
+class NumberNode extends ASTNodeCommon {
+  private _value: number;
+  type = 'number';
+  constructor(public numValue: number) {
+    super();
+    this._value = numValue;
+  }
+
+  get value() {
+    return this._value;
+  }
+}
+
+class OperatorNode extends ASTNodeCommon {
+  type = 'operator';
+  constructor(public operator: OperatorChars, public left: ASTNode, public right: ASTNode) {
+    super();
+  }
+
+  get value() {
+    const left = this.left.value;
+    const right = this.right.value;
+    switch (this.operator) {
+      case '+':
+        return left + right;
+      case '-':
+        return left - right;
+      case '*':
+        return left * right;
+      case '/':
+        return left / right;
+      default:
+        throw new Error('Invalid operator');
+    }
+  }
+}
+
+class GroupNode extends ASTNodeCommon {
+  type = 'group';
+  
+  constructor(public value: ASTNode) {
+    super();
+  }
+
+
 }
 
 type NegationNode = {