Add new day script and update README for environment setup

Author: lundgren2

.gitignore

@@ -1 +1,2 @@
 node_modules
+.env

README.md

@@ -12,4 +12,20 @@ To run:
 bun run index.js
 ```
 
+## Start new day script
+
+To create a new day's structure and download the input automatically:
+
+1.  Create a `.env` file in the root directory and add your Advent of Code session cookie:
+
+    ```env
+    AOC_SESSION=your_session_cookie_here
+    ```
+
+2.  Run the setup script with the day number:
+
+    ```bash
+    ./new_day.sh <day_number>
+    ```
+
 This project was created using `bun init` in bun v1.0.2. [Bun](https://bun.sh) is a fast all-in-one JavaScript runtime.

new_day.sh

@@ -0,0 +1,64 @@
+#!/bin/bash
+
+# Usage: ./new_day.sh <day_number>
+
+YEAR=2025
+DAY=$1
+
+# Load .env file if it exists
+BASE_DIR=$(dirname "$0")
+ENV_FILE="$BASE_DIR/.env"
+if [ -f "$ENV_FILE" ]; then
+  export $(grep -v '^#' "$ENV_FILE" | xargs)
+fi
+
+if [ -z "$DAY" ]; then
+  echo "Usage: $0 <day>"
+  exit 1
+fi
+
+PADDED_DAY=$(printf "%02d" $DAY)
+
+# Define paths
+TEMPLATE_DIR="$BASE_DIR/src/$YEAR/day00"
+TARGET_DIR="$BASE_DIR/src/$YEAR/day$PADDED_DAY"
+
+# Check if target directory exists
+if [ -d "$TARGET_DIR" ]; then
+  echo "Directory $TARGET_DIR already exists."
+else
+  echo "Creating $TARGET_DIR..."
+  mkdir -p "$TARGET_DIR"
+  
+  # Copy template files
+  cp "$TEMPLATE_DIR/part1.ts" "$TARGET_DIR/"
+  cp "$TEMPLATE_DIR/part2.ts" "$TARGET_DIR/"
+  cp "$TEMPLATE_DIR/test.spec.ts" "$TARGET_DIR/"
+  # Create empty input.txt if not downloading
+  touch "$TARGET_DIR/input.txt"
+
+  # Update test.spec.ts with the correct day
+  sed -i '' "s/Day x/Day $DAY/g" "$TARGET_DIR/test.spec.ts"
+fi
+
+# Open problem page
+URL="https://adventofcode.com/$YEAR/day/$DAY"
+echo "Opening $URL..."
+open "$URL"
+
+# Download input
+INPUT_URL="https://adventofcode.com/$YEAR/day/$DAY/input"
+INPUT_FILE="$TARGET_DIR/input.txt"
+
+# Check for AOC_SESSION environment variable
+if [ -n "$AOC_SESSION" ]; then
+  echo "Downloading input to $INPUT_FILE..."
+  curl -s --cookie "session=$AOC_SESSION" "$INPUT_URL" > "$INPUT_FILE"
+else
+  echo "AOC_SESSION env var not set. Cannot download input automatically."
+  echo "To enable auto-download, set AOC_SESSION in .env file."
+  open "$INPUT_URL"
+fi
+
+echo "Done ✅ Day $DAY ready in $TARGET_DIR"
+