nightpass, a card game engine

nightpass is a high-performance Java application designed to simulate a card game between two players — the Survivor and the Stranger. It efficiently manages a shared deck of cards and selects the optimal card for each battle using a priority-based strategy and custom-built data structures.

The engine handles dynamic card stat updates after combat, score tracking, and card stealing mechanics, all while maintaining O(log n) query performance across two dimensions simultaneously.

Features

• Nested AVL Tree Deck: The deck is an AttackTree (outer AVL keyed by attack) where each node holds a HealthTree (inner AVL keyed by health), enabling fast range queries across both stats at once.
• Priority-Based Card Selection: Each battle evaluates up to 4 priorities — survive and kill, survive but not kill, die but kill, die and deal max damage — picking the optimal card accordingly.
• Dynamic Stat Updates: Cards that survive combat have their health and attack recalculated proportionally and are reinserted into the deck.
• Card Stealing: The Stranger can steal cards exceeding both attack and health thresholds from the Survivor's deck.
• Score Tracking: Points are awarded to each player depending on battle outcome and priority used.

Technical Implementation

Custom implementation of core data structures without standard Java Collections (except ArrayList).

Data Structures

• Custom AVL Tree (AttackTree.java, HealthTree.java):

  • Standard AVL balancing with rotations after insertion and deletion.
  • Supports searchMinGT (minimum key ≥ threshold) and searchMaxLT (maximum key < threshold) for range-based card lookups.
  • Each AttackNode holds its own HealthTree, forming a nested two-dimensional search structure.

• Card Queue (HealthNode.java):

  • Each HealthNode holds an ArrayList of cards with identical attack and health values.
  • Managed as a queue via firstIndex and lastIndex pointers for O(1) enqueue and dequeue.

Object-Oriented Design

• Encapsulation: Card, AttackNode, HealthNode, AttackTree, HealthTree are cleanly separated by responsibility.
• Command Pattern: Main.java parses a stream of string commands and dispatches to the appropriate game logic method.

Project Structure

• Main.java — Entry point. Parses input, processes commands (draw_card, battle, steal_card, etc.), manages scoring.
• AttackTree.java — Outer AVL tree keyed by current attack value.
• AttackNode.java — Holds attack key and an inner HealthTree.
• HealthTree.java — Inner AVL tree keyed by current health value.
• HealthNode.java — Holds health key and a queue of cards with matching stats.
• Card.java — Card model with initial, base, and current attack/health values.

Installation & Usage

1. Clone the repository:

git clone https://github.com/winterwitchy/nightpass
cd nightpass

2. Compile:

cd src && javac *.java

3. Run:

java Main <input_file> <output_file>

Example Input

draw_card Dragon 50 120
draw_card Goblin 10 30
battle 40 45 0
find_winning
deck_count