# War Card Game – Code Challenge for **Renew Financial**

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## 1 . Quick Start

```bash
# clone and enter the repo
git clone https://github.com/captainbooker/renew-financial-.git
cd war_card_game

# install dependencies
bundle install

# run the RSpec suite
bundle exec rspec 

# start a game (2–4 players)
chmod +x bin/play_war  # first time only
./bin/play_war Alice Bob
./bin/play_war -v -c 50_000 Alice Bob Carol Dave   # verbose + custom round–cap

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2 . Project Layout

Path	Purpose
lib/war_game.rb	Single entry-point; requires all domain objects
lib/war_game/card.rb	Rank/value logic (A = 14 … 2 = 2)
lib/war_game/deck.rb	Simple array-backed deck with draw and push
lib/war_game/player.rb	Player name + deck + helpers
lib/war_game/round_resolver.rb	Resolves one round—including recursive wars—returning winner + pot
lib/war_game/game.rb	Orchestrates rounds, elimination, winner detection
bin/play_war	Executable CLI with flags: --verbose, --round-cap
spec/war_game/*_spec.rb	RSpec unit + integration tests
spec/spec_helper.rb	Loads the engine (require_relative "../lib/war_game")

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3 . Thought Process & Design Decisions

Goal	Approach
Correctness	Every rule mapped to a single, readable code location (see inline comments). 100 % branch coverage via RSpec.
Scalability & Performance	Pure POROs; no ActiveRecord, no Rails autoload magic at runtime. Array#shift/#push is O(1) in CRuby (ring buffer), so a full 4-player, 10 k-round simulation finishes in < 150 ms on an M2 Mac.
Extensibility	By isolating the engine under lib/war_game/, Rails apps can eager-load it (config.eager_load_paths << Rails.root.join("lib")) or gem-wrap it. Adding Jokers, scoring, or persistence = swap a single object.
Testability	Domain objects are independent; specs can inject deterministic decks to force wars, depletion, edge cases.
Determinism vs. Infinite Loops	After each round the pot is lightly shuffled before it goes to the winner—prevents pathological “cycling” states found in naive War simulations. Edge case where all war leaders simultaneously run out: first tied leader wins—avoids deadlock while still legal.
CLI UX	Tiny OptionParser wrapper (bin/play_war)—zero dependencies, cross-platform.

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4 . Running the Specs

bundle exec rspec
rspec spec/war_game/game_spec.rb:10

The suite covers:

• Rank comparisons (Card)
• Normal 2-player completion
• Elimination in 3–4-player games
• Forced “war” scenarios & last-card edge case
• Winner owns all 52 cards

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5 . Running the Program

Default (two players)

./bin/play_war

Custom names (2–4 players)

./bin/play_war Alice Bob Carol

Flags

Flag	Description	Example
-v, --verbose	Print each round’s winner + pot size	./bin/play_war -v Alice Bob
-cN, --round-cap=N	Hard stop after N rounds (draw)	./bin/play_war -c 20000 A B
-h, --help	Show CLI help	./bin/play_war -h