Conway's Game of Life

A Swift implementation of Conway's Game of Life with:

• An iOS app (SwiftUI) under ConwayGame with Core Data pagination for large datasets
• A reusable engine as a Swift Package under ConwayGameEngine
• A CLI executable target conway-cli for terminal simulations
• A REST API under ConwayAPI (Vapor)

Packages

• ConwayGameEngine: Core simulation logic and patterns; includes conway-cli.
  • Tests: cd ConwayGameEngine && swift test
  • CLI: cd ConwayGameEngine && swift run conway-cli --help
• ConwayAPI: REST API exposing the engine via HTTP.
  • Docs: see ConwayAPI/README.md
  • Local run: cd ConwayAPI && swift run conway-api
  • Docker: cd ConwayAPI && docker compose up

Quick Start (App)

• Requirements: Xcode 15+, iOS 16+ simulator/device, macOS 13+
• Open the project: open ConwayGame.xcodeproj
• Select the ConwayGame scheme and run on a simulator or device.

CLI Usage

The CLI lives in the Swift package at ConwayGameEngine.

• Build and run from the package directory:

  • cd ConwayGameEngine
  • swift run conway-cli --help

• Commands:

  • conway-cli run <width> <height> <generations> [pattern] [--density=<value>] [--rules=<name>]
    • Runs a simulation with the given grid size and generation count
    • Optional pattern: random, empty, or a named pattern
    • --density: Random density (0.0-1.0), default: 0.25
    • --rules: Rule preset (conway, highlife, daynight), default: conway
  • conway-cli pattern <name> [--rules=<name>]
    • Runs a predefined pattern for a short showcase
    • --rules: Rule preset (conway, highlife, daynight), default: conway

• Examples:

  • swift run conway-cli run 20 20 50 random
  • swift run conway-cli run 10 10 25 empty --density=0.4
  • swift run conway-cli run 15 15 30 random --rules=highlife
  • swift run conway-cli pattern glider --rules=daynight

Available patterns: block, beehive, blinker, toad, beacon, glider, pulsar, gospergun.

Output uses * for alive and . for dead.

Rules & Variants

The engine supports multiple configurable rule sets:

Conway's Game of Life (Default)

• Neighborhood: Moore (8 surrounding cells)
• Survival: a live cell with 2 or 3 neighbors stays alive
• Birth: a dead cell with exactly 3 neighbors becomes alive
• Otherwise: the cell is dead in the next generation

Additional Rule Variants

• HighLife: Conway rules + birth on 6 neighbors
• Day and Night: Survival on 3,4,6,7,8 neighbors; birth on 3,6,7,8 neighbors

Use --rules=<name> in CLI or configure programmatically in the iOS app.

Finish Criteria & Limits

• Finished states (engine/app/CLI):
  • Extinction: all cells are dead.
  • Cycle detected: a previously seen board state recurs (includes still lifes with period 1 and oscillators with period > 1).
• iOS app limits:
  • Auto-play cap: pauses after 500 steps per run.
  • Final state search cap: attempts up to 500 generations; if living cells remain with no cycle/extinction, it reports that the generation limit was reached.
• CLI behavior:
  • run: runs exactly the number of generations requested, but stops early on extinction or when a repeated state is detected.
  • pattern: showcases up to configurable generations (default: 50) with short delays; also stops early if the pattern stabilizes.

Assumptions

• Bounded grid: no wrap-around at edges (cells outside the grid are always dead).
• Synchronous updates: the next generation is computed from the entire current state.
• CLI random starts with configurable density (default: 25% alive cells).
• Sim termination hints in CLI: stops on extinction or when a previously seen state recurs (cycle detected).

Development

• Engine tests: cd ConwayGameEngine && swift test
• iOS app tests: xcodebuild -scheme ConwayGame -destination 'platform=iOS Simulator,name=iPhone 16 Pro' test
• Build CLI only: cd ConwayGameEngine && swift build
• Run CLI: cd ConwayGameEngine && swift run conway-cli ...

Engine entry points:

• ConwayGameEngine.computeNextState(_:) — next generation.
• ConwayGameEngine.computeStateAtGeneration(_:generation:) — advance multiple generations.

Performance & Scalability:

• Core Data pagination handles large board collections efficiently
• Comprehensive performance benchmarks validate scaling characteristics

CI

GitHub Actions runs tests on Linux and macOS for Swift 5.10 and 6.0:

• ConwayAPI unit/integration tests
• ConwayGameEngine tests
• conway-cli build check

See the workflow at .github/workflows/conwayapi-ci.yml.

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