🌐 Multiplayer Banking Kata (Unconference Edition)

An interactive, multi-node evolution of the classic Bank Account Kata designed for 1–2 hour unconference workshop sessions.

Participants implement their own bank node in Kotlin using Outside-In TDD and Object Calisthenics, then connect their node to a live SWIFT Clearing House and battle on the real-time scoreboard under live customer traffic.

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🚀 Quick Links & Guides

• 📖 Participant Quickstart Guide: 5-minute setup, TDD milestones, and webhook specs.
• 🎙️ Facilitator Workshop Guide: 2-hour agenda, live scoreboard setup, traffic burst controls.

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🏗️ Repository Architecture

This repository is built with Gradle Kotlin DSL (build.gradle.kts) and Kotlin 2.x targeting JVM 25:

Bank-kata/
├── build.gradle.kts
├── settings.gradle.kts
├── requests/                    # IntelliJ HTTP Client request suite & environments
│   ├── http-client.env.json     # Environment variables (local-alpha, local-beta, workshop-live)
│   ├── bank-api.http            # Participant bank API test collection (click-to-run)
│   └── swift-hub.http           # Facilitator SWIFT network & simulator controls
├── shared-contracts/            # Shared DTOs, BIC/IBAN validation models, JSON serializers
│   └── src/main/kotlin/org/craftedsw/contracts/
├── bank-starter/                # Participant bank starter template
│   ├── src/main/kotlin/org/craftedsw/bank/
│   │   ├── domain/              # Calisthenics domain (Account, Amount, Statement, etc.)
│   │   ├── api/                 # Embedded Ktor HTTP webhook routes
│   │   ├── client/              # SWIFT network client
│   │   └── BankApplication.kt   # Runnable entrypoint
│   └── src/test/kotlin/org/craftedsw/bank/
├── swift-hub/                   # Facilitator SWIFT network clearing house & scoreboard
│   ├── src/main/kotlin/org/craftedsw/swift/
│   │   ├── router/              # BIC registry, transfer router, audit ledger
│   │   ├── simulator/           # Customer traffic & surge generator
│   │   ├── ui/                  # Live web scoreboard dashboard
│   │   └── SwiftHubApplication.kt
│   └── src/test/kotlin/org/craftedsw/swift/
├── docs/                        # Facilitator and participant documentation
└── scripts/                     # Helper launch and tunnel scripts

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⚡ Running the Project

1. Run all tests

./gradlew test

2. Start the Facilitator SWIFT Hub (Port 9000)

./gradlew :swift-hub:run
# Open live scoreboard dashboard at http://localhost:9000

3. Register Your Bank & Get BIC Code

Visit the registration page at http://<FACILITATOR_IP>:9000/register (or scan the QR code on the live facilitator scoreboard). Enter your Bank Name and Webhook URL to receive your assigned 8-character ASCII BIC code (e.g. BANKXXXX).

4. Start a Participant Bank (Port 8080)

PORT=8080 BIC=<YOUR_GENERATED_BIC> BANK_NAME="Bank Alpha" ./gradlew :bank-starter:run

5. Interactive API Testing (IntelliJ HTTP Client)

• Open requests/bank-api.http to test participant bank operations (deposit, withdraw, statements, inter-bank transfers).
• Open requests/swift-hub.http to trigger simulated traffic bursts or inspect the central audit ledger.
• Choose your environment (local-alpha, local-beta, workshop-live) from the top-right dropdown and click ▶ on any request.

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🧘 The 9 Object Calisthenics Constraints

1. Only One Level of Indentation per Method
2. Don’t Use the else Keyword
3. Wrap All Primitives and Strings (e.g. @JvmInline value class Amount(val value: Int))
4. First-Class Collections (e.g. Statement, AuditLedger)
5. One Dot per Line (Law of Demeter)
6. Don’t Abbreviate
7. Keep All Entities Small (<= 50 lines)
8. No Classes with More Than Two Instance Variables
9. No Getters / Setters / Properties for State Extraction (Tell-Don't-Ask)