# Every Matrix Homework

**Repository Path**: weikebing/every-matrix-homework

## Basic Information

- **Project Name**: Every Matrix Homework
- **Description**: No description available
- **Primary Language**: Unknown
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2026-01-25
- **Last Updated**: 2026-01-30

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# Betting Server - Simplified Implementation Guide

## Project Overview
HTTP-based backend for managing betting offer stakes with three endpoints.

## Requirements Met
- ✅ **GET /{customerId}/session** - 10-minute sessions, same within 10 minutes
- ✅ **POST /{betOfferId}/stake?sessionkey={key}** - Only valid sessions accepted
- ✅ **GET /{betOfferId}/highstakes?sessionkey={key}** - Top 20 stakes, one per customer, sorted descending
- ✅ **No persistence** - In-memory storage only
- ✅ **High concurrency** - Thread-safe with ConcurrentHashMap
- ✅ **No external frameworks** - Uses only JDK built-in libraries

## Project Structure
```
src/com/betting/
├── BettingServer.java      # Main HTTP server
├── ManualTest.java         # Manual test utilities
├── server/                 # HTTP server components
│   ├── HttpHandler.java
│   ├── HttpRequestAdapter.java
│   ├── HttpResponse.java
│   ├── HttpUtils.java
│   ├── Router.java
│   └── endpoint/
│       ├── RootEndpoint.java
│       ├── SessionEndpoint.java
│       └── StakeEndpoint.java
├── session/                # Session management
│   ├── SessionManager.java
│   └── SessionData.java
└── stake/                  # Stake storage and retrieval
    ├── StakeManager.java
    └── StakeEntry.java
```

## How to Use

### 1. Build the Project

**Windows:**
```cmd
build.bat
```

**Linux/macOS:**
```bash
./build.sh
```

Generates: `BettingServer.jar`

### 2. Run the Server
```bash
java -jar BettingServer.jar
```
Server starts on: `http://localhost:8080`

### 3. Test the API
```bash
# Get session
curl http://localhost:8080/1234/session

# Post stake (replace SESSION_KEY)
curl -X POST -d 5000 "http://localhost:8080/888/stake?sessionkey=SESSION_KEY"

# Get high stakes
curl http://localhost:8080/888/highstakes?sessionkey=SESSION_KEY
```

## API Endpoints

### 1. Create Session
```
GET /1234/session
→ ABC1234
```

### 2. Submit Stake
```
POST /888/stake?sessionkey=ABC1234
Body: 5000
→ (empty response, HTTP 200)
```

### 3. Get High Stakes
```
GET /888/highstakes?sessionkey=ABC1234
→ 1234=5000,5678=3000
```

## Key Features

### Session Management
- Sessions expire after 10 minutes
- Same session returned within 10 minutes
- 32-character alphanumeric keys (letters and digits only), generated using SecureRandom
- Session key is tied to a specific customer ID
- Periodic cleanup of expired sessions (does not affect stakes)

### Stake Management
- Only the highest stake per customer per offer (Top20 maintained; submissions below the current cutoff and not already in Top20 are dropped to keep memory bounded)
- When Top20 is full, new stakes must exceed the lowest stake (or equal with lower customer ID) to be included
- Per-offer Top-20 structure maintained incrementally using TreeSet (O(log 20) updates)
- Thread-safe per-offer locking with ReentrantLock for consistent updates/logging

### Performance
- Updates are O(log 20) per stake post (bounded Top-20 maintenance using TreeSet)
- High stakes query is O(20) to format result
- ConcurrentHashMap for thread-safe session and offer storage
- Fixed thread pool (10-50 threads) with CallerRunsPolicy for request handling

## Design Decisions

### Why No Persistence?
- Requirement: "no persistence"
- Simpler implementation
- Faster read/write operations

### Why Periodic Session Cleanup?
- Long-running stability: prevents expired sessions accumulating indefinitely
- Stakes are not deleted when sessions expire (per requirements)



## Notes
- Data is lost on server restart
- Each customer appears once in high stakes
- Maximum 20 results returned
- Empty string returned for no stakes