# Docker Python Development & Debugging Guide

This guide outlines the setup for a lean, telemetry-free development environment using **VSCodium**, **Docker**, and **tmux**. It is designed to be consistent across Windows, Mac, and Linux.

---

## 1. Project Structure
Create the following files in your project root to keep the configuration modular and "neat".

```text
.
├── .tmux.conf                # tmux customisation
├── .vscode/
│   ├── launch.json           # VSCodium debugger config
│   └── tasks.json            # Automation for tmux attach
├── docker-compose.yml        # Production base
├── docker-compose.override.yml # Development extensions
├── Dockerfile                # Image definition
└── main.py                   # Your application code
```

---

## 2. The Configuration Files

### Dockerfile
Ensures all tools (**tmux**, **debugpy**) and system upgrades are baked into the image.

```dockerfile
FROM python:3.10-slim

WORKDIR /usr/src/app

# System upgrades and tmux installation
RUN apt-get update && apt-get upgrade -y && \
    apt-get install -y tmux && \
    rm -rf /var/lib/apt/lists/*

# Upgrade pip and install requirements
COPY requirements.txt ./
RUN pip install --no-cache-dir --upgrade pip
RUN pip install --no-cache-dir -r requirements.txt debugpy

# Copy tmux config to root
COPY .tmux.conf /root/.tmux.conf

COPY . .

# Default production command
CMD [ "python", "./main.py" ]
```

### docker-compose.yml (Production Base)
```yaml
version: '3'
services:
  bank_analysis_excel:
    build: .
    container_name: bank_analysis_excel
```

### docker-compose.override.yml (Development)
```yaml
version: '3'
services:
  bank_analysis_excel:
    volumes:
      - .:/usr/src/app
    ports:
      - "5678:5678"
    tty: true
    stdin_open: true
    # Overrides the Dockerfile CMD to keep the workshop open
    command: tail -f /dev/null
```

### .tmux.conf
Enables mouse support and customises the interface.

```bash
# Enable mouse mode for clicking/resizing
set -g mouse on

# Visual improvements
set -g default-terminal "screen-256color"
set -g history-limit 10000
set -g status-bg black
set -g status-fg white
set -g status-left ""
set -g status-right "#[fg=green]#H #[fg=white]%H:%M"
```

### .vscode/launch.json
```json
{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "Python: Docker Attach",
            "type": "debugpy",
            "request": "attach",
            "connect": {
                "host": "localhost",
                "port": 5678
            },
            "pathMappings": [
                {
                    "localRoot": "${workspaceFolder}",
                    "remoteRoot": "/usr/src/app"
                }
            ]
        }
    ]
}
```

---

## 3. The Daily Workflow

### Step 1: Start the Container
Run in your host terminal (PowerShell, bash, or zsh):
```bash
docker compose up -d
```

### Step 2: Open VSCodium & Attach
If you set up the `tasks.json` automation, VSCodium will attach automatically. Otherwise, run:
```bash
docker compose exec bank_analysis_excel tmux
```

### Step 3: Start the Persistent Loop
In your primary **tmux** pane, run this loop so the debugger is always ready:
```bash
while true; do python3 -m debugpy --listen 0.0.0.0:5678 --wait-for-client main.py; done
```

### Step 4: Split and Work
* **Prefix Key**: `Ctrl + b`
* **Split Vertically**: `Prefix` then `%`
* **Switch Panes**: `Prefix` then `Arrow Keys` (or just click with your mouse).

---

## 4. Deploying to Production
When the code is fixed and ready for a live environment:
1. Copy only `docker-compose.yml`, `Dockerfile`, and your code.
2. **Do not** copy `docker-compose.override.yml`.
3. Run `docker compose up -d`. The container will automatically execute `main.py` and close when finished.