# Car Log API

Simple car on/off event logging system with interval analysis.

## Endpoints

### `GET /`
Returns this documentation.

### `GET /on?psw=PASSWORD`
Log a car "on" event with current timestamp.

**Response:**
```json
{
  "success": true,
  "timestamp": "2025-08-25 14:30:00",
  "event": "on"
}
```

### `GET /off?psw=PASSWORD`
Log a car "off" event with current timestamp.

**Response:**
```json
{
  "success": true,
  "timestamp": "2025-08-25 16:45:00",
  "event": "off"
}
```

### `GET /intervals?psw=PASSWORD[&start-date=YYYY-MM-DD][&end-date=YYYY-MM-DD]`
Analyze car usage intervals with optional date filtering.

**Query Parameters:**
- `start-date` (optional): Filter intervals from this date (YYYY-MM-DD format)
- `end-date` (optional): Filter intervals until this date (YYYY-MM-DD format)

**Features:**
- Pairs "on" and "off" events into usage intervals
- Splits intervals crossing midnight (00:00 Czech time)
- Caps single rides at maximum 6 hours
- Returns intervals sorted by start time

**Response:**
```json
[
  {
    "start": "2025-08-25 14:30:00",
    "end": "2025-08-25 16:45:00",
    "duration": 2.25
  },
  {
    "start": "2025-08-25 23:30:00",
    "end": "2025-08-25 23:59:59",
    "duration": 0.5
  },
  {
    "start": "2025-08-26 00:00:00",
    "end": "2025-08-26 01:30:00",
    "duration": 1.5
  }
]
```

## Data Storage

- Events are stored in CSV format: `timestamp,event`
- All timestamps are in Czech local time (CET/CEST)
- Data persists across server restarts

## Error Responses

```json
{
  "success": false,
  "error": "Unauthorized"
}
```

```json
{
  "success": false,
  "error": "Invalid start-date format. Use yyyy-mm-dd"
}
```