# Simon-Lab Pipeline Label Generator

> REST API and web UI for creating ISO 20560-compliant pipeline identification labels. Labels auto-size based on pipe diameter.

Base URL: https://label.simon-lab.org/

## REST API

POST to `/api/generate` with JSON body. Returns `downloadUrl` to fetch the generated label.

### Decision Order (Important!)

1. **Choose pipe size first** - determines label dimensions and max text length
2. **Set substance text** - if chemical formula like H2SO4, set `isChemicalFormula: true`
3. **Add hazards** - if `hazardous: true`, MUST include `ghs` array with pictogram IDs
4. **Check response warnings** - API returns warnings array if issues detected

### Required Fields

- `mediumType`: WATER, GAS, ACIDS, ALKALIS, LIQUID_SOLID, COMPRESSED_AIR, FIRE_SUPPRESSION
- `substance`: Main text (max ~20 chars for DN50, ~40 chars for DN150)

### Optional Fields

- `info`: Second line of text (reduces max text height by 40%)
- `hazardous`: boolean - REQUIRES `ghs` array if true, otherwise yellow band is empty
- `ghs`: array of IDs: GHS01_Explosive, GHS02_Flame, GHS03_Oxidizer, GHS04_GasCylinder, GHS05_Corrosion, GHS06_SkullAndCrossbones, GHS07_Exclamation, GHS08_HealthHazard, GHS09_Environment
- `isChemicalFormula`: true - renders H2O as H₂O with subscripts
- `flowDirection`: left, right, bidirectional, none
- `pipeSize`: "50" (default), "100", "150", "200", etc. (DN standard)
- `format`: "pdf" (default), "png", "json"

### Common Mistakes to Avoid

- Setting `hazardous: true` without `ghs` array → empty yellow band with no symbols
- Long text on small pipes → text truncation (check warnings in response)
- Chemical formulas without `isChemicalFormula: true` → numbers not rendered as subscripts

### Example Request

```json
{
  "mediumType": "ACIDS",
  "substance": "H2SO4",
  "isChemicalFormula": true,
  "hazardous": true,
  "ghs": ["GHS05_Corrosion"],
  "pipeSize": "100",
  "format": "png"
}
```

### Example Response

```json
{
  "success": true,
  "warnings": [],
  "downloadUrl": "/api/download/label_xxx.png",
  "meta": { "width": 85, "height": 42 }
}
```

## Docs

- [API Schema](https://label.simon-lab.org/api/schema): Full endpoint documentation with all options
- [Health Check](https://label.simon-lab.org/api/health): Server status and rate limits

## Web Interface

- [Label Designer](https://label.simon-lab.org/): Interactive web UI for manual label creation