Draw.io Professional Diagrams

## When to use this skill
- User requests a database diagram, ERD, or entity-relationship diagram
- User requests a class diagram or UML class structure
- User requests a sequence diagram or interaction diagram
- User requests a flowchart or process flow
- User requests an architecture diagram or system overview
- User mentions "draw.io", "diagram", "table", "entity", "class", "sequence", "flow"

---

## ⚠️ MANDATORY RULES — READ BEFORE GENERATING ANYTHING

1. **ALWAYS detect the diagram type first** before writing any XML
2. **NEVER mix styles** between diagram types — each type has its own strict XML structure
3. **ALWAYS assign unique sequential IDs** to every `mxCell` starting from 0
4. **NEVER use `\n` inside a `value` attribute** — use separate rows/cells instead
5. **ALWAYS calculate table/class heights correctly** using the formulas provided
6. **ALWAYS validate the XML structure** before saving
7. **ALWAYS export to PNG and include the PNG in the response before asking about other formats** — this step is non-negotiable
8. **NEVER use generic rounded rectangles** for database tables or class entities
9. **ALWAYS apply consistent spacing between diagram elements**
   - Horizontal spacing between elements: **minimum 120px**
   - Vertical spacing between rows or steps: **minimum 100px**
   - Tables/classes must not overlap
   - Relationship lines must not cross through table headers

---

## STEP 0 — Diagram Type Detection

Before generating any XML, identify the diagram type from the user's request:

| User says... | Diagram type |
|---|---|
| "database", "ERD", "tables", "entities", "foreign key" | → **TYPE 1: ERD** |
| "class", "UML", "inheritance", "attributes", "methods" | → **TYPE 2: Class Diagram** |
| "sequence", "interaction", "lifeline", "actor calls" | → **TYPE 3: Sequence Diagram** |
| "flowchart", "flow", "process", "decision", "steps" | → **TYPE 4: Flowchart** |
| "architecture", "system", "services", "components" | → **TYPE 5: Architecture** |

---

## Diagram Type References
Use the detailed rules/templates in these files based on the detected type.

- ERD / Database: `ERD.md`
- UML Class: `CLASS.md`
- Sequence: `SEQUENCE.md`
- Flowchart: `FLOWCHART.md`
- Architecture: `LAYOUT.md`


---

## Generation Workflow — ALWAYS follow this exact order

### Step 1 — Identify diagram type
Determine TYPE 1–5 from the user's message before writing any XML.

### Step 2 — Plan all elements
List every entity/class/participant and all relationships before coding.

### Step 3 — Create output folder
```bash
mkdir -p ./diagrams
```

### Step 4 — Write and save the XML
Save to `./diagrams/<diagram-name>.drawio`

**Mandatory pre-save checklist:**
- [ ] All `mxCell` elements have unique sequential numeric IDs
- [ ] ERD tables use `shape=table` with `shape=tableRow` rows (never generic shapes)
- [ ] Class diagrams use `swimlane` with attribute block, divider line, and method block
- [ ] Sequence diagrams have lifelines, activation boxes, and correct arrow styles
- [ ] ERD relationship arrows connect to **row cell IDs**, not table container IDs
- [ ] Heights calculated correctly: `30 + (columns x 30)` for ERD tables
- [ ] No literal `\n` in value attributes (use `&#xa;` for multiline text cells only)
- [ ] XML is well-formed and all tags are closed

### Step 5 — Export to PNG
```bash
# macOS
/Applications/draw.io.app/Contents/MacOS/draw.io -x -f png --scale 2 -o ./diagrams/<name>.png ./diagrams/<name>.drawio

# Linux / headless
xvfb-run -a drawio -x -f png --scale 2 -o ./diagrams/<name>.png ./diagrams/<name>.drawio
```

### Step 6 — Verify output
```bash
ls -lh ./diagrams/<name>.png
```

### Step 7 — Show PNG first (MANDATORY)

Always respond with the PNG image first (embed/attach it in the response).

### Step 8 — Ask the user for delivery format (MANDATORY)

After showing the PNG, ALWAYS ask the user which additional format they want:

---
The diagram is ready! Which format would you like?

1 - PNG image (ready to view)
2 - .drawio file (editable in draw.io)
3 - SVG (scalable vector)
4 - PDF
5 - All of the above

Reply with the number(s) of your choice.
---

Then based on the response:
- **1** → send the PNG file
- **2** → send the .drawio file
- **3** → export SVG and send it
- **4** → export PDF and send it
- **5** → send all formats
- **Multiple numbers** (e.g. "1 2") → send all requested formats

---

## Other export formats
```bash
# SVG (scalable vector)
/Applications/draw.io.app/Contents/MacOS/draw.io -x -f svg -o ./diagrams/<name>.svg ./diagrams/<name>.drawio

# PDF
/Applications/draw.io.app/Contents/MacOS/draw.io -x -f pdf -o ./diagrams/<name>.pdf ./diagrams/<name>.drawio

# High-res PNG (scale 3)
/Applications/draw.io.app/Contents/MacOS/draw.io -x -f png --scale 3 -o ./diagrams/<name>_hd.png ./diagrams/<name>.drawio

# Transparent background
/Applications/draw.io.app/Contents/MacOS/draw.io -x -f png -t --scale 2 -o ./diagrams/<name>_transparent.png ./diagrams/<name>.drawio
```