gen-uml

Overview

Generate a Mermaid diagram from existing code — architecture, flow, or sequence — and verify it reflects what the code actually does, not what it was supposed to do.

Steps

1. Read the real code for the slice you're diagramming (entry points, modules, call/data flow). Diagram what exists.
2. Pick the diagram type that answers the question being asked (below).
3. Emit Mermaid.
4. Match-check (required): walk the diagram against the code one node/edge at a time. Every box maps to a real module/function; every arrow to a real call/dependency. Drop or fix anything you can't point to in the source. A diagram that quietly diverges is worse than none.

Types & examples

Architecture (modules/dependencies):

graph TD
  UI[UI] --> UC[Use cases]
  UC --> SVC[Services]
  SVC --> REPO[Repository]
  REPO --> DB[(Store)]

Flow (a process / decision path):

flowchart TD
  A[Receive task] --> B{Brownfield?}
  B -- yes --> C[Explore code]
  B -- no --> D[Brainstorm]
  C --> D --> E[Plan]

Sequence (interaction over time):

sequenceDiagram
  participant C as Client
  participant R as Repo
  participant DB as Store
  C->>R: save(entity)
  R->>DB: update(blob)
  DB-->>R: version
  R-->>C: ok

Output

The Mermaid block plus one line per diagram confirming the match-check passed (or listing what was corrected).