moomaid

Mermaid diagram renderer written in MoonBit. Outputs ASCII art or SVG.

Install

moon add mizchi/moomaid

CLI

# Render from file
just cli diagram.mmd
just cli --svg diagram.mmd

# Render from stdin
echo 'graph LR
  A --> B --> C' | just cli-stdin

# Sequence diagram from stdin
cat <<EOF | just cli-stdin
sequenceDiagram
  participant Client
  participant API
  participant DB
  Client->>API: Request
  API->>DB: Query
  DB-->>API: Result
  API-->>Client: Response
EOF

Options

--svg          Output SVG (default: ASCII)
--ascii        Output ASCII art
--width <n>    Max width for ASCII (default: 80)
--help         Show help

Diagram Types

Flowchart (graph LR / graph TD)

Use for visualizing data flow, module dependencies, and process graphs.

graph LR
  Input --> Process --> Output

graph TD
  Start[Start] --> Auth{Auth}
  Auth -->|pass| Load[Load Data]
  Auth -->|fail| Error[Error Page]
  Load --> Validate{Validate}
  Validate -->|ok| Process[Process]
  Validate -->|ng| Error
  Process --> Save[Save]
  Save --> Done[Done]
  Error --> Done

Sequence Diagram (sequenceDiagram)

Use for describing layer boundaries and API call flows.

sequenceDiagram
  participant Browser
  participant API
  participant Auth
  participant DB
  Browser->>API: POST /login
  API->>Auth: Validate token
  Auth-->>API: OK
  API->>DB: SELECT user
  DB-->>API: User data
  API-->>Browser: 200 JSON

Other supported types

• stateDiagram-v2 - State machine diagrams
• classDiagram - Class diagrams

Library Usage

// ASCII output
let ascii = @moomaid.render_to_string("graph LR\n  A --> B")

// ASCII with options
let options : @moomaid.Options = {
  use_ascii: false,
  padding_x: 2,
  padding_y: 1,
  box_border_padding: 1,
  max_width: 80,
}
let ascii2 = @moomaid.render_to_string("graph LR\n  A --> B", options~)

// SVG output (experimental)
let svg = @moomaid.experimental_render_to_svg("graph LR\n  A --> B")

TUI Viewer

Interactive terminal viewer with tab switching and Kitty graphics protocol support.

just tui

• Tab / Shift+Tab: Switch diagrams
• Up / Down: Scroll
• s: Toggle ASCII / SVG mode (Kitty-compatible terminals)
• q: Quit

License

Apache-2.0