Overview

Modality is a Flutter/Rust library for building interactive educational content. It provides three modalities — Whiteboard, Worksheet, and Lesson Plan — each with template compilation, Loro CRDT sync, and AI-powered generation.

Architecture at a Glance

graph TD
    A[modality_core] -->|pure traits + types| B[modality_session]
    B -->|Session orchestrator| C[modality_ai]
    B --> D[modality_export]
    C --> E[Whiteboard]
    C --> F[Worksheet]
    C --> G[Lesson Plan]
    D --> E
    D --> F
    D --> G
    E --> H[modality_rust / API]
    F --> H
    G --> H
    H --> I[Flutter / Dart]

Three Traits, One Struct

Each modality (Whiteboard, Worksheet, LessonPlan) implements three core traits:

Trait	Concern
Reducer	State management via static reduce() + instance dispatch()
Component	Compilation from state to rendered output
Modality	Layout orchestration, placements, snapshots

Key Concepts

• Element — leaf rendered primitive (things on the canvas/page)
• Component — reusable templated layout that compiles to elements
• Position — modality-specific spatial info (WhiteboardPosition, GridPosition, SlidePosition)
• ComponentPlacement<P> — a placed component instance stored in synced state
• Session<M, I> — single orchestrator that owns modality, persistence, cache, AI, and export

Tech Stack

Layer	Technology
UI	Flutter / Dart
Bridge	Flutter Rust Bridge (FRB)
Core	Rust (traits, state, compilation)
Persistence	Loro CRDT
AI	rig-core (OpenAI compatible)
Export	PDF via modality_export

Dependency Graph

graph TD
    CORE[modality_core] -->|pure traits + types| SESSION[modality_session]
    SESSION -->|Session orchestrator| AI[modality_ai]
    SESSION --> EXPORT[modality_export]
    AI --> MOD[modality crates]
    EXPORT --> MOD
    MOD --> API[modality_rust / API]