Architecture

Pipeline

Typed numbers (integers) → model (integers) → evaluated geometry (floats, segments + arcs) → SVG (d). Details: ADR-0005.

Layers

Imports only go to the listed layers. Source table: eslint/settings/layers.ts (enforced by import-x/no-restricted-paths and local/kind-in-layer).

Layer	Role	May import	DOM	@kind
src/math/	scalars, vectors, tolerances, robust predicates	—	no	math
src/geometry/	segments, arcs, intersections, corner radius, offset, booleans	math	no	math, geometry
src/model/	shapes, symbols, ports, configurations, business types, views, pipes	math, geometry	no	domain
src/routing/	orthogonal pipe routing	math, geometry, model	no	geometry, domain
src/io/	SVG / JSON serialization	math, geometry, model	no	format
src/render/	model → SVG elements	all but interaction	yes	format, procedure
src/interaction/	tools, hit-testing, snapping, commands	every src/ layer	yes	domain, procedure
playground/	demonstration application	public API src/index.ts only	yes	procedure

A layer exists on disk only from its first module on (an empty folder has no meaningful barrel). Layers present after E01: math, geometry, model, io, render. The pure decisions of an interaction (which vertices a click selects, F03) live in model; interaction will hold the effects (events, hit-testing).

Functional core, imperative shell (ADR-0014)

• Core (math → io): pure functions. No mutation, no let, no imperative loop, no throw, no access to document, window, console, Math.random, Date.now…
• Shell (render, interaction, playground): effects allowed (DOM, events), but never reassigning a property of a parameter, nor mutating the model (its types are readonly).

In practice: every decision is taken in the core; the shell only applies it.

Portability (ADR-0025)

The core runs in any ECMAScript engine (browser, Node.js, server, worker) and can be transcribed into another language function by function:

• ECMAScript only — no DOM, Node.js or host API (lint: eslint/scopes/pure-layers.ts);
• plain read-only data in and out; no class, closure returned or exception;
• the TSDoc states the mathematical intent where JavaScript differs from other languages (% sign, .at with a negative index, -0, NaN);
• number is IEEE 754 binary64; EPSILON and SVG_DECIMALS are part of the specification.