# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Commands

```bash
npm run build      # tsc emits individual ESM modules to dist/ (no bundling)
npm run typecheck  # tsc --noEmit
npm run lint       # oxlint over src/
npm run format     # Prettier formatting
```

Linting runs on `oxlint`, not ESLint/`@typescript-eslint`. This project pins `typescript@^7.0.2`, and `@typescript-eslint` has no released version that supports it (peer range caps at `<6.1.0`, and even loading `@typescript-eslint/parser` crashes against TS 7's package shape). `oxlint` has its own parser and doesn't touch the `typescript` package, so it works regardless of TS version — the tradeoff is no type-aware rules (no `no-floating-promises`, `no-unnecessary-condition`, etc.). Revisit once `@typescript-eslint` supports TS 7.

There are no tests in this project. To preview components locally, open `index.html` in a browser with any static-file server.

## Architecture

This library wraps [Leaflet.js](https://leafletjs.com/) as native Web Components (Custom Elements). Each HTML element maps 1:1 to a Leaflet object.

### `WithProps` mixin: `src/core/with-props.ts`

The `WithProps(Base, PROPS)` mixin factory replaces the old `LeafletElement` base class. Each component defines a `PROPS` table (a const record mapping kebab-case attribute names to `PropDef` descriptors), then extends `WithProps(HTMLElement, PROPS)`. The mixin handles:

- `observedAttributes` getter derived from the PROPS table keys.
- `definePropAccessors` — property getters/setters on the prototype that sync attributes.
- On connect, `initOptions()` builds a Leaflet options object from current attributes + PROPS defaults, then calls `createLeafletObject()`.
- On attribute change, `updateLeafletObject()` by default dispatches to the matching Leaflet setter (e.g. `setOpacity`, `setRadius`). Components override this for custom attribute handling (e.g. lat/lng pairs).
- Every Leaflet event the created object fires is re-emitted on the element as `leaflet:<type>` (e.g. `leaflet:zoomend`, `leaflet:dragend`), carrying the original Leaflet event object as `event.detail`. This is generic and automatic: `WithProps` wraps the object's own `fire()` method, so no per-component or per-event-type registration is needed. Not bubbling — Leaflet already propagates layer events up to the map, so `<leaflet-map>` would otherwise see each one twice.

### `leaflet-map`: `src/components/leaflet-map.ts`

`LeafletMap` extends `HTMLElement` directly and uses Shadow DOM. It is the root of the component tree and terminates all bubbling `leaflet-register` events by calling `layer.addTo(this.map)`. Uses a `ResizeObserver` on the host element to call `map.invalidateSize()` automatically.

### Child component pattern

All non-map components extend `WithProps(HTMLElement, PROPS)`. To add a new component:

1. Define a `PROPS = {...}` const table mapping kebab-case attributes to `PropDef` entries.
2. Declare `class LeafletFoo extends WithProps(HTMLElement, PROPS)` implementing `createLeafletObject(): L.Layer`.
3. Override `updateLeafletObject(name, val)` only if the default setter-based update won't work (common for coordinate pairs).
4. Call `customElements.define('leaflet-foo', LeafletFoo)` at the bottom.
5. Export from `src/index.ts`.

### Special cases

- **`leaflet-polygon`** uses `<leaflet-line>` children for vertices. The polygon collects lat/lng from child `leaflet-line` elements rather than having them as direct attributes.
- **`leaflet-popup`** / **`leaflet-tooltip`**: content comes from `innerHTML`, not attributes. `leaflet-popup` watches for DOM mutations to keep Leaflet in sync.
- **`leaflet-layer-group`** / **`leaflet-feature-group`**: passthrough containers built with `WithProps({})` (an empty props table) — they have no options of their own, but still get the standard lifecycle, child registration, and `leaflet:` event forwarding for free. Children register themselves into them via the standard bubble mechanism.

### Output

`tsc` compiles `src/` → `dist/` as individual ESM modules (`.js` + `.d.ts` + `.d.ts.map`) — no bundling step. Consumers import `dist/index.js` (or any individual module) directly; there is no CJS or UMD build. Leaflet is always external (never bundled). Imports within source use `.ts` extensions; `rewriteRelativeImportExtensions` in tsconfig strips them to `.js` in the tsc output (`tsconfig.json:16`).