APPLICATION.md

Application construction

gods-eye-view/application exports createApplication. Importing it does not create a viewer, discover configuration, start requests, or attach browser listeners. Construction is also inactive until the caller invokes start().

The caller supplies four constructors, in this order:

Constructor	Receives	Standalone implementation
createScene	signal, defer	Viewer, attribution and initial map
createControls	scene, signal, defer	Style manager and camera presentation
createData	scene, controls, signal, defer	Layer catalog, registration and restoration
createTools	scene, controls, data, signal, defer	Scenes, annotations, voice and page listeners

Each constructor returns its component object, or a promise for that object. Those objects are passed unchanged to later constructors. Configuration and service instances belong in the caller's closures; the application does not interpret provider names, environment variables, endpoints, or module paths. There is no module discovery or automatic import mechanism.

import { createApplication } from 'gods-eye-view/application';
import { createApplicationViewer } from 'gods-eye-view/application/viewer';

const app = createApplication({
  createScene({ defer }) {
    const viewer = createApplicationViewer({ container, creditContainer });
    defer(() => viewer.destroy());
    return { viewer };
  },
  createControls,
  createData,
  createTools,
});
const unsubscribe = app.subscribe(({ status, phase }) => {
  // Update the caller's startup presentation.
});
await app.start();
// When the application is no longer needed:
unsubscribe();
await app.destroy();

The example's containers and three remaining constructors are supplied by the consumer. The viewer helper preserves the standalone viewer's render settings; it neither selects map sources nor reads keys. Supply a visible credit container and retain all attribution required by the chosen sources. Cesium is external to this export: the consuming build must provide the same instance used elsewhere in its application.

Lifecycle and ownership

Register defer(cleanup) immediately after acquiring each resource, before any await. Cleanup registration remains open until that constructor settles. Each callback may return a promise. Within a phase, callbacks run in reverse order. Across phases, teardown runs tools, controls, data, scene: controls must cancel restoration while their data manager and viewer are still alive.

start() returns the same promise on repeated calls. destroy() is terminal and also returns the same promise on repeated calls. It aborts the shared signal immediately, waits for an in-flight constructor to settle, and runs all registered cleanup callbacks. Constructors must forward the signal to cancellable operations and check it after awaits. If a provider cannot cancel construction, register cleanup for its late result before returning. Destruction waits for that result; it does not pretend a pending resource has already been released.

A constructor failure triggers the same cleanup before rejecting startup. Cleanup failures do not stop the remaining callbacks; they are reported through an AggregateError. Constructors own cleanup for resources created internally, including anything allocated before their own construction throws.

getState() returns a frozen { status, phase } snapshot. Status is created, starting, ready, destroying, destroyed, or failed. phase identifies the constructor during startup. subscribe(listener) immediately reports the current snapshot and returns an unsubscribe function. Install observers before start() to receive every startup phase. Observer failures cannot interrupt startup or teardown. getComponents() returns a frozen, shallow snapshot of the currently constructed component objects; the component instances themselves remain mutable.

ready means all constructors have returned. Background feed activity and the standalone share-restoration result keep their existing separate contracts.

Standalone wiring

src/main.js reads the existing browser configuration and starts src/standalone/application.js. That module selects the four implementations in its directory. Scene setup, controls, layer registration, tools and loading chrome have separate owners. The existing window.__godsEyeView debugging shape is preserved while the app is running.

The standalone controls and layer modules still contain page-scoped state. Only one standalone application may be constructed per page. Shutdown releases its runtime resources and debugging handles; reload the page to start again. It is not an embeddable, removable HTML shell or a multiple-viewer implementation. Consumers of the small application export supply their own component ownership; the lifecycle controller itself has no shared instance state.

Later component extractions can replace a constructor's internals without changing the startup contract or moving standalone imports into the package. Run the unit suite, package boundary gate, build, tracking and first-run browser checks when changing this wiring.

Geospatial services

src/search owns forward/reverse geocoding, place search and route provider interfaces. createStandaloneApplication({ geospatial }) accepts endpoints and providers; the defaults preserve Google/Photon search, Google place context and the local OSRM route proxy. Location, annotations, HUD labels and voice use the composed service. Provider-specific credentials belong in the selected transport; server secrets never belong in browser configuration.

For a compatible protocol, configure geocode, photon, reverse, textSearch, nearby or route endpoints. These are developer-selected configuration, not URLs accepted from page queries or model arguments. A different protocol supplies an adapter function instead. The exported createDefaultPlaceSearch constructor supports the same options for direct composition:

const services = createDefaultPlaceSearch({
  resolveApiKey,
  signal,
  endpoints: { photon: 'https://search.example/api/', route: '/api/routes' },
  providers: {
    route: routeProvider,
    routeProfiles: ['foot', 'car'],
  },
});

Forward providers.geocode is the existing ordered geocoder array. Other operations are independent functions: reverseGeocode(latitude, longitude, { signal }), textSearch(query, point, { signal }), nearby(point, { signal }) and route(coordinates, profile, { signal }). Points use latitude, longitude and radiusM; route coordinates use [longitude, latitude] in WGS84. Routes return { geometry, distanceM, durationS } with metres and seconds. Unavailable routes return null, retaining the explicitly labelled direct-line fallback. Place search returns normalized place arrays; reverse lookup returns address, locality, region, country and label fields used by scene context. Unsupported operations are reported in capabilities; adapters can provide attribution and supported route profiles. A provider's lifetime and caller cancellation both invalidate late response bodies.

Node middleware is configured separately. googlePlacesContextProxy accepts endpoints: { nearby, textSearch }, resolveApiKey and fetchImpl. overpassProxy({ routing: { endpoints: { foot, car, bike }, fetchImpl } }) selects compatible OSRM base URLs while preserving coordinate/span limits. regionalBriefProxy({ placeProvider }) accepts the regional lookup function; createRegionalPlaceProvider({ endpoint, requestJson }) supplies the existing serialized Nominatim implementation. Configuration is per instance, including routing and regional caches. Request parameters cannot override these endpoints.

Voice connections and controls

Voice controls accept an action runner and a controller factory through createVoiceCommands (./voice/commands). The default Realtime controller owns microphone tracks, playback, push-to-talk, tool cancellation and radio handoff. Its backend supplies requestToken({ tier, signal }) and negotiate({ offerSdp, credential, signal }). The Realtime-compatible adapter (./voice/realtime-backend) accepts separate token and connection transports and endpoints. Only the short-lived client secret reaches the SDP endpoint. Stopping or ending the application lifetime aborts connection requests and rejects delayed responses; a new start requests a fresh secret. Secret expiry limits connection creation and does not describe the connected session lifetime.

createStandaloneApplication({ voice }) passes these construction options to the controls. An incompatible protocol needs a separate controller adapter; changing an endpoint alone does not translate protocol messages. No alternate model is bundled by this extraction. The Node Realtime provider accepts realtime: { endpoint, models: { standard, mini }, resolveApiKey, fetchImpl }; existing environment variables remain the default configuration. Model choices come from server configuration. Keep secret keys in the server adapter. Tool schemas, model defaults and cost estimates are unchanged. Unknown model IDs retain the existing conservative estimate until their rates are registered.

Composing the existing application components

application/scene, application/controls, application/data and application/tools expose the existing globe, controls, catalog and tools as separate constructors. Pass these to createApplication; use its signal and defer for ownership. The compatibility catalog is still page-scoped: construct one application per page. Controls, actions and renderers use the same layer instances. Configure sources with application/sources before registration or state restoration, and release them after the consumers stop.

application/services accepts boundary, terrain, regional-context, weather and summary services. application/requests supplies the existing HTTP protocols with configurable endpoints and a scoped transport. Changing an endpoint works only for a compatible protocol; another protocol supplies a service adapter. Cancellation discards late response bodies, and replacing a source invalidates its pending results. Source disposal does not silently reinstate a default.

ui/composition supplies the default engines to the shell. Applications can supply a HUD implementation or request policy through control services. The shared chrome owns the welcome/loading transition; standalone composition adds Provider Settings. build/html expands an allowlist of component markers from src/ui/templates; unknown names cannot read arbitrary filesystem paths. The standalone document expands to the same markup as before this extraction.