import type { IFocusChainService } from './interfaces';
/**
* Service that manages the focus chain hierarchy.
* Only one element can be "active" at a time.
* When an element is active, its entire ancestor chain is "focused".
*/
export class FocusChainService implements IFocusChainService {
private activeElementId: string | null = null;
private parentMap = new Map<string, string>();
/**
* Set the currently active element
* Only one element can be active in the entire application
*/
setActive(elementId: string | null): void {
this.activeElementId = elementId;
}
/**
* Get the currently active element
*/
getActive(): string | null {
return this.activeElementId;
}
/**
* Register a parent-child relationship
* Used to build the focus chain
*/
registerParent(childId: string, parentId: string): void {
this.parentMap.set(childId, parentId);
}
/**
* Get the focus chain: [active element, ...ancestors]
* The entire chain is considered "focused"
* If no active element, returns chain starting from 'app' (root)
*/
getFocusChain(): string[] {
// If there's an active element, return it and its ancestors
if (this.activeElementId) {
const chain: string[] = [this.activeElementId];
let currentId = this.activeElementId;
// Walk up the parent chain
while (this.parentMap.has(currentId)) {
const parentId = this.parentMap.get(currentId)!;
chain.push(parentId);
currentId = parentId;
}
return chain;
}
// If no active element, build chain from app down
// This ensures we always have a valid focus chain
const chain: string[] = [];
// Start with app if it exists
if (this.parentMap.has('navigation') && !this.parentMap.get('navigation')) {
// navigation's parent is app (or undefined), so app is root
chain.push('app');
}
return chain;
}
/**
* Check if an element is in the focus chain
* (either active or an ancestor of the active element)
*/
isInFocusChain(elementId: string): boolean {
return this.getFocusChain().includes(elementId);
}
/**
* Clear parent registration for an element
* Called when element is unmounted
*/
unregisterElement(elementId: string): void {
// Remove as parent of any children
for (const [childId, parentId] of this.parentMap.entries()) {
if (parentId === elementId) {
this.parentMap.delete(childId);
}
}
// Remove own parent registration
this.parentMap.delete(elementId);
// If this was the active element, clear active state
if (this.activeElementId === elementId) {
this.activeElementId = null;
}
}
}
