PodTui/src/utils/event-bus.ts

/**
 * Simple event bus for inter-component communication.
 *
 * This provides a decoupled way for components to communicate without
 * direct dependencies. Components can publish events and subscribe to
 * events they're interested in.
 *
 * Usage:
 * ```tsx
 * // Subscribe to events
 * const unsub = EventBus.on("theme.changed", (data) => {
 *   console.log("Theme changed to:", data.theme)
 * })
 *
 * // Publish events
 * EventBus.emit("theme.changed", { theme: "dark" })
 *
 * // Cleanup
 * unsub()
 * ```
 */

type EventHandler<T = unknown> = (data: T) => void;

// Export EventHandler type for external use
export type { EventHandler };

interface EventBusInstance {
	on<T = unknown>(event: string, handler: EventHandler<T>): () => void;
	once<T = unknown>(event: string, handler: EventHandler<T>): () => void;
	off<T = unknown>(event: string, handler: EventHandler<T>): void;
	emit<T = unknown>(event: string, data: T): void;
	clear(): void;
}

function createEventBus(): EventBusInstance {
	const handlers = new Map<string, Set<EventHandler>>();

	return {
		on<T = unknown>(event: string, handler: EventHandler<T>): () => void {
			if (!handlers.has(event)) {
				handlers.set(event, new Set());
			}
			handlers.get(event)!.add(handler as EventHandler);

			// Return unsubscribe function
			return () => {
				this.off(event, handler);
			};
		},

		once<T = unknown>(event: string, handler: EventHandler<T>): () => void {
			const wrappedHandler: EventHandler<T> = (data) => {
				this.off(event, wrappedHandler);
				handler(data);
			};
			return this.on(event, wrappedHandler);
		},

		off<T = unknown>(event: string, handler: EventHandler<T>): void {
			const eventHandlers = handlers.get(event);
			if (eventHandlers) {
				eventHandlers.delete(handler as EventHandler);
				if (eventHandlers.size === 0) {
					handlers.delete(event);
				}
			}
		},

		emit<T = unknown>(event: string, data: T): void {
			const eventHandlers = handlers.get(event);
			if (eventHandlers) {
				for (const handler of eventHandlers) {
					try {
						handler(data);
					} catch (error) {
						console.error(`Error in event handler for "${event}":`, error);
					}
				}
			}
		},

		clear(): void {
			handlers.clear();
		},
	};
}

// Singleton event bus instance
const EventBus = createEventBus();

import type { KeybindActionName } from "@/context/KeybindContext";
import type { TABS } from "@/utils/navigation";
import type { PaneId, NavMode } from "@/context/NavigationContext";

// Common event types for the application
export type AppEvents = {
	"theme.changed": { theme: string; mode: "dark" | "light" };
	"theme.mode.changed": { mode: "dark" | "light" };
	"theme.reload": {};
	"navigation.tab.changed": { tab: string; previousTab?: string };
	"navigation.layer.changed": { depth: number; previousDepth: number };
	"feed.subscribed": { feedId: string; feedUrl: string };
	"feed.unsubscribed": { feedId: string };
	"player.play": { episodeId: string };
	"player.pause": { episodeId: string };
	"player.stop": {};
	// Emitted when a NEW episode begins playback (not on resume).
	"player.started": { episodeId: string };
	"toast.show": {
		message: string;
		variant: "info" | "success" | "warning" | "error";
		title?: string;
		duration?: number;
	};
	"dialog.open": { dialogId: string };
	"dialog.close": { dialogId?: string };
	"command.execute": { command: string; args?: unknown };
	// Yazi-style unified router → active page dispatch. The Shell router
	// emits these; each page subscribes to the subset it implements.
	"nav.action": {
		action: KeybindActionName;
		tab: TABS;
		pane: PaneId;
		mode: NavMode;
	};
	"clipboard.copied": { text: string };
	"selection.start": { x: number; y: number };
	"selection.end": { text: string };

	// Multimedia key events (emitted by useMultimediaKeys, consumed by useAudio)
	"media.toggle": {};
	"media.volumeUp": {};
	"media.volumeDown": {};
	"media.speedCycle": {};
};

// Type-safe emit and on functions
export function emit<K extends keyof AppEvents>(
	event: K,
	data: AppEvents[K],
): void {
	EventBus.emit(event, data);
}

export function on<K extends keyof AppEvents>(
	event: K,
	handler: EventHandler<AppEvents[K]>,
): () => void {
	return EventBus.on(event, handler);
}

export function once<K extends keyof AppEvents>(
	event: K,
	handler: EventHandler<AppEvents[K]>,
): () => void {
	return EventBus.once(event, handler);
}

export function off<K extends keyof AppEvents>(
	event: K,
	handler: EventHandler<AppEvents[K]>,
): void {
	EventBus.off(event, handler);
}