/**
 * Scheduler Adapter — Common Interface
 * RFC-0101 §6
 *
 * All scheduler adapters implement this interface.
 * The runtime selects an adapter at install time and uses it for all scheduled tasks.
 */
// ScheduledTask duplicated here to avoid cross-package import resolution issues
// in the workspace. Replace with:
//   import type { ScheduledTask } from "@pi/autonomous-runtime";
export type ScheduledTask = {
	id: string;
	taskTemplate: Record<string, unknown>;
	schedule:
		| { kind: "cron"; expression: string }
		| { kind: "interval"; intervalMs: number }
		| { kind: "once"; at: string };
	enabled: boolean;
	lastFiredAt?: string;
	nextFireAt?: string;
};

/**
 * Supported scheduler adapter backends.
 * Set at install time; can be changed via config.
 */
export type SchedulerAdapterKind = "systemd" | "cron" | "launchd" | "internal";

export interface SchedulerAdapter {
	/** Human-readable name. */
	readonly name: SchedulerAdapterKind;

	/**
	 * Install the scheduler adapter.
	 * Idempotent — re-running does not duplicate units.
	 * @throws if installation fails (e.g. no systemd on this system)
	 */
	install(): Promise<void>;

	/**
	 * Schedule a task. Installs the timer/unit if not yet installed.
	 * @param task The scheduled task to materialise
	 */
	schedule(task: ScheduledTask): Promise<void>;

	/**
	 * Remove a scheduled task.
	 * @param taskId The id of the task to unschedule
	 */
	unschedule(taskId: string): Promise<void>;

	/**
	 * List all scheduled tasks currently installed by this adapter.
	 */
	listScheduled(): Promise<ScheduledTask[]>;

	/**
	 * Check if the adapter is healthy (e.g. systemd is running).
	 */
	healthCheck(): Promise<{ healthy: boolean; error?: string }>;
}