/**
 * Cross-extension publication of the effective foreground sandbox policy.
 *
 * The contract is deliberately narrow: a frozen status snapshot travels over
 * `pi.events`, and nothing else. No function, no controller, no way to run a
 * command — a consumer can read what the policy is and enforce it itself, and
 * that is all.
 *
 * Consumers snapshot at launch time. `pi.events` has no replay, so an extension
 * that loads late can ask for the current policy on the request channel and
 * receive it on the policy channel.
 */

import type { EventBus } from "@earendil-works/pi-coding-agent";

import type { ForegroundSandboxStatus } from "./state.ts";

/** Channel carrying every effective-policy change. Payload: ForegroundSandboxPolicyEvent. */
export const FOREGROUND_SANDBOX_POLICY_CHANNEL = "pi-better-sandbox:policy";

/** Channel a late-loading consumer emits on to ask for the current policy. */
export const FOREGROUND_SANDBOX_POLICY_REQUEST_CHANNEL = "pi-better-sandbox:policy-request";

/** The immutable payload published on the policy channel. */
export type ForegroundSandboxPolicyEvent = ForegroundSandboxStatus;

/** Deep-freeze a status so a consumer cannot mutate another consumer's copy. */
export function freezePolicy(status: ForegroundSandboxStatus): ForegroundSandboxPolicyEvent {
    return Object.freeze({ ...status, denyWrite: Object.freeze([...status.denyWrite]) });
}

/** Publish the current effective policy to every subscribed extension. */
export function publishForegroundSandboxPolicy(
    events: EventBus,
    status: ForegroundSandboxStatus,
): ForegroundSandboxPolicyEvent {
    const payload = freezePolicy(status);
    events.emit(FOREGROUND_SANDBOX_POLICY_CHANNEL, payload);
    return payload;
}

/** Subscribe to effective-policy changes. Returns an unsubscribe function. */
export function subscribeForegroundSandboxPolicy(
    events: EventBus,
    handler: (policy: ForegroundSandboxPolicyEvent) => void,
): () => void {
    return events.on(FOREGROUND_SANDBOX_POLICY_CHANNEL, (data) => {
        handler(data as ForegroundSandboxPolicyEvent);
    });
}

/** Ask the sandbox extension to re-publish the current effective policy. */
export function requestForegroundSandboxPolicy(events: EventBus): void {
    events.emit(FOREGROUND_SANDBOX_POLICY_REQUEST_CHANNEL, undefined);
}