/**
 * Mid-session lifecycle reconciliation for `ask_user_question`.
 *
 * WHY THIS EXISTS — read before changing it.
 *
 * Subagent children run headless (`ctx.hasUI === false`). They must never be
 * able to block waiting on a human, and they must never route a question up to
 * the supervisor. Stripping the tool from the active set is the mechanism that
 * enforces that: the LLM in a headless run never sees the tool, so it cannot
 * call it, so it cannot stall a background run forever.
 *
 * Do NOT "improve" this into an escalation bridge. See
 * docs/specs/pi-ask-user-question.md §2 and §7 — no-subagent-escalation is an
 * explicit non-goal, not an oversight.
 *
 * Unlike @juicesharp/rpiv-ask-user-question there is no carve-out for
 * `ctx.mode === "rpc"`, because this package ships no RPC dialog fallback:
 * `hasUI` is the only signal and it is honest here.
 *
 * The in-handler `!ctx.hasUI` guard in ask-user-question.ts stays as a
 * one-turn backstop in case a future pi release snapshots the tool list before
 * `before_agent_start` runs.
 */

import type { ExtensionAPI, ExtensionContext } from "@earendil-works/pi-coding-agent";
import { TOOL_NAME } from "./tool/schema.ts";

/**
 * Strip or restore the tool to match `ctx.hasUI`. Idempotent: when the tool is
 * already in the right state, the active set (and every sibling tool in it) is
 * left untouched.
 */
export function reconcileTool(pi: ExtensionAPI, ctx: ExtensionContext): void {
	const active = pi.getActiveTools();
	const present = active.includes(TOOL_NAME);
	if (!ctx.hasUI && present) {
		pi.setActiveTools(active.filter((name) => name !== TOOL_NAME));
	} else if (ctx.hasUI && !present) {
		pi.setActiveTools([...active, TOOL_NAME]);
	}
}

export function registerReconciler(pi: ExtensionAPI): void {
	pi.on("before_agent_start", (_event, ctx) => {
		reconcileTool(pi, ctx);
	});
}