import { isEnoent } from "@oh-my-pi/pi-utils";
import { InternalUrlRouter, type LocalProtocolOptions } from "../internal-urls";

/** The session's active plan, resolved for handoff into a subagent's context. */
export interface OverallPlanReference {
	/** The `local://` reference path (e.g. `local://my-feature.md`), kept for display. */
	path: string;
	/** The full plan markdown, as written to disk. */
	content: string;
}

/**
 * Load the session's active overall plan for subagent handoff.
 *
 * Returns the plan referenced by `planReferencePath` when it exists on disk with
 * non-empty content, or `undefined` when there is no plan (the file is absent or
 * empty). This mirrors `AgentSession.#buildPlanReferenceMessage`'s gating so a
 * subagent sees exactly the plan the main agent treats as its active reference.
 *
 * Callers MUST skip this during plan mode itself — read-only plan exploration
 * uses a different prompt and a draft plan should not be handed off as approved.
 */
export async function loadOverallPlanReference(
	planReferencePath: string,
	localProtocolOptions: LocalProtocolOptions,
): Promise<OverallPlanReference | undefined> {
	const resolved = await InternalUrlRouter.instance().requireLocal(
		planReferencePath,
		"load plan from",
		{ localProtocolOptions },
		{ create: true },
	);
	let content: string;
	try {
		content = await Bun.file(resolved).text();
	} catch (error) {
		if (isEnoent(error)) return undefined;
		throw error;
	}
	if (!content.trim()) return undefined;
	return { path: planReferencePath, content };
}