import type { UlwLoopItem, UlwLoopPlan } from "./domain-types.js";
import type { UlwLoopSteeringPlanSnapshot } from "./steering-types.js";

/**
 * Compact before/after snapshots for steering ledger entries.
 *
 * Ledger entries used to embed the FULL plan (every goal, criterion, and
 * evidence string) twice per audit and twice more at the entry top level.
 * That made each accepted steer O(plan size) on disk, so the ledger grew
 * quadratically over a run, and every dedup scan re-hydrated all of it into
 * memory. A snapshot instead records plan-level counters plus only the goals
 * the mutation actually touched, keeping each entry O(changed goals).
 */
export function buildSteeringPlanSnapshot(
	plan: UlwLoopPlan,
	changedGoalIds: ReadonlySet<string>,
): UlwLoopSteeringPlanSnapshot {
	const snapshot: UlwLoopSteeringPlanSnapshot = {
		updatedAt: plan.updatedAt,
		goalCount: plan.goals.length,
		goalIds: plan.goals.map((goal) => goal.id),
		goals: plan.goals.filter((goal) => changedGoalIds.has(goal.id)),
	};
	return plan.activeGoalId === undefined ? snapshot : { ...snapshot, activeGoalId: plan.activeGoalId };
}

/** Ids of goals that differ between two plans, including added or removed goals. */
export function changedGoalIdsBetween(before: UlwLoopPlan, after: UlwLoopPlan): Set<string> {
	const beforeById = new Map<string, UlwLoopItem>(before.goals.map((goal) => [goal.id, goal]));
	const changed = new Set<string>();
	for (const goal of after.goals) {
		const prior = beforeById.get(goal.id);
		if (prior === undefined || JSON.stringify(prior) !== JSON.stringify(goal)) changed.add(goal.id);
		beforeById.delete(goal.id);
	}
	for (const id of beforeById.keys()) changed.add(id);
	return changed;
}