import type { SessionEntry } from "@earendil-works/pi-coding-agent";
import type { CompactionStats } from "./types";

export function collectCompactionStats(
	branch: SessionEntry[],
	checkpointEntryId: string,
): CompactionStats {
	const checkpointIndex = branch.findIndex((entry) => entry.id === checkpointEntryId);
	const stats: CompactionStats = {
		compactedMessageCount: 0,
	};

	if (checkpointIndex === -1) {
		return stats;
	}

	const compacted = branch.slice(checkpointIndex + 1);
	stats.compactedMessageCount = compacted.length;

	if (compacted.length > 0) {
		stats.compactedFrom = compacted[0]?.timestamp;
		stats.compactedTo = compacted[compacted.length - 1]?.timestamp;
	}

	return stats;
}