import type { CtxVarsConfig } from "./config.ts";
import { VarStore } from "./store.ts";
import { fullText, kindOf, estimateTokens } from "./serialize.ts";
import { derivedId, type MessageLike } from "./ids.ts";

/** Roles that are populated into the variable store in realtime. */
const POPULATED_ROLES = new Set(["user", "assistant", "toolResult"]);

/**
 * Realtime variable population: called on every message_end. Stores the full
 * message content as a variable immediately (no summary, no decisions — those
 * happen at compaction time). Never touches compaction state.
 *
 * @param entryId real session entry id when resolvable (see ids.ts); falls
 *        back to a deterministic derived id so population and compaction
 *        always agree on the same row.
 */
export function populateFromMessage(store: VarStore, cfg: CtxVarsConfig, message: MessageLike, entryId?: string | null): number | null {
	if (!cfg.realtimePopulation) return null;
	if (!message?.role || !POPULATED_ROLES.has(message.role)) return null;
	const content = fullText(message);
	return store.populate(entryId || derivedId(message), kindOf(message), content, estimateTokens(content));
}