import { createHash } from "node:crypto";

export interface MessageLike {
	id?: string;
	role: string;
	timestamp?: number;
	content?: unknown;
	toolCallId?: string;
	[_: string]: unknown;
}

export interface SessionManagerLike {
	getBranch?: () => Array<{ type?: string; id?: string; message?: unknown }>;
	getEntries?: () => Array<{ type?: string; id?: string; message?: unknown }>;
}

/**
 * pi messages (AgentMessage) carry no id — the id lives on the session entry
 * (MessageEntry). The message object stored in the entry is the SAME reference
 * that flows through message_end and session_before_compact, so entries can be
 * matched to messages by reference.
 */
export function findEntryId(sessionManager: SessionManagerLike | undefined, message: MessageLike): string | null {
	if (!sessionManager) return null;
	const entries = sessionManager.getBranch?.() ?? sessionManager.getEntries?.() ?? [];
	for (let i = entries.length - 1; i >= 0; i--) {
		const e = entries[i];
		if (e?.type === "message" && e.message === message && typeof e.id === "string" && e.id) {
			return e.id;
		}
	}
	return null;
}

/**
 * Deterministic fallback id when the session entry cannot be resolved:
 * - tool results: the provider's stable toolCallId
 * - otherwise: sha1 of role|timestamp|content
 * Stable across runs and identical between realtime population and compaction,
 * so rows never duplicate.
 */
export function derivedId(m: MessageLike): string {
	if (m.role === "toolResult" && typeof m.toolCallId === "string" && m.toolCallId) {
		return `tool_${m.toolCallId}`;
	}
	const canonical = JSON.stringify({ role: m.role, timestamp: m.timestamp ?? 0, content: m.content ?? null });
	return `h_${createHash("sha1").update(canonical).digest("hex").slice(0, 16)}`;
}