/**
 * Error Purging Rule
 *
 * Removes resolved errors from context.
 * If an error is followed by a successful retry of the same operation,
 * the error can be pruned as it's no longer relevant.
 */

import type { PruneRule } from "../types";
import { isErrorMessage, isSameOperation } from "../metadata";

export const errorPurgingRule: PruneRule = {
	name: "error-purging",
	description: "Remove resolved errors from context",

	/**
	 * Prepare phase: Identify errors and check if they were resolved
	 */
	prepare(msg, ctx) {
		// Mark if message is an error
		const isError = isErrorMessage(msg.message);
		msg.metadata.isError = isError;

		if (isError) {
			// Look ahead for a successful retry of the same operation
			const laterSuccess = ctx.messages
				.slice(ctx.index + 1)
				.find((m) => isSameOperation(m.message, msg.message) && !isErrorMessage(m.message));

			msg.metadata.errorResolved = !!laterSuccess;

			if (ctx.config.debug && laterSuccess) {
				console.log(`[pi-dcp] ErrorPurging: found resolved error at index ${ctx.index}`);
			}
		}
	},

	/**
	 * Process phase: Mark resolved errors for pruning
	 */
	process(msg, ctx) {
		// Skip if already marked for pruning
		if (msg.metadata.shouldPrune) return;

		// Never prune user messages
		if (msg.message.role === "user") return;

		// Prune if it's an error that was resolved
		if (msg.metadata.isError && msg.metadata.errorResolved) {
			msg.metadata.shouldPrune = true;
			msg.metadata.pruneReason = "error resolved by later success";

			if (ctx.config.debug) {
				console.log(`[pi-dcp] ErrorPurging: marking resolved error at index ${ctx.index}`);
			}
		}
	},
};