/**
 * Superseded Writes Rule
 *
 * Removes older file write/edit operations when newer versions exist.
 * If the same file is written multiple times, only the latest write is kept.
 */

import type { PruneRule } from "../types";
import { extractFilePath, hashMessage } from "../metadata";

export const supersededWritesRule: PruneRule = {
	name: "superseded-writes",
	description: "Remove older file writes when newer versions exist",

	/**
	 * Prepare phase: Extract file paths from write/edit operations
	 */
	prepare(msg, ctx) {
		// Extract file path from write/edit tool results
		const filePath = extractFilePath(msg.message);

		if (filePath) {
			msg.metadata.filePath = filePath;
			// Store a version identifier (hash of the result)
			msg.metadata.fileVersion = hashMessage(msg.message);

			if (ctx.config.debug) {
				console.log(`[pi-dcp] SupersededWrites: found file operation at index ${ctx.index}: ${filePath}`);
			}
		}
	},

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	 * Process phase: Mark superseded writes for pruning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

		// Skip if not a file operation
		if (!msg.metadata.filePath) return;

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

		// Check if there's a later write to the same file
		const laterWrite = ctx.messages
			.slice(ctx.index + 1)
			.find((m) => m.metadata.filePath === msg.metadata.filePath);

		if (laterWrite) {
			msg.metadata.shouldPrune = true;
			msg.metadata.pruneReason = `superseded by later write to ${msg.metadata.filePath}`;

			if (ctx.config.debug) {
				console.log(
					`[pi-dcp] SupersededWrites: marking superseded write at index ${ctx.index}: ${msg.metadata.filePath}`,
				);
			}
		}
	},
};