n8n/packages/workflow/src/connections-diff.ts

import type { IConnection, IConnections } from '.';

type ConnectionEntry = {
	sourceIndex: number;
	value: { index: number; connection: IConnection } | null;
};

export type INodeConnectionsDiff = Record<string, ConnectionEntry[]>;

export type ConnectionsDiff = {
	added: Record<string, INodeConnectionsDiff>;
	removed: Record<string, INodeConnectionsDiff>;
};

export function compareConnections(prev: IConnections, next: IConnections): ConnectionsDiff {
	const added: Record<string, INodeConnectionsDiff> = {};
	const removed: Record<string, INodeConnectionsDiff> = {};

	// Get all unique node names from both connection objects
	const allNodeNames = new Set([...Object.keys(prev), ...Object.keys(next)]);

	for (const nodeName of allNodeNames) {
		const prevNodeConnections = prev[nodeName] ?? {};
		const nextNodeConnections = next[nodeName] ?? {};

		// Get all unique input names for this node
		const allInputNames = new Set([
			...Object.keys(prevNodeConnections),
			...Object.keys(nextNodeConnections),
		]);

		for (const inputName of allInputNames) {
			const prevInputConnections = prevNodeConnections[inputName] ?? [];
			const nextInputConnections = nextNodeConnections[inputName] ?? [];

			// Compare each source index
			const maxLength = Math.max(prevInputConnections.length, nextInputConnections.length);

			for (let sourceIndex = 0; sourceIndex < maxLength; sourceIndex++) {
				const prevConnections = prevInputConnections[sourceIndex] ?? [];
				const nextConnections = nextInputConnections[sourceIndex] ?? [];

				// Build maps for easier comparison
				const prevMap = new Map(
					prevConnections.map((conn, idx) => [
						JSON.stringify(conn),
						{ index: idx, connection: conn },
					]),
				);
				const nextMap = new Map(
					nextConnections.map((conn, idx) => [
						JSON.stringify(conn),
						{ index: idx, connection: conn },
					]),
				);

				// Find added connections
				for (const [key, value] of nextMap) {
					if (!prevMap.has(key)) {
						if (!added[nodeName]) added[nodeName] = {};
						if (!added[nodeName][inputName]) added[nodeName][inputName] = [];

						added[nodeName][inputName].push({
							sourceIndex,
							value,
						});
					}
				}

				// Find removed connections
				for (const [key, value] of prevMap) {
					if (!nextMap.has(key)) {
						if (!removed[nodeName]) removed[nodeName] = {};
						if (!removed[nodeName][inputName]) removed[nodeName][inputName] = [];

						removed[nodeName][inputName].push({
							sourceIndex,
							value,
						});
					}
				}
			}
		}
	}

	return { added, removed };
}