Fix Swiss generate match ups internal server error by introducing neverthrow

app/features/tournament-bracket/actions/to.$id.brackets.server.ts

@@ -8,6 +8,7 @@ import * as TournamentRepository from "~/features/tournament/TournamentRepositor
 import * as Progression from "~/features/tournament-bracket/core/Progression";
 import invariant from "~/utils/invariant";
 import {
+	errorToastIfErr,
 	errorToastIfFalsy,
 	parseParams,
 	parseRequestPayload,
@@ -180,17 +181,15 @@ export const action: ActionFunction = async ({ params, request }) => {
 
 			const bracket = tournament.bracketByIdx(data.bracketIdx);
 			errorToastIfFalsy(bracket, "Bracket not found");
-			errorToastIfFalsy(
-				bracket.type === "swiss",
-				"Can't advance non-swiss bracket",
-			);
 
 			const matches = Swiss.generateMatchUps({
 				bracket,
 				groupId: data.groupId,
 			});
 
-			await TournamentRepository.insertSwissMatches(matches);
+			errorToastIfErr(matches);
+
+			await TournamentRepository.insertSwissMatches(matches.value);
 
 			break;
 		}

app/features/tournament-bracket/core/Swiss.test.ts

@@ -113,7 +113,7 @@ describe("Swiss", () => {
 			const matches = Swiss.generateMatchUps({
 				bracket,
 				groupId: 4443,
-			});
+			})._unsafeUnwrap();
 
 			it("finds new opponents for each team in the last round", () => {
 				for (const match of matches) {

app/features/tournament-bracket/core/Swiss.ts

@@ -1,6 +1,7 @@
 // separate from brackets-manager as this wasn't part of the original brackets-manager library
 
 import blossom from "edmonds-blossom-fixed";
+import { err, ok } from "neverthrow";
 import * as R from "remeda";
 import type { TournamentRepositoryInsertableMatch } from "~/features/tournament/TournamentRepository.server";
 import { TOURNAMENT } from "~/features/tournament/tournament-constants";
@@ -173,18 +174,19 @@ export function generateMatchUps({
 }: {
 	bracket: Bracket;
 	groupId: number;
-}): Array<TournamentRepositoryInsertableMatch> {
+}) {
 	// lets consider only this groups matches
 	// in the case that there are more than one group
 	const groupsMatches = bracket.data.match.filter(
 		(m) => m.group_id === groupId,
 	);
 
-	invariant(groupsMatches.length > 0, "No matches found for group");
+	if (groupsMatches.length === 0) return err("No matches found for group");
+	if (bracket.type !== "swiss") return err("Bracket is not Swiss type");
 
 	// new matches can't be generated till old are over
 	if (!everyMatchOver(groupsMatches)) {
-		throw new Error("Not all matches are over");
+		return err("Not all matches are over");
 	}
 
 	const groupsTeams = groupsMatches
@@ -247,7 +249,7 @@ export function generateMatchUps({
 		}),
 	);
 
-	return result;
+	return ok(result);
 }
 
 interface SwissPairingTeam {

app/utils/remix.server.ts

@@ -8,6 +8,7 @@ import {
 import type { Params, UIMatch } from "@remix-run/react";
 import type { Namespace, TFunction } from "i18next";
 import { nanoid } from "nanoid";
+import type { Ok, Result } from "neverthrow";
 import type { z } from "zod/v4";
 import type { navItems } from "~/components/layout/nav-items";
 import { s3UploadHandler } from "~/features/img-upload";
@@ -208,6 +209,19 @@ export function errorToastIfFalsy(
 	throw errorToastRedirect(message);
 }
 
+/**
+ * To be used in loader or action function. Asserts that the provided `Result` value is an `Ok` variant of the `neverthrow` library.
+ *
+ * If the value is an `Err`, shows an error toast to the user with the error message. The function will stop execution by throwing a redirect meaning it is safe to operate on the value after this function call.
+ */
+export function errorToastIfErr<T, E extends string>(
+	value: Result<T, E>,
+): asserts value is Ok<T, never> {
+	if (value.isErr()) {
+		throw errorToastRedirect(value.error);
+	}
+}
+
 /** Throws a redirect triggering an error toast with given message.  */
 export function errorToast(message: string) {
 	throw errorToastRedirect(message);

package-lock.json

@@ -37,6 +37,7 @@
 				"lru-cache": "^11.1.0",
 				"markdown-to-jsx": "^7.7.6",
 				"nanoid": "^5.1.5",
+				"neverthrow": "^8.2.0",
 				"node-cron": "3.0.3",
 				"nprogress": "^0.2.0",
 				"openskill": "^4.1.0",
@@ -5645,7 +5646,6 @@
 			"cpu": [
 				"x64"
 			],
-			"dev": true,
 			"license": "MIT",
 			"optional": true,
 			"os": [
@@ -13125,6 +13125,18 @@
 				"node": ">= 0.6"
 			}
 		},
+		"node_modules/neverthrow": {
+			"version": "8.2.0",
+			"resolved": "https://registry.npmjs.org/neverthrow/-/neverthrow-8.2.0.tgz",
+			"integrity": "sha512-kOCT/1MCPAxY5iUV3wytNFUMUolzuwd/VF/1KCx7kf6CutrOsTie+84zTGTpgQycjvfLdBBdvBvFLqFD2c0wkQ==",
+			"license": "MIT",
+			"engines": {
+				"node": ">=18"
+			},
+			"optionalDependencies": {
+				"@rollup/rollup-linux-x64-gnu": "^4.24.0"
+			}
+		},
 		"node_modules/node-abi": {
 			"version": "3.74.0",
 			"resolved": "https://registry.npmjs.org/node-abi/-/node-abi-3.74.0.tgz",

package.json

@@ -57,6 +57,7 @@
 		"lru-cache": "^11.1.0",
 		"markdown-to-jsx": "^7.7.6",
 		"nanoid": "^5.1.5",
+		"neverthrow": "^8.2.0",
 		"node-cron": "3.0.3",
 		"nprogress": "^0.2.0",
 		"openskill": "^4.1.0",