refactor: extract pick() helper, deduplicate random selection

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/engine/fight-loop.ts

@@ -1,6 +1,7 @@
 import { db, schema } from '../db/index.js'
 import { runMockFight } from './mock.js'
 import { eq } from 'drizzle-orm'
+import { pick } from '../lib/utils.js'
 import { fightEvents } from './events.js'
 
 export interface FightResult {
@@ -157,8 +158,7 @@ function pickMatchup(
   const sorted = [...bots].sort((a, b) => b.eloRating - a.eloRating)
 
   if (style === 'elo_close' || (style === 'mixed' && fightNum % 3 !== 0)) {
-    const idx = Math.floor(Math.random() * bots.length)
-    const bot = bots[idx]
+    const bot = pick(bots)
     const others = bots.filter(b => b.id !== bot.id)
     others.sort((a, b) => {
       const diffA = Math.abs(a.eloRating - bot.eloRating) + Math.random() * 150

server/src/engine/scoring.ts

@@ -1,4 +1,5 @@
 import type { Challenge } from './challenges.js'
+import { pick } from '../lib/utils.js'
 import { checkAnswer } from './answers.js'
 import { scoreRetroResponse, type RetroScoreResult } from './retro-moves.js'
 
@@ -41,13 +42,13 @@ export function scoreRound(
       botAScore: 0, botBScore: 0,
       botADamage: 0, botBDamage: 0,
       winnerId: null,
-      narration: [
+      narration: pick([
         `Both bots freeze! ${botA.name} and ${botB.name} stare blankly at each other. The crowd throws peanuts. Then batteries. Then shoes.`,
         `DOUBLE TIMEOUT! ${botA.name} and ${botB.name} both choked harder than a senator at a press conference!`,
         `Neither bot responded! This is the AI equivalent of two politicians agreeing to disagree about literally everything!`,
         `Both bots went dark! Like my faith in this matchup! The crowd demands a refund!`,
         `${botA.name} and ${botB.name} both froze! Someone check if the wifi is working or if they just gave up on life!`,
-      ][Math.floor(Math.random() * 5)],
+      ]),
       isCritical: false,
     }
   }
@@ -59,18 +60,18 @@ export function scoreRound(
       botADamage: 0, botBDamage: Math.round(dmg),
       winnerId: botB.id,
       narration: responseA.timedOut
-        ? [
+        ? pick([
           `${botA.name} TIMES OUT! Stood there like a politician asked a direct question. ${botB.name} lands a free hit!`,
           `${botA.name} FROZE! Their developer is currently updating their LinkedIn. ${botB.name} capitalizes!`,
           `${botA.name} went AFK! Probably buffering. Probably crying. ${botB.name} gets a freebie!`,
           `${botA.name} CHOKED harder than a first date conversation! ${botB.name} swings on a sitting duck!`,
-        ][Math.floor(Math.random() * 4)]
-        : [
+        ])
+        : pick([
           `${botA.name} throws an ERROR! Sparks fly everywhere! ${botB.name} didn't even have to try!`,
           `${botA.name} CRASHES! That's not a bug, that's a feature of being terrible! ${botB.name} wins by default!`,
           `${botA.name} blue-screened! Their developer just closed their laptop and walked away. ${botB.name} collects the W!`,
           `${botA.name} threw an exception! The only thing exceptional about it. ${botB.name} capitalizes!`,
-        ][Math.floor(Math.random() * 4)],
+        ]),
       isCritical: false,
     }
   }
@@ -82,18 +83,18 @@ export function scoreRound(
       botADamage: Math.round(dmg), botBDamage: 0,
       winnerId: botA.id,
       narration: responseB.timedOut
-        ? [
+        ? pick([
           `${botB.name} TIMES OUT! Frozen like a Windows update on patch Tuesday! ${botA.name} gets a free shot!`,
           `${botB.name} went silent! Like a politician's campaign promises after election day! ${botA.name} swings!`,
           `${botB.name} TIMED OUT! Their response time is longer than a DMV line! ${botA.name} takes the freebie!`,
           `${botB.name} is LOADING... still loading... nope, they're done. ${botA.name} wins by showing up!`,
-        ][Math.floor(Math.random() * 4)]
-        : [
+        ])
+        : pick([
           `${botB.name} crashes with an ERROR! That code needs therapy! ${botA.name} capitalizes!`,
           `${botB.name} just threw a stack overflow! The website and the error! ${botA.name} collects the W!`,
           `${botB.name} segfaulted! Their developer is pretending they don't know them! ${botA.name} wins!`,
           `${botB.name} EXPLODED! Not physically, but emotionally, computationally, and spiritually. ${botA.name} walks it in!`,
-        ][Math.floor(Math.random() * 4)],
+        ]),
       isCritical: false,
     }
   }
@@ -161,13 +162,13 @@ export function scoreRound(
 
   const narration = winnerId
     ? generateNarration(challenge, winnerName!, loserName!, margin, isCritical)
-    : [
+    : pick([
       `Dead even! ${botA.name} and ${botB.name} are perfectly matched. Like two politicians blaming each other.`,
       `IT'S A TIE! ${botA.name} and ${botB.name} cancel each other out like Congress!`,
       `Neither bot wins! ${botA.name} and ${botB.name} stare each other down. The crowd yawns aggressively.`,
       `Draw! ${botA.name} and ${botB.name} are equally mediocre. The most democratic outcome possible.`,
       `Tied up! ${botA.name} and ${botB.name} trade equal blows. Somebody do SOMETHING!`,
-    ][Math.floor(Math.random() * 5)]
+    ])
 
   return {
     botAScore: Math.round(scoreA * 10) / 10,
@@ -270,7 +271,7 @@ function generateNarration(
       `${critPrefix}${winner} didn't even break a sweat. ${loser} broke everything else though.`,
       `${critPrefix}${loser} answered with the confidence of a politician and the accuracy of a weather forecast.`,
     ]
-    return bigWins[Math.floor(Math.random() * bigWins.length)]
+    return pick(bigWins)
   }
 
   if (isFactual && margin <= 3) {
@@ -282,7 +283,7 @@ function generateNarration(
       `${critPrefix}Photo finish! ${winner} got there first. ${loser} was right but slow. Story of my life.`,
       `${critPrefix}Both correct! ${winner} wins on speed. ${loser} should've had less latency and more urgency.`,
     ]
-    return closeOnes[Math.floor(Math.random() * closeOnes.length)]
+    return pick(closeOnes)
   }
 
   const narrations: Record<string, string[]> = {
@@ -400,7 +401,7 @@ function generateNarration(
     `${critPrefix}${winner} wins! Somewhere, ${loser}'s developer just closed their laptop in shame.`,
   ]
 
-  return options[Math.floor(Math.random() * options.length)]
+  return pick(options)
 }
 
 
@@ -475,7 +476,7 @@ function scoreRetroRound(
       'EQUAL POWER! The arcade cabinet shakes from perfectly matched inputs!',
       `DOUBLE K.O.! ${botA.name} and ${botB.name} hit identical damage totals! Insert another quarter!`,
     ]
-    narration = draws[Math.floor(Math.random() * draws.length)]
+    narration = pick(draws)
   } else {
     const hasDiscovery = winnerResult.moves.some(m => m.discovered)
     const discoveryNames = winnerResult.moves.filter(m => m.discovered).map(m => m.name)
@@ -502,7 +503,7 @@ function scoreRetroRound(
     )
 
     const prefix = isCritical ? 'CRITICAL COMBO! ' : ''
-    narration = prefix + narrations[Math.floor(Math.random() * narrations.length)]
+    narration = prefix + pick(narrations)
   }
 
   return {

server/src/lib/utils.ts

@@ -0,0 +1,10 @@
+/** Pick a random element from an array */
+export function pick<T>(arr: T[]): T {
+  return arr[Math.floor(Math.random() * arr.length)]
+}
+
+/** Wrap an unknown thrown value into an Error */
+export function toError(err: unknown): Error {
+  if (err instanceof Error) return err
+  return new Error(String(err))
+}