feat: implement daily character seed from environment variable and enhance selection logic with hashing

.env.example

@@ -7,3 +7,8 @@ ORIGIN=""
 # For production use 32 characters and generated with high entropy
 # https://www.better-auth.com/docs/installation
 BETTER_AUTH_SECRET=""
+
+# Daily Character Selection
+# Seed for daily character selection (default: "onepiecedle")
+# Can be any string - will be hashed to generate the rotation
+DAILY_CHARACTER_SEED=onepiecedle

src/lib/server/daily-character.ts

@@ -2,6 +2,22 @@ import { db } from '$lib/server/db';
 import { arc, character, characterHistory, characterOverride, devilFruit } from '$lib/server/db/schema';
 import { desc, eq, inArray, and } from 'drizzle-orm';
 
+// Get daily character seed from environment or use default
+const DAILY_CHARACTER_SEED_STRING = process.env.DAILY_CHARACTER_SEED || 'onepiecedle';
+
+// Convert string seed to number using a simple hash function
+function hashString(str: string): number {
+	let hash = 0;
+	for (let i = 0; i < str.length; i++) {
+		const char = str.charCodeAt(i);
+		hash = ((hash << 5) - hash) + char;
+		hash = hash & hash; // Convert to 32bit integer
+	}
+	return Math.abs(hash);
+}
+
+const DAILY_CHARACTER_SEED = hashString(DAILY_CHARACTER_SEED_STRING);
+
 const characterWithRelationsSelect = {
 	id: character.id,
 	name: character.name,
@@ -151,9 +167,9 @@ export function normalizeDay(date: Date = new Date()): Date {
 
 function pickDailyCharacter(characters: CharacterWithRelations[], date: Date): CharacterWithRelations {
 	const timestamp = getDateKey(date);
-	const seed = Math.floor(timestamp / 1000 / 60 / 60 / 24);
-	const index = seed % characters.length;
-	return characters[index];
+	const daysSinceEpoch = Math.floor(timestamp / 1000 / 60 / 60 / 24);
+	const seed = (daysSinceEpoch + DAILY_CHARACTER_SEED) % characters.length;
+	return characters[seed];
 }
 
 export async function getDailyModeCharacters(): Promise<CharacterWithRelations[]> {