feat: add i18n system with English locale

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

src/lib/i18n/index.ts

@@ -0,0 +1,46 @@
+type Translations = Record<string, string>;
+
+export function createI18n(translations: Translations) {
+	function t(key: string, vars?: Record<string, string>): string {
+		let value = translations[key];
+		if (value === undefined) return key;
+
+		if (vars) {
+			for (const [varName, varValue] of Object.entries(vars)) {
+				value = value.replaceAll(`{${varName}}`, varValue);
+			}
+		}
+
+		return value;
+	}
+
+	return { t };
+}
+
+function flattenObject(obj: Record<string, unknown>, prefix = ''): Translations {
+	const result: Translations = {};
+	for (const [key, value] of Object.entries(obj)) {
+		const fullKey = prefix ? `${prefix}.${key}` : key;
+		if (typeof value === 'object' && value !== null && !Array.isArray(value)) {
+			Object.assign(result, flattenObject(value as Record<string, unknown>, fullKey));
+		} else {
+			result[fullKey] = String(value);
+		}
+	}
+	return result;
+}
+
+let cachedI18n: ReturnType<typeof createI18n> | null = null;
+
+export async function loadI18n(locale = 'en'): Promise<ReturnType<typeof createI18n>> {
+	if (cachedI18n) return cachedI18n;
+
+	const localeData = await import(`./locales/${locale}.json`);
+	const flat = flattenObject(localeData.default || localeData);
+	cachedI18n = createI18n(flat);
+	return cachedI18n;
+}
+
+export function resetI18nCache(): void {
+	cachedI18n = null;
+}

src/lib/i18n/locales/en.json

@@ -0,0 +1,163 @@
+{
+	"common": {
+		"save": "Save",
+		"cancel": "Cancel",
+		"delete": "Delete",
+		"edit": "Edit",
+		"create": "Create",
+		"back": "Back",
+		"search": "Search",
+		"filter": "Filter",
+		"loading": "Loading...",
+		"noResults": "No results found",
+		"confirm": "Are you sure?",
+		"yes": "Yes",
+		"no": "No",
+		"submit": "Submit",
+		"required": "Required",
+		"optional": "Optional",
+		"actions": "Actions",
+		"status": "Status",
+		"date": "Date",
+		"name": "Name",
+		"email": "Email",
+		"phone": "Phone",
+		"notes": "Notes",
+		"description": "Description"
+	},
+	"auth": {
+		"login": "Log In",
+		"logout": "Log Out",
+		"register": "Register",
+		"email": "Email",
+		"password": "Password",
+		"currentPassword": "Current Password",
+		"newPassword": "New Password",
+		"confirmPassword": "Confirm Password",
+		"changePassword": "Change Password",
+		"invalidCredentials": "Invalid email or password",
+		"accountInactive": "Account is not active",
+		"passwordMinLength": "Password must be at least 8 characters",
+		"passwordsDoNotMatch": "Passwords do not match"
+	},
+	"nav": {
+		"home": "Home",
+		"pets": "Our Pets",
+		"about": "About",
+		"events": "Events",
+		"donate": "Donate",
+		"contact": "Contact",
+		"apply": "Apply",
+		"adoptionProcess": "Adoption Process",
+		"becomeAFoster": "Become a Foster",
+		"howToHelp": "How to Help",
+		"volunteer": "Volunteer",
+		"whyAdopt": "Why Adopt",
+		"happyTails": "Happy Tails",
+		"sponsors": "Sponsors",
+		"fosterResources": "Foster Resources",
+		"nameGenerator": "Name Generator"
+	},
+	"pets": {
+		"title": "Our Pets",
+		"available": "Available for Adoption",
+		"featured": "Featured Pets",
+		"noFeatured": "No featured pets at the moment",
+		"noPets": "No pets available at the moment",
+		"adoptionFee": "Adoption Fee",
+		"learnMore": "Learn More",
+		"applyToAdopt": "Apply to Adopt",
+		"applyToFoster": "Apply to Foster",
+		"filterSpecies": "Species",
+		"filterAge": "Age",
+		"filterSex": "Sex",
+		"all": "All"
+	},
+	"applications": {
+		"adoption": "Adoption Application",
+		"foster": "Foster Application",
+		"volunteer": "Volunteer Application",
+		"surrender": "Surrender Application",
+		"thankYou": "Thank you for your application!",
+		"weWillReview": "We will review your application and get back to you soon."
+	},
+	"foster": {
+		"portal": "Foster Portal",
+		"myPets": "My Foster Pets",
+		"submitUpdate": "Submit Update",
+		"requestSupplies": "Request Supplies",
+		"noPets": "You don't have any foster pets assigned yet."
+	},
+	"admin": {
+		"dashboard": "Dashboard",
+		"pets": "Pets",
+		"applications": "Applications",
+		"sponsors": "Sponsors",
+		"donations": "Donations",
+		"expenses": "Expenses",
+		"vets": "Vets",
+		"events": "Events",
+		"content": "Content",
+		"newsletter": "Newsletter",
+		"happyTails": "Happy Tails",
+		"users": "Users",
+		"volunteers": "Volunteers",
+		"fosters": "Fosters",
+		"mentors": "Mentors",
+		"intake": "Intake",
+		"moderation": "Moderation",
+		"reports": "Reports",
+		"analytics": "Analytics",
+		"traffic": "Live Traffic",
+		"messages": "Messages",
+		"import": "Import",
+		"system": "System",
+		"fosterDashboard": "My Fosters"
+	},
+	"setup": {
+		"welcome": "Welcome to FosterFlow!",
+		"letsGetStarted": "Let's get your rescue set up.",
+		"step1Title": "Organization Info",
+		"step2Title": "Branding",
+		"step3Title": "Application Forms",
+		"step4Title": "Integrations",
+		"step5Title": "Import Data",
+		"next": "Next",
+		"previous": "Previous",
+		"finish": "Finish Setup"
+	},
+	"home": {
+		"hero": "Find Your Forever Friend",
+		"heroSubtitle": "We rescue, rehabilitate, and rehome animals in need.",
+		"viewPets": "View Our Pets",
+		"howToHelp": "How to Help",
+		"stats": {
+			"adopted": "Pets Adopted",
+			"inCare": "Currently in Care",
+			"fosters": "Active Fosters"
+		},
+		"upcomingEvents": "Upcoming Events",
+		"recentHappyTails": "Recent Happy Tails"
+	},
+	"contact": {
+		"title": "Contact Us",
+		"send": "Send Message",
+		"sent": "Message sent! We'll get back to you soon."
+	},
+	"newsletter": {
+		"subscribe": "Subscribe to Our Newsletter",
+		"emailPlaceholder": "Your email address",
+		"subscribed": "Thanks for subscribing!"
+	},
+	"donate": {
+		"title": "Donate",
+		"support": "Support Our Mission",
+		"oneTime": "One-Time Donation",
+		"monthly": "Monthly Donation"
+	},
+	"footer": {
+		"quickLinks": "Quick Links",
+		"connect": "Connect With Us",
+		"copyright": "All rights reserved."
+	}
+}

tests/unit/i18n.test.ts

@@ -0,0 +1,26 @@
+import { describe, it, expect } from 'vitest';
+import { createI18n } from '$lib/i18n';
+
+describe('i18n', () => {
+	const i18n = createI18n({
+		'common.save': 'Save',
+		'common.cancel': 'Cancel',
+		'pets.title': 'Our Pets',
+		'pets.count': '{count} pets available',
+		'greeting': 'Hello, {name}!'
+	});
+
+	it('returns translated string by key', () => {
+		expect(i18n.t('common.save')).toBe('Save');
+		expect(i18n.t('pets.title')).toBe('Our Pets');
+	});
+
+	it('returns key when translation is missing', () => {
+		expect(i18n.t('missing.key')).toBe('missing.key');
+	});
+
+	it('interpolates variables', () => {
+		expect(i18n.t('greeting', { name: 'Justin' })).toBe('Hello, Justin!');
+		expect(i18n.t('pets.count', { count: '5' })).toBe('5 pets available');
+	});
+});