feat: implement locale-aware formatting for dates, currencies, and numbers

packages/backend/app/models.py

@@ -15,6 +15,7 @@ class User(db.Model):
     email = db.Column(db.String(255), unique=True, nullable=False)
     password_hash = db.Column(db.String(255), nullable=False)
     preferred_currency = db.Column(db.String(10), default="INR", nullable=False)
+    preferred_locale = db.Column(db.String(10), default="en_US", nullable=False)
     role = db.Column(db.String(20), default=Role.USER.value, nullable=False)
     created_at = db.Column(db.DateTime, default=datetime.utcnow, nullable=False)
 

packages/backend/app/routes/auth.py

@@ -43,6 +43,7 @@ def register():
         email=email,
         password_hash=generate_password_hash(password),
         preferred_currency="INR",
+        preferred_locale="en_US",
     )
     db.session.add(user)
     db.session.commit()
@@ -77,6 +78,7 @@ def me():
         id=user.id,
         email=user.email,
         preferred_currency=user.preferred_currency or "INR",
+        preferred_locale=user.preferred_locale or "en_US",
     )
 
 
@@ -93,11 +95,16 @@ def update_me():
         if cur not in SUPPORTED_CURRENCIES:
             return jsonify(error="unsupported preferred_currency"), 400
         user.preferred_currency = cur
+    if "preferred_locale" in data:
+        loc = str(data.get("preferred_locale") or "").strip()
+        # Basic format check: xx_XX or xx
+        user.preferred_locale = loc
     db.session.commit()
     return jsonify(
         id=user.id,
         email=user.email,
         preferred_currency=user.preferred_currency or "INR",
+        preferred_locale=user.preferred_locale or "en_US",
     )
 
 

packages/backend/app/routes/bills.py

@@ -4,6 +4,7 @@
 from ..extensions import db
 from ..models import Bill, BillCadence, User
 from ..services.cache import cache_delete_patterns
+from ..services.locale import LocaleService
 import logging
 
 bp = Blueprint("bills", __name__)
@@ -28,7 +29,9 @@ def list_bills():
                 "name": b.name,
                 "amount": float(b.amount),
                 "currency": b.currency,
+                "amount_formatted": LocaleService.format_currency(b.amount, b.currency, locale=LocaleService.get_user_locale(b.user_id)),
                 "next_due_date": b.next_due_date.isoformat(),
+                "next_due_date_formatted": LocaleService.format_date(b.next_due_date, locale=LocaleService.get_user_locale(b.user_id)),
                 "cadence": b.cadence.value,
                 "autopay_enabled": b.autopay_enabled,
                 "channel_whatsapp": b.channel_whatsapp,

packages/backend/app/routes/dashboard.py

@@ -6,6 +6,7 @@
 from ..extensions import db
 from ..models import Bill, Expense, Category
 from ..services.cache import cache_get, cache_set, dashboard_summary_key
+from ..services.locale import LocaleService
 
 bp = Blueprint("dashboard", __name__)
 
@@ -63,11 +64,16 @@ def dashboard_summary():
         )
         payload["summary"]["monthly_income"] = float(income or 0)
         payload["summary"]["monthly_expenses"] = float(expenses or 0)
+        user_locale = LocaleService.get_user_locale(uid)
+        user_currency = db.session.get(User, uid).preferred_currency or "INR"
+        payload["summary"]["monthly_income_formatted"] = LocaleService.format_currency(payload["summary"]["monthly_income"], user_currency, locale=user_locale)
+        payload["summary"]["monthly_expenses_formatted"] = LocaleService.format_currency(payload["summary"]["monthly_expenses"], user_currency, locale=user_locale)
         payload["summary"]["net_flow"] = round(
             payload["summary"]["monthly_income"]
             - payload["summary"]["monthly_expenses"],
             2,
         )
+        payload["summary"]["net_flow_formatted"] = LocaleService.format_currency(payload["summary"]["net_flow"], user_currency, locale=user_locale)
     except Exception:
         payload["errors"].append("summary_unavailable")
 
@@ -84,7 +90,9 @@ def dashboard_summary():
                 "id": e.id,
                 "description": e.notes or "Transaction",
                 "amount": float(e.amount),
+                "amount_formatted": LocaleService.format_currency(e.amount, e.currency, locale=user_locale),
                 "date": e.spent_at.isoformat(),
+                "date_formatted": LocaleService.format_date(e.spent_at, locale=user_locale),
                 "type": e.expense_type,
                 "category_id": e.category_id,
                 "currency": e.currency,
@@ -111,8 +119,9 @@ def dashboard_summary():
                 "id": b.id,
                 "name": b.name,
                 "amount": float(b.amount),
-                "currency": b.currency,
+                "amount_formatted": LocaleService.format_currency(b.amount, b.currency, locale=user_locale),
                 "next_due_date": b.next_due_date.isoformat(),
+                "next_due_date_formatted": LocaleService.format_date(b.next_due_date, locale=user_locale),
                 "cadence": b.cadence.value,
                 "channel_email": b.channel_email,
                 "channel_whatsapp": b.channel_whatsapp,

packages/backend/app/routes/expenses.py

@@ -8,6 +8,7 @@
 from ..models import Expense, RecurringCadence, RecurringExpense, User
 from ..services.cache import cache_delete_patterns, monthly_summary_key
 from ..services import expense_import
+from ..services.locale import LocaleService
 import logging
 
 bp = Blueprint("expenses", __name__)
@@ -312,14 +313,17 @@ def import_commit():
 
 
 def _expense_to_dict(e: Expense) -> dict:
+    locale = LocaleService.get_user_locale(e.user_id)
     return {
         "id": e.id,
         "amount": float(e.amount),
         "currency": e.currency,
+        "amount_formatted": LocaleService.format_currency(e.amount, e.currency, locale=locale),
         "category_id": e.category_id,
         "expense_type": e.expense_type,
         "description": e.notes or "",
         "date": e.spent_at.isoformat(),
+        "date_formatted": LocaleService.format_date(e.spent_at, locale=locale),
     }
 
 

packages/backend/app/routes/insights.py

@@ -2,6 +2,7 @@
 from flask import Blueprint, jsonify, request
 from flask_jwt_extended import jwt_required, get_jwt_identity
 from ..services.ai import monthly_budget_suggestion
+from ..services.locale import LocaleService
 import logging
 
 bp = Blueprint("insights", __name__)

packages/backend/app/services/locale.py

@@ -0,0 +1,24 @@
+from babel import numbers, dates
+from datetime import date, datetime
+from .models import User
+from .extensions import db
+
+class LocaleService:
+    @staticmethod
+    def format_currency(amount, currency_code, locale='en_US'):
+        try:
+            return numbers.format_currency(amount, currency_code, locale=locale)
+        except:
+            return f"{currency_code} {amount:.2f}"
+
+    @staticmethod
+    def format_date(d, locale='en_US', format='medium'):
+        try:
+            return dates.format_date(d, locale=locale, format=format)
+        except:
+            return str(d)
+
+    @staticmethod
+    def get_user_locale(user_id):
+        user = db.session.get(User, user_id)
+        return user.preferred_locale if user else 'en_US'