Inital commit

splitchat/core/models.py

@@ -0,0 +1,177 @@
+import uuid
+from decimal import Decimal
+from django.db import models
+from django.contrib.auth.models import User
+from django.utils import timezone
+
+
+class ChatRoom(models.Model):
+    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
+    name = models.CharField(max_length=100)
+    description = models.TextField(blank=True)
+    invite_code = models.CharField(max_length=12, unique=True, blank=True)
+    created_by = models.ForeignKey(User, on_delete=models.SET_NULL, null=True, related_name='created_rooms')
+    created_at = models.DateTimeField(auto_now_add=True)
+
+    def save(self, *args, **kwargs):
+        if not self.invite_code:
+            self.invite_code = uuid.uuid4().hex[:8].upper()
+        super().save(*args, **kwargs)
+
+    def __str__(self):
+        return self.name
+
+    @property
+    def member_count(self):
+        return self.memberships.filter(is_active=True).count()
+
+
+class Membership(models.Model):
+    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name='memberships')
+    room = models.ForeignKey(ChatRoom, on_delete=models.CASCADE, related_name='memberships')
+    joined_at = models.DateTimeField(auto_now_add=True)
+    is_active = models.BooleanField(default=True)
+    is_admin = models.BooleanField(default=False)
+
+    class Meta:
+        unique_together = ('user', 'room')
+
+    def __str__(self):
+        return f"{self.user.username} in {self.room.name}"
+
+
+class Message(models.Model):
+    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
+    room = models.ForeignKey(ChatRoom, on_delete=models.CASCADE, related_name='messages')
+    sender = models.ForeignKey(User, on_delete=models.SET_NULL, null=True, related_name='messages')
+    content = models.TextField()
+    msg_type = models.CharField(max_length=20, default='chat',
+        choices=[('chat', 'Chat'), ('system', 'System'), ('event', 'Event'), ('expense', 'Expense')])
+    created_at = models.DateTimeField(auto_now_add=True)
+
+    class Meta:
+        ordering = ['created_at']
+
+    def __str__(self):
+        return f"{self.sender}: {self.content[:50]}"
+
+
+class Event(models.Model):
+    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
+    room = models.ForeignKey(ChatRoom, on_delete=models.CASCADE, related_name='events')
+    created_by = models.ForeignKey(User, on_delete=models.SET_NULL, null=True, related_name='created_events')
+    title = models.CharField(max_length=200)
+    description = models.TextField(blank=True)
+    location = models.CharField(max_length=200, blank=True)
+    event_date = models.DateTimeField(null=True, blank=True)
+    created_at = models.DateTimeField(auto_now_add=True)
+    is_settled = models.BooleanField(default=False)
+
+    class Meta:
+        ordering = ['-created_at']
+
+    def __str__(self):
+        return self.title
+
+    @property
+    def total_amount(self):
+        return self.expenses.aggregate(total=models.Sum('amount'))['total'] or Decimal('0')
+
+    def compute_balances(self):
+        """Returns dict: {user_id: net_balance} positive=owed, negative=owes"""
+        balances = {}
+        for expense in self.expenses.prefetch_related('splits'):
+            payer_id = expense.paid_by_id
+            balances[payer_id] = balances.get(payer_id, Decimal('0')) + expense.amount
+            for split in expense.splits.all():
+                uid = split.user_id
+                balances[uid] = balances.get(uid, Decimal('0')) - split.amount
+        return balances
+
+    def compute_settlements(self):
+        """Simplify debts: returns list of (debtor_user, creditor_user, amount)"""
+        balances = self.compute_balances()
+        # Fetch users
+        user_ids = list(balances.keys())
+        users = {u.id: u for u in User.objects.filter(id__in=user_ids)}
+
+        debtors = sorted(
+            [(uid, -bal) for uid, bal in balances.items() if bal < -Decimal('0.01')],
+            key=lambda x: -x[1]
+        )
+        creditors = sorted(
+            [(uid, bal) for uid, bal in balances.items() if bal > Decimal('0.01')],
+            key=lambda x: -x[1]
+        )
+
+        settlements = []
+        i, j = 0, 0
+        debtors = [[uid, amt] for uid, amt in debtors]
+        creditors = [[uid, amt] for uid, amt in creditors]
+
+        while i < len(debtors) and j < len(creditors):
+            debtor_id, debt = debtors[i]
+            creditor_id, credit = creditors[j]
+            amount = min(debt, credit)
+            if amount > Decimal('0.01'):
+                settlements.append((users.get(debtor_id), users.get(creditor_id), round(amount, 2)))
+            debtors[i][1] -= amount
+            creditors[j][1] -= amount
+            if debtors[i][1] < Decimal('0.01'):
+                i += 1
+            if creditors[j][1] < Decimal('0.01'):
+                j += 1
+
+        return settlements
+
+
+class Expense(models.Model):
+    SPLIT_EQUAL = 'equal'
+    SPLIT_CUSTOM = 'custom'
+    SPLIT_CHOICES = [(SPLIT_EQUAL, 'Equal'), (SPLIT_CUSTOM, 'Custom')]
+
+    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
+    event = models.ForeignKey(Event, on_delete=models.CASCADE, related_name='expenses')
+    description = models.CharField(max_length=200)
+    amount = models.DecimalField(max_digits=10, decimal_places=2)
+    paid_by = models.ForeignKey(User, on_delete=models.SET_NULL, null=True, related_name='paid_expenses')
+    split_type = models.CharField(max_length=10, choices=SPLIT_CHOICES, default=SPLIT_EQUAL)
+    created_at = models.DateTimeField(auto_now_add=True)
+
+    class Meta:
+        ordering = ['-created_at']
+
+    def __str__(self):
+        return f"{self.description}: ${self.amount}"
+
+
+class ExpenseSplit(models.Model):
+    expense = models.ForeignKey(Expense, on_delete=models.CASCADE, related_name='splits')
+    user = models.ForeignKey(User, on_delete=models.CASCADE, related_name='expense_splits')
+    amount = models.DecimalField(max_digits=10, decimal_places=2)
+
+    class Meta:
+        unique_together = ('expense', 'user')
+
+    def __str__(self):
+        return f"{self.user.username}: ${self.amount}"
+
+
+class UserProfile(models.Model):
+    user = models.OneToOneField(User, on_delete=models.CASCADE, related_name='profile')
+    display_name = models.CharField(max_length=100, blank=True)
+    avatar_color = models.CharField(max_length=7, default='#6366f1')
+
+    def __str__(self):
+        return f"Profile({self.user.username})"
+
+    @property
+    def name(self):
+        return self.display_name or self.user.get_full_name() or self.user.username
+
+    def get_avatar_initials(self):
+        name = self.name
+        parts = name.split()
+        if len(parts) >= 2:
+            return (parts[0][0] + parts[-1][0]).upper()
+        return name[:2].upper()