added supabase routes and payment handling

backend/src/payments/payment_handler.py

@@ -0,0 +1,70 @@
+from typing import Literal
+import paypalrestsdk
+from pydantic import BaseModel
+from fastapi import HTTPException
+import logging
+
+
+# Model for payment request body
+class PaymentRequest(BaseModel):
+    user_id: str
+    credit_amount: Literal[10, 50, 100]
+    currency: Literal["USD", "EUR", "CHF"]  
+    description: str = "Purchase of credits"
+
+
+# Payment handler class for managing PayPal payments
+class PaymentHandler:
+
+    payment_id: str
+
+    def __init__(self, transaction_details: PaymentRequest):
+        self.details = transaction_details
+        self.logger = logging.getLogger(__name__)
+
+    # Only support purchase of credit 'bundles': 10, 50 or 100 credits worth of trip generation
+    def fetch_price(self) -> float:
+        """
+        Fetches the price of credits in the specified currency.
+        """
+        result = self.supabase.table("prices").select("credit_amount").eq("currency", self.details.currency).single().execute()
+        if result.data:
+            return result.data.get("price")
+        else:
+            self.logger.error(f"Unsupported currency: {self.details.currency}")
+            return None
+
+    def create_paypal_payment(self) -> str:
+        """
+        Creates a PayPal payment and returns the approval URL.
+        """
+        price = self.fetch_price()
+        payment = paypalrestsdk.Payment({
+            "intent": "sale",
+            "payer": {
+                "payment_method": "paypal"
+            },
+            "transactions": [{
+                "amount": {
+                    "total": f"{price:.2f}",
+                    "currency": self.details.currency
+                },
+                "description": self.details.description
+            }],
+            "redirect_urls": {
+                "return_url": "http://localhost:8000/payment/success",
+                "cancel_url": "http://localhost:8000/payment/cancel"
+            }
+        })
+
+        if payment.create():
+            self.logger.info("Payment created successfully")
+            self.payment_id = payment.id
+
+            # Get the approval URL and return it for the user to approve
+            for link in payment.links:
+                if link.rel == "approval_url":
+                    return link.href
+        else:
+            self.logger.error(f"Failed to create payment: {payment.error}")
+            raise HTTPException(status_code=500, detail="Payment creation failed")