import os
from google.cloud import billing

class BillingAgent:
    def __init__(self):
        self.project_id = os.environ.get("GOOGLE_CLOUD_PROJECT")
        if not self.project_id:
            raise ValueError("GOOGLE_CLOUD_PROJECT environment variable not set.")
        self.billing_client = billing.CloudBillingClient()

    def get_summary(self):
        """
        Retrieves the billing summary for the last 30 days.
        """
        # This is a simplified example. The Cloud Billing API does not have a direct
        # "summary" endpoint. You would typically query for cost data over a time range.
        # This implementation will be a placeholder.
        return {
            "summary": "Billing summary data would be here.",
            "project_id": self.project_id
        }

    def get_forecast(self):
        """
        Retrieves a billing forecast based on the last 7 days.
        """
        # The Cloud Billing API does not provide a direct forecast API.
        # This would require custom logic to calculate.
        # This implementation will be a placeholder.
        return {
            "forecast": "Billing forecast data would be here.",
            "project_id": self.project_id
        }

    def get_credits(self):
        """
        Retrieves active billing credits.
        """
        # This is a simplified example. You would need to query for billing account
        # information and then check for credits.
        return {
            "credits": "Billing credits information would be here.",
            "project_id": self.project_id
        }

if __name__ == '__main__':
    agent = BillingAgent()
    print("Summary:", agent.get_summary())
    print("Forecast:", agent.get_forecast())
    print("Credits:", agent.get_credits())