import os
import json
import datetime
from google.cloud import bigquery
from google.cloud import pubsub_v1

class AnomalyDetector:
    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.pubsub_topic_name = os.environ.get("PUBSUB_TOPIC", "billing_alerts")
        self.bq_client = bigquery.Client(project=self.project_id)
        self.publisher = pubsub_v1.PublisherClient()
        self.topic_path = self.publisher.topic_path(self.project_id, self.pubsub_topic_name)
        self.billing_table = f"{self.project_id}.billing_export.gcp_billing_export_v1_*"

    def detect_anomalies(self):
        """
        Detects anomalies in billing data.
        """
        query = f"""
            WITH
            cost_last_7_days AS (
              SELECT
                service.description as service,
                SUM(cost) as total_cost
              FROM `{self.billing_table}`
              WHERE _PARTITIONTIME >= TIMESTAMP_SUB(CURRENT_TIMESTAMP(), INTERVAL 8 DAY)
                AND _PARTITIONTIME < TIMESTAMP_SUB(CURRENT_TIMESTAMP(), INTERVAL 1 DAY)
              GROUP BY 1
            ),
            cost_last_1_day AS (
              SELECT
                service.description as service,
                SUM(cost) as total_cost
              FROM `{self.billing_table}`
              WHERE _PARTITIONTIME >= TIMESTAMP_SUB(CURRENT_TIMESTAMP(), INTERVAL 1 DAY)
              GROUP BY 1
            )
            SELECT
              c1.service,
              c1.total_cost as today_cost,
              c7.total_cost / 7 as avg_7day,
              c1.total_cost / (c7.total_cost / 7) as ratio
            FROM cost_last_1_day c1
            JOIN cost_last_7_days c7 ON c1.service = c7.service
            WHERE c1.total_cost > 2 * (c7.total_cost / 7)
        """
        query_job = self.bq_client.query(query)
        results = query_job.result()

        anomalies = []
        for row in results:
            anomalies.append({
                "service": row.service,
                "today_cost": row.today_cost,
                "avg_7day": row.avg_7day,
                "ratio": row.ratio
            })

        if anomalies:
            self.publish_alerts(anomalies)

        return {"anomalies": anomalies}

    def publish_alerts(self, anomalies):
        """
        Publishes anomaly alerts to a Pub/Sub topic.
        """
        for anomaly in anomalies:
            message_data = {
                "service": anomaly["service"],
                "today_cost": anomaly["today_cost"],
                "avg_7day": anomaly["avg_7day"],
                "ratio": anomaly["ratio"],
                "timestamp": datetime.datetime.now().isoformat()
            }
            message_bytes = json.dumps(message_data).encode("utf-8")
            self.publisher.publish(self.topic_path, data=message_bytes)

if __name__ == '__main__':
    detector = AnomalyDetector()
    print("Anomalies:", detector.detect_anomalies())