import json
import boto3

sns_client = boto3.client("sns", region_name="ap-northeast-1")
TOPIC_ARN = "arn:aws:sns:ap-northeast-1:123456789012:pipeline-pressure-alert"
LOW_PRESSURE_THRESHOLD = 2.0  # bar，低於此值可能代表洩漏
HIGH_PRESSURE_THRESHOLD = 10.0  # bar，高於此值可能代表堵塞或超壓

def lambda_handler(event, context):
    segment_id = event.get("segment_id", "unknown")
    pressure = event.get("pressure")

    if pressure is None:
        return {"statusCode": 400, "body": "缺少pressure欄位"}

    if pressure < LOW_PRESSURE_THRESHOLD:
        message = f"⚠️管段{segment_id}壓力驟降至{pressure} bar，疑似洩漏，請立即派員確認"
        sns_client.publish(TopicArn=TOPIC_ARN, Subject="管線壓力驟降告警", Message=message)
    elif pressure > HIGH_PRESSURE_THRESHOLD:
        message = f"⚠️管段{segment_id}壓力異常升高至{pressure} bar，請檢查是否堵塞"
        sns_client.publish(TopicArn=TOPIC_ARN, Subject="管線壓力異常升高告警", Message=message)
    else:
        print(f"管段{segment_id}壓力正常：{pressure} bar")

    return {"statusCode": 200, "body": json.dumps("處理完成")}