import random
import string
import json
from app.core.cache import redis_client
from app.core.config import settings

# Aliyun SDK imports
try:
    # Use dypnsapi (Number Auth) as requested
    from alibabacloud_dypnsapi20170525.client import Client as DypnsApiClient
    from alibabacloud_tea_openapi import models as open_api_models
    from alibabacloud_dypnsapi20170525 import models as dypns_api_models
    from alibabacloud_tea_util import models as util_models
except ImportError:
    DypnsApiClient = None

class SmsService:
    _client = None

    @classmethod
    def get_client(cls):
        if cls._client:
            return cls._client
        
        if not settings.ALIYUN_ACCESS_KEY_ID or not settings.ALIYUN_ACCESS_KEY_SECRET:
            raise ValueError("Aliyun AccessKey config missing")

        config = open_api_models.Config(
            access_key_id=settings.ALIYUN_ACCESS_KEY_ID,
            access_key_secret=settings.ALIYUN_ACCESS_KEY_SECRET
        )
        # Endpoint for dypns (SMS Authentication Service)
        config.endpoint = 'dypnsapi.aliyuncs.com'
        cls._client = DypnsApiClient(config)
        return cls._client

    @staticmethod
    def send_code(mobile: str) -> str:
        """
        Generates and 'sends' a code.
        Returns the code for dev/mock purposes (or logs it).
        """
        # 1. Check Rate Limit (1 minute)
        limit_key = f"SMS_LIMIT:{mobile}"
        if redis_client.exists(limit_key):
            # Using local import to avoid circular dependency if any, 
            # though HTTPException is from fastapi which is fine.
            from fastapi import HTTPException
            raise HTTPException(status_code=400, detail="发送过于频繁，请1分钟后再试")

        if settings.SMS_PROVIDER == "aliyun":
            code = SmsService.send_aliyun_sms(mobile)
        else:
            code = SmsService.send_mock_sms(mobile)
        
        # 2. Set Rate Limit (60 seconds)
        redis_client.setex(limit_key, 60, "1")

        return code

    @staticmethod
    def send_mock_sms(mobile: str) -> str:
        code = ''.join(random.choices(string.digits, k=6))
        
        # Store in Redis: SMS:{mobile} -> code
        key = f"SMS:{mobile}"
        # Expire in 5 minutes
        redis_client.setex(key, 300, code)
        
        # In production, call actual SMS provider here.
        print(f"=======================================")
        print(f" [MOCK SMS] To: {mobile}, Code: {code}")
        print(f"=======================================")
        
        return code

    @staticmethod
    def send_aliyun_sms(mobile: str) -> str:
        if DypnsApiClient is None:
            print("Aliyun Dypns SDK not installed, falling back to mock")
            return SmsService.send_mock_sms(mobile)

        try:
            client = SmsService.get_client()
            
            # Use SendSmsVerifyCode API from SMS Authentication Service
            # We request the code to be returned so we can store it in Redis
            # TemplateParam logic: 
            # - code: mapped to ##code## (Dypns generates this)
            # - min: mapped to expiration time in minutes
            expire_minutes = str(int(settings.CAPTCHA_EXPIRE_SECONDS / 60))
            template_param = json.dumps({"code": "##code##", "min": expire_minutes})

            request = dypns_api_models.SendSmsVerifyCodeRequest(
                phone_number=mobile,
                sign_name=settings.ALIYUN_SMS_SIGN_NAME,
                template_code=settings.ALIYUN_SMS_TEMPLATE_CODE,
                template_param=template_param,
                return_verify_code=True,
                valid_time=settings.CAPTCHA_EXPIRE_SECONDS
            )
            
            runtime = util_models.RuntimeOptions()
            response = client.send_sms_verify_code_with_options(request, runtime)
            
            if response.body.code == 'OK':
                # For Dypns SendSmsVerifyCode, the code is in the Model
                verify_code = response.body.model.verify_code
                request_id = response.body.request_id
                biz_id = response.body.model.biz_id
                
                # Store in Redis
                key = f"SMS:{mobile}"
                redis_client.setex(key, settings.CAPTCHA_EXPIRE_SECONDS, verify_code)
                
                print(f" [ALIYUN SMS AUTH] To: {mobile}, Code: {verify_code} (Sent via SendSmsVerifyCode)")
                print(f" [ALIYUN SMS AUTH DEBUG] RequestId: {request_id}, BizId: {biz_id}")
                return verify_code
            else:
                error_msg = response.body.message or "Unknown error"
                request_id = response.body.request_id
                print(f" [ALIYUN SMS ERROR] {error_msg} | RequestId: {request_id}")
                raise Exception(f"Aliyun SMS failed: {error_msg}")
                
        except Exception as error:
            print(f" [ALIYUN SMS EXCEPTION] {error}")
            raise error

    @staticmethod
    def verify_code(mobile: str, code: str) -> bool:
        key = f"SMS:{mobile}"
        stored_code = redis_client.get(key)
        
        if not stored_code:
            return False
            
        if stored_code == code:
            redis_client.delete(key) # One-time use
            return True
        return False