import os
import glob
import json
import logging
from datetime import datetime
from typing import Set
from app.core.minio import minio_storage
from app.core.scheduler import scheduler
from apscheduler.triggers.cron import CronTrigger

logger = logging.getLogger(__name__)

# 备份目录路径（项目根目录的 backups 文件夹）
# 在 Docker 容器中，需要挂载这个目录
BACKUP_DIR = os.getenv("DB_BACKUP_DIR", "/app/backups")
# 记录已上传文件的文件路径
UPLOADED_RECORD_FILE = os.path.join(BACKUP_DIR, ".uploaded_backups.json")

class DatabaseBackupUploadService:
    @staticmethod
    def _load_uploaded_records() -> Set[str]:
        """加载已上传的文件记录"""
        if not os.path.exists(UPLOADED_RECORD_FILE):
            return set()
        
        try:
            with open(UPLOADED_RECORD_FILE, 'r', encoding='utf-8') as f:
                data = json.load(f)
                return set(data.get('uploaded_files', []))
        except Exception as e:
            logger.error(f"Failed to load uploaded records: {e}")
            return set()
    
    @staticmethod
    def _save_uploaded_record(filename: str):
        """保存已上传的文件记录"""
        records = DatabaseBackupUploadService._load_uploaded_records()
        records.add(filename)
        
        try:
            os.makedirs(os.path.dirname(UPLOADED_RECORD_FILE), exist_ok=True)
            with open(UPLOADED_RECORD_FILE, 'w', encoding='utf-8') as f:
                json.dump({'uploaded_files': list(records)}, f, indent=2)
        except Exception as e:
            logger.error(f"Failed to save uploaded record: {e}")
    
    @staticmethod
    def _get_backup_files() -> list:
        """获取备份目录中的所有 .sql.gz 文件"""
        if not os.path.exists(BACKUP_DIR):
            logger.warning(f"Backup directory does not exist: {BACKUP_DIR}")
            return []
        
        pattern = os.path.join(BACKUP_DIR, "*.sql.gz")
        files = glob.glob(pattern)
        # 按修改时间排序，最新的在前
        files.sort(key=os.path.getmtime, reverse=True)
        return files
    
    @staticmethod
    def _is_file_stable(file_path: str, wait_seconds: int = 60) -> bool:
        """
        检查文件是否稳定（不再变化）
        如果文件在 wait_seconds 秒内没有变化，认为备份已完成
        """
        try:
            stat = os.stat(file_path)
            current_time = datetime.now().timestamp()
            file_mtime = stat.st_mtime
            
            # 如果文件最后修改时间距离现在超过 wait_seconds 秒，认为稳定
            return (current_time - file_mtime) >= wait_seconds
        except Exception as e:
            logger.error(f"Failed to check file stability: {e}")
            return False
    
    @staticmethod
    def upload_new_backups():
        """检查并上传新的备份文件"""
        logger.info("Starting database backup upload check...")
        
        if not minio_storage.client:
            logger.error("MinIO client not available, skipping upload")
            return
        
        uploaded_records = DatabaseBackupUploadService._load_uploaded_records()
        backup_files = DatabaseBackupUploadService._get_backup_files()
        
        uploaded_count = 0
        skipped_count = 0
        failed_count = 0
        
        for file_path in backup_files:
            filename = os.path.basename(file_path)
            
            # 跳过已上传的文件
            if filename in uploaded_records:
                skipped_count += 1
                continue
            
            # 检查文件是否稳定（备份是否完成）
            if not DatabaseBackupUploadService._is_file_stable(file_path):
                logger.info(f"File {filename} is still being written, skipping...")
                continue
            
            # 上传文件
            try:
                logger.info(f"Uploading database backup: {filename}")
                object_name = minio_storage.upload_db_backup(file_path, filename)
                DatabaseBackupUploadService._save_uploaded_record(filename)
                uploaded_count += 1
                logger.info(f"Successfully uploaded {filename} to MinIO: {object_name}")
            except Exception as e:
                logger.error(f"Failed to upload {filename}: {e}")
                failed_count += 1
        
        logger.info(
            f"Backup upload check completed. "
            f"Uploaded: {uploaded_count}, Skipped: {skipped_count}, Failed: {failed_count}"
        )
    
    @staticmethod
    def init_scheduler():
        """初始化定时任务，每小时检查一次"""
        # 每小时的第5分钟执行（避免与备份时间冲突）
        trigger = CronTrigger(minute=5)
        
        scheduler.add_job(
            DatabaseBackupUploadService.upload_new_backups,
            trigger=trigger,
            id="db_backup_upload_job",
            replace_existing=True
        )
        logger.info("Database backup upload scheduler initialized (runs every hour at :05)")