from sqlalchemy import select, update, and_
from sqlalchemy.dialects.postgresql import insert as pg_insert
from .database import db_instance
from .utils import normalize_url

class CrawlerService:
    def __init__(self):
        self.db = db_instance

    def register_task(self, url: str):
        """注册新任务并初始化队列"""
        clean_url = normalize_url(url)
        with self.db.engine.begin() as conn:
            # 1. 查重
            find_stmt = select(self.db.tasks.c.id).where(self.db.tasks.c.root_url == clean_url)
            existing = conn.execute(find_stmt).fetchone()
            
            if existing:
                return {"task_id": existing[0], "is_new_task": False}
            
            # 2. 插入新任务
            new_task = conn.execute(
                pg_insert(self.db.tasks).values(root_url=clean_url).returning(self.db.tasks.c.id)
            ).fetchone()
            task_id = new_task[0]
            
            # 3. 初始化首个 URL 到队列
            conn.execute(
                pg_insert(self.db.queue).values(task_id=task_id, url=clean_url, status='pending')
            )
            return {"task_id": task_id, "is_new_task": True}

    def add_urls(self, task_id: int, urls: list):
        """批量存入新发现的待处理 URL（自动去重）"""
        added_count = 0
        with self.db.engine.begin() as conn:
            for url in urls:
                clean_url = normalize_url(url)
                stmt = pg_insert(self.db.queue).values(
                    task_id=task_id,
                    url=clean_url,
                    status='pending'
                ).on_conflict_do_nothing(index_elements=['task_id', 'url'])
                
                res = conn.execute(stmt)
                if res.rowcount > 0:
                    added_count += 1
        return {"added_count": added_count}

    def get_pending_urls(self, task_id: int, limit: int):
        """原子化获取待处理 URL 并锁定"""
        with self.db.engine.begin() as conn:
            stmt = select(self.db.queue.c.url).where(
                and_(self.db.queue.c.task_id == task_id, self.db.queue.c.status == 'pending')
            ).limit(limit)
            
            urls = [r[0] for r in conn.execute(stmt).fetchall()]
            
            if urls:
                conn.execute(
                    update(self.db.queue).where(
                        and_(self.db.queue.c.task_id == task_id, self.db.queue.c.url.in_(urls))
                    ).values(status='processing')
                )
        return {"urls": urls}

    def save_results(self, task_id: int, results: list):
        """保存正文、向量并闭环队列状态"""
        with self.db.engine.begin() as conn:
            for res in results:
                clean_url = normalize_url(res.url)
                # 存入数据
                conn.execute(
                    pg_insert(self.db.chunks).values(
                        task_id=task_id,
                        source_url=clean_url,
                        title=res.title,
                        content=res.content,
                        embedding=res.embedding
                    )
                )
                # 更新状态
                conn.execute(
                    update(self.db.queue).where(
                        and_(self.db.queue.c.task_id == task_id, self.db.queue.c.url == clean_url)
                    ).values(status='completed')
                )
        return {"inserted": len(results)}

# 全局单例
crawler_service = CrawlerService()