import requests
from bs4 import BeautifulSoup
import re
import time
import random

# 定义一个爬虫类
class BilibiliCrawler:
    def __init__(self):
        # 设置请求头，模拟浏览器访问
        self.headers = {
            'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36',
            'Referer': 'https://www.bilibili.com/'
        }
        self.session = requests.Session()
        self.session.headers.update(self.headers)

    def search_videos(self, keyword, pages=3):
        """搜索视频，获取视频ID列表"""
        print("正在搜索视频...")
        video_ids = []
        
        for page in range(1, pages + 1):
            try:
                # 构造搜索URL
                url = f'https://search.bilibili.com/all'
                params = {
                    'keyword': keyword,
                    'page': page,
                    'order': 'totalrank'  # 综合排序
                }
                
                response = self.session.get(url, params=params, timeout=10)
                response.encoding = 'utf-8'
                
                # 使用BeautifulSoup解析HTML
                soup = BeautifulSoup(response.text, 'html.parser')
                
                # 查找视频链接（改进的选择器）
                video_links = soup.find_all('a', href=re.compile(r'//www.bilibili.com/video/(BV[0-9A-Za-z]+)'))
                
                for link in video_links:
                    href = link.get('href')
                    if 'BV' in href:
                        # 提取视频BV号
                        bv_match = re.search(r'BV[0-9A-Za-z]+', href)
                        if bv_match:
                            video_ids.append(bv_match.group())
                
                print(f'第{page}页搜索完成，找到{len(video_links)}个视频')
                
                # 随机延时，避免请求过快
                time.sleep(random.uniform(1, 3))
                
            except Exception as e:
                print(f'搜索第{page}页时出错: {e}')
                continue
        
        # 去重
        video_ids = list(set(video_ids))
        print(f'共找到{len(video_ids)}个唯一视频')
        return video_ids[:20]  # 限制视频数量，避免请求过多

    def get_danmaku(self, bvid):
        """获取视频的弹幕"""
        try:
            # 先获取视频的cid（弹幕ID）
            video_info_url = f'https://api.bilibili.com/x/web-interface/view'
            params = {'bvid': bvid}
            
            response = self.session.get(video_info_url, params=params, timeout=10)
            video_info = response.json()
            
            if video_info['code'] != 0:
                print(f"无法获取视频{bvid}信息")
                return []
            
            cid = video_info['data']['cid']
            
            # 获取弹幕
            danmaku_url = f'https://api.bilibili.com/x/v1/dm/list.so'
            params = {'oid': cid}
            
            response = self.session.get(danmaku_url, params=params, timeout=10)
            response.encoding = 'utf-8'
            
            # 解析XML格式的弹幕
            soup = BeautifulSoup(response.text, 'xml')
            danmakus = soup.find_all('d')
            
            danmaku_list = []
            for danmaku in danmakus:
                text = danmaku.get_text()
                if text and len(text.strip()) > 0:
                    danmaku_list.append(text.strip())
            
            print(f'视频{bvid}获取到{len(danmaku_list)}条弹幕')
            return danmaku_list
            
        except Exception as e:
            print(f'获取视频{bvid}弹幕时出错: {e}')
            return []

    def crawl(self, keywords, output_file='danmaku.txt'):
        """主爬取函数"""
        all_danmakus = []
        
        for keyword in keywords:
            print(f'\n开始爬取关键词: {keyword}')
            video_ids = self.search_videos(keyword)
            
            for i, bvid in enumerate(video_ids):
                print(f'正在处理第{i+1}/{len(video_ids)}个视频: {bvid}')
                danmakus = self.get_danmaku(bvid)
                all_danmakus.extend(danmakus)
                
                # 保存进度
                with open(output_file, 'w', encoding='utf-8') as f:
                    for danmaku in all_danmakus:
                        f.write(danmaku + '\n')
                
                # 延时
                time.sleep(random.uniform(0.5, 1.5))
        
        print(f'\n爬取完成！共获取{len(all_danmakus)}条弹幕，已保存到{output_file}')
        return all_danmakus

# 主程序
if __name__ == '__main__':
    crawler = BilibiliCrawler()
    
    # 搜索关键词
    keywords = ['大语言模型', 'LLM', '大模型']
    
    # 开始爬取
    danmakus = crawler.crawl(keywords, 'bilibili_danmaku.txt')
    
    # 打印一些统计信息
    print(f"\n最终统计:")
    print(f"总弹幕数: {len(danmakus)}")
    if danmakus:
        print("前10条弹幕示例:")
        for i, dm in enumerate(danmakus[:10]):
            print(f"{i+1}. {dm}")