import requests
import re

count = 0 # 用来记录已经获取了多少条视频的弹幕

def get_page_url(n):
    """
    此函数用于获取页面的url
    n代表获取的页数
    返回一个存储各页面url的列表
    """
    page_url_list = []  # 存储页面网址的列表
    # 获取B站视频页面
    for i in range(n):
        if i == 0:
            page_url = "https://search.bilibili.com/all?keyword=2024%E5%B7%B4%E9%BB%8E%E5%A5%A5%E8%BF%90%E4%BC%9A&from_source=webtop_search&spm_id_from=333.1007&search_source=5"
            page_url_list.append(page_url)
            i += 1
        else:
            page_url = f"https://search.bilibili.com/all?keyword=2024%E5%B7%B4%E9%BB%8E%E5%A5%A5%E8%BF%90%E4%BC%9A&from_source=webtop_search&spm_id_from=333.1007&search_source=5&page={i + 1}&o={i * 36}"
            page_url_list.append(page_url)
            i += 1
    return page_url_list

# 设置请求头。为了应对B站的反爬虫，我们需要伪装成浏览器进行请求
header = {"user-agent":"Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/128.0.0.0 Safari/537.36 Edg/128.0.0.0"}

def get_cid(page_url_list):
    """
    本函数用于获取各个页面视频的cid
    返回存储综合排序前300的视频的cid的列表
    """
    global count
    cid_list = [] # 存储cid的列表
    for page_url in page_url_list: # 按照页面的顺序进行爬取
        if count >= 300:
            break
        else:
            # 先获取bvid
            response = requests.get(url = page_url,headers = header)
            response.encoding = 'utf-8'
            data = response.text
            content = re.findall('"//www.bilibili.com/video/(.*?)/"',data)
            # 爬取的bvid会有重复，因此我们要进行去重操作
            content = set(content)
            content = list(content)
            # 通过bvid获取cid
            for bvid in content:
                url = f"https://api.bilibili.com/x/player/pagelist?bvid={bvid}&jsonp=jsonp"
                response = requests.get(url=url, headers=header)
                response.encoding = 'utf-8'
                data = response.text
                content = re.findall('{"cid":(.*?),', data)
                cid_list.append(content[0])
                count += 1
                if count >= 300:
                    break

    return cid_list

def get_danmu(cid_list):
    """
    本函数用于获取弹幕
    """
    danmu_list = []
    for cid in cid_list:
        url = f"https://comment.bilibili.com/{cid}.xml"
        response = requests.get(url=url, headers=header)
        response.encoding = 'utf-8'
        data = response.text
        content = re.findall('<d p=".*?">(.*?)</d>', data) # 使用正则表达式获取弹幕
        danmu_list.extend(content)
    return danmu_list

cid_list = get_cid(get_page_url(10))
danmu_list = get_danmu(cid_list) # 获取弹幕
for danmu in danmu_list:  # 遍历弹幕
    with open('danmu.txt', 'a', encoding='utf-8') as f:  # 打开文件准备写入
        f.write(danmu + '\n')  # 写入弹幕