import socket
import ssl


def parsed_url(url):
   protocol = 'http'
   if url[:7] == 'http://':
       u = url.split('://')[1]
   elif url[:8] == 'https://':
       protocol = 'https'
       u = url.split('://')[1]
   else:
       u = url
   i = u.find('/')
   if i == -1:
       host = u
       path = '/'
   else:
       host = u[:i]
       path = u[i:]
   # 默认端口
   port_dict = {
       'http': 80,
       'https': 443,
   }
   port = port_dict[protocol]
   if host.find(':') != -1:
       h = host.split(':')
       host = h[0]
       port = int(h[1])
   return protocol, host, port, path


# 分析 url,得到协议,主机,端口,路径

def socket_by_protocol(protocol):
   """"
   根据协议返回一个 socket 实例
   """
   if protocol == 'http':
       s = socket.socket()
   else:
       s = ssl.wrap_socket(socket.socket())
   return s

# 客户端 接收 响应
def response_by_socket(s):
   response = b''
   buffer_size = 1024
   while True:
       r = s.recv(buffer_size)
       if len(r) == 0:
           break
       response += r
   return response


# 分析响应得到 status_code,headers,body
def parsed_response(r):
   header, body = r.split('\r\n\r\n', 1)
   h = header.split('\r\n')
   status_code = h[0].split()[1]
   status_code = int(status_code)

   headers = {}
   headers = {}
   # for line in h[1:]:
   #     k, v = line.split(': ')
   #     headers[k] = v
   for line in h[1:]:
       k, v = line.split(': ')
       headers[k] = v
   return status_code, headers, body


def get(url):
   # 用 GET 请求 url并返回响应
   protocol, host, port, path = parsed_url(url)
   s = socket_by_protocol(protocol)
   s.connect((host, port))

   request = 'GET {} HTTP/1.1\r\nhost: {}\r\nConnection: close\r\n\r\n'.format(path, host)
   encoding = 'utf-8'
   s.send(request.encode(encoding))

   response = response_by_socket(s)
   r = response.decode(encoding)

   status_code, headers, body = parsed_response(r)
   if status_code == 301:
       url = headers['Location']
       return get(url)

   return status_code, headers, body


def main():
   url = 'g.cn'
   status_code, headers, body = get(url)
   print(status_code, headers, body)



if __name__ == '__main__':
   main()