feat: simple rick-rolling implementation

A Flask server that takes a URL in parameter, and serves the same
page, but with all the links pointing to YouTube's rick-rolling video.

.gitignore

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+*.pyc
+__pycache__
+venv

Dockerfile

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+FROM python:3.9-alpine3.15
+
+COPY requirements.txt /app/
+RUN pip install -r /app/requirements.txt
+
+COPY assets /app/assets
+COPY templates /app/templates
+COPY rickroller.py server.py /app/
+
+ENTRYPOINT ["python", "/app/server.py"]

assets/style.css

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+:root {
+    --main-font: monospace;
+    --main-letter-spacing: -0.5px;
+    --background: #EFEFEF;
+    --text-color: #111;
+
+    --primary: #333;
+    --input-background: #F9F9F9; /* #CECECE */
+}
+
+
+body {
+    font-family: var(--main-font);
+    letter-spacing: var(--main-letter-spacing);
+    font-size: 1.3rem;
+    line-height: 1.3rem;
+    padding: 10px;
+    background: var(--background);
+    color: var(--text-color);
+    text-align: center;
+
+    background-image: url('https://cdn.vox-cdn.com/thumbor/9j-s_MPUfWM4bWdZfPqxBxGkvlw=/1400x1050/filters:format(jpeg)/cdn.vox-cdn.com/uploads/chorus_asset/file/22312759/rickroll_4k.jpg');
+    background-blend-mode: color-burn;
+    background-size: cover;
+}
+
+form {
+    margin-top: 3em;
+}
+
+
+input[type=url] {
+    display: block;
+    margin: 10pt auto;
+    background: var(--input-background);
+    border: none;
+    font-family: monospace;
+    font-size: .9em;
+    color: var(--text-color);
+    padding: 8px 5px;
+    outline: none !important;
+}
+
+input:-webkit-autofill,
+input:-webkit-autofill:hover,
+input:-webkit-autofill:active,
+input:-webkit-autofill:focus {
+    background-color: var(--input-background) !important;
+    color: var(--text-color) !important;
+    -webkit-box-shadow: 0 0 0 1000px var(--input-background) inset !important;
+    -webkit-text-fill-color: var(--text-color) !important;
+}
+
+input:-webkit-autofill::first-line {
+    font-family: var(--main-font) !important;
+}

requirements.txt

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+flask
+beautifulsoup4
+requests
+validators

rickroller.py

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+import requests
+from bs4 import BeautifulSoup
+from urllib.parse import urljoin
+import re
+
+class RickRoller:
+
+    __RICK_ROLL_URL__ = 'https://www.youtube.com/watch?v=dQw4w9WgXcQ'
+
+    @classmethod
+    def rickroll(self, url: str) -> str:
+        soup = self.__get_soup(url)
+
+        for a in soup.find('body').find_all('a'):
+            a.attrs['href'] =self.__RICK_ROLL_URL__
+
+        args = [soup, url]
+        self.__absolutize('link', 'href', *args)
+        self.__absolutize('script', 'src', *args)
+        self.__absolutize('img', 'src', *args)
+
+        self.__fix_srcset(*args)
+
+        return str(soup)
+
+    @staticmethod
+    def __absolutize(tagname, attr, soup, url):
+        for elt in soup.find_all(tagname, **{attr: True}):
+            elt.attrs[attr] = urljoin(url, elt.attrs[attr])
+
+    @staticmethod
+    def __fix_srcset(soup, url):
+        # for responsive images
+        # e.g. "/static/563761cc22ded851baff4921ecc27649/e4a55/python-url-decode.jpg 256w, /static/563761cc22ded851baff4921ecc27649/36dd4/python-url-decode.jpg 512w, /static/563761cc22ded851baff4921ecc27649/72e01/python-url-decode.jpg 1024w, /static/563761cc22ded851baff4921ecc27649/ac99c/python-url-decode.jpg 1536w, /static/563761cc22ded851baff4921ecc27649/0f98f/python-url-decode.jpg 1920w"
+        for elt in soup.find_all('img', srcset=True):
+            srcset = elt.attrs['srcset']
+
+            transformed = []
+            for entry in re.split(" *, *", srcset):
+                items = re.split(" +", entry)
+                transformed.append(" ".join([urljoin(url, items[0])] + items[1:]))
+
+            elt.attrs['srcset'] = ",".join(transformed)
+            print(srcset)
+            print(elt.attrs['srcset'])
+            print("----")
+
+
+    @staticmethod
+    def __get_soup(url: str) -> BeautifulSoup:
+        try:
+            response =  requests.get(url)
+            if response.status_code != 200:
+                raise 
+            return BeautifulSoup(response.text, 'html.parser')
+
+        except Exception as e:
+            pass

server.py

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+from flask import Flask, request, render_template
+from validators.url import url as urlvalidate
+from rickroller import RickRoller
+import urllib
+
+app = Flask(__name__, static_folder='assets')
+
+@app.route('/')
+def rickroll():
+    if (url := request.args.get('u')) is not None:
+        url = urllib.parse.unquote(url) # may be url-encoded
+        if not urlvalidate(url):
+            return f'Invalid URL {url}'
+
+        return RickRoller.rickroll(url)
+
+    return render_template('index.html')
+
+if __name__ == '__main__':
+    import argparse
+    parser = argparse.ArgumentParser()
+    parser.add_argument('-d', '--debug', action='store_true')
+    args = parser.parse_args()
+
+    app.run(host='0.0.0.0', port=8080, debug=args.debug)

templates/index.html

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+<!doctype html>
+
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+
+  <title>URL RickRolling</title>
+  <meta name="description" content="Transform all links into a rick-roll.">
+  <meta name="author" content="derlin">
+
+  <link rel="icon" href="/favicon.ico">
+  <link rel="icon" href="/favicon.svg" type="image/svg+xml">
+  <link rel="apple-touch-icon" href="/apple-touch-icon.png">
+
+  <link rel="stylesheet" href="{{ url_for('static', filename='style.css') }}">
+</head>
+
+<body>
+  <h2>Rick Roll Any URL</h2>
+  <form>
+    <!--label for="url">Enter an URL and press 'enter'</label-->
+
+    <input type="url" name="u" id="url"
+          placeholder="Enter an URL here and press 'enter'"
+          pattern="https?://.*\..*" size="100"
+          required>
+  </form>
+</body>
+</html>