Allow defining custom redirects with `WHOOGLE_REDIRECTS`

Redirects to alternative frontends can now be defined using the
WHOOGLE_REDIRECTS environment variable. Usage is documented in the
readme, but is basically defined as <parent>:<new>.

Closes #988

README.md

@@ -33,10 +33,11 @@ Contents
 5. [Usage](#usage)
 6. [Extra Steps](#extra-steps)
     1. [Set Primary Search Engine](#set-whoogle-as-your-primary-search-engine)
-    2. [Prevent Downtime (Heroku Only)](#prevent-downtime-heroku-only)
+	2. [Custom Redirecting](#custom-redirecting)
-    3. [Manual HTTPS Enforcement](#https-enforcement)
+    3. [Prevent Downtime (Heroku Only)](#prevent-downtime-heroku-only)
-    4. [Using with Firefox Containers](#using-with-firefox-containers)
+    4. [Manual HTTPS Enforcement](#https-enforcement)
-    5. [Reverse Proxying](#reverse-proxying)
+    5. [Using with Firefox Containers](#using-with-firefox-containers)
+    6. [Reverse Proxying](#reverse-proxying)
         1. [Nginx](#nginx)
 7. [Contributing](#contributing)
 8. [FAQ](#faq)
@@ -401,6 +402,7 @@ There are a few optional environment variables available for customizing a Whoog
 | WHOOGLE_USER_AGENT   | The desktop user agent to use. Defaults to a randomly generated one.                      |
 | WHOOGLE_USER_AGENT_MOBILE | The mobile user agent to use. Defaults to a randomly generated one.                  |
 | WHOOGLE_USE_CLIENT_USER_AGENT | Enable to use your own user agent for all requests. Defaults to false.           |
+| WHOOGLE_REDIRECTS    | Specify sites that should be redirected elsewhere. See (custom redirecting)(#custom-redirecting). |
 | EXPOSE_PORT          | The port where Whoogle will be exposed.                                                   |
 | HTTPS_ONLY           | Enforce HTTPS. (See [here](https://github.com/benbusby/whoogle-search#https-enforcement)) |
 | WHOOGLE_ALT_TW       | The twitter.com alternative to use when site alternatives are enabled in the config. Set to "" to disable. |
@@ -451,6 +453,7 @@ Same as most search engines, with the exception of filtering by time range.
 To filter by a range of time, append ":past <time>" to the end of your search, where <time> can be `hour`, `day`, `month`, or `year`. Example: `coronavirus updates :past hour`
 
 ## Extra Steps
+
 ### Set Whoogle as your primary search engine
 *Note: If you're using a reverse proxy to run Whoogle Search, make sure the "Root URL" config option on the home page is set to your URL before going through these steps.*
 
@@ -495,6 +498,32 @@ Browser settings:
     - Manual
       - Under search engines > manage search engines > add, manually enter your Whoogle instance details with a `<whoogle url>/search?q=%s` formatted search URL.
 
+### Custom Redirecting
+You can set custom site redirects using the `WHOOGLE_REDIRECTS` environment
+variable. A lot of sites, such as Twitter, Reddit, etc, have built-in redirects
+to [Farside links](https://sr.ht/~benbusby/farside), but you may want to define
+your own.
+
+To do this, you can use the following syntax:
+
+```
+WHOOGLE_REDIRECTS="<parent_domain>:<new_domain>"
+```
+
+For example, if you want to redirect from "badsite.com" to "goodsite.com":
+
+```
+WHOOGLE_REDIRECTS="badsite.com:goodsite.com"
+```
+
+This can be used for multiple sites as well, with comma separation:
+
+```
+WHOOGLE_REDIRECTS="badA.com:goodA.com,badB.com:goodB.com"
+```
+
+NOTE: Do not include "http(s)://" when defining your redirect.
+
 ### Prevent Downtime (Heroku only)
 Part of the deal with Heroku's free tier is that you're allocated 550 hours/month (meaning it can't stay active 24/7), and the app is temporarily shut down after 30 minutes of inactivity. Once it becomes inactive, any Whoogle searches will still work, but it'll take an extra 10-15 seconds for the app to come back online before displaying the result, which can be frustrating if you're in a hurry.
 

app/utils/misc.py

@@ -79,3 +79,10 @@ def get_abs_url(url, page_url):
     elif url.startswith('./'):
         return f'{page_url}{url[2:]}'
     return url
+
+
+def list_to_dict(lst: list) -> dict:
+    if len(lst) < 2:
+        return {}
+    return {lst[i].replace(' ', ''): lst[i+1].replace(' ', '')
+            for i in range(0, len(lst), 2)}

app/utils/results.py

@@ -1,5 +1,6 @@
 from app.models.config import Config
 from app.models.endpoint import Endpoint
+from app.utils.misc import list_to_dict
 from bs4 import BeautifulSoup, NavigableString
 import copy
 from flask import current_app
@@ -43,6 +44,9 @@ SITE_ALTS = {
     'quora.com': os.getenv('WHOOGLE_ALT_QUORA', 'farside.link/quetre')
 }
 
+# Include custom site redirects from WHOOGLE_REDIRECTS
+SITE_ALTS.update(list_to_dict(re.split(',|:', os.getenv('WHOOGLE_REDIRECTS', ''))))
+
 
 def contains_cjko(s: str) -> bool:
     """This function check whether or not a string contains Chinese, Japanese,