From 8cfac8df6a4cbc005b798fb18ca94919534f33eb Mon Sep 17 00:00:00 2001
From: Thomas Sileo <t@a4.io>
Date: Thu, 4 Aug 2022 07:31:18 +0200
Subject: [PATCH] Allow to replace URL dynamically (for Nitter, Teddit...)

---
 app/ap_object.py   | 19 +++++++++++++++++--
 app/config.py      |  9 +++++++++
 docs/user_guide.md | 22 ++++++++++++++++++++++
 3 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/app/ap_object.py b/app/ap_object.py
index 16b91cd..72fd871 100644
--- a/app/ap_object.py
+++ b/app/ap_object.py
@@ -2,6 +2,7 @@ import hashlib
 from datetime import datetime
 from functools import cached_property
 from typing import Any
+from urllib.parse import urlparse
 
 import pydantic
 from bs4 import BeautifulSoup  # type: ignore
@@ -11,6 +12,7 @@ from app import activitypub as ap
 from app.actor import LOCAL_ACTOR
 from app.actor import Actor
 from app.actor import RemoteActor
+from app.config import PRIVACY_REPLACE
 from app.media import proxied_media_url
 from app.utils.datetime import now
 from app.utils.datetime import parse_isoformat
@@ -175,9 +177,22 @@ class Object:
 
         # PeerTube returns the content as markdown
         if self.ap_object.get("mediaType") == "text/markdown":
-            return markdown(content, extensions=["mdx_linkify"])
+            content = markdown(content, extensions=["mdx_linkify"])
 
-        return content
+        if not PRIVACY_REPLACE:
+            return content
+
+        soup = BeautifulSoup(content, "html5lib")
+        links = soup.find_all("a", href=True)
+
+        for link in links:
+            parsed_href = urlparse(link.attrs["href"])
+            if new_netloc := PRIVACY_REPLACE.get(
+                parsed_href.netloc.removeprefix("www.")
+            ):
+                link.attrs["href"] = parsed_href._replace(netloc=new_netloc).geturl()
+
+        return soup.find("body").decode_contents()
 
     @property
     def summary(self) -> str | None:
diff --git a/app/config.py b/app/config.py
index d567e8f..e64060c 100644
--- a/app/config.py
+++ b/app/config.py
@@ -31,6 +31,11 @@ USER_AGENT = f"microblogpub/{VERSION}"
 AP_CONTENT_TYPE = "application/activity+json"
 
 
+class _PrivacyReplace(pydantic.BaseModel):
+    domain: str
+    replace_by: str
+
+
 class Config(pydantic.BaseModel):
     domain: str
     username: str
@@ -43,6 +48,7 @@ class Config(pydantic.BaseModel):
     debug: bool = False
     trusted_hosts: list[str] = ["127.0.0.1"]
     manually_approves_followers: bool = False
+    privacy_replace: list[_PrivacyReplace] | None = None
 
     # Config items to make tests easier
     sqlalchemy_database: str | None = None
@@ -84,6 +90,9 @@ _SCHEME = "https" if CONFIG.https else "http"
 ID = f"{_SCHEME}://{DOMAIN}"
 USERNAME = CONFIG.username
 MANUALLY_APPROVES_FOLLOWERS = CONFIG.manually_approves_followers
+PRIVACY_REPLACE = None
+if CONFIG.privacy_replace:
+    PRIVACY_REPLACE = {pr.domain: pr.replace_by for pr in CONFIG.privacy_replace}
 BASE_URL = ID
 DEBUG = CONFIG.debug
 DB_PATH = CONFIG.sqlalchemy_database or ROOT_DIR / "data" / "microblogpub.db"
diff --git a/docs/user_guide.md b/docs/user_guide.md
index fa3bd9c..7109119 100644
--- a/docs/user_guide.md
+++ b/docs/user_guide.md
@@ -31,6 +31,28 @@ You can tweak your profile by tweaking these items:
 
 Whenever one of these config items is updated, an `Update` activity will be sent to all know server to update your remote profile.
 
+### Privacy replace
+
+You can define domain to be rewrited to more "privacy friendly" alternatives, like [Invidious](https://invidious.io/)
+or [Nitter](https://nitter.net/about).
+
+To do so, just add as these extra config items, this is a sample config that rewrite URLs for Twitter, Youtube, Reddit and Medium:
+
+```toml
+[[privacy_replace]]
+domain = "youtube.com"
+replace_by  ="yewtu.be"
+[[privacy_replace]]
+domain = "twitter.com"
+replace_by = "nitter.net"
+[[privacy_replace]]
+domain = "medium.com"
+replace_by = "scribe.rip"
+[[privacy_replace]]
+domain = "reddit.com"
+replace_by = "teddit.net"
+```
+
 ### Customization
 
 #### Custom emoji