[feat] engines: add tusksearch (web, news, videos, images) (#6267)

The code that reads the value of variable `x` from `embed.js`, decodes
it to ASCII and based on that sets `window["tuskheader"]` and `window["tuskkey"]`
is attached below. The only real way to figure out what this is doing is
by stepping through it with the debugger, otherwise it's almost hopeless.

```js
function fe() {
  const B = pe => pe.map(_e => String.fromCharCode(_e)).join(''),
  ae = window,
  o = ae.x;
  if (o?.length) {
    const pe = o.length / 2;
    for (let _e = 0; _e < pe; _e++) ae[B(o[_e])] = B(o[pe + _e]);
    ae.x = void 0
  }
}
```

Minimal script for testing the engine:

```py
import random
from json import loads
import requests

resp = requests.get("https://api.tusksearch.com/revcontent/embed.js")
data = loads(resp.text[6:])

def _decode(text: list[int]) -> str:
    return "".join([chr(x) for x in text])

header = _decode(data[3])
value = _decode(data[4])

resp = requests.get(
    "https://api.tusksearch.com/Search/Web?q=test&p=1&l=center&nextArgs=&prevArgs=",
    # "https://api.tusksearch.com/Search/Image?q=test&p=1&l=center",
    headers={
        header: value,
        'x-lon': str(random.random() * 90),
        'x-lat': str(random.random() * 90),
    },
)
print(resp.text)
```

1 files changed, 162 insertions, 0 deletions

diff --git a/searx/engines/tusksearch.py b/searx/engines/tusksearch.py
new file mode 100644
index 000000000..f85e17c12
--- /dev/null
+++ b/searx/engines/tusksearch.py
@@ -0,0 +1,162 @@
+# SPDX-License-Identifier: AGPL-3.0-or-later
+"""Tusksearch_ is an American search engine that claims to fight censorship.
+Its search results are (at least partially) from Brave.
+
+.. _Tusksearch: https://tusksearch.com/about
+"""
+
+from json import loads
+import random
+import typing as t
+from urllib.parse import urlencode
+from dateutil import parser
+
+from searx.exceptions import SearxEngineAPIException
+from searx.network import get
+from searx.utils import html_to_text
+from searx.result_types import EngineResults
+
+if t.TYPE_CHECKING:
+    from searx.extended_types import SXNG_Response
+    from searx.search.processors import OnlineParams
+
+about = {
+    "website": "https://tusksearch.com",
+    "wikidata_id": None,
+    "official_api_documentation": None,
+    "use_official_api": False,
+    "require_api_key": False,
+    "results": "JSON",
+}
+
+paging = True
+
+categories = ["general"]
+tusk_categ = "web"
+"""Category to search in. Can be either "web", "images", "videos" or "news"."""
+
+
+api_url = "https://api.tusksearch.com"
+
+
+def init(_):
+    if tusk_categ not in ("web", "images", "videos", "news"):
+        raise ValueError("invalid search type: %s" % tusk_categ)
+
+
+def _obtain_x_sid() -> tuple[str, str]:
+    """
+    The session ID ("sid") is encoded as a byte array in ``embed.js``.
+    It is only valid for exactly one request, so we can't cache it.
+
+    The header key is usually called `x-sid-{UUIDv4}`, and the value is
+    usually a plain UUIDv4 (but a different one than in the header key).
+    """
+    resp = get(f"{api_url}/revcontent/embed.js")
+    if not resp.ok:
+        raise SearxEngineAPIException("failed to obtain request x-sid token")
+
+    # data is prefixed by 'var x='
+    data_array = loads(resp.text[6:])
+
+    def _byte_array_to_ascii(text: list[int]) -> str:
+        """
+        Converts a byte array (e.g. [81, 101, 97, 114, 88, 78, 71]) to the ASCII
+        string representation (e.g. "SearXNG").
+        """
+        return "".join([chr(x) for x in text])
+
+    x_sid_header = _byte_array_to_ascii(data_array[3])
+    x_sid_value = _byte_array_to_ascii(data_array[4])
+    return x_sid_header, x_sid_value
+
+
+def request(query: str, params: "OnlineParams") -> None:
+    # images don't support pagination, news and videos only support two pages
+    if tusk_categ == "images" and params["pageno"] > 1 or tusk_categ in ("news", "videos") and params["pageno"] > 2:
+        params["url"] = None
+        return
+
+    args = {
+        "q": query,
+        "p": params["pageno"],
+        "l": "center",  # political direction: "left", "center" or "right"
+    }
+    if tusk_categ == "images":
+        params["url"] = f"{api_url}/Search/Image?{urlencode(args)}"
+    else:
+        # web response also contains news and videos
+        params["url"] = f"{api_url}/Search/Web?{urlencode(args)}"
+
+    x_sid_header, x_sid_value = _obtain_x_sid()
+    params["headers"] = {
+        x_sid_header: x_sid_value,
+        # required - we send a random longitude and latitude instead of the actual user location
+        'x-lon': str(random.random() * 90),
+        'x-lat': str(random.random() * 90),
+    }
+
+
+def response(resp: "SXNG_Response"):
+    res = EngineResults()
+
+    json_resp = resp.json()["results"]
+
+    if tusk_categ == "web":
+        for result in (json_resp.get("web") or {}).get("results", []):
+            res.add(
+                res.types.MainResult(
+                    url=result["url"],
+                    title=html_to_text(result["title"]),
+                    content=html_to_text(result["description"]),
+                    thumbnail=(result["thumbnail"] or {}).get("src") or "",
+                )
+            )
+    elif tusk_categ == "news":
+        for result in (json_resp.get("news") or {}).get("results", []):
+            publishedDate = None
+            try:
+                publishedDate = parser.parse(result["age"])
+            except parser.ParserError:
+                pass
+
+            res.add(
+                res.types.MainResult(
+                    url=result["url"],
+                    title=html_to_text(result["title"]),
+                    content=html_to_text(result["description"]),
+                    thumbnail=result["thumbnail"]["src"],
+                    publishedDate=publishedDate,
+                )
+            )
+    elif tusk_categ == "videos":
+        for result in (json_resp.get("videos") or {}).get("results", []):
+            publishedDate = None
+            try:
+                publishedDate = parser.parse(result["age"])
+            except parser.ParserError:
+                pass
+
+            res.add(
+                res.types.LegacyResult(
+                    template="videos.html",
+                    url=result["url"],
+                    title=html_to_text(result["title"]),
+                    content=html_to_text(result["description"]),
+                    thumbnail=result["thumbnail"]["src"],
+                    publishedDate=publishedDate,
+                    length=result["video"].get("duration"),
+                )
+            )
+    elif tusk_categ == "images":
+        for result in json_resp:
+            res.add(
+                res.types.Image(
+                    url=result["url"],
+                    title=html_to_text(result["title"]),
+                    img_src=result["properties"]["url"],
+                    thumbnail_src=result["thumbnail"]["src"],
+                )
+            )
+
+    return res