feat: add wayback plugin (Wayback Machine lookup)

Query Wayback Machine availability API via urllib + executor.
Supports optional timestamp parameter for date-targeted lookups.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

plugins/wayback.py

@@ -0,0 +1,85 @@
+"""Plugin: Wayback Machine snapshot lookup."""
+
+from __future__ import annotations
+
+import asyncio
+import json
+import logging
+import urllib.request
+
+from derp.plugin import command
+
+log = logging.getLogger(__name__)
+
+_API_URL = "https://archive.org/wayback/available"
+_TIMEOUT = 10
+_USER_AGENT = "derp/1.0"
+
+
+def _lookup(url: str, timestamp: str = "") -> dict:
+    """Blocking Wayback Machine availability check."""
+    params = f"url={url}"
+    if timestamp:
+        params += f"&timestamp={timestamp}"
+
+    req = urllib.request.Request(
+        f"{_API_URL}?{params}",
+        headers={"User-Agent": _USER_AGENT},
+    )
+
+    try:
+        resp = urllib.request.urlopen(req, timeout=_TIMEOUT)
+        data = json.loads(resp.read().decode("utf-8"))
+        resp.close()
+        return data
+    except Exception as exc:
+        return {"error": str(exc)[:100]}
+
+
+@command("wayback", help="Wayback Machine: !wayback <url> [YYYYMMDD]")
+async def cmd_wayback(bot, message):
+    """Check Wayback Machine for archived snapshots.
+
+    Usage:
+        !wayback example.com
+        !wayback https://example.com/page 20240101
+    """
+    parts = message.text.split(None, 3)
+    if len(parts) < 2:
+        await bot.reply(message, "Usage: !wayback <url> [YYYYMMDD]")
+        return
+
+    url = parts[1]
+    if not url.startswith(("http://", "https://")):
+        url = f"https://{url}"
+
+    timestamp = parts[2] if len(parts) >= 3 else ""
+
+    loop = asyncio.get_running_loop()
+    result = await loop.run_in_executor(None, _lookup, url, timestamp)
+
+    if "error" in result:
+        await bot.reply(message, f"{url} -> error: {result['error']}")
+        return
+
+    snapshots = result.get("archived_snapshots", {})
+    closest = snapshots.get("closest")
+
+    if not closest:
+        await bot.reply(message, f"{url} -> no snapshots found")
+        return
+
+    snap_url = closest.get("url", "")
+    snap_ts = closest.get("timestamp", "")
+    snap_status = closest.get("status", "")
+    available = closest.get("available", False)
+
+    # Format timestamp: YYYYMMDDHHMMSS -> YYYY-MM-DD HH:MM:SS
+    ts_fmt = snap_ts
+    if len(snap_ts) >= 14:
+        ts_fmt = (f"{snap_ts[:4]}-{snap_ts[4:6]}-{snap_ts[6:8]}"
+                  f" {snap_ts[8:10]}:{snap_ts[10:12]}:{snap_ts[12:14]}")
+
+    status = f"{snap_status} " if snap_status else ""
+    avail = "available" if available else "unavailable"
+    await bot.reply(message, f"{url} -> {avail} | {status}{ts_fmt} | {snap_url}")