feat(webdav3): implement proxy download functionality with CORS support

.gitignore

@@ -4,3 +4,4 @@ files/*
 node_modules/*
 package-lock.json
 __pycache__/*
+api/*

webdav3.py

@@ -43,7 +43,7 @@ from http.server import HTTPServer, BaseHTTPRequestHandler
 from socketserver import ThreadingMixIn
 import urllib.request, urllib.parse, urllib.error, urllib.parse
 from time import timezone, strftime, localtime, gmtime
-import os, sys, re, shutil, struct, threading, uuid, hashlib, mimetypes, base64, socket
+import os, sys, re, shutil, struct, threading, uuid, hashlib, mimetypes, base64, socket, json
 
 _ws_lock    = threading.Lock()
 _ws_clients: set = set()   # connected WebSocket sockets
@@ -541,8 +541,17 @@ class DAVRequestHandler(BaseHTTPRequestHandler):
       return False 
 
   def do_OPTIONS(self):
+    # CORS preflight for /proxy-download (called by browser before POST)
+    if self.path == '/proxy-download':
+      self.send_response(204)
+      self.send_header('Access-Control-Allow-Origin', '*')
+      self.send_header('Access-Control-Allow-Methods', 'POST, OPTIONS')
+      self.send_header('Access-Control-Allow-Headers', 'Content-Type')
+      self.send_header('Content-Length', '0')
+      self.end_headers()
+      return
     if self.WebAuth():
-      return 
+      return
     self.send_response(200, DAVRequestHandler.server_version)
     self.send_header('Allow', 'GET, HEAD, POST, PUT, DELETE, OPTIONS, PROPFIND, PROPPATCH, MKCOL, LOCK, UNLOCK, MOVE, COPY')
     self.send_header('Content-length', '0')
@@ -936,6 +945,64 @@ class DAVRequestHandler(BaseHTTPRequestHandler):
       self.send_header('Content-length', '0')
       self.end_headers()
 
+  # ── Proxy download ─────────────────────────────────────────────────────────
+  # The browser cannot fetch third-party binary URLs that return duplicate
+  # Access-Control-Allow-Origin headers (e.g. Assembly64 /search/bin/).
+  # POST /proxy-download { "url": "...", "dest": "/sd/downloads/file.d64",
+  #                        "headers": { "Client-Id": "Ultimate", ... } }
+  # The server fetches the URL with Python (no CORS restrictions) and saves
+  # the binary to the filesystem under the WebDAV root.
+
+  def _json_response(self, status: int, data: dict):
+    body = json.dumps(data).encode('utf-8')
+    self.send_response(status)
+    self.send_header('Content-Type', 'application/json')
+    self.send_header('Content-Length', str(len(body)))
+    self.send_header('Access-Control-Allow-Origin', '*')
+    self.end_headers()
+    self.wfile.write(body)
+
+  def do_POST(self):
+    if self.path != '/proxy-download':
+      self.send_error(404, 'Not found')
+      return
+    try:
+      size = int(self.headers.get('Content-Length', 0))
+      body = self.rfile.read(size)
+      req_data = json.loads(body)
+      url  = req_data['url']
+      dest = req_data['dest']
+      extra_headers = req_data.get('headers', {})
+    except Exception as e:
+      self._json_response(400, {'error': f'Bad request: {e}'})
+      return
+    # Map virtual dest path (/sd/downloads/foo.d64) to filesystem path
+    vpath = urllib.parse.unquote(dest).lstrip('/')
+    if '..' in vpath.split('/'):
+      self._json_response(400, {'error': 'Invalid path'})
+      return
+    fspath = os.path.join(self.server.root.fsname, *vpath.split('/'))
+    # Fetch the URL server-side (no browser CORS restrictions apply here)
+    try:
+      req = urllib.request.Request(url, headers=extra_headers)
+      with urllib.request.urlopen(req, timeout=30) as resp:
+        data = resp.read()
+    except Exception as e:
+      _log('PROXY', f'Fetch failed: {url} → {e}')
+      self._json_response(502, {'error': f'Fetch failed: {e}'})
+      return
+    # Save to filesystem, creating directories as needed
+    try:
+      os.makedirs(os.path.dirname(fspath), exist_ok=True)
+      with open(fspath, 'wb') as f:
+        f.write(data)
+    except Exception as e:
+      _log('PROXY', f'Save failed: {fspath} → {e}')
+      self._json_response(500, {'error': f'Save failed: {e}'})
+      return
+    _log('PROXY', f'{url} → {fspath} ({len(data)} bytes)')
+    self._json_response(200, {'ok': True, 'bytes': len(data)})
+
   def split_path(self, path):
     """Splits path string in form '/dir1/dir2/file' into parts"""
     p = path.split('/')[1:]