httpserver: Rewrite without the cgi module

It is removed in Python 3.13

src/httpserver.py

@@ -1,5 +1,5 @@
 ###
-# Copyright (c) 2011-2021, Valentin Lorentz
+# Copyright (c) 2011-2024, Valentin Lorentz
 # All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -32,8 +32,8 @@ An embedded and centralized HTTP server for Supybot's plugins.
 """
 
 import os
-import cgi
 import socket
+import urllib.parse
 from threading import Thread
 
 import supybot.log as log
@@ -164,6 +164,114 @@ def get_template(filename):
         with open(path + '.example', 'r') as fd:
             return fd.read()
 
+class HttpHeader:
+    __slots__ = ('name', 'value')
+
+    def __init__(self, name, value):
+        self.name = name
+        self.value = value
+
+    def __repr__(self):
+        """Return printable representation."""
+        return "HttpHeader(%r, %r)" % (self.name, self.value)
+
+class HttpHeaders:
+    """Copy of `cgi.FieldStorage
+    <https://github.com/python/cpython/blob/v3.12.3/Lib/cgi.py#L512-L594>`
+    before it was removed from the stdlib.
+    """
+    __slots__ = ('list',)
+    def __init__(self, headers):
+        self.list = headers
+
+    def __repr__(self):
+        return 'HttpHeaders(%r)' % self.list
+
+    def __iter__(self):
+        return iter(self.keys())
+
+    def __getattr__(self, name):
+        if name != 'value':
+            raise AttributeError(name)
+        if self.file:
+            self.file.seek(0)
+            value = self.file.read()
+            self.file.seek(0)
+        elif self.list is not None:
+            value = self.list
+        else:
+            value = None
+        return value
+
+    def __getitem__(self, key):
+        """Dictionary style indexing."""
+        if self.list is None:
+            raise TypeError("not indexable")
+        found = []
+        for item in self.list:
+            if item.name == key: found.append(item)
+        if not found:
+            raise KeyError(key)
+        if len(found) == 1:
+            return found[0]
+        else:
+            return found
+
+    def getvalue(self, key, default=None):
+        """Dictionary style get() method, including 'value' lookup."""
+        if key in self:
+            value = self[key]
+            if isinstance(value, list):
+                return [x.value for x in value]
+            else:
+                return value.value
+        else:
+            return default
+
+    def getfirst(self, key, default=None):
+        """ Return the first value received."""
+        if key in self:
+            value = self[key]
+            if isinstance(value, list):
+                return value[0].value
+            else:
+                return value.value
+        else:
+            return default
+
+    def getlist(self, key):
+        """ Return list of received values."""
+        if key in self:
+            value = self[key]
+            if isinstance(value, list):
+                return [x.value for x in value]
+            else:
+                return [value.value]
+        else:
+            return []
+
+    def keys(self):
+        """Dictionary style keys() method."""
+        if self.list is None:
+            raise TypeError("not indexable")
+        return list(set(item.name for item in self.list))
+
+    def __contains__(self, key):
+        """Dictionary style __contains__ method."""
+        if self.list is None:
+            raise TypeError("not indexable")
+        return any(item.name == key for item in self.list)
+
+    def __len__(self):
+        """Dictionary style len(x) support."""
+        return len(self.keys())
+
+    def __bool__(self):
+        if self.list is None:
+            raise TypeError("Cannot be converted to bool.")
+        return bool(self.list)
+
+
 class SupyHTTPRequestHandler(BaseHTTPRequestHandler):
     def do_X(self, callbackMethod, *args, **kwargs):
         if self.path == '/':
@@ -199,12 +307,11 @@ class SupyHTTPRequestHandler(BaseHTTPRequestHandler):
         if 'Content-Type' not in self.headers:
             self.headers['Content-Type'] = 'application/x-www-form-urlencoded'
         if self.headers['Content-Type'] == 'application/x-www-form-urlencoded':
-            form = cgi.FieldStorage(
-                fp=self.rfile,
-                headers=self.headers,
-                environ={'REQUEST_METHOD':'POST',
-                         'CONTENT_TYPE':self.headers['Content-Type'],
-                         })
+            length = min(100000, int(self.headers.get('Content-Length', '100000')))
+            qs = self.rfile.read(length).decode()
+            form = HttpHeaders([
+                HttpHeader(k, v) for (k, v) in urllib.parse.parse_qsl(qs)
+            ])
         else:
             content_length = int(self.headers.get('Content-Length', '0'))
             form = self.rfile.read(content_length)