1 files changed, 152 insertions, 0 deletions
diff --git a/app.py b/app.py
new file mode 100755
index 0000000..82a1616
--- /dev/null
+++ b/app.py
@@ -0,0 +1,152 @@
+#!/usr/bin/env python3
+
+# Copyright (c) 2022 Egor Tensin <Egor.Tensin@gmail.com>
+# This file is part of the "void" project.
+# For details, see https://github.com/egor-tensin/void.
+# Distributed under the MIT License.
+
+import argparse
+import cgi
+from enum import Enum
+import http.server
+import os
+import sys
+from threading import Lock
+
+
+class Response:
+    DEFAULT_STATUS = http.server.HTTPStatus.OK
+
+    def __init__(self, body, status=None):
+        if status is None:
+            status = Response.DEFAULT_STATUS
+        self.status = status
+        self.body = body
+
+    def headers(self):
+        yield 'Content-Type', 'text/html; charset=utf-8'
+
+    def encode_body(self):
+        return self.body.encode(errors='replace')
+
+    def write_as_cgi_script(self):
+        self.write_headers_as_cgi_script()
+        self.write_body_as_cgi_script()
+
+    def write_headers_as_cgi_script(self):
+        for name, val in self.headers():
+            print(f'{name}: {val}')
+        print()
+
+    def write_body_as_cgi_script(self):
+        if self.body is not None:
+            print(self.body)
+
+    def write_to_request_handler(self, handler):
+        handler.send_response(self.status)
+        self.write_headers_to_request_handler(handler)
+        self.write_body_to_request_handler(handler)
+
+    def write_headers_to_request_handler(self, handler):
+        for name, val in self.headers():
+            handler.send_header(name, val)
+        handler.end_headers()
+
+    def write_body_to_request_handler(self, handler):
+        if self.body is not None:
+            handler.wfile.write(self.encode_body())
+
+
+class Void:
+    def __init__(self, backup_path):
+        self.lck = Lock()
+        self.cnt = 0
+        self.backup_path = backup_path
+        if backup_path is not None:
+            self.backup_path = os.path.abspath(backup_path)
+
+    def __enter__(self):
+        if self.backup_path is not None and os.path.exists(self.backup_path):
+            self.restore(self.backup_path)
+        return self
+
+    def __exit__(self, type, value, traceback):
+        if self.backup_path is not None:
+            os.makedirs(os.path.dirname(self.backup_path), exist_ok=True)
+            self.save(self.backup_path)
+
+    def write(self, fd):
+        with self.lck:
+            cnt = self.cnt
+        fd.write(str(cnt))
+
+    def read(self, fd):
+        src = fd.read()
+        cnt = int(src)
+        with self.lck:
+            self.cnt = cnt
+
+    def save(self, path):
+        with open(path, 'w') as fd:
+            self.write(fd)
+
+    def restore(self, path):
+        with open(path) as fd:
+            self.read(fd)
+
+    def scream_once(self):
+        with self.lck:
+            self.cnt += 1
+            cnt = self.cnt
+        return Response(str(cnt))
+
+    def get_numof_screams(self):
+        with self.lck:
+            cnt = self.cnt
+        return Response(str(cnt))
+
+
+class Request(Enum):
+    SCREAM_ONCE = 'scream'
+    HOW_MANY_SCREAMS = 'screams'
+
+    def __str__(self):
+        return self.value
+
+    @staticmethod
+    def from_http_path(path):
+        if not path or path[0] != '/':
+            raise ValueError('HTTP path must start with a forward slash /')
+        return Request(path[1:])
+
+    def process(self, void):
+        if self is Request.SCREAM_ONCE:
+            return void.scream_once()
+        if self is Request.HOW_MANY_SCREAMS:
+            return void.get_numof_screams()
+        raise NotImplementedError(f'unknown request: {self}')
+
+
+def process_cgi_request(void):
+    params = cgi.FieldStorage()
+    what = params['what'].value
+    Request(what).process(void).write_as_cgi_script()
+
+
+def parse_args(args=None):
+    if args is None:
+        args = sys.argv[1:]
+    parser = argparse.ArgumentParser()
+    parser.add_argument('-v', '--void', metavar='PATH', dest='backup',
+                        help='set path to the void')
+    return parser.parse_args(args)
+
+
+def main(args=None):
+    args = parse_args(args)
+    with Void(args.backup) as void:
+        process_cgi_request(void)
+
+
+if __name__ == '__main__':
+    main()