"""W41 回归用的窄代理：HTTP 全放行，只把 /ws/chat 掐掉。

用途：模拟「WS 断了但 HTTP 通」——W41 三级阶梯应该在这种情况下
探测 /api/v1/health 成功、回落 POST /api/v1/chat 把消息发出去。

仅本机开发用；这个文件**在 git 里**（`devtools/ws-block-proxy/`），不再放 `app/build/`——
那里被 gitignore，一次 `gradlew clean` 就把它扫没了。用法见同目录的 README.md。
用法：python ws_block_proxy.py <listen_port> <target_port>
"""

import http.client
import socketserver
import sys

LISTEN = int(sys.argv[1])
TARGET = int(sys.argv[2])
BLOCK = "/ws/chat"

HOP_BY_HOP = {
    "connection", "keep-alive", "proxy-authenticate", "proxy-authorization",
    "te", "trailers", "transfer-encoding", "upgrade",
}


class Handler(socketserver.BaseRequestHandler):
    def handle(self):
        self.request.settimeout(30)
        buf = b""
        while b"\r\n\r\n" not in buf:
            chunk = self.request.recv(4096)
            if not chunk:
                return
            buf += chunk
        head, _, rest = buf.partition(b"\r\n\r\n")
        lines = head.decode("latin-1").split("\r\n")
        method, path, _ = lines[0].split(" ", 2)

        if path.split("?")[0] == BLOCK:
            body = b"ws blocked by test proxy"
            self.request.sendall(
                b"HTTP/1.1 503 Service Unavailable\r\n"
                b"Content-Type: text/plain\r\n"
                b"Content-Length: " + str(len(body)).encode() + b"\r\n\r\n" + body
            )
            print("BLOCKED %s %s" % (method, path), flush=True)
            return

        headers = {}
        for line in lines[1:]:
            k, _, v = line.partition(":")
            if k.lower() in HOP_BY_HOP:
                continue
            headers[k.strip()] = v.strip()

        length = int(headers.get("Content-Length") or 0)
        body = rest
        while len(body) < length:
            more = self.request.recv(length - len(body))
            if not more:
                break
            body += more

        conn = http.client.HTTPConnection("127.0.0.1", TARGET, timeout=60)
        try:
            conn.request(method, path, body=body if length else None, headers=headers)
            resp = conn.getresponse()
            payload = resp.read()
            out = ["HTTP/1.1 %d %s" % (resp.status, resp.reason)]
            for k, v in resp.getheaders():
                if k.lower() in HOP_BY_HOP or k.lower() == "content-length":
                    continue
                out.append("%s: %s" % (k, v))
            out.append("Content-Length: %d" % len(payload))
            self.request.sendall(("\r\n".join(out) + "\r\n\r\n").encode("latin-1") + payload)
            print("PASS %s %s -> %d" % (method, path, resp.status), flush=True)
        except Exception as exc:  # noqa: BLE001
            self.request.sendall(b"HTTP/1.1 502 Bad Gateway\r\nContent-Length: 0\r\n\r\n")
            print("ERR %s %s -> %r" % (method, path, exc), flush=True)
        finally:
            conn.close()


class Server(socketserver.ThreadingTCPServer):
    allow_reuse_address = True
    daemon_threads = True


if __name__ == "__main__":
    print("proxy %d -> 127.0.0.1:%d, blocking %s" % (LISTEN, TARGET, BLOCK), flush=True)
    Server(("127.0.0.1", LISTEN), Handler).serve_forever()