iai-mcp-opencode/src/iai_mcp/http_server.py

"""Tier-1 localhost HTTP adapter over core.dispatch (PoC).

Sibling transport to socket_server.py: both are thin adapters around the
single transport-agnostic entry point ``core.dispatch(store, method, params)``
(D7-08 -- one dispatch function per method, no transport branching). This one
speaks HTTP/1.0 on 127.0.0.1 so an MCP host that has *no* server->client push
mechanism (e.g. OpenCode, which ignores the MCP ``instructions`` field) can
still pull session memory into its system prompt by fetching a URL.

PoC SCOPE / NON-GOALS (deliberately minimal -- Tier 1):
  - localhost-only bind. NEVER 0.0.0.0. The unix socket's security boundary is
    filesystem perms (chmod 0o600, T-04-07); a TCP port has none, so we limit
    blast radius to loopback and ship NO auth here. Token auth is the Tier-2
    follow-up before this is anything but a local convenience.
  - one request per connection (Connection: close). No keep-alive, no chunked
    encoding, no HTTP/1.1 pipelining. Simplest robust thing for fetch() clients.
  - disabled unless IAI_DAEMON_HTTP_PORT is set (see daemon.main wiring). Absent
    => no TCP surface at all, identical to today.

Constitutional guards (mirror socket_server.py):
  - C-DISPATCHER-FSM-ISOLATION: this adapter calls core.dispatch ONLY; it never
    touches the daemon FSM. FSM transitions stay owned by daemon.py's tick.
  - C3 ZERO API COST: stdlib + core.dispatch only; no SDK references.
  - C5 LITERAL PRESERVATION: transport-only; zero record mutation here.
  - R3 head-of-line: dispatch is sync + 50-500 ms, so it runs on
    asyncio.to_thread exactly like socket_server.py:257.
  - R5 fail-loud: dispatch raises map to HTTP status codes (see _STATUS_FOR).
"""

from __future__ import annotations

import asyncio
import json
import os
import sys
import time
from pathlib import Path
from typing import Any
from urllib.parse import parse_qs, urlsplit

from iai_mcp.concurrency import SOCKET_PATH
from iai_mcp.core import UnknownMethodError, dispatch

# Discovery file: consumers (OpenCode plugin) read the live port from here,
# mirroring the SOCKET_PATH convention (~/.iai-mcp/.daemon.sock). Sits next to
# the socket so both transports share the one well-known dir.
HTTP_PORT_FILE: Path = SOCKET_PATH.parent / ".http.port"

# dispatch-exception -> HTTP status, mirroring socket_server.py's JSON-RPC code
# mapping (ERR_METHOD_NOT_FOUND/-32601, ERR_INVALID_PARAMS/-32602, ...).
_BAD_REQUEST = 400
_NOT_FOUND = 404
_METHOD_NOT_ALLOWED = 405
_INTERNAL = 500

_MAX_BODY_BYTES = 1 << 20  # 1 MiB cap on POST bodies; refuse larger with 400.


def _payload_to_text(result: Any) -> str:
    """Flatten a session_start_payload dict into a system-prompt-ready block.

    Best-effort and forgiving: any missing/empty key is skipped, so this is
    correct at every wake_depth:
      - standard/deep populate the human-readable content layers
        (l0/l1/rich_club/l2) -- the useful case for system-prompt injection.
      - minimal (the default) leaves those empty and emits only the compact
        pointer/handle fields (~30 tok). Those are opaque references, not
        content; we still surface them on a trailing line so the block is
        never silently empty, but a host that wants real memory text in the
        prompt must run wake_depth>=standard.
    Token-accounting ints and breakpoint_marker are dropped.
    """
    if not isinstance(result, dict):
        return str(result)
    parts: list[str] = []
    headers = {"l0": "## L0 Identity", "l1": "## L1 Recent Summary", "rich_club": "## Rich Club"}
    for key in ("l0", "l1", "rich_club"):
        val = result.get(key)
        if isinstance(val, str) and val.strip():
            parts.append(f"{headers[key]}\n{val.strip()}")
    l2 = result.get("l2")
    if isinstance(l2, list):
        for item in l2:
            text = item if isinstance(item, str) else json.dumps(item, ensure_ascii=False)
            if text.strip():
                parts.append(f"## L2 Episode\n{text.strip()}")
    # Compact handles (populated at minimal; also present at standard/deep).
    handles = [
        result.get(k)
        for k in ("identity_pointer", "compact_handle", "brain_handle", "topic_cluster_hint")
    ]
    handles = [h for h in handles if isinstance(h, str) and h.strip()]
    if handles:
        parts.append(f"## Handles\n{' '.join(handles)}")
    return "\n\n".join(parts)


class HttpServer:
    """Per-connection HTTP/1.0 server routing to core.dispatch.

    Routes (all GET unless noted):
      - GET  /healthz                      -> {"ok": true} (no dispatch)
      - GET  /memory/session-context       -> dispatch("session_start_payload",
                                              {session_id?}); ?format=text returns
                                              a flattened text/plain block.
      - POST /rpc  {method, params}         -> dispatch(method, params); generic
                                              passthrough mirroring the socket.

    Constructor args mirror SocketServer: a shared MemoryStore singleton plus
    bind knobs. shutdown_event lets daemon.main drain gracefully.
    """

    def __init__(
        self,
        store: Any,
        *,
        host: str = "127.0.0.1",
        port: int = 0,
        port_file: Path | None = None,
    ) -> None:
        self.store = store
        self.host = host
        self.port = port  # 0 => OS-assigned ephemeral port (written to port_file)
        self.port_file = port_file if port_file is not None else HTTP_PORT_FILE
        self.bound_port: int | None = None
        self.last_activity_ts: float = time.monotonic()
        self.active_connections: int = 0
        self.shutdown_event: asyncio.Event = asyncio.Event()

    # -- request parsing ----------------------------------------------------

    async def _read_request(
        self, reader: asyncio.StreamReader
    ) -> tuple[str, str, dict[str, str], bytes] | None:
        """Parse one HTTP request. Returns (method, target, headers, body) or None on EOF."""
        request_line = await reader.readline()
        if not request_line:
            return None
        try:
            method, target, _version = request_line.decode("latin-1").rstrip("\r\n").split(" ", 2)
        except ValueError:
            raise _HttpError(_BAD_REQUEST, "malformed request line")
        headers: dict[str, str] = {}
        while True:
            line = await reader.readline()
            if line in (b"\r\n", b"\n", b""):
                break
            raw = line.decode("latin-1").rstrip("\r\n")
            if ":" in raw:
                name, _, value = raw.partition(":")
                headers[name.strip().lower()] = value.strip()
        body = b""
        length = headers.get("content-length")
        if length is not None:
            try:
                n = int(length)
            except ValueError:
                raise _HttpError(_BAD_REQUEST, "bad content-length")
            if n > _MAX_BODY_BYTES:
                raise _HttpError(_BAD_REQUEST, "body too large")
            if n > 0:
                body = await reader.readexactly(n)
        return method.upper(), target, headers, body

    # -- routing ------------------------------------------------------------

    async def _route(self, method: str, target: str, body: bytes) -> tuple[int, str, str]:
        """Return (status, content_type, text). Raises _HttpError for 4xx/5xx shapes."""
        split = urlsplit(target)
        path = split.path
        query = parse_qs(split.query)

        if path == "/healthz":
            if method != "GET":
                raise _HttpError(_METHOD_NOT_ALLOWED, "GET only")
            return 200, "application/json", json.dumps({"ok": True})

        if path == "/memory/session-context":
            if method != "GET":
                raise _HttpError(_METHOD_NOT_ALLOWED, "GET only")
            session_id = (query.get("session_id") or [None])[0]
            params: dict = {}
            if session_id:
                params["session_id"] = session_id
            # Per-call wake_depth override (minimal|standard|deep). standard/deep
            # populate l0/l1/l2/rich_club -- the content worth injecting into a
            # system prompt; core.py validates and ignores junk values.
            wake_depth = (query.get("wake_depth") or [None])[0]
            if wake_depth:
                params["wake_depth"] = wake_depth
            result = await self._dispatch("session_start_payload", params)
            if (query.get("format") or ["json"])[0] == "text":
                return 200, "text/plain; charset=utf-8", _payload_to_text(result)
            return 200, "application/json", json.dumps(result, ensure_ascii=False)

        if path == "/rpc":
            if method != "POST":
                raise _HttpError(_METHOD_NOT_ALLOWED, "POST only")
            try:
                envelope = json.loads(body or b"{}")
            except json.JSONDecodeError as e:
                raise _HttpError(_BAD_REQUEST, f"invalid json: {e}")
            if not isinstance(envelope, dict) or not isinstance(envelope.get("method"), str):
                raise _HttpError(_BAD_REQUEST, "expected {method, params}")
            result = await self._dispatch(envelope["method"], envelope.get("params") or {})
            return 200, "application/json", json.dumps(result, ensure_ascii=False)

        raise _HttpError(_NOT_FOUND, f"no route for {path}")

    async def _dispatch(self, method: str, params: dict) -> Any:
        """Run core.dispatch off-loop (R3) and map raises to _HttpError (R5)."""
        try:
            # CRITICAL R3: dispatch is sync + 50-500 ms; to_thread prevents
            # head-of-line blocking across connections (same as socket_server).
            return await asyncio.to_thread(dispatch, self.store, method, params)
        except UnknownMethodError as e:
            raise _HttpError(_NOT_FOUND, f"unknown method '{e.args[0]}'")
        except KeyError as e:
            raise _HttpError(_BAD_REQUEST, f"missing required param: {e.args[0]!r}")
        except TypeError as e:
            raise _HttpError(_BAD_REQUEST, str(e))
        except Exception as e:  # noqa: BLE001 -- HTTP must never crash daemon
            raise _HttpError(_INTERNAL, str(e))

    # -- connection handler -------------------------------------------------

    async def handle(self, reader: asyncio.StreamReader, writer: asyncio.StreamWriter) -> None:
        """One coroutine per connection. Reads one request, responds, closes."""
        self.active_connections += 1
        t0 = time.monotonic()
        method, target = "-", "-"
        try:
            self.last_activity_ts = t0
            try:
                parsed = await self._read_request(reader)
                if parsed is None:
                    return
                method, target, _headers, body = parsed
                status, content_type, text = await self._route(method, target, body)
            except _HttpError as e:
                status, content_type, text = e.status, "application/json", json.dumps(
                    {"error": e.message}
                )
            except asyncio.IncompleteReadError:
                status, content_type, text = _BAD_REQUEST, "application/json", json.dumps(
                    {"error": "truncated body"}
                )
            self._write_response(writer, status, content_type, text)
            await writer.drain()
            # Per-request access log -> stderr (journal). Matches the daemon's
            # existing {"event":...} JSON-line style so it greps cleanly.
            print(
                json.dumps({
                    "event": "http_request",
                    "method": method,
                    "target": target,
                    "status": status,
                    "bytes": len(text.encode("utf-8")),
                    "ms": round((time.monotonic() - t0) * 1000),
                }),
                file=sys.stderr,
                flush=True,
            )
        except (ConnectionResetError, BrokenPipeError, ConnectionAbortedError):
            # Client hung up mid-write (fetch aborted, host killed). Expected;
            # not a daemon fault -- mirrors socket_server.py's handling.
            pass
        finally:
            self.active_connections -= 1
            try:
                writer.close()
                await writer.wait_closed()
            except Exception:
                pass

    @staticmethod
    def _write_response(
        writer: asyncio.StreamWriter, status: int, content_type: str, text: str
    ) -> None:
        body = text.encode("utf-8")
        reason = {
            200: "OK", 400: "Bad Request", 404: "Not Found",
            405: "Method Not Allowed", 500: "Internal Server Error",
        }.get(status, "OK")
        head = (
            f"HTTP/1.0 {status} {reason}\r\n"
            f"Content-Type: {content_type}\r\n"
            f"Content-Length: {len(body)}\r\n"
            "Connection: close\r\n"
            "\r\n"
        )
        writer.write(head.encode("latin-1") + body)

    # -- lifecycle ----------------------------------------------------------

    async def serve(self) -> None:
        """Bind 127.0.0.1:port, write the port-file, serve until shutdown_event."""
        server = await asyncio.start_server(self.handle, host=self.host, port=self.port)
        self.bound_port = server.sockets[0].getsockname()[1]
        # Discovery: publish the live port so consumers needn't guess. Best
        # effort -- a failed write just means callers must be told the port.
        try:
            self.port_file.parent.mkdir(parents=True, exist_ok=True)
            self.port_file.write_text(str(self.bound_port), encoding="utf-8")
            os.chmod(self.port_file, 0o600)
        except OSError:
            pass
        try:
            async with server:
                await self.shutdown_event.wait()
                server.close()
                await server.wait_closed()
        finally:
            try:
                self.port_file.unlink()
            except (FileNotFoundError, OSError):
                pass


class _HttpError(Exception):
    """Internal control-flow exception carrying an HTTP status + message."""

    def __init__(self, status: int, message: str) -> None:
        super().__init__(message)
        self.status = status
        self.message = message