cleveragents-core/tools/_mcp_common.py

"""Shared helpers for the project's MCP servers.

Each ``tools/mcp_*_server.py`` is a per-server process (per the design
in ``docs/development/...`` — graphify, ci, forgejo, git, handoff,
block_store), but they all share:

1. **Forgejo runtime context.** The ``_claim_runtime`` helpers expect
   a ``RuntimeContext`` protocol object with ``token``,
   ``request_timeout_s``, ``api_retries``, ``claim_ttl_seconds``,
   ``owner``, ``repo``. Three MCPs (``ci``, ``forgejo``, ``git``) all
   need to build one from env. Factored out so a PAT rotation or
   default-tweak lands in one place.

2. **Identity selection (HAL9000 vs HAL9001).** Most write operations
   use the worker identity (``FORGEJO_PAT`` — HAL9000), but the
   reviewer's formal review submissions and umbrella-PR approvals use
   the reviewer identity (``FORGEJO_REVIEWER_PAT`` — HAL9001). Passing
   ``reviewer=True`` to :class:`ForgejoCfg` produces a context with
   the HAL9001 token while leaving owner/repo/timeouts alone.

3. **Sibling-module loader bootstrap.** Every MCP server inserts
   ``tools/`` into ``sys.path`` and imports ``load_sibling`` to load
   non-package siblings (``_claim_runtime``, ``_review_fetch``, etc.).
   :func:`bootstrap_loader` does the path insert + import in one call.

4. **Error envelope shape.** Tools return ``{"error": str, **fields}``
   so the agent's parser branches once on a single key. Centralised
   here as :func:`error_envelope`.

5. **Process entrypoint.** Every server's ``main()`` is the same
   try/run/KeyboardInterrupt/Exception wrapper. :func:`make_main`
   builds one bound to the server name for stderr labelling.

Kept deliberately small. If something only one MCP needs, it lives in
that MCP's file — not here.
"""
from __future__ import annotations

import os
import sys
from pathlib import Path
from types import ModuleType
from typing import Any, Callable


# ─── Runtime tuning ────────────────────────────────────────────────
# Per-call HTTP timeout for Forgejo API requests issued from the MCP
# servers. The default matches what the dispatchers use for similar
# read paths; bump via env if a slow Forgejo causes spurious tool
# errors during a long worker cycle.
_FORGEJO_TIMEOUT_S = int(os.environ.get("MCP_FORGEJO_TIMEOUT_S", "15"))
_FORGEJO_RETRIES = int(os.environ.get("MCP_FORGEJO_RETRIES", "3"))


class ForgejoCfg:
    """Minimal RuntimeContext satisfying ``_claim_runtime``'s
    protocol, plus the ``owner`` / ``repo`` fields the ``_review_*``
    helpers read directly.

    Constructed per-call (cheap — just env reads) so a PAT rotation
    on the dispatcher side is picked up without restarting the MCP
    server. The ``reviewer`` flag selects HAL9001's PAT instead of
    HAL9000's — used by tools that act on behalf of the umbrella
    approver identity (notably the reviewer worker's review-submit
    path).
    """

    def __init__(self, *, reviewer: bool = False) -> None:
        if reviewer:
            self.token = os.environ.get("FORGEJO_REVIEWER_PAT", "")
        else:
            self.token = os.environ.get("FORGEJO_PAT", "")
        self.request_timeout_s = _FORGEJO_TIMEOUT_S
        self.api_retries = _FORGEJO_RETRIES
        # Unused by reads but required by the RuntimeContext protocol.
        # Defaults match the implementer dispatcher's own claim_ttl.
        self.claim_ttl_seconds = int(os.environ.get("MCP_CLAIM_TTL_S", "7200"))
        # ``_review_*`` helpers read these directly off cfg rather
        # than the module-level fallbacks in ``_claim_runtime``.
        self.owner = os.environ.get("FORGEJO_OWNER", "cleveragents")
        self.repo = os.environ.get("FORGEJO_REPO", "cleveragents-core")


def require_token(cfg: ForgejoCfg, identity_label: str) -> str | None:
    """Return ``None`` if ``cfg.token`` is set; otherwise an
    error-message string the MCP tool can return verbatim to the
    agent. Centralised so every tool prints the same actionable
    message ("set X env var") instead of opaque HTTP-401 errors."""
    if cfg.token:
        return None
    env_name = (
        "FORGEJO_REVIEWER_PAT" if identity_label == "reviewer" else "FORGEJO_PAT"
    )
    return (
        f"{env_name} not set in MCP environment "
        f"(identity={identity_label}). The MCP server inherits env from "
        "the OpenCode process that spawned it — restart OpenCode after "
        "sourcing tools/launch_fork.sh."
    )


# ─── Sibling-module loader ──────────────────────────────────────────


def bootstrap_loader() -> Callable[[str, str], ModuleType]:
    """Insert ``tools/`` into ``sys.path`` and return ``load_sibling``.

    Every MCP server starts with the same 3-line dance:

        sys.path.insert(0, str(Path(__file__).parent))
        from _loader import load_sibling

    Wrapped here so a server's prelude becomes one expression::

        load_sibling = bootstrap_loader()
        _claim_runtime = load_sibling("_claim_runtime", "_claim_runtime.py")
    """
    tools_dir = str(Path(__file__).resolve().parent)
    if tools_dir not in sys.path:
        sys.path.insert(0, tools_dir)
    from _loader import load_sibling  # noqa: E402 — deliberately late
    return load_sibling


# ─── Error envelope ────────────────────────────────────────────────


def error_envelope(error: str, **fields: Any) -> dict[str, Any]:
    """Uniform error envelope shape used by every MCP tool.

    Tools return ``{"error": str, **fields}`` so the agent's parser
    branches once on the ``error`` key. Tools that return collections
    on success include the empty collection in ``fields`` so the
    agent's parsing code stays the same on error and success.
    """
    return {"error": error, **fields}


# ─── Process entrypoint ────────────────────────────────────────────


def make_main(server: Any, server_name: str) -> Callable[[], int]:
    """Build a ``main()`` for an MCP server bound to ``server``.

    Returns a zero-arg function suitable for ``sys.exit(main())``.
    Same shape every MCP used to inline: KeyboardInterrupt → 0,
    any other Exception → log to stderr + return 1.

    ``server_name`` appears in the stderr fatal line; OpenCode logs
    that to its server output so operators can tell which MCP died.
    """
    def main() -> int:
        try:
            server.run()
        except KeyboardInterrupt:
            return 0
        except Exception as exc:  # noqa: BLE001 — top-of-process catch
            print(f"{server_name}: fatal: {exc!r}", file=sys.stderr)
            return 1
        return 0
    return main


__all__ = (
    "ForgejoCfg",
    "bootstrap_loader",
    "error_envelope",
    "make_main",
    "require_token",
)