unreal-engine-mcp-system-plugin/ue_side/variables.py

"""Blueprint member-variable authoring ops.

Wraps the (already-compiled) C++ helpers on unreal.MCPGraphLibrary:
  AddMemberVariable / SetVariableDefaultValue / SetVariableMetadata /
  RenameVariable / DeleteVariable / DescribeBlueprintJson.

Reachable from JS as the `variable_op` tool, and also merged into `asset_op`'s
op-table for zero-restart availability (see assets.py).

Ops:
  add    {bp_path, name, type, default?, instance_editable?, expose_on_spawn?,
          category?, tooltip?}   — create a member variable, optionally set its
                                    default value + metadata. type is one of
                                    bool|int|float|double|string|name|text or a
                                    class path / short name for an object ref.
  set_default {bp_path, name, value}
  set_meta    {bp_path, name, instance_editable?, expose_on_spawn?, category?, tooltip?}
  rename      {bp_path, old, new}
  delete      {bp_path, name}
  list        {bp_path}          — current member variables (name+type) as JSON.
"""
from __future__ import annotations

import json
import os
import traceback

try:
    import unreal  # type: ignore
except ImportError:
    unreal = None


def _lib():
    L = getattr(unreal, "MCPGraphLibrary", None)
    if L is None:
        raise RuntimeError("MCPGraphLibrary missing — rebuild C++ plugin")
    return L


def _load_bp(path: str):
    a = unreal.EditorAssetLibrary.load_asset(path)
    if not isinstance(a, unreal.Blueprint):
        raise RuntimeError(f"not a blueprint: {path!r}")
    return a


def _compile_save(bp):
    _lib().compile_and_save_blueprint(bp)
    unreal.EditorAssetLibrary.save_loaded_asset(bp)


def _variables(bp) -> list:
    """Return [{name,type,...}] from DescribeBlueprintJson."""
    try:
        info = json.loads(_lib().describe_blueprint_json(bp))
        return info.get("variables", [])
    except Exception:  # noqa: BLE001
        return []


def _has_var(bp, name: str) -> bool:
    return any(v.get("name") == name for v in _variables(bp))


def add(args: dict) -> dict:
    bp = _load_bp(args["bp_path"])
    name = args["name"]
    type_spec = args.get("type") or args.get("type_spec")
    if not name or not type_spec:
        return {"ok": False, "error": "add requires {name, type}"}
    if _has_var(bp, name):
        return {"ok": False, "error": f"variable {name!r} already exists", "exists": True}

    ok = bool(_lib().add_member_variable(bp, name, type_spec))
    if not ok:
        return {"ok": False, "error": f"add_member_variable failed (bad type {type_spec!r}?)"}

    # Optional default value + metadata in the same transaction.
    if "default" in args and args["default"] is not None:
        _lib().set_variable_default_value(bp, name, str(args["default"]))
    if any(k in args for k in ("instance_editable", "expose_on_spawn", "category", "tooltip")):
        _lib().set_variable_metadata(
            bp, name,
            bool(args.get("instance_editable", False)),
            bool(args.get("expose_on_spawn", False)),
            str(args.get("category", "")),
            str(args.get("tooltip", "")),
        )
    _compile_save(bp)
    return {"ok": True, "name": name, "type": type_spec}


def set_default(args: dict) -> dict:
    bp = _load_bp(args["bp_path"])
    ok = bool(_lib().set_variable_default_value(bp, args["name"], str(args.get("value", ""))))
    if ok: _compile_save(bp)
    return {"ok": ok, "name": args["name"]}


def set_meta(args: dict) -> dict:
    bp = _load_bp(args["bp_path"])
    ok = bool(_lib().set_variable_metadata(
        bp, args["name"],
        bool(args.get("instance_editable", False)),
        bool(args.get("expose_on_spawn", False)),
        str(args.get("category", "")),
        str(args.get("tooltip", "")),
    ))
    if ok: _compile_save(bp)
    return {"ok": ok, "name": args["name"]}


def rename(args: dict) -> dict:
    bp = _load_bp(args["bp_path"])
    ok = bool(_lib().rename_variable(bp, args["old"], args["new"]))
    if ok: _compile_save(bp)
    return {"ok": ok, "old": args["old"], "new": args["new"]}


def delete(args: dict) -> dict:
    bp = _load_bp(args["bp_path"])
    ok = bool(_lib().delete_variable(bp, args["name"]))
    if ok: _compile_save(bp)
    return {"ok": ok, "name": args["name"]}


def list_vars(args: dict) -> dict:
    bp = _load_bp(args["bp_path"])
    return {"ok": True, "variables": _variables(bp)}


# op-table — also merged into assets.OPS for zero-restart availability.
VAR_OPS = {
    "add_variable":     add,
    "add":              add,
    "set_var_default":  set_default,
    "set_default":      set_default,
    "set_var_meta":     set_meta,
    "set_meta":         set_meta,
    "rename_variable":  rename,
    "rename":           rename,
    "delete_variable":  delete,
    "delete":           delete,
    "list_variables":   list_vars,
    "list":             list_vars,
}


def entrypoint(payload_json: str) -> str:
    try:
        p = json.loads(payload_json)
    except Exception as e:  # noqa: BLE001
        return _tee({"ok": False, "error": f"bad json: {e}"}, {})
    op = p.get("op")
    fn = VAR_OPS.get(op)
    if not fn:
        return _tee({"ok": False, "error": f"unknown op {op!r}", "available": sorted(VAR_OPS)}, p)
    try:
        return _tee(fn(p), p)
    except Exception as e:  # noqa: BLE001
        return _tee({"ok": False, "error": str(e), "traceback": traceback.format_exc()}, p)


def _tee(result: dict, p: dict) -> str:
    txt = json.dumps(result)
    try:
        if unreal is not None:
            sd = unreal.Paths.project_saved_dir() + "MCP/"
            os.makedirs(sd, exist_ok=True)
            rid = p.get("__rid") or "last"
            with open(sd + "last.json", "w", encoding="utf-8") as f:
                f.write(txt)
            if rid != "last":
                with open(sd + f"{rid}.json", "w", encoding="utf-8") as f:
                    f.write(txt)
            unreal.log("[MCP-VARS] " + txt[:1500])
    except Exception:
        pass
    return txt