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

"""Preset library — typical Blueprint patterns packaged as one-line MCP calls.

Each preset is a pure function: args dict → NodeSpec graph dict (apply_graph format).
The dispatcher then runs apply_graph on it.

Add a new preset:
  1. Write `def my_preset(args): return {...nodes/edges...}` below.
  2. Register it in PRESETS at the bottom.
  3. Call via MCP: preset_op({name: "my_preset", args: {...}}).

Ships with:
  print_on_begin_play   {bp_path, text?}              — BeginPlay → PrintString
  print_on_event        {bp_path, event, text?}       — any event → PrintString
  toggle_visibility     {bp_path, event, component}   — event → ToggleVisibility on a component
  damage_drops_health   {bp_path, health_var}         — AnyDamage → Health -= Damage, branch on <=0 → DestroyActor
"""
from __future__ import annotations

import json
import os
import traceback

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


# --- preset implementations ---------------------------------------------------

def print_on_begin_play(args: dict) -> dict:
    text = args.get("text", "BeginPlay")
    return {
        "bp_path": args["bp_path"],
        "function": "EventGraph",
        "mode": "append",
        "nodes": [
            {"id": "ev",    "kind": "event",         "target": "ReceiveBeginPlay", "position": [0, 0]},
            {"id": "print", "kind": "call_function", "target": "/Script/Engine.KismetSystemLibrary:PrintString",
                            "position": [300, 0], "params": {"InString": text}},
        ],
        "edges": [{"from": ["ev", "then"], "to": ["print", "execute"]}],
    }


def print_on_event(args: dict) -> dict:
    event = args["event"]  # e.g. "ReceiveActorBeginOverlap"
    text = args.get("text", event)
    return {
        "bp_path": args["bp_path"],
        "function": "EventGraph",
        "mode": "append",
        "nodes": [
            {"id": "ev",    "kind": "event",         "target": event, "position": [0, 0]},
            {"id": "print", "kind": "call_function", "target": "/Script/Engine.KismetSystemLibrary:PrintString",
                            "position": [300, 0], "params": {"InString": text}},
        ],
        "edges": [{"from": ["ev", "then"], "to": ["print", "execute"]}],
    }


def toggle_visibility(args: dict) -> dict:
    event = args.get("event", "ReceiveActorBeginOverlap")
    comp = args["component"]  # variable name of a SceneComponent on this BP
    return {
        "bp_path": args["bp_path"],
        "function": "EventGraph",
        "mode": "append",
        "nodes": [
            {"id": "ev",     "kind": "event",        "target": event, "position": [0, 0]},
            {"id": "getc",   "kind": "variable_get", "target": comp,  "position": [180, 80]},
            {"id": "toggle", "kind": "call_function",
                             "target": "/Script/Engine.SceneComponent:ToggleVisibility",
                             "position": [380, 0]},
        ],
        "edges": [
            {"from": ["ev",   "then"], "to": ["toggle", "execute"]},
            {"from": ["getc", comp],   "to": ["toggle", "self"]},
        ],
    }


def damage_drops_health(args: dict) -> dict:
    """AnyDamage → Health -= Damage; if Health<=0 → DestroyActor."""
    hv = args.get("health_var", "Health")
    return {
        "bp_path": args["bp_path"],
        "function": "EventGraph",
        "mode": "append",
        "nodes": [
            {"id": "ev",       "kind": "event",         "target": "ReceiveAnyDamage", "position": [-200, 0]},
            {"id": "getH",     "kind": "variable_get",  "target": hv,                  "position": [-20, 60]},
            {"id": "sub",      "kind": "call_function",
                               "target": "/Script/Engine.KismetMathLibrary:Subtract_FloatFloat",
                               "position": [160, 60]},
            {"id": "setH",     "kind": "variable_set",  "target": hv,                  "position": [340, 0]},
            {"id": "getH2",    "kind": "variable_get",  "target": hv,                  "position": [560, 80]},
            {"id": "le",       "kind": "call_function",
                               "target": "/Script/Engine.KismetMathLibrary:LessEqual_FloatFloat",
                               "position": [720, 60]},
            {"id": "br",       "kind": "branch",        "position": [900, 0]},
            {"id": "destroy",  "kind": "call_function",
                               "target": "/Script/Engine.Actor:K2_DestroyActor",
                               "position": [1080, 0]},
        ],
        "edges": [
            {"from": ["ev",    "then"],         "to": ["setH", "execute"]},
            {"from": ["getH",  hv],             "to": ["sub",  "A"]},
            {"from": ["ev",   "Damage"],        "to": ["sub",  "B"]},
            {"from": ["sub",  "ReturnValue"],   "to": ["setH", hv]},
            {"from": ["setH", "then"],          "to": ["br",   "execute"]},
            {"from": ["getH2", hv],             "to": ["le",   "A"]},
            {"from": ["le",   "ReturnValue"],   "to": ["br",   "Condition"]},
            {"from": ["br",   "then"],          "to": ["destroy", "execute"]},
        ],
    }


# --- dispatch -----------------------------------------------------------------

PRESETS = {
    "print_on_begin_play":  print_on_begin_play,
    "print_on_event":       print_on_event,
    "toggle_visibility":    toggle_visibility,
    "damage_drops_health":  damage_drops_health,
}


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}"}, {})
    name = p.get("name")
    if name == "__list__":
        return _tee({"ok": True, "presets": sorted(PRESETS.keys())}, p)
    fn = PRESETS.get(name)
    if not fn:
        return _tee({"ok": False, "error": f"unknown preset {name!r}", "available": sorted(PRESETS.keys())}, p)
    try:
        spec = fn(p.get("args") or {})
        # Run through apply_graph
        import importlib, apply_graph
        importlib.reload(apply_graph)
        result = apply_graph.apply(spec)
        result["preset"] = name
        return _tee(result, p)
    except Exception as e:  # noqa: BLE001
        return _tee({"ok": False, "error": str(e), "traceback": traceback.format_exc(), "preset": name}, 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-PRESET] " + txt[:1500])
    except Exception:
        pass
    return txt