"""
Debugger API — pause / resume / step an in-flight pipeline.

The engine is set by main.py on startup via `set_engine(...)`. If no
engine is registered (e.g. when running the mock server), endpoints
return a structured error rather than crashing.
"""

from fastapi import APIRouter
from typing import Optional, Any

router = APIRouter(prefix="/debugger", tags=["debugger"])

# Single in-memory engine reference (set by main.py)
_ENGINE: Optional[Any] = None
_DEBUG_STATE: dict = {
    "paused": False,
    "current_step": 0,
    "history": [],
}


def set_engine(engine):
    global _ENGINE
    _ENGINE = engine


def get_engine():
    return _ENGINE


# -----------------------------
# RESUME
# -----------------------------
@router.post("/resume")
def resume():
    _DEBUG_STATE["paused"] = False
    if _ENGINE and hasattr(_ENGINE, "resume"):
        _ENGINE.resume()
    return {"state": "running"}


# -----------------------------
# PAUSE
# -----------------------------
@router.post("/pause")
def pause():
    _DEBUG_STATE["paused"] = True
    if _ENGINE and hasattr(_ENGINE, "pause"):
        _ENGINE.pause()
    return {"state": "paused"}


# -----------------------------
# STEP
# -----------------------------
@router.post("/step")
def step():
    if _ENGINE and hasattr(_ENGINE, "step"):
        _ENGINE.step()
    _DEBUG_STATE["current_step"] += 1
    return {"state": "stepped", "step": _DEBUG_STATE["current_step"]}


# -----------------------------
# STEP BACK (replay-only)
# -----------------------------
@router.post("/step-back")
def step_back():
    if _DEBUG_STATE["current_step"] > 0:
        _DEBUG_STATE["current_step"] -= 1
    return {"state": "stepped_back", "step": _DEBUG_STATE["current_step"]}


# -----------------------------
# STATE
# -----------------------------
@router.get("/state")
def state():
    eng = _ENGINE
    active = eng and hasattr(eng, "is_active") and eng.is_active()
    return {
        "paused": _DEBUG_STATE["paused"],
        "current_step": _DEBUG_STATE["current_step"],
        "engine_attached": eng is not None,
        "engine_active": active,
    }


# -----------------------------
# Legacy wrapper for api.py facade
# -----------------------------
def debugger_endpoint(session_id, registry=None, bus=None):
    """Legacy — return current debugger state for a session."""
    return {
        "session_id": session_id,
        "paused": _DEBUG_STATE["paused"],
        "current_step": _DEBUG_STATE["current_step"],
        "engine_attached": _ENGINE is not None,
    }