import asyncio
import logging
import app.state as state

logger = logging.getLogger(__name__)

# Constants matching ESP_Code.ino FSM timings (in seconds)
TIME_PER_FLOOR = 2.0
TIME_DOOR_OPENING = 1.5
TIME_DOORS_OPEN = 4.0
TIME_DOOR_CLOSING = 1.5

async def run_elevator_simulator():
    """
    Virtual Elevator Simulator that runs as a background task.
    Monitors state.elevator_cmd_event, updates state.elevator_state,
    and broadcasts state transitions via Server-Sent Events (SSE).
    """
    logger.info("Virtual Elevator Simulator started")
    
    # Initialize state
    state.elevator_state.Floor = 1
    state.elevator_state.Dir = "IDLE"
    state.elevator_state.Doors = "CLOSED"
    state.elevator_state.State = "IDLE"
    
    while True:
        try:
            # Wait until a command is set
            await state.elevator_cmd_event.wait()
            
            cmd = state.elevator_cmd
            if not cmd or not cmd.startswith("CALL_"):
                state.elevator_cmd_event.clear()
                await asyncio.sleep(0.1)
                continue
                
            try:
                target_floor = int(cmd.split("_")[1])
            except (IndexError, ValueError):
                logger.error("Invalid elevator command format: %s", cmd)
                state.elevator_cmd = None
                state.elevator_cmd_event.clear()
                continue
                
            current_floor = state.elevator_state.Floor
            if target_floor == current_floor:
                logger.info("Elevator is already at target floor %d", target_floor)
                state.elevator_cmd = None
                state.elevator_cmd_event.clear()
                continue
                
            # Consume the command
            state.elevator_cmd = None
            state.elevator_cmd_event.clear()
            
            # 1. State: MOVING
            state.elevator_state.State = "MOVING"
            state.elevator_state.Dir = "UP" if target_floor > current_floor else "DOWN"
            state.elevator_state.Doors = "CLOSED"
            
            logger.info("Elevator moving from floor %d to %d (%s)", current_floor, target_floor, state.elevator_state.Dir)
            await state.broadcast("elevator", {
                "Floor": state.elevator_state.Floor,
                "Dir": state.elevator_state.Dir,
                "Doors": state.elevator_state.Doors,
                "State": state.elevator_state.State,
            })
            
            # Move floor-by-floor
            step = 1 if target_floor > current_floor else -1
            while state.elevator_state.Floor != target_floor:
                await asyncio.sleep(TIME_PER_FLOOR)
                state.elevator_state.Floor += step
                logger.info("Elevator reached floor %d", state.elevator_state.Floor)
                await state.broadcast("elevator", {
                    "Floor": state.elevator_state.Floor,
                    "Dir": state.elevator_state.Dir,
                    "Doors": state.elevator_state.Doors,
                    "State": state.elevator_state.State,
                })
                
            # 2. State: DOORS_OPENING
            state.elevator_state.Dir = "IDLE"
            state.elevator_state.State = "DOORS_OPENING"
            state.elevator_state.Doors = "OPENING"
            logger.info("Elevator arrived at floor %d. Opening doors...", state.elevator_state.Floor)
            await state.broadcast("elevator", {
                "Floor": state.elevator_state.Floor,
                "Dir": state.elevator_state.Dir,
                "Doors": state.elevator_state.Doors,
                "State": state.elevator_state.State,
            })
            await asyncio.sleep(TIME_DOOR_OPENING)
            
            # 3. State: DOORS_OPEN
            state.elevator_state.State = "DOORS_OPEN"
            state.elevator_state.Doors = "OPEN"
            logger.info("Elevator doors are OPEN at floor %d", state.elevator_state.Floor)
            await state.broadcast("elevator", {
                "Floor": state.elevator_state.Floor,
                "Dir": state.elevator_state.Dir,
                "Doors": state.elevator_state.Doors,
                "State": state.elevator_state.State,
            })
            await asyncio.sleep(TIME_DOORS_OPEN)
            
            # 4. State: DOORS_CLOSING
            state.elevator_state.State = "DOORS_CLOSING"
            state.elevator_state.Doors = "CLOSING"
            logger.info("Elevator doors are CLOSING at floor %d", state.elevator_state.Floor)
            await state.broadcast("elevator", {
                "Floor": state.elevator_state.Floor,
                "Dir": state.elevator_state.Dir,
                "Doors": state.elevator_state.Doors,
                "State": state.elevator_state.State,
            })
            await asyncio.sleep(TIME_DOOR_CLOSING)
            
            # 5. State: IDLE / CLOSED
            state.elevator_state.State = "IDLE"
            state.elevator_state.Doors = "CLOSED"
            logger.info("Elevator is now IDLE at floor %d", state.elevator_state.Floor)
            await state.broadcast("elevator", {
                "Floor": state.elevator_state.Floor,
                "Dir": state.elevator_state.Dir,
                "Doors": state.elevator_state.Doors,
                "State": state.elevator_state.State,
            })
            
        except asyncio.CancelledError:
            logger.info("Elevator simulator task cancelled")
            break
        except Exception as e:
            logger.error("Exception in elevator simulator: %s", e, exc_info=True)
            await asyncio.sleep(1.0)