"""
scenarios/cutin.py
------------------
Adjacent Lane Cut-In Scenario.

An NPC vehicle is spawned in the adjacent lane, slightly ahead of the
ego. At a configurable frame it is forced to change into the ego's lane,
simulating an unexpected lane cut-in event.
"""

import sys
import os

sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))

import config
from scenarios.base import ScenarioBase


class CutInScenario(ScenarioBase):
    """
    Scenario: Adjacent lane cut-in.

    Timeline
    --------
    Frame 1 … CUTIN_FRAME-1 : NPC drives in adjacent lane, ahead of ego.
    Frame CUTIN_FRAME+       : TM forced lane change into ego lane.
    """

    NPC_DISTANCE_M  = getattr(config, "SCENARIO_CUTIN_DISTANCE", 15)
    CUTIN_FRAME     = getattr(config, "SCENARIO_CUTIN_FRAME",    60)
    LANE_OFFSET     = -1   # -1 = left lane, 1 = right lane

    def __init__(self):
        super().__init__()
        self._npc = None
        self._cut_triggered = False

    # ------------------------------------------------------------------
    # ScenarioBase interface
    # ------------------------------------------------------------------

    @property
    def name(self) -> str:
        return "cutin"

    def setup(self, world, ego_vehicle, traffic_manager) -> None:
        self._world = world
        self._ego   = ego_vehicle
        self._tm    = traffic_manager

        bp_lib  = world.get_blueprint_library()
        npc_bps = bp_lib.filter("vehicle.audi.*")
        if not npc_bps:
            npc_bps = bp_lib.filter("vehicle.*")
        npc_bp = npc_bps[0]

        # Spawn in adjacent lane, ahead of ego
        spawn_wp = self._get_waypoint_ahead(
            self.NPC_DISTANCE_M, lane_offset=self.LANE_OFFSET
        )
        if spawn_wp is None:
            raise RuntimeError(
                f"[CutInScenario] No adjacent lane waypoint found "
                f"(lane_offset={self.LANE_OFFSET}). "
                "Try a map with multiple lanes."
            )

        self._npc = world.try_spawn_actor(npc_bp, spawn_wp.transform)
        if self._npc is None:
            raise RuntimeError(
                "[CutInScenario] Failed to spawn NPC at "
                f"{spawn_wp.transform.location}. Spot may be occupied."
            )

        self._actors.append(self._npc)

        self._npc.set_autopilot(True, traffic_manager.get_port())
        traffic_manager.auto_lane_change(self._npc, False)   # prevent random changes
        traffic_manager.vehicle_percentage_speed_difference(self._npc, 0)

        print(
            f"[{self.name}] NPC spawned in adjacent lane "
            f"{self.NPC_DISTANCE_M} m ahead. Cut-in at frame {self.CUTIN_FRAME}."
        )

    def step(self, frame_count: int, ego_vehicle, pbar=None) -> None:
        if frame == self.CUTIN_FRAME and not self._cut_triggered:
            if self._npc and self._npc.is_alive:
                # force_lane_change: True = left, False = right
                force_left = (self.LANE_OFFSET < 0)
                self._tm.force_lane_change(self._npc, force_left)
                self._cut_triggered = True
                print(f"[{self.name}] Lane change triggered at frame {frame}.")

    def cleanup(self) -> None:
        self._destroy_actors()
        print(f"[{self.name}] Cleanup complete.")

    # ------------------------------------------------------------------
    # Optional overrides
    # ------------------------------------------------------------------

    def get_scenario_metadata(self) -> dict:
        return {
            "scenario":       self.name,
            "npc_distance_m": self.NPC_DISTANCE_M,
            "cutin_frame":    self.CUTIN_FRAME,
            "lane_offset":    self.LANE_OFFSET,
            "cut_triggered":  self._cut_triggered,
        }