import os
from typing import Callable

from gym.wrappers.monitoring import video_recorder

from stable_baselines3.common import logger
from stable_baselines3.common.vec_env.base_vec_env import VecEnv, VecEnvObs, VecEnvStepReturn, VecEnvWrapper
from stable_baselines3.common.vec_env.dummy_vec_env import DummyVecEnv
from stable_baselines3.common.vec_env.subproc_vec_env import SubprocVecEnv


class VecVideoRecorder(VecEnvWrapper):
    """
    Wraps a VecEnv or VecEnvWrapper object to record rendered image as mp4 video.
    It requires ffmpeg or avconv to be installed on the machine.

    :param venv:
    :param video_folder: Where to save videos
    :param record_video_trigger: Function that defines when to start recording.
                                        The function takes the current number of step,
                                        and returns whether we should start recording or not.
    :param video_length:  Length of recorded videos
    :param name_prefix: Prefix to the video name
    """

    def __init__(
        self,
        venv: VecEnv,
        video_folder: str,
        record_video_trigger: Callable[[int], bool],
        video_length: int = 200,
        name_prefix: str = "rl-video",
    ):

        VecEnvWrapper.__init__(self, venv)

        self.env = venv
        # Temp variable to retrieve metadata
        temp_env = venv

        # Unwrap to retrieve metadata dict
        # that will be used by gym recorder
        while isinstance(temp_env, VecEnvWrapper):
            temp_env = temp_env.venv

        if isinstance(temp_env, DummyVecEnv) or isinstance(temp_env, SubprocVecEnv):
            metadata = temp_env.get_attr("metadata")[0]
        else:
            metadata = temp_env.metadata

        self.env.metadata = metadata

        self.record_video_trigger = record_video_trigger
        self.video_recorder = None

        self.video_folder = os.path.abspath(video_folder)
        # Create output folder if needed
        os.makedirs(self.video_folder, exist_ok=True)

        self.name_prefix = name_prefix
        self.step_id = 0
        self.video_length = video_length

        self.recording = False
        self.recorded_frames = 0

    def reset(self) -> VecEnvObs:
        obs = self.venv.reset()
        self.start_video_recorder()
        return obs

    def start_video_recorder(self) -> None:
        self.close_video_recorder()

        video_name = f"{self.name_prefix}-step-{self.step_id}-to-step-{self.step_id + self.video_length}"
        base_path = os.path.join(self.video_folder, video_name)
        self.video_recorder = video_recorder.VideoRecorder(
            env=self.env, base_path=base_path, metadata={"step_id": self.step_id}
        )

        self.video_recorder.capture_frame()
        self.recorded_frames = 1
        self.recording = True

    def _video_enabled(self) -> bool:
        return self.record_video_trigger(self.step_id)

    def step_wait(self) -> VecEnvStepReturn:
        obs, rews, dones, infos = self.venv.step_wait()

        self.step_id += 1
        if self.recording:
            self.video_recorder.capture_frame()
            self.recorded_frames += 1
            if self.recorded_frames > self.video_length:
                logger.info("Saving video to ", self.video_recorder.path)
                self.close_video_recorder()
        elif self._video_enabled():
            self.start_video_recorder()

        return obs, rews, dones, infos

    def close_video_recorder(self) -> None:
        if self.recording:
            self.video_recorder.close()
        self.recording = False
        self.recorded_frames = 1

    def close(self) -> None:
        VecEnvWrapper.close(self)
        self.close_video_recorder()

    def __del__(self):
        self.close()
