# Copyright (c) 2021 PaddlePaddle Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
This code is based on https://github.com/Zhongdao/Towards-Realtime-MOT/blob/master/tracker/multitracker.py
"""

import numpy as np
from collections import defaultdict
from collections import deque, OrderedDict
from ..matching import jde_matching as matching

__all__ = [
    'TrackState',
    'BaseTrack',
    'STrack',
    'joint_stracks',
    'sub_stracks',
    'remove_duplicate_stracks',
]


class TrackState(object):
    New = 0
    Tracked = 1
    Lost = 2
    Removed = 3


class BaseTrack(object):
    _count_dict = defaultdict(int)  # support single class and multi classes

    track_id = 0
    is_activated = False
    state = TrackState.New

    history = OrderedDict()
    features = []
    curr_feat = None
    score = 0
    start_frame = 0
    frame_id = 0
    time_since_update = 0

    # multi-camera
    location = (np.inf, np.inf)

    @property
    def end_frame(self):
        return self.frame_id

    @staticmethod
    def next_id(cls_id):
        BaseTrack._count_dict[cls_id] += 1
        return BaseTrack._count_dict[cls_id]

    # @even: reset track id
    @staticmethod
    def init_count(num_classes):
        """
        Initiate _count for all object classes
        :param num_classes:
        """
        for cls_id in range(num_classes):
            BaseTrack._count_dict[cls_id] = 0

    @staticmethod
    def reset_track_count(cls_id):
        BaseTrack._count_dict[cls_id] = 0

    def activate(self, *args):
        raise NotImplementedError

    def predict(self):
        raise NotImplementedError

    def update(self, *args, **kwargs):
        raise NotImplementedError

    def mark_lost(self):
        self.state = TrackState.Lost

    def mark_removed(self):
        self.state = TrackState.Removed


class STrack(BaseTrack):
    def __init__(self, tlwh, score, cls_id, buff_size=30, temp_feat=None):
        # wait activate
        self._tlwh = np.asarray(tlwh, dtype=np.float)
        self.score = score
        self.cls_id = cls_id
        self.track_len = 0

        self.kalman_filter = None
        self.mean, self.covariance = None, None
        self.is_activated = False

        self.use_reid = True if temp_feat is not None else False
        if self.use_reid:
            self.smooth_feat = None
            self.update_features(temp_feat)
            self.features = deque([], maxlen=buff_size)
            self.alpha = 0.9

    def update_features(self, feat):
        # L2 normalizing, this function has no use for BYTETracker
        feat /= np.linalg.norm(feat)
        self.curr_feat = feat
        if self.smooth_feat is None:
            self.smooth_feat = feat
        else:
            self.smooth_feat = self.alpha * self.smooth_feat + (
                1.0 - self.alpha) * feat
        self.features.append(feat)
        self.smooth_feat /= np.linalg.norm(self.smooth_feat)

    def predict(self):
        mean_state = self.mean.copy()
        if self.state != TrackState.Tracked:
            mean_state[7] = 0
        self.mean, self.covariance = self.kalman_filter.predict(
            mean_state, self.covariance)

    @staticmethod
    def multi_predict(tracks, kalman_filter):
        if len(tracks) > 0:
            multi_mean = np.asarray([track.mean.copy() for track in tracks])
            multi_covariance = np.asarray(
                [track.covariance for track in tracks])
            for i, st in enumerate(tracks):
                if st.state != TrackState.Tracked:
                    multi_mean[i][7] = 0
            multi_mean, multi_covariance = kalman_filter.multi_predict(
                multi_mean, multi_covariance)
            for i, (mean, cov) in enumerate(zip(multi_mean, multi_covariance)):
                tracks[i].mean = mean
                tracks[i].covariance = cov

    def reset_track_id(self):
        self.reset_track_count(self.cls_id)

    def activate(self, kalman_filter, frame_id):
        """Start a new track"""
        self.kalman_filter = kalman_filter
        # update track id for the object class
        self.track_id = self.next_id(self.cls_id)
        self.mean, self.covariance = self.kalman_filter.initiate(
            self.tlwh_to_xyah(self._tlwh))

        self.track_len = 0
        self.state = TrackState.Tracked  # set flag 'tracked'

        if frame_id == 1:  # to record the first frame's detection result
            self.is_activated = True

        self.frame_id = frame_id
        self.start_frame = frame_id

    def re_activate(self, new_track, frame_id, new_id=False):
        self.mean, self.covariance = self.kalman_filter.update(
            self.mean, self.covariance, self.tlwh_to_xyah(new_track.tlwh))
        if self.use_reid:
            self.update_features(new_track.curr_feat)
        self.track_len = 0
        self.state = TrackState.Tracked
        self.is_activated = True
        self.frame_id = frame_id
        if new_id:  # update track id for the object class
            self.track_id = self.next_id(self.cls_id)

    def update(self, new_track, frame_id, update_feature=True):
        self.frame_id = frame_id
        self.track_len += 1

        new_tlwh = new_track.tlwh
        self.mean, self.covariance = self.kalman_filter.update(
            self.mean, self.covariance, self.tlwh_to_xyah(new_tlwh))
        self.state = TrackState.Tracked  # set flag 'tracked'
        self.is_activated = True  # set flag 'activated'

        self.score = new_track.score
        if update_feature and self.use_reid:
            self.update_features(new_track.curr_feat)

    @property
    def tlwh(self):
        """Get current position in bounding box format `(top left x, top left y,
                width, height)`.
        """
        if self.mean is None:
            return self._tlwh.copy()

        ret = self.mean[:4].copy()
        ret[2] *= ret[3]
        ret[:2] -= ret[2:] / 2
        return ret

    @property
    def tlbr(self):
        """Convert bounding box to format `(min x, min y, max x, max y)`, i.e.,
        `(top left, bottom right)`.
        """
        ret = self.tlwh.copy()
        ret[2:] += ret[:2]
        return ret

    @staticmethod
    def tlwh_to_xyah(tlwh):
        """Convert bounding box to format `(center x, center y, aspect ratio,
        height)`, where the aspect ratio is `width / height`.
        """
        ret = np.asarray(tlwh).copy()
        ret[:2] += ret[2:] / 2
        ret[2] /= ret[3]
        return ret

    def to_xyah(self):
        return self.tlwh_to_xyah(self.tlwh)

    @staticmethod
    def tlbr_to_tlwh(tlbr):
        ret = np.asarray(tlbr).copy()
        ret[2:] -= ret[:2]
        return ret

    @staticmethod
    def tlwh_to_tlbr(tlwh):
        ret = np.asarray(tlwh).copy()
        ret[2:] += ret[:2]
        return ret

    def __repr__(self):
        return 'OT_({}-{})_({}-{})'.format(self.cls_id, self.track_id,
                                           self.start_frame, self.end_frame)


def joint_stracks(tlista, tlistb):
    exists = {}
    res = []
    for t in tlista:
        exists[t.track_id] = 1
        res.append(t)
    for t in tlistb:
        tid = t.track_id
        if not exists.get(tid, 0):
            exists[tid] = 1
            res.append(t)
    return res


def sub_stracks(tlista, tlistb):
    stracks = {}
    for t in tlista:
        stracks[t.track_id] = t
    for t in tlistb:
        tid = t.track_id
        if stracks.get(tid, 0):
            del stracks[tid]
    return list(stracks.values())


def remove_duplicate_stracks(stracksa, stracksb):
    pdist = matching.iou_distance(stracksa, stracksb)
    pairs = np.where(pdist < 0.15)
    dupa, dupb = list(), list()
    for p, q in zip(*pairs):
        timep = stracksa[p].frame_id - stracksa[p].start_frame
        timeq = stracksb[q].frame_id - stracksb[q].start_frame
        if timep > timeq:
            dupb.append(q)
        else:
            dupa.append(p)
    resa = [t for i, t in enumerate(stracksa) if not i in dupa]
    resb = [t for i, t in enumerate(stracksb) if not i in dupb]
    return resa, resb
