import json
import urllib.request, urllib.error, urllib.parse

import numpy as np
import pandas as pd

from utils import get_blocked_videos
from utils import interpolated_prec_rec
from utils import segment_iou
from utils import wrapper_segment_iou

class ANETproposal(object):

    GROUND_TRUTH_FIELDS = ['database', 'taxonomy', 'version']
    PROPOSAL_FIELDS = ['results', 'version', 'external_data']

    def __init__(self, ground_truth_filename=None, proposal_filename=None,
                 ground_truth_fields=GROUND_TRUTH_FIELDS,
                 proposal_fields=PROPOSAL_FIELDS,
                 tiou_thresholds=np.linspace(0.5, 0.95, 10),
                 max_avg_nr_proposals=None,
                 subset='validation', verbose=False,
                 check_status=True):
        if not ground_truth_filename:
            raise IOError('Please input a valid ground truth file.')
        if not proposal_filename:
            raise IOError('Please input a valid proposal file.')
        self.subset = subset
        self.tiou_thresholds = tiou_thresholds
        self.max_avg_nr_proposals = max_avg_nr_proposals
        self.verbose = verbose
        self.gt_fields = ground_truth_fields
        self.pred_fields = proposal_fields
        self.recall = None
        self.avg_recall = None
        self.proposals_per_video = None
        self.check_status = check_status
        # Retrieve blocked videos from server.
        if self.check_status:
            self.blocked_videos = get_blocked_videos()
        else:
            self.blocked_videos = list()
        # Import ground truth and proposals.
        self.ground_truth, self.activity_index = self._import_ground_truth(
            ground_truth_filename)
        self.proposal = self._import_proposal(proposal_filename)

        if self.verbose:
            print('[INIT] Loaded annotations from {} subset.'.format(subset))
            nr_gt = len(self.ground_truth)
            print('\tNumber of ground truth instances: {}'.format(nr_gt))
            nr_pred = len(self.proposal)
            print('\tNumber of proposals: {}'.format(nr_pred))
            print('\tFixed threshold for tiou score: {}'.format(self.tiou_thresholds))

    def _import_ground_truth(self, ground_truth_filename):
        """Reads ground truth file, checks if it is well formatted, and returns
           the ground truth instances and the activity classes.

        Parameters
        ----------
        ground_truth_filename : str
            Full path to the ground truth json file.

        Outputs
        -------
        ground_truth : df
            Data frame containing the ground truth instances.
        activity_index : dict
            Dictionary containing class index.
        """
        with open(ground_truth_filename, 'r') as fobj:
            data = json.load(fobj)
        # Checking format
        if not all([field in list(data.keys()) for field in self.gt_fields]):
            raise IOError('Please input a valid ground truth file.')

        # Read ground truth data.
        activity_index, cidx = {}, 0
        video_lst, t_start_lst, t_end_lst, label_lst = [], [], [], []
        for videoid, v in data['database'].items():
            if self.subset != v['subset']:
                continue
            if videoid in self.blocked_videos:
                continue
            for ann in v['annotations']:
                if ann['label'] not in activity_index:
                    activity_index[ann['label']] = cidx
                    cidx += 1
                video_lst.append(videoid)
                t_start_lst.append(ann['segment'][0])
                t_end_lst.append(ann['segment'][1])
                label_lst.append(activity_index[ann['label']])

        ground_truth = pd.DataFrame({'video-id': video_lst,
                                     't-start': t_start_lst,
                                     't-end': t_end_lst,
                                     'label': label_lst})
        return ground_truth, activity_index

    def _import_proposal(self, proposal_filename):
        """Reads proposal file, checks if it is well formatted, and returns
           the proposal instances.

        Parameters
        ----------
        proposal_filename : str
            Full path to the proposal json file.

        Outputs
        -------
        proposal : df
            Data frame containing the proposal instances.
        """
        with open(proposal_filename, 'r') as fobj:
            data = json.load(fobj)
        # Checking format...
        if not all([field in list(data.keys()) for field in self.pred_fields]):
            raise IOError('Please input a valid proposal file.')

        # Read predictions.
        video_lst, t_start_lst, t_end_lst = [], [], []
        score_lst = []
        for videoid, v in data['results'].items():
            if videoid in self.blocked_videos:
                continue
            for result in v:
                video_lst.append(videoid)
                t_start_lst.append(result['segment'][0])
                t_end_lst.append(result['segment'][1])
                score_lst.append(result['score'])
        proposal = pd.DataFrame({'video-id': video_lst,
                                   't-start': t_start_lst,
                                   't-end': t_end_lst,
                                   'score': score_lst})
        return proposal

    def evaluate(self):
        """Evaluates a proposal file. To measure the performance of a
        method for the proposal task, we computes the area under the 
        average recall vs average number of proposals per video curve.
        """
        recall, avg_recall, proposals_per_video = average_recall_vs_avg_nr_proposals(
                self.ground_truth, self.proposal,
                max_avg_nr_proposals=self.max_avg_nr_proposals,
                tiou_thresholds=self.tiou_thresholds)

        area_under_curve = np.trapz(avg_recall, proposals_per_video)

        if self.verbose:
            print('[RESULTS] Performance on ActivityNet proposal task.')
            print('\tArea Under the AR vs AN curve: {}%'.format(100.*float(area_under_curve)/proposals_per_video[-1]))

        self.recall = recall
        self.avg_recall = avg_recall
        self.proposals_per_video = proposals_per_video

def average_recall_vs_avg_nr_proposals(ground_truth, proposals,
                                       max_avg_nr_proposals=None,
                                       tiou_thresholds=np.linspace(0.5, 0.95, 10)):
    """ Computes the average recall given an average number 
        of proposals per video.
    
    Parameters
    ----------
    ground_truth : df
        Data frame containing the ground truth instances.
        Required fields: ['video-id', 't-start', 't-end']
    proposal : df
        Data frame containing the proposal instances.
        Required fields: ['video-id, 't-start', 't-end', 'score']
    tiou_thresholds : 1darray, optional
        array with tiou thresholds.
        
    Outputs
    -------
    recall : 2darray
        recall[i,j] is recall at ith tiou threshold at the jth average number of average number of proposals per video.
    average_recall : 1darray
        recall averaged over a list of tiou threshold. This is equivalent to recall.mean(axis=0).
    proposals_per_video : 1darray
        average number of proposals per video.
    """

    # Get list of videos.
    video_lst = ground_truth['video-id'].unique()

    if not max_avg_nr_proposals:
        max_avg_nr_proposals = float(proposals.shape[0])/video_lst.shape[0]

    ratio = max_avg_nr_proposals*float(video_lst.shape[0])/proposals.shape[0]

    # Adaptation to query faster
    ground_truth_gbvn = ground_truth.groupby('video-id')
    proposals_gbvn = proposals.groupby('video-id')

    # For each video, computes tiou scores among the retrieved proposals.
    score_lst = []
    total_nr_proposals = 0
    for videoid in video_lst:
        # Get ground-truth instances associated to this video.
        ground_truth_videoid = ground_truth_gbvn.get_group(videoid)
        this_video_ground_truth = ground_truth_videoid.loc[:,['t-start', 't-end']].values

        # Get proposals for this video.
        try:
            proposals_videoid = proposals_gbvn.get_group(videoid)
        except:
            n = this_video_ground_truth.shape[0]
            score_lst.append(np.zeros((n, 1)))
            continue

        this_video_proposals = proposals_videoid.loc[:, ['t-start', 't-end']].values

        if this_video_proposals.shape[0] == 0:
            n = this_video_ground_truth.shape[0]
            score_lst.append(np.zeros((n, 1)))
            continue

        # Sort proposals by score.
        sort_idx = proposals_videoid['score'].argsort()[::-1]
        this_video_proposals = this_video_proposals[sort_idx, :]

        if this_video_proposals.ndim != 2:
            this_video_proposals = np.expand_dims(this_video_proposals, axis=0)
        if this_video_ground_truth.ndim != 2:
            this_video_ground_truth = np.expand_dims(this_video_ground_truth, axis=0)

        nr_proposals = np.minimum(int(this_video_proposals.shape[0] * ratio), this_video_proposals.shape[0])
        total_nr_proposals += nr_proposals
        this_video_proposals = this_video_proposals[:nr_proposals, :]

        # Compute tiou scores.
        tiou = wrapper_segment_iou(this_video_proposals, this_video_ground_truth)
        score_lst.append(tiou)

    # Given that the length of the videos is really varied, we 
    # compute the number of proposals in terms of a ratio of the total 
    # proposals retrieved, i.e. average recall at a percentage of proposals 
    # retrieved per video.

    # Computes average recall.
    pcn_lst = np.arange(1, 101) / 100.0 *(max_avg_nr_proposals*float(video_lst.shape[0])/total_nr_proposals)
    matches = np.empty((video_lst.shape[0], pcn_lst.shape[0]))
    positives = np.empty(video_lst.shape[0])
    recall = np.empty((tiou_thresholds.shape[0], pcn_lst.shape[0]))
    # Iterates over each tiou threshold.
    for ridx, tiou in enumerate(tiou_thresholds):

        # Inspect positives retrieved per video at different 
        # number of proposals (percentage of the total retrieved).
        for i, score in enumerate(score_lst):
            # Total positives per video.
            positives[i] = score.shape[0]
            # Find proposals that satisfies minimum tiou threshold.
            true_positives_tiou = score >= tiou
            # Get number of proposals as a percentage of total retrieved.
            pcn_proposals = np.minimum((score.shape[1] * pcn_lst).astype(np.int), score.shape[1])

            for j, nr_proposals in enumerate(pcn_proposals):
                # Compute the number of matches for each percentage of the proposals
                matches[i, j] = np.count_nonzero((true_positives_tiou[:, :nr_proposals]).sum(axis=1))

        # Computes recall given the set of matches per video.
        recall[ridx, :] = matches.sum(axis=0) / positives.sum()

    # Recall is averaged.
    avg_recall = recall.mean(axis=0)

    # Get the average number of proposals per video.
    proposals_per_video = pcn_lst * (float(total_nr_proposals) / video_lst.shape[0])

    return recall, avg_recall, proposals_per_video

