import os
import numpy as np


def iou_batch(bboxes1, bboxes2):
    """
    From SORT: Computes IOU between two bboxes in the form [x1,y1,x2,y2]
    """
    bboxes2 = np.expand_dims(bboxes2, 0)
    bboxes1 = np.expand_dims(bboxes1, 1)
    
    xx1 = np.maximum(bboxes1[..., 0], bboxes2[..., 0])
    yy1 = np.maximum(bboxes1[..., 1], bboxes2[..., 1])
    xx2 = np.minimum(bboxes1[..., 2], bboxes2[..., 2])
    yy2 = np.minimum(bboxes1[..., 3], bboxes2[..., 3])
    w = np.maximum(0., xx2 - xx1)
    h = np.maximum(0., yy2 - yy1)
    wh = w * h
    o = wh / ((bboxes1[..., 2] - bboxes1[..., 0]) * (bboxes1[..., 3] - bboxes1[..., 1])                                      
        + (bboxes2[..., 2] - bboxes2[..., 0]) * (bboxes2[..., 3] - bboxes2[..., 1]) - wh)                                              
    return(o)  


def giou_batch(bboxes1, bboxes2):
    """
    :param bbox_p: predict of bbox(N,4)(x1,y1,x2,y2)
    :param bbox_g: groundtruth of bbox(N,4)(x1,y1,x2,y2)
    :return:
    """
    # for details should go to https://arxiv.org/pdf/1902.09630.pdf
    # ensure predict's bbox form
    bboxes2 = np.expand_dims(bboxes2, 0)
    bboxes1 = np.expand_dims(bboxes1, 1)

    xx1 = np.maximum(bboxes1[..., 0], bboxes2[..., 0])
    yy1 = np.maximum(bboxes1[..., 1], bboxes2[..., 1])
    xx2 = np.minimum(bboxes1[..., 2], bboxes2[..., 2])
    yy2 = np.minimum(bboxes1[..., 3], bboxes2[..., 3])
    w = np.maximum(0., xx2 - xx1)
    h = np.maximum(0., yy2 - yy1)
    wh = w * h
    union = ((bboxes1[..., 2] - bboxes1[..., 0]) * (bboxes1[..., 3] - bboxes1[..., 1])                                      
        + (bboxes2[..., 2] - bboxes2[..., 0]) * (bboxes2[..., 3] - bboxes2[..., 1]) - wh)  
    iou = wh / union

    xxc1 = np.minimum(bboxes1[..., 0], bboxes2[..., 0])
    yyc1 = np.minimum(bboxes1[..., 1], bboxes2[..., 1])
    xxc2 = np.maximum(bboxes1[..., 2], bboxes2[..., 2])
    yyc2 = np.maximum(bboxes1[..., 3], bboxes2[..., 3])
    wc = xxc2 - xxc1 
    hc = yyc2 - yyc1 
    assert((wc > 0).all() and (hc > 0).all())
    area_enclose = wc * hc 
    giou = iou - (area_enclose - union) / area_enclose
    giou = (giou + 1.)/2.0 # resize from (-1,1) to (0,1)
    return giou


def diou_batch(bboxes1, bboxes2):
    """
    :param bbox_p: predict of bbox(N,4)(x1,y1,x2,y2)
    :param bbox_g: groundtruth of bbox(N,4)(x1,y1,x2,y2)
    :return:
    """
    # for details should go to https://arxiv.org/pdf/1902.09630.pdf
    # ensure predict's bbox form
    bboxes2 = np.expand_dims(bboxes2, 0)
    bboxes1 = np.expand_dims(bboxes1, 1)

    # calculate the intersection box
    xx1 = np.maximum(bboxes1[..., 0], bboxes2[..., 0])
    yy1 = np.maximum(bboxes1[..., 1], bboxes2[..., 1])
    xx2 = np.minimum(bboxes1[..., 2], bboxes2[..., 2])
    yy2 = np.minimum(bboxes1[..., 3], bboxes2[..., 3])
    w = np.maximum(0., xx2 - xx1)
    h = np.maximum(0., yy2 - yy1)
    wh = w * h
    union = ((bboxes1[..., 2] - bboxes1[..., 0]) * (bboxes1[..., 3] - bboxes1[..., 1])                                      
        + (bboxes2[..., 2] - bboxes2[..., 0]) * (bboxes2[..., 3] - bboxes2[..., 1]) - wh) 
    iou = wh / union
    centerx1 = (bboxes1[..., 0] + bboxes1[..., 2]) / 2.0
    centery1 = (bboxes1[..., 1] + bboxes1[..., 3]) / 2.0
    centerx2 = (bboxes2[..., 0] + bboxes2[..., 2]) / 2.0
    centery2 = (bboxes2[..., 1] + bboxes2[..., 3]) / 2.0

    inner_diag = (centerx1 - centerx2) ** 2 + (centery1 - centery2) ** 2

    xxc1 = np.minimum(bboxes1[..., 0], bboxes2[..., 0])
    yyc1 = np.minimum(bboxes1[..., 1], bboxes2[..., 1])
    xxc2 = np.maximum(bboxes1[..., 2], bboxes2[..., 2])
    yyc2 = np.maximum(bboxes1[..., 3], bboxes2[..., 3])

    outer_diag = (xxc2 - xxc1) ** 2 + (yyc2 - yyc1) ** 2
    diou = iou - inner_diag / outer_diag

    return (diou + 1) / 2.0 # resize from (-1,1) to (0,1)

def ciou_batch(bboxes1, bboxes2):
    """
    :param bbox_p: predict of bbox(N,4)(x1,y1,x2,y2)
    :param bbox_g: groundtruth of bbox(N,4)(x1,y1,x2,y2)
    :return:
    """
    # for details should go to https://arxiv.org/pdf/1902.09630.pdf
    # ensure predict's bbox form
    bboxes2 = np.expand_dims(bboxes2, 0)
    bboxes1 = np.expand_dims(bboxes1, 1)

    # calculate the intersection box
    xx1 = np.maximum(bboxes1[..., 0], bboxes2[..., 0])
    yy1 = np.maximum(bboxes1[..., 1], bboxes2[..., 1])
    xx2 = np.minimum(bboxes1[..., 2], bboxes2[..., 2])
    yy2 = np.minimum(bboxes1[..., 3], bboxes2[..., 3])
    w = np.maximum(0., xx2 - xx1)
    h = np.maximum(0., yy2 - yy1)
    wh = w * h
    union = ((bboxes1[..., 2] - bboxes1[..., 0]) * (bboxes1[..., 3] - bboxes1[..., 1])                                      
        + (bboxes2[..., 2] - bboxes2[..., 0]) * (bboxes2[..., 3] - bboxes2[..., 1]) - wh) 
    iou = wh / union

    centerx1 = (bboxes1[..., 0] + bboxes1[..., 2]) / 2.0
    centery1 = (bboxes1[..., 1] + bboxes1[..., 3]) / 2.0
    centerx2 = (bboxes2[..., 0] + bboxes2[..., 2]) / 2.0
    centery2 = (bboxes2[..., 1] + bboxes2[..., 3]) / 2.0

    inner_diag = (centerx1 - centerx2) ** 2 + (centery1 - centery2) ** 2

    xxc1 = np.minimum(bboxes1[..., 0], bboxes2[..., 0])
    yyc1 = np.minimum(bboxes1[..., 1], bboxes2[..., 1])
    xxc2 = np.maximum(bboxes1[..., 2], bboxes2[..., 2])
    yyc2 = np.maximum(bboxes1[..., 3], bboxes2[..., 3])

    outer_diag = (xxc2 - xxc1) ** 2 + (yyc2 - yyc1) ** 2
    
    w1 = bboxes1[..., 2] - bboxes1[..., 0]
    h1 = bboxes1[..., 3] - bboxes1[..., 1]
    w2 = bboxes2[..., 2] - bboxes2[..., 0]
    h2 = bboxes2[..., 3] - bboxes2[..., 1]

    # prevent dividing over zero. add one pixel shift
    h2 = h2 + 1.
    h1 = h1 + 1.
    arctan = np.arctan(w2/h2) - np.arctan(w1/h1)
    v = (4 / (np.pi ** 2)) * (arctan ** 2)
    S = 1 - iou 
    alpha = v / (S+v)
    ciou = iou - inner_diag / outer_diag - alpha * v
    
    return (ciou + 1) / 2.0 # resize from (-1,1) to (0,1)


def ct_dist(bboxes1, bboxes2):
    """
        Measure the center distance between two sets of bounding boxes,
        this is a coarse implementation, we don't recommend using it only
        for association, which can be unstable and sensitive to frame rate
        and object speed.
    """
    bboxes2 = np.expand_dims(bboxes2, 0)
    bboxes1 = np.expand_dims(bboxes1, 1)

    centerx1 = (bboxes1[..., 0] + bboxes1[..., 2]) / 2.0
    centery1 = (bboxes1[..., 1] + bboxes1[..., 3]) / 2.0
    centerx2 = (bboxes2[..., 0] + bboxes2[..., 2]) / 2.0
    centery2 = (bboxes2[..., 1] + bboxes2[..., 3]) / 2.0

    ct_dist2 = (centerx1 - centerx2) ** 2 + (centery1 - centery2) ** 2

    ct_dist = np.sqrt(ct_dist2)

    # The linear rescaling is a naive version and needs more study
    ct_dist = ct_dist / ct_dist.max()
    return ct_dist.max() - ct_dist # resize to (0,1)



def speed_direction_batch(dets, tracks):
    tracks = tracks[..., np.newaxis]
    CX1, CY1 = (dets[:,0] + dets[:,2])/2.0, (dets[:,1]+dets[:,3])/2.0
    CX2, CY2 = (tracks[:,0] + tracks[:,2]) /2.0, (tracks[:,1]+tracks[:,3])/2.0
    dx = CX1 - CX2 
    dy = CY1 - CY2 
    norm = np.sqrt(dx**2 + dy**2) + 1e-6
    dx = dx / norm 
    dy = dy / norm
    return dy, dx # size: num_track x num_det


def linear_assignment(cost_matrix):
    try:
        import lap
        _, x, y = lap.lapjv(cost_matrix, extend_cost=True)
        return np.array([[y[i],i] for i in x if i >= 0]) #
    except ImportError:
        from scipy.optimize import linear_sum_assignment
        x, y = linear_sum_assignment(cost_matrix)
        return np.array(list(zip(x, y)))


def associate_detections_to_trackers(detections,trackers,iou_threshold = 0.3):
    """
    Assigns detections to tracked object (both represented as bounding boxes)
    Returns 3 lists of matches, unmatched_detections and unmatched_trackers
    """
    if(len(trackers)==0):
        return np.empty((0,2),dtype=int), np.arange(len(detections)), np.empty((0,5),dtype=int)

    iou_matrix = iou_batch(detections, trackers)

    if min(iou_matrix.shape) > 0:
        a = (iou_matrix > iou_threshold).astype(np.int32)
        if a.sum(1).max() == 1 and a.sum(0).max() == 1:
            matched_indices = np.stack(np.where(a), axis=1)
        else:
            matched_indices = linear_assignment(-iou_matrix)
    else:
        matched_indices = np.empty(shape=(0,2))

    unmatched_detections = []
    for d, det in enumerate(detections):
        if(d not in matched_indices[:,0]):
            unmatched_detections.append(d)
    unmatched_trackers = []
    for t, trk in enumerate(trackers):
        if(t not in matched_indices[:,1]):
            unmatched_trackers.append(t)

    #filter out matched with low IOU
    matches = []
    for m in matched_indices:
        if(iou_matrix[m[0], m[1]]<iou_threshold):
            unmatched_detections.append(m[0])
            unmatched_trackers.append(m[1])
        else:
            matches.append(m.reshape(1,2))
    if(len(matches)==0):
        matches = np.empty((0,2),dtype=int)
    else:
        matches = np.concatenate(matches,axis=0)

    return matches, np.array(unmatched_detections), np.array(unmatched_trackers)


def associate(detections, trackers, iou_threshold, velocities, previous_obs, vdc_weight):    
    if(len(trackers)==0):
        return np.empty((0,2),dtype=int), np.arange(len(detections)), np.empty((0,5),dtype=int)

    Y, X = speed_direction_batch(detections, previous_obs)
    inertia_Y, inertia_X = velocities[:,0], velocities[:,1]
    inertia_Y = np.repeat(inertia_Y[:, np.newaxis], Y.shape[1], axis=1)
    inertia_X = np.repeat(inertia_X[:, np.newaxis], X.shape[1], axis=1)
    diff_angle_cos = inertia_X * X + inertia_Y * Y
    diff_angle_cos = np.clip(diff_angle_cos, a_min=-1, a_max=1)
    diff_angle = np.arccos(diff_angle_cos)
    diff_angle = (np.pi /2.0 - np.abs(diff_angle)) / np.pi

    valid_mask = np.ones(previous_obs.shape[0])
    valid_mask[np.where(previous_obs[:,4]<0)] = 0
    
    iou_matrix = iou_batch(detections, trackers)
    scores = np.repeat(detections[:,-1][:, np.newaxis], trackers.shape[0], axis=1)
    # iou_matrix = iou_matrix * scores # a trick sometiems works, we don't encourage this
    valid_mask = np.repeat(valid_mask[:, np.newaxis], X.shape[1], axis=1)

    angle_diff_cost = (valid_mask * diff_angle) * vdc_weight
    angle_diff_cost = angle_diff_cost.T
    angle_diff_cost = angle_diff_cost * scores

    if min(iou_matrix.shape) > 0:
        a = (iou_matrix > iou_threshold).astype(np.int32)
        if a.sum(1).max() == 1 and a.sum(0).max() == 1:
            matched_indices = np.stack(np.where(a), axis=1)
        else:
            matched_indices = linear_assignment(-(iou_matrix+angle_diff_cost))
    else:
        matched_indices = np.empty(shape=(0,2))

    unmatched_detections = []
    for d, det in enumerate(detections):
        if(d not in matched_indices[:,0]):
            unmatched_detections.append(d)
    unmatched_trackers = []
    for t, trk in enumerate(trackers):
        if(t not in matched_indices[:,1]):
            unmatched_trackers.append(t)

    # filter out matched with low IOU
    matches = []
    for m in matched_indices:
        if(iou_matrix[m[0], m[1]]<iou_threshold):
            unmatched_detections.append(m[0])
            unmatched_trackers.append(m[1])
        else:
            matches.append(m.reshape(1,2))
    if(len(matches)==0):
        matches = np.empty((0,2),dtype=int)
    else:
        matches = np.concatenate(matches,axis=0)

    return matches, np.array(unmatched_detections), np.array(unmatched_trackers)


def associate_kitti(detections, trackers, det_cates, iou_threshold, 
        velocities, previous_obs, vdc_weight):
    if(len(trackers)==0):
        return np.empty((0,2),dtype=int), np.arange(len(detections)), np.empty((0,5),dtype=int)

    """
        Cost from the velocity direction consistency
    """
    Y, X = speed_direction_batch(detections, previous_obs)
    inertia_Y, inertia_X = velocities[:,0], velocities[:,1]
    inertia_Y = np.repeat(inertia_Y[:, np.newaxis], Y.shape[1], axis=1)
    inertia_X = np.repeat(inertia_X[:, np.newaxis], X.shape[1], axis=1)
    diff_angle_cos = inertia_X * X + inertia_Y * Y
    diff_angle_cos = np.clip(diff_angle_cos, a_min=-1, a_max=1)
    diff_angle = np.arccos(diff_angle_cos)
    diff_angle = (np.pi /2.0 - np.abs(diff_angle)) / np.pi

    valid_mask = np.ones(previous_obs.shape[0])
    valid_mask[np.where(previous_obs[:,4]<0)]=0  
    valid_mask = np.repeat(valid_mask[:, np.newaxis], X.shape[1], axis=1)

    scores = np.repeat(detections[:,-1][:, np.newaxis], trackers.shape[0], axis=1)
    angle_diff_cost = (valid_mask * diff_angle) * vdc_weight
    angle_diff_cost = angle_diff_cost.T
    angle_diff_cost = angle_diff_cost * scores

    """
        Cost from IoU
    """
    iou_matrix = iou_batch(detections, trackers)
    

    """
        With multiple categories, generate the cost for catgory mismatch
    """
    num_dets = detections.shape[0]
    num_trk = trackers.shape[0]
    cate_matrix = np.zeros((num_dets, num_trk))
    for i in range(num_dets):
            for j in range(num_trk):
                if det_cates[i] != trackers[j, 4]:
                        cate_matrix[i][j] = -1e6
    
    cost_matrix = - iou_matrix -angle_diff_cost - cate_matrix

    if min(iou_matrix.shape) > 0:
        a = (iou_matrix > iou_threshold).astype(np.int32)
        if a.sum(1).max() == 1 and a.sum(0).max() == 1:
            matched_indices = np.stack(np.where(a), axis=1)
        else:
            matched_indices = linear_assignment(cost_matrix)
    else:
        matched_indices = np.empty(shape=(0,2))

    unmatched_detections = []
    for d, det in enumerate(detections):
        if(d not in matched_indices[:,0]):
            unmatched_detections.append(d)
    unmatched_trackers = []
    for t, trk in enumerate(trackers):
        if(t not in matched_indices[:,1]):
            unmatched_trackers.append(t)

    #filter out matched with low IOU
    matches = []
    for m in matched_indices:
        if(iou_matrix[m[0], m[1]]<iou_threshold):
            unmatched_detections.append(m[0])
            unmatched_trackers.append(m[1])
        else:
            matches.append(m.reshape(1,2))
    if(len(matches)==0):
        matches = np.empty((0,2),dtype=int)
    else:
        matches = np.concatenate(matches,axis=0)

    return matches, np.array(unmatched_detections), np.array(unmatched_trackers)