import numpy as np


def box3d_iou(corners1, corners2):
    ''' Compute 3D bounding box IoU.

    Input:
        corners1: numpy array (8,3), assume up direction is Z
        corners2: numpy array (8,3), assume up direction is Z
    Output:
        iou: 3D bounding box IoU

    '''
    x_min_1, x_max_1, y_min_1, y_max_1, z_min_1, z_max_1 = get_box3d_min_max(corners1)
    x_min_2, x_max_2, y_min_2, y_max_2, z_min_2, z_max_2 = get_box3d_min_max(corners2)
    xA = np.maximum(x_min_1, x_min_2)
    yA = np.maximum(y_min_1, y_min_2)
    zA = np.maximum(z_min_1, z_min_2)
    xB = np.minimum(x_max_1, x_max_2)
    yB = np.minimum(y_max_1, y_max_2)
    zB = np.minimum(z_max_1, z_max_2)
    inter_vol = np.maximum((xB - xA), 0) * np.maximum((yB - yA), 0) * np.maximum((zB - zA), 0)
    box_vol_1 = (x_max_1 - x_min_1) * (y_max_1 - y_min_1) * (z_max_1 - z_min_1)
    box_vol_2 = (x_max_2 - x_min_2) * (y_max_2 - y_min_2) * (z_max_2 - z_min_2)
    iou = inter_vol / (box_vol_1 + box_vol_2 - inter_vol + 1e-8)

    return iou


def get_box3d_min_max(corner):
    ''' Compute min and max coordinates for 3D bounding box
        Note: only for axis-aligned bounding boxes

    Input:
        corners: numpy array (8,3), assume up direction is Z (batch of N samples)
    Output:
        box_min_max: an array for min and max coordinates of 3D bounding box IoU

    '''
    min_coord = corner.min(axis=0)
    max_coord = corner.max(axis=0)
    x_min, x_max = min_coord[0], max_coord[0]
    y_min, y_max = min_coord[1], max_coord[1]
    z_min, z_max = min_coord[2], max_coord[2]
    
    return x_min, x_max, y_min, y_max, z_min, z_max


def get_3d_box(center, box_size):
    ''' box_size is array(l,w,h), heading_angle is radius clockwise from pos x axis, center is xyz of box center
        output (8,3) array for 3D box cornders
        Similar to utils/compute_orientation_3d
    '''
    l,w,h = box_size
    # x_corners = [l/2,l/2,-l/2,-l/2,l/2,l/2,-l/2,-l/2]
    # y_corners = [h/2,h/2,h/2,h/2,-h/2,-h/2,-h/2,-h/2]
    # z_corners = [w/2,-w/2,-w/2,w/2,w/2,-w/2,-w/2,w/2]
    x_corners = [l/2,l/2,-l/2,-l/2,l/2,l/2,-l/2,-l/2]
    y_corners = [w/2,-w/2,-w/2,w/2,w/2,-w/2,-w/2,w/2]
    z_corners = [h/2,h/2,h/2,h/2,-h/2,-h/2,-h/2,-h/2]
    corners_3d = np.vstack([x_corners,y_corners,z_corners])
    corners_3d[0,:] = corners_3d[0,:] + center[0]
    corners_3d[1,:] = corners_3d[1,:] + center[1]
    corners_3d[2,:] = corners_3d[2,:] + center[2]
    corners_3d = np.transpose(corners_3d)
    return corners_3d