import numpy as np

class Camera(object):
    def __init__(self, c2w):
        c2w_mat = np.array(c2w).reshape(4, 4)
        self.c2w_mat = c2w_mat
        self.w2c_mat = np.linalg.inv(c2w_mat)

def parse_matrix(matrix_str):
    """Parse camera matrix string from JSON format"""
    rows = matrix_str.strip().split('] [')
    matrix = []
    for row in rows:
        row = row.replace('[', '').replace(']', '')
        matrix.append(list(map(float, row.split())))
    return np.array(matrix)

def get_relative_pose(cam_params):
    """Calculate relative camera poses"""
    abs_w2cs = [cam_param.w2c_mat for cam_param in cam_params]
    abs_c2ws = [cam_param.c2w_mat for cam_param in cam_params]

    cam_to_origin = 0
    target_cam_c2w = np.array([
        [1, 0, 0, 0],
        [0, 1, 0, -cam_to_origin],
        [0, 0, 1, 0],
        [0, 0, 0, 1]
    ])
    abs2rel = target_cam_c2w @ abs_w2cs[0]
    ret_poses = [target_cam_c2w, ] + [abs2rel @ abs_c2w for abs_c2w in abs_c2ws[1:]]
    ret_poses = np.array(ret_poses, dtype=np.float32)
    return ret_poses