# Copyright (C) 2021 Istituto Italiano di Tecnologia (IIT). All rights reserved.
# This software may be modified and distributed under the terms of the
# GNU Lesser General Public License v2.1 or any later version.

import jax.numpy as jnp
import numpy as np
from jax import grad, jit, vmap

from adam.core.rbd_algorithms import RBDAlgorithms
from adam.jax.jax_like import SpatialMath
from adam.model import Model, URDFModelFactory


class KinDynComputations:
    """This is a small class that retrieves robot quantities using Jax
    in mixed representation, for Floating Base systems - as humanoid robots.
    """

    def __init__(
        self,
        urdfstring: str,
        joints_name_list: list,
        root_link: str = "root_link",
        gravity: np.array = jnp.array([0, 0, -9.80665, 0, 0, 0]),
    ) -> None:
        """
        Args:
            urdfstring (str): path of the urdf
            joints_name_list (list): list of the actuated joints
            root_link (str, optional): the first link. Defaults to 'root_link'.
        """
        math = SpatialMath()
        factory = URDFModelFactory(path=urdfstring, math=math)
        model = Model.build(factory=factory, joints_name_list=joints_name_list)
        self.rbdalgos = RBDAlgorithms(model=model, math=math)
        self.NDoF = self.rbdalgos.NDoF
        self.g = gravity

    def mass_matrix(self, base_transform: jnp.array, joint_positions: jnp.array):
        """Returns the Mass Matrix functions computed the CRBA

        Args:
            base_transform (jnp.array): The homogenous transform from base to world frame
            joint_positions (jnp.array): The joints position

        Returns:
            M (jax): Mass Matrix
        """
        [M, _] = self.rbdalgos.crba(base_transform, joint_positions)
        return M.array

    def centroidal_momentum_matrix(
        self, base_transform: jnp.array, joint_positions: jnp.array
    ):
        """Returns the Centroidal Momentum Matrix functions computed the CRBA

        Args:
            base_transform (jnp.array): The homogenous transform from base to world frame
            joint_positions (jnp.array): The joints position

        Returns:
            Jcc (jnp.array): Centroidal Momentum matrix
        """
        [_, Jcm] = self.rbdalgos.crba(base_transform, joint_positions)
        return Jcm.array

    def relative_jacobian(self, frame: str, joint_positions: jnp.array):
        """Returns the Jacobian between the root link and a specified frame frames

        Args:
            frame (str): The tip of the chain
            joint_positions (jnp.array): The joints position

        Returns:
            J (jnp.array): The Jacobian between the root and the frame
        """
        return self.rbdalgos.relative_jacobian(frame, joint_positions).array

    def forward_kinematics(
        self, frame: str, base_transform: jnp.array, joint_positions: jnp.array
    ):
        """Computes the forward kinematics relative to the specified frame

        Args:
            frame (str): The frame to which the fk will be computed
            base_transform (jnp.array): The homogenous transform from base to world frame
            joint_positions (jnp.array): The joints position

        Returns:
            T_fk (jnp.array): The fk represented as Homogenous transformation matrix
        """
        return self.rbdalgos.forward_kinematics(
            frame, base_transform, joint_positions
        ).array

    def forward_kinematics_fun(self, frame):
        return lambda T, joint_positions: self.forward_kinematics(
            frame, T, joint_positions
        )

    def jacobian(self, frame: str, base_transform, joint_positions):
        """Returns the Jacobian relative to the specified frame

        Args:
            base_transform (jnp.array): The homogenous transform from base to world frame
            s (jnp.array): The joints position
            frame (str): The frame to which the jacobian will be computed

        Returns:
            J_tot (jnp.array): The Jacobian relative to the frame
        """
        return self.rbdalgos.jacobian(frame, base_transform, joint_positions).array

    def bias_force(
        self,
        base_transform: jnp.array,
        joint_positions: jnp.array,
        base_velocity: jnp.array,
        s_dot: jnp.array,
    ) -> jnp.array:
        """Returns the bias force of the floating-base dynamics ejoint_positionsuation,
        using a reduced RNEA (no acceleration and external forces)

        Args:
            base_transform (jnp.array): The homogenous transform from base to world frame
            joint_positions (jnp.array): The joints position
            base_velocity (jnp.array): The base velocity in mixed representation
            s_dot (jnp.array): The joints velocity

        Returns:
            h (jnp.array): the bias force
        """
        return self.rbdalgos.rnea(
            base_transform, joint_positions, base_velocity, s_dot, self.g
        ).array.squeeze()

    def coriolis_term(
        self,
        base_transform: jnp.array,
        joint_positions: jnp.array,
        base_velocity: jnp.array,
        s_dot: jnp.array,
    ) -> jnp.array:
        """Returns the coriolis term of the floating-base dynamics ejoint_positionsuation,
        using a reduced RNEA (no acceleration and external forces)

        Args:
            base_transform (jnp.array): The homogenous transform from base to world frame
            joint_positions (jnp.array): The joints position
            base_velocity (jnp.array): The base velocity in mixed representation
            s_dot (jnp.array): The joints velocity

        Returns:
            C (jnp.array): the Coriolis term
        """
        return self.rbdalgos.rnea(
            base_transform,
            joint_positions,
            base_velocity.reshape(6, 1),
            s_dot,
            np.zeros(6),
        ).array.squeeze()

    def gravity_term(
        self, base_transform: jnp.array, joint_positions: jnp.array
    ) -> jnp.array:
        """Returns the gravity term of the floating-base dynamics ejoint_positionsuation,
        using a reduced RNEA (no acceleration and external forces)

        Args:
            base_transform (jnp.array): The homogenous transform from base to world frame
            joint_positions (jnp.array): The joints position

        Returns:
            G (jnp.array): the gravity term
        """
        return self.rbdalgos.rnea(
            base_transform,
            joint_positions,
            np.zeros(6).reshape(6, 1),
            np.zeros(self.NDoF),
            self.g,
        ).array.squeeze()

    def CoM_position(
        self, base_transform: jnp.array, joint_positions: jnp.array
    ) -> jnp.array:
        """Returns the CoM positon

        Args:
            base_transform (jnp.array): The homogenous transform from base to world frame
            joint_positions (jnp.array): The joints position

        Returns:
            com (jnp.array): The CoM position
        """
        return self.rbdalgos.CoM_position(
            base_transform, joint_positions
        ).array.squeeze()

    def get_total_mass(self) -> float:
        """Returns the total mass of the robot

        Returns:
            mass: The total mass
        """
        return self.rbdalgos.get_total_mass()
