  import numpy as np
import os
from mpi4py import MPI
from tacs import TACS, elements, constitutive, functions

# Load mesh from BDF file
mesh = TACS.MeshLoader(comm)
mesh.scanBDFFile(os.path.join(os.getcwd(), "input.bdf"))

# Set constitutive properties
props = constitutive.MaterialProperties(rho=2.5, E=70e3, nu=0.3, ys=220e3, G=0, t=0.01)

# Loop over components of the mesh
for comp in mesh.getComponents():
    # Create stiffness and element object for each component
    stiffness = elements.StiffnessProperties(props)
    element = elements.Element2D(stiffness)

    # Create a TACS assembler object from the mesh loader
    assembler = TACS.Assembler(mesh, element)

# Create a KS function and get the design variable values
ks_func = functions.KSFailure(assembler, 1e-8, 100)
ks_func.setDesignVars(assembler.getDesignVars())

# Get the node locations and create the forces
nodes = assembler.createNodeVec()
forces = assembler.createVec()

# Set up and solve the analysis problem
assembler.setVariables(nodes)
assembler.assembleJacobian(forces, assembler.getDesignVars(), ks_func)
assembler.factor()
assembler.solve(forces)

# Evaluate the function and solve for the adjoint variables
ks_func.evalFunctions(nodes, assembler.getDesignVars(), forces)
ks_func.evalAdjoint(nodes, assembler.getDesignVars(), forces)

# Compute the total derivative with respect to material design variables
derivs = assembler.createVec()
assembler.getAdjoint(derivs)

# Create a random direction along which to perturb the nodes
perturb_dir = np.random.rand(3)

# Set the complex step and compute the perturbed solution
perturbed_nodes = assembler.createNodeVec()
perturbed_nodes.setComplexStep(perturb_dir)
assembler.setVariables(perturbed_nodes)
assembler.assembleJacobian(forces, assembler.getDesignVars(), ks_func)
assembler.factor()
assembler.solve(forces)

# Evaluate the function for the perturbed solution
ks_func.evalFunctions(perturbed_nodes, assembler.getDesignVars(), forces)

# Compute the projected derivative
projected_deriv = assembler.createVec()
projected_deriv.setComplexStep(perturb_dir)
assembler.getAdjoint(projected_deriv)

# Output the results for visualization
output_file = open("output.dat", "w")
output_file.write("VARIABLES = X, Y, Z, DISPLACEMENT_X, DISPLACEMENT_Y, DISPLACEMENT_Z, FORCE_X, FORCE_Y, FORCE_Z\n")
for i in range(nodes.getNumOwnedNodes()):
    node = nodes.getNode(i)
    disp = forces.getValues(i)
    force = assembler.getAdjoint(i)
    output_file.write("{:.12f} {:.12f} {:.12f} {:.12f} {:.12f} {:.12f} {:.12f} {:.12f} {:.12f}\n".format(
        node[0], node[1], node[2], disp[0], disp[1], disp[2], force[0], force[1], force[2]))
output_file.close()