import numpy as np
import os
from mpi4py import MPI
from tacs import TACS

# Load structural mesh from BDF file
mesh = TACS.TACSMeshLoader(MPI.COMM_WORLD)
mesh.scanBDFFile("structural_mesh.bdf")

# Set constitutive properties
density = 2700.0
E = 70e9
nu = 0.3
kcorr = 5.0/6.0
ys = 350e6
thickness = 0.1

# Loop over components and create stiffness and element objects
for comp_num in range(mesh.getNumComponents()):
    stiffness = TACS.TACSOrthotropicMaterial(density, E, nu, kcorr, ys, thickness)
    element = TACS.LinearElasticity3D(stiffness)
    mesh.setElementObject(comp_num, element)

# Create TACS assembler object
assembler = TACS.createTACSAssembler(mesh)

# Create KS function and get design variable values
ks_function = TACS.KSFailure(assembler, ksWeight=1.0)
x = ks_function.createDesignVec()

# Get node locations and create forces
forces = TACS.Vector(assembler.getNumGlobalNodes()*3)
assembler.setVariables(x)
assembler.getResidual(forces)

# Set up and solve analysis problem
ans = TACS.TACSAnalysis(assembler, ks_function)
ans.setVariables(x)
ans.solve()

# Evaluate function and solve for adjoint variables
ans.evalFunctions([0.0], [0.0], [0.0])

# Compute total derivative with respect to material design variables and nodal locations
ans.computePartials()

# Create random direction for perturbation
dx = TACS.Vector(assembler.getNumDesignVars())
dx.setRandom()

# Compute total derivative with respect to nodal locations
ans.setVariables(x)
ans.setDesignVars(dx)
ans.computeTotalDeriv()

# Set complex step and compute perturbed solution
ans.setVariables(x)
ans.setComplexStep(1e-30)
ans.solve()

# Evaluate function for perturbed solution and compute projected derivative
ans.evalFunctions([0.0], [0.0], [0.0])

# Output results for visualization
viewer = TACS.ToFH5(assembler, TACS.PY_PLANE_STRESS, "output.f5")
viewer.writeToFile()