# Copyright (C) 2020-2021 Jørgen S. Dokken
#
# This file is part of DOLFINX_MPC
#
# SPDX-License-Identifier:    MIT

from typing import List, Optional, Tuple

import cffi
import dolfinx.cpp as _cpp
import dolfinx.fem as _fem
import numba
import numpy
import numpy.typing as npt
from dolfinx.common import Timer
from dolfinx_mpc.assemble_matrix import create_sparsity_pattern
from dolfinx_mpc.multipointconstraint import MultiPointConstraint
from petsc4py import PETSc as _PETSc

from .helpers import _bcs, _forms, extract_slave_cells, pack_slave_facet_info
from .numba_setup import initialize_petsc, sink

mode = _PETSc.InsertMode.ADD_VALUES
insert = _PETSc.InsertMode.INSERT_VALUES
ffi, set_values_local = initialize_petsc()


def assemble_matrix(form: _forms, constraint: MultiPointConstraint,
                    bcs: Optional[List[_bcs]] = None, diagval: _PETSc.ScalarType = 1.,
                    A: Optional[_PETSc.Mat] = None):
    """
    Assembles a compiled DOLFINx form with given a multi point constraint and possible
    Dirichlet boundary conditions.
    NOTE: Strong Dirichlet conditions cannot be on master dofs.

    Args:
        form: The compiled bilinear form
        constraint: The multi point constraint
        bcs: List of Dirichlet boundary conditions
        diagval: Value to set on the diagonal of the matrix
        A: PETSc matrix to assemble into (optional)
    """
    timer_matrix = Timer("~MPC: Assemble matrix (numba)")

    V = constraint.function_space
    dofmap = V.dofmap
    dofs = dofmap.list

    # Pack MPC data for numba kernels
    coefficients = constraint.coefficients()[0]
    masters_adj = constraint.masters
    c_to_s_adj = constraint.cell_to_slaves
    cell_to_slave = c_to_s_adj.array
    c_to_s_off = c_to_s_adj.offsets
    is_slave = constraint.is_slave
    mpc_data = (masters_adj.array, coefficients, masters_adj.offsets, cell_to_slave, c_to_s_off, is_slave)
    slave_cells = extract_slave_cells(c_to_s_off)

    # Create 1D bc indicator for matrix assembly
    num_dofs_local = (dofmap.index_map.size_local + dofmap.index_map.num_ghosts) * dofmap.index_map_bs
    is_bc = numpy.zeros(num_dofs_local, dtype=bool)
    bcs = [] if bcs is None else [bc._cpp_object for bc in bcs]
    if len(bcs) > 0:
        for bc in bcs:
            is_bc[bc.dof_indices()[0]] = True

    # Get data from mesh
    x_dofs = V.mesh.geometry.dofmap
    x = V.mesh.geometry.x

    # Pack constants and coefficients
    form_coeffs = _cpp.fem.pack_coefficients(form._cpp_object)
    form_consts = _cpp.fem.pack_constants(form._cpp_object)
    # Create sparsity pattern and matrix if not supplied
    if A is None:
        pattern = create_sparsity_pattern(form, constraint)
        pattern.finalize()
        A = _cpp.la.petsc.create_matrix(V.mesh.comm, pattern)
    A.zeroEntries()

    # Assemble the matrix with all entries
    _cpp.fem.petsc.assemble_matrix(A, form._cpp_object, form_consts, form_coeffs, bcs, False)

    # General assembly data
    block_size = dofmap.dof_layout.block_size
    num_dofs_per_element = dofmap.dof_layout.num_dofs

    tdim = V.mesh.topology.dim

    # Assemble over cells
    subdomain_ids = form._cpp_object.integral_ids(_fem.IntegralType.cell)
    num_cell_integrals = len(subdomain_ids)

    e0 = form.function_spaces[0].element
    e1 = form.function_spaces[1].element

    # Get dof transformations
    needs_transformation_data = e0.needs_dof_transformations or e1.needs_dof_transformations or \
        form._cpp_object.needs_facet_permutations
    cell_perms = numpy.array([], dtype=numpy.uint32)
    if needs_transformation_data:
        V.mesh.topology.create_entity_permutations()
        cell_perms = V.mesh.topology.get_cell_permutation_info()
    # NOTE: Here we need to add the apply_dof_transformation and apply_dof_transformation transpose functions
    # to support more exotic elements
    if e0.needs_dof_transformations or e1.needs_dof_transformations:
        raise NotImplementedError("Dof transformations not implemented")

    is_complex = numpy.issubdtype(_PETSc.ScalarType, numpy.complexfloating)
    nptype = "complex128" if is_complex else "float64"
    ufcx_form = form.ufcx_form
    if num_cell_integrals > 0:
        # NOTE: This depends on enum ordering in ufcx.h
        cell_form_pos = ufcx_form.form_integral_offsets[0]
        V.mesh.topology.create_entity_permutations()
        for i, id in enumerate(subdomain_ids):
            coeffs_i = form_coeffs[(_fem.IntegralType.cell, id)]

            cell_kernel = getattr(ufcx_form.form_integrals[cell_form_pos + i], f"tabulate_tensor_{nptype}")
            active_cells = form._cpp_object.domains(_fem.IntegralType.cell, id)
            assemble_slave_cells(A.handle, cell_kernel, active_cells[numpy.isin(active_cells, slave_cells)],
                                 (x_dofs, x), coeffs_i, form_consts, cell_perms, dofs,
                                 block_size, num_dofs_per_element, mpc_data, is_bc)

    # Assemble over exterior facets
    subdomain_ids = form._cpp_object.integral_ids(_fem.IntegralType.exterior_facet)
    num_exterior_integrals = len(subdomain_ids)

    if num_exterior_integrals > 0:
        V.mesh.topology.create_entities(tdim - 1)
        V.mesh.topology.create_connectivity(tdim - 1, tdim)

        # Get facet permutations if required
        facet_perms = numpy.array([], dtype=numpy.uint8)

        if form._cpp_object.needs_facet_permutations:
            facet_perms = V.mesh.topology.get_facet_permutations()
        perm = (cell_perms, form._cpp_object.needs_facet_permutations, facet_perms)
        # NOTE: This depends on enum ordering in ufcx.h
        ext_facet_pos = ufcx_form.form_integral_offsets[1]
        for i, id in enumerate(subdomain_ids):

            facet_kernel = getattr(ufcx_form.form_integrals[ext_facet_pos + i], f"tabulate_tensor_{nptype}")
            facets = form._cpp_object.domains(_fem.IntegralType.exterior_facet, id)
            coeffs_i = form_coeffs[(_fem.IntegralType.exterior_facet, id)]
            facet_info = pack_slave_facet_info(facets, slave_cells)
            num_facets_per_cell = len(V.mesh.topology.connectivity(tdim, tdim - 1).links(0))
            assemble_exterior_slave_facets(A.handle, facet_kernel, (x_dofs, x), coeffs_i, form_consts,
                                           perm, dofs, block_size, num_dofs_per_element, facet_info, mpc_data, is_bc,
                                           num_facets_per_cell)

    # Add mpc entries on diagonal
    slaves = constraint.slaves
    num_local_slaves = constraint.num_local_slaves
    add_diagonal(A.handle, slaves[:num_local_slaves], diagval)

    # Add one on diagonal for diriclet bc and slave dofs
    # NOTE: In the future one could use a constant in the dirichletbc
    if form.function_spaces[0] is form.function_spaces[1]:
        A.assemblyBegin(_PETSc.Mat.AssemblyType.FLUSH)
        A.assemblyEnd(_PETSc.Mat.AssemblyType.FLUSH)
        _cpp.fem.petsc.insert_diagonal(A, form.function_spaces[0], bcs, diagval)

    A.assemble()
    timer_matrix.stop()
    return A


@numba.njit
def add_diagonal(A: int, dofs: npt.NDArray[numpy.int32], diagval: _PETSc.ScalarType = 1):
    """
    Insert value on diagonal of matrix for given dofs.
    """
    ffi_fb = ffi.from_buffer
    dof_list = numpy.zeros(1, dtype=numpy.int32)
    dof_value = numpy.full(1, diagval, dtype=_PETSc.ScalarType)
    for dof in dofs:
        dof_list[0] = dof
        ierr_loc = set_values_local(A, 1, ffi_fb(dof_list), 1, ffi_fb(dof_list), ffi_fb(dof_value), mode)
        assert ierr_loc == 0
    sink(dof_list, dof_value)


@numba.njit
def assemble_slave_cells(A: int,
                         kernel: cffi.FFI,
                         active_cells: npt.NDArray[numpy.int32],
                         mesh: Tuple[npt.NDArray[numpy.int32],
                                     npt.NDArray[numpy.float64]],
                         coeffs: npt.NDArray[_PETSc.ScalarType],
                         constants: npt.NDArray[_PETSc.ScalarType],
                         permutation_info: npt.NDArray[numpy.uint32],
                         dofmap: npt.NDArray[numpy.int32],
                         block_size: int,
                         num_dofs_per_element: int,
                         mpc: Tuple[npt.NDArray[numpy.int32], npt.NDArray[_PETSc.ScalarType],
                                    npt.NDArray[numpy.int32], npt.NDArray[numpy.int32],
                                    npt.NDArray[numpy.int32], npt.NDArray[numpy.int32]],
                         is_bc: npt.NDArray[numpy.bool_]):
    """
    Assemble MPC contributions for cell integrals
    """
    ffi_fb = ffi.from_buffer

    # Get mesh and geometry data
    x_dofmap, x = mesh

    # Empty arrays mimicking Nullpointers
    facet_index = numpy.zeros(0, dtype=numpy.intc)
    facet_perm = numpy.zeros(0, dtype=numpy.uint8)

    # NOTE: All cells are assumed to be of the same type
    num_xdofs_per_cell = x_dofmap.shape[1]
    geometry = numpy.zeros((num_xdofs_per_cell, 3))
    A_local = numpy.zeros((block_size * num_dofs_per_element, block_size
                           * num_dofs_per_element), dtype=_PETSc.ScalarType)
    masters, coefficients, offsets, c_to_s, c_to_s_off, is_slave = mpc

    # Loop over all cells
    local_dofs = numpy.zeros(block_size * num_dofs_per_element, dtype=numpy.int32)
    for cell in active_cells:
        # Compute vertices of cell from mesh data
        geometry[:, :] = x[x_dofmap[cell]]

        # Assemble local contributions
        A_local.fill(0.0)
        kernel(ffi_fb(A_local), ffi_fb(coeffs[cell, :]), ffi_fb(constants), ffi_fb(geometry),
               ffi_fb(facet_index), ffi_fb(facet_perm))

        # NOTE: Here we need to apply dof transformations

        local_blocks = dofmap[cell]

        # Remove all contributions for dofs that are in the Dirichlet bcs
        for j in range(num_dofs_per_element):
            for k in range(block_size):
                if is_bc[local_blocks[j] * block_size + k]:
                    A_local[j * block_size + k, :] = 0
                    A_local[:, j * block_size + k] = 0

        A_local_copy: numpy.typing.NDArray[_PETSc.ScalarType] = A_local.copy()

        # Find local position of slaves
        slaves = c_to_s[c_to_s_off[cell]: c_to_s_off[cell + 1]]
        mpc_cell = (slaves, masters, coefficients, offsets, is_slave)
        modify_mpc_cell(A, num_dofs_per_element, block_size, A_local, local_blocks, mpc_cell)

        # Remove already assembled contribution to matrix
        A_contribution = A_local - A_local_copy

        # Expand local blocks to dofs
        for i in range(num_dofs_per_element):
            for j in range(block_size):
                local_dofs[i * block_size + j] = local_blocks[i] * block_size + j

        # Insert local contribution
        ierr_loc = set_values_local(A, block_size * num_dofs_per_element, ffi_fb(local_dofs),
                                    block_size * num_dofs_per_element, ffi_fb(local_dofs), ffi_fb(A_contribution), mode)
        assert ierr_loc == 0

    sink(A_contribution, local_dofs)


@numba.njit
def modify_mpc_cell(A: int, num_dofs: int, block_size: int,
                    Ae: npt.NDArray[_PETSc.ScalarType],
                    local_blocks: npt.NDArray[numpy.int32],
                    mpc_cell: Tuple[npt.NDArray[numpy.int32], npt.NDArray[numpy.int32],
                                    npt.NDArray[_PETSc.ScalarType], npt.NDArray[numpy.int32],
                                    npt.NDArray[numpy.int8]]):
    """
    Given an element matrix Ae, modify the contributions to respect the MPCs, and add contributions to appropriate
    places in the global matrix A.
    """
    slaves, masters, coefficients, offsets, is_slave = mpc_cell

    # Locate which local dofs are slave dofs and compute the local index of the slave
    # Additionally count the number of masters we will needed in the flattened structures
    local_index0 = numpy.empty(len(slaves), dtype=numpy.int32)
    num_flattened_masters = 0
    for i in range(num_dofs):
        for j in range(block_size):
            slave = local_blocks[i] * block_size + j
            if is_slave[slave]:
                location = numpy.flatnonzero(slaves == slave)[0]
                local_index0[location] = i * block_size + j
                num_flattened_masters += offsets[slave + 1] - offsets[slave]
    # Strip a copy of Ae of all columns and rows belonging to a slave
    Ae_original = numpy.copy(Ae)
    Ae_stripped = numpy.zeros((block_size * num_dofs, block_size * num_dofs), dtype=_PETSc.ScalarType)
    for i in range(num_dofs):
        for b in range(block_size):
            is_slave0 = is_slave[local_blocks[i] * block_size + b]
            for j in range(num_dofs):
                for c in range(block_size):
                    is_slave1 = is_slave[local_blocks[j] * block_size + c]
                    Ae_stripped[i * block_size + b, j * block_size
                                + c] = (not (is_slave0 and is_slave1)) * Ae_original[i * block_size + b,
                                                                                     j * block_size + c]
    flattened_masters = numpy.zeros(num_flattened_masters, dtype=numpy.int32)
    flattened_slaves = numpy.zeros(num_flattened_masters, dtype=numpy.int32)
    flattened_coeffs = numpy.zeros(num_flattened_masters, dtype=_PETSc.ScalarType)
    c = 0
    for i, slave in enumerate(slaves):
        local_masters = masters[offsets[slave]: offsets[slave + 1]]
        local_coeffs = coefficients[offsets[slave]: offsets[slave + 1]]
        num_masters = len(local_masters)
        for j in range(num_masters):
            flattened_slaves[c + j] = local_index0[i]
            flattened_masters[c + j] = local_masters[j]
            flattened_coeffs[c + j] = local_coeffs[j]
        c += num_masters
    m0 = numpy.zeros(1, dtype=numpy.int32)
    m1 = numpy.zeros(1, dtype=numpy.int32)
    Am0m1 = numpy.zeros((1, 1), dtype=_PETSc.ScalarType)
    Arow = numpy.zeros(block_size * num_dofs, dtype=_PETSc.ScalarType)
    Acol = numpy.zeros(block_size * num_dofs, dtype=_PETSc.ScalarType)
    mpc_dofs = numpy.zeros(block_size * num_dofs, dtype=numpy.int32)
    ffi_fb = ffi.from_buffer
    for i in range(num_flattened_masters):
        local_index = flattened_slaves[i]
        master = flattened_masters[i]
        coeff = flattened_coeffs[i]
        Ae[:, local_index] = 0
        Ae[local_index, :] = 0
        m0[0] = master
        Arow[:] = coeff * Ae_stripped[:, local_index]
        Acol[:] = coeff * Ae_stripped[local_index, :]
        Am0m1[0, 0] = coeff**2 * Ae_original[local_index, local_index]
        for j in range(num_dofs):
            for k in range(block_size):
                mpc_dofs[j * block_size + k] = local_blocks[j] * block_size + k
        mpc_dofs[local_index] = master
        ierr_row = set_values_local(A, block_size * num_dofs, ffi_fb(mpc_dofs), 1, ffi_fb(m0), ffi_fb(Arow), mode)
        assert ierr_row == 0

        # Add slave row to master row
        ierr_col = set_values_local(A, 1, ffi_fb(m0), block_size * num_dofs, ffi_fb(mpc_dofs), ffi_fb(Acol), mode)
        assert ierr_col == 0

        ierr_master = set_values_local(A, 1, ffi_fb(m0), 1, ffi_fb(m0), ffi_fb(Am0m1), mode)
        assert ierr_master == 0

        # Add contributions for other masters relating to slaves on the given cell
        for j in range(num_flattened_masters):
            if i == j:
                continue
            other_local_index = flattened_slaves[j]
            other_master = flattened_masters[j]
            other_coeff = flattened_coeffs[j]
            m1[0] = other_master
            Am0m1[0, 0] = coeff * other_coeff * Ae_original[local_index, other_local_index]
            ierr_other_masters = set_values_local(A, 1, ffi_fb(m0), 1, ffi_fb(m1), ffi_fb(Am0m1), mode)
            assert ierr_other_masters == 0

    sink(Arow, Acol, Am0m1, m0, m1, mpc_dofs)


@numba.njit
def assemble_exterior_slave_facets(A: int, kernel: cffi.FFI,
                                   mesh: Tuple[npt.NDArray[numpy.int32],
                                               npt.NDArray[numpy.float64]],
                                   coeffs: npt.NDArray[_PETSc.ScalarType],
                                   consts: npt.NDArray[_PETSc.ScalarType],
                                   perm: npt.NDArray[numpy.uint32],
                                   dofmap: npt.NDArray[numpy.int32],
                                   block_size: int,
                                   num_dofs_per_element: int,
                                   facet_info: npt.NDArray[numpy.int32],
                                   mpc: Tuple[npt.NDArray[numpy.int32], npt.NDArray[_PETSc.ScalarType],
                                              npt.NDArray[numpy.int32], npt.NDArray[numpy.int32],
                                              npt.NDArray[numpy.int32], npt.NDArray[numpy.int32]],
                                   is_bc: npt.NDArray[numpy.bool_],
                                   num_facets_per_cell: int):
    """Assemble MPC contributions over exterior facet integrals"""
    # Unpack mpc data
    masters, coefficients, offsets, c_to_s, c_to_s_off, is_slave = mpc

    # Mesh data
    x_dofmap, x = mesh

    # Empty arrays for facet information
    facet_index = numpy.zeros(1, dtype=numpy.int32)
    facet_perm = numpy.zeros(1, dtype=numpy.uint8)

    # NOTE: All cells are assumed to be of the same type
    geometry = numpy.zeros((x_dofmap.shape[1], 3))

    # Numpy data used in facet loop
    A_local = numpy.zeros((num_dofs_per_element * block_size,
                           num_dofs_per_element * block_size), dtype=_PETSc.ScalarType)
    local_dofs = numpy.zeros(block_size * num_dofs_per_element, dtype=numpy.int32)

    # Permutation info
    cell_perms, needs_facet_perm, facet_perms = perm

    # Loop over all external facets that are active
    for i in range(facet_info.shape[0]):
        #  Get cell index (local to process) and facet index (local to cell)
        cell_index, local_facet = facet_info[i]
        # Get mesh geometry
        facet_index[0] = local_facet
        geometry[:, :] = x[x_dofmap[cell_index]]

        # Assemble local matrix
        A_local.fill(0.0)
        if needs_facet_perm:
            facet_perm[0] = facet_perms[cell_index * num_facets_per_cell + local_facet]
        kernel(ffi.from_buffer(A_local), ffi.from_buffer(coeffs[cell_index, :]), ffi.from_buffer(consts),
               ffi.from_buffer(geometry), ffi.from_buffer(facet_index), ffi.from_buffer(facet_perm))
        # NOTE: Here we need to add the apply_dof_transformation and apply_dof_transformation transpose functions

        # Extract local blocks of dofs
        local_blocks = dofmap[cell_index]

        # Remove all contributions for dofs that are in the Dirichlet bcs
        for j in range(num_dofs_per_element):
            for k in range(block_size):
                if is_bc[local_blocks[j] * block_size + k]:
                    A_local[j * block_size + k, :] = 0
                    A_local[:, j * block_size + k] = 0

        A_local_copy: numpy.typing.NDArray[_PETSc.ScalarType] = A_local.copy()
        slaves = c_to_s[c_to_s_off[cell_index]: c_to_s_off[cell_index + 1]]
        mpc_cell = (slaves, masters, coefficients, offsets, is_slave)
        modify_mpc_cell(A, num_dofs_per_element, block_size, A_local, local_blocks, mpc_cell)

        # Remove already assembled contribution to matrix
        A_contribution = A_local - A_local_copy

        # Expand local blocks to dofs
        for i in range(num_dofs_per_element):
            for j in range(block_size):
                local_dofs[i * block_size + j] = local_blocks[i] * block_size + j

        # Insert local contribution
        ierr_loc = set_values_local(A, block_size * num_dofs_per_element, ffi.from_buffer(local_dofs),
                                    block_size * num_dofs_per_element, ffi.from_buffer(local_dofs),
                                    ffi.from_buffer(A_contribution), mode)
        assert ierr_loc == 0

    sink(A_contribution, local_dofs)
