"""
Copyright (c) Meta, Inc. and its affiliates.

This source code is licensed under the MIT license found in the
LICENSE file in the root directory of this source tree.
"""

from __future__ import annotations

import os

import torch
import torch.nn as nn

from onescience.models.UMA.base import BackboneInterface, HeadInterface
from onescience.models.esen.graph import GraphModelMixin
from onescience.utils.uma.common.registry import registry
from onescience.utils.uma.common.utils import conditional_grad

from onescience.modules.layer.esen.common.rotation import (
    init_edge_rot_mat,
    rotation_to_wigner,
)
from onescience.modules.layer.esen.common.so3 import (
    CoefficientMapping,
    SO3_Grid,
)
from onescience.modules.layer.esen.esen_block import eSEN_Block
from onescience.modules.layer.esen.nn.embedding import EdgeDegreeEmbedding
from onescience.modules.layer.esen.nn.layer_norm import (
    EquivariantLayerNormArray,
    EquivariantLayerNormArraySphericalHarmonics,
    EquivariantRMSNormArraySphericalHarmonicsV2,
    get_normalization_layer,
)
from onescience.modules.layer.esen.nn.radial import EnvelopedBesselBasis, GaussianSmearing
from onescience.modules.layer.esen.nn.so3_layers import SO3_Linear
from onescience.modules.func_utils.esen_path_utils import resolve_esen_jd_path


@registry.register_model("esen_backbone")
class eSEN_Backbone(nn.Module, GraphModelMixin):
    def __init__(
        self,
        max_num_elements: int = 100,
        sphere_channels: int = 128,
        lmax: int = 2,
        mmax: int = 2,
        grid_resolution: int | None = None,
        otf_graph: bool = False,
        max_neighbors: int = 300,
        use_pbc: bool = True,
        use_pbc_single: bool = False,
        cutoff: float = 5.0,
        edge_channels: int = 128,
        distance_function: str = "gaussian",
        num_distance_basis: int = 512,
        direct_forces: bool = True,
        regress_forces: bool = True,
        regress_stress: bool = False,
        # escnmd specific
        num_layers: int = 2,
        hidden_channels: int = 128,
        norm_type: str = "rms_norm_sh",
        act_type: str = "s2",
        mlp_type: str = "grid",
        use_envelope: bool = False,
        activation_checkpointing: bool = False,
        jd_path: str | None = None,
    ):
        super().__init__()

        self.max_num_elements = max_num_elements
        self.lmax = lmax
        self.mmax = mmax
        self.sphere_channels = sphere_channels
        self.grid_resolution = grid_resolution

        self.regress_forces = regress_forces
        self.direct_forces = direct_forces
        self.regress_stress = regress_stress

        self.otf_graph = otf_graph
        self.max_neighbors = max_neighbors
        self.use_pbc = use_pbc
        self.use_pbc_single = use_pbc_single
        self.enforce_max_neighbors_strictly = False
        self.activation_checkpointing = activation_checkpointing

        self.mlp_type = mlp_type
        self.use_envelope = use_envelope

        # rotation utils
        Jd_list = torch.load(resolve_esen_jd_path(jd_path))
        for l in range(self.lmax + 1):
            self.register_buffer(f"Jd_{l}", Jd_list[l])
        self.sph_feature_size = int((self.lmax + 1) ** 2)
        self.mappingReduced = CoefficientMapping(self.lmax, self.mmax)

        # lmax_lmax for node, lmax_mmax for edge
        self.SO3_grid = nn.ModuleDict()
        self.SO3_grid["lmax_lmax"] = SO3_Grid(
            self.lmax, self.lmax, resolution=grid_resolution, rescale=True
        )
        self.SO3_grid["lmax_mmax"] = SO3_Grid(
            self.lmax, self.mmax, resolution=grid_resolution, rescale=True
        )

        # atom embedding
        self.sphere_embedding = nn.Embedding(
            self.max_num_elements, self.sphere_channels
        )

        # edge distance embedding
        self.cutoff = cutoff
        self.edge_channels = edge_channels
        self.distance_function = distance_function
        self.num_distance_basis = num_distance_basis

        if self.distance_function == "gaussian":
            self.distance_expansion = GaussianSmearing(
                0.0,
                self.cutoff,
                self.num_distance_basis,
                2.0,
            )
        elif self.distance_function == "bessel":
            self.distance_expansion = EnvelopedBesselBasis(
                num_radial=self.num_distance_basis,
                cutoff=cutoff,
            )
            self.distance_expansion.offset = [self.cutoff]
            self.distance_expansion.num_output = self.num_distance_basis
        else:
            raise ValueError("Unknown distance function")

        # equivariant initial embedding
        self.source_embedding = nn.Embedding(self.max_num_elements, self.edge_channels)
        self.target_embedding = nn.Embedding(self.max_num_elements, self.edge_channels)
        nn.init.uniform_(self.source_embedding.weight.data, -0.001, 0.001)
        nn.init.uniform_(self.target_embedding.weight.data, -0.001, 0.001)

        self.edge_channels_list = [
            self.num_distance_basis + 2 * self.edge_channels,
            self.edge_channels,
            self.edge_channels,
        ]

        self.edge_degree_embedding = EdgeDegreeEmbedding(
            sphere_channels=self.sphere_channels,
            lmax=self.lmax,
            mmax=self.mmax,
            max_num_elements=self.max_num_elements,
            edge_channels_list=self.edge_channels_list,
            rescale_factor=5.0,
            cutoff=self.cutoff,
            mappingReduced=self.mappingReduced,
            out_mask=self.SO3_grid["lmax_lmax"].mapping.coefficient_idx(
                self.lmax, self.mmax
            ),
            use_envelope=use_envelope,
        )

        self.num_layers = num_layers
        self.hidden_channels = hidden_channels
        self.norm_type = norm_type
        self.act_type = act_type

        # Initialize the blocks for each layer
        self.blocks = nn.ModuleList()
        for _ in range(self.num_layers):
            block = eSEN_Block(
                self.sphere_channels,
                self.hidden_channels,
                self.lmax,
                self.mmax,
                self.mappingReduced,
                self.SO3_grid,
                self.edge_channels_list,
                self.cutoff,
                self.norm_type,
                self.act_type,
                self.mlp_type,
                self.use_envelope,
            )
            self.blocks.append(block)

        self.norm = get_normalization_layer(
            self.norm_type,
            lmax=self.lmax,
            num_channels=self.sphere_channels,
        )

    def get_rotmat_and_wigner(self, edge_distance_vecs):
        edge_rot_mat = init_edge_rot_mat(
            edge_distance_vecs, rot_clip=(not self.direct_forces)
        )

        Jd_buffers = [
            getattr(self, f"Jd_{l}").type(edge_rot_mat.dtype)
            for l in range(self.lmax + 1)
        ]

        wigner = rotation_to_wigner(
            edge_rot_mat,
            0,
            self.lmax,
            Jd_buffers,
            rot_clip=(not self.direct_forces),
        )
        wigner_inv = torch.transpose(wigner, 1, 2).contiguous()

        return edge_rot_mat, wigner, wigner_inv

    def generate_graph(self, *args, **kwargs):
        graph = super().generate_graph(*args, **kwargs)
        return {
            "edge_index": graph.edge_index,
            "edge_distance": graph.edge_distance,
            "edge_distance_vec": graph.edge_distance_vec,
            "cell_offsets": graph.cell_offsets,
            "offset_distances": None,
            "neighbors": None,
            "node_offset": 0,
            "batch_full": graph.batch_full,
            "atomic_numbers_full": graph.atomic_numbers_full,
        }

    @conditional_grad(torch.enable_grad())
    def forward(self, data_dict) -> dict[str, torch.Tensor]:
        ###############################################################
        # gradient-based forces/stress
        ###############################################################
        data_dict["atomic_numbers"] = data_dict["atomic_numbers"].long()

        displacement = None
        orig_cell = None
        if self.regress_stress and not self.direct_forces:
            displacement = torch.zeros(
                (3, 3),
                dtype=data_dict["pos"].dtype,
                device=data_dict["pos"].device,
            )
            # num_batch = data_dict["num_graphs"]
            num_batch = data_dict.get("num_graphs", len(data_dict["natoms"]))
            displacement = displacement.view(-1, 3, 3).expand(num_batch, 3, 3)
            displacement.requires_grad_(True)
            symmetric_displacement = 0.5 * (
                displacement + displacement.transpose(-1, -2)
            )

            data_dict["pos"].requires_grad_(True)
            data_dict["pos"] = data_dict["pos"] + torch.bmm(
                data_dict["pos"].unsqueeze(-2),
                torch.index_select(symmetric_displacement, 0, data_dict["batch"]),
            ).squeeze(-2)

            orig_cell = data_dict["cell"]
            data_dict["cell"] = data_dict["cell"] + torch.bmm(
                data_dict["cell"], symmetric_displacement
            )

        if not self.regress_stress and self.regress_forces and not self.direct_forces:
            data_dict["pos"].requires_grad_(True)

        if self.otf_graph:
            graph_dict = self.generate_graph(data_dict)
        else:
            cell_per_edge = data_dict["cell"].repeat_interleave(
                data_dict["nedges"], dim=0
            )
            shifts = torch.einsum(
                "ij,ijk->ik",
                data_dict["cell_offsets"].to(cell_per_edge.dtype),
                cell_per_edge,
            )
            edge_distance_vec = (
                data_dict["pos"][data_dict["edge_index"][0]]
                - data_dict["pos"][data_dict["edge_index"][1]]
                + shifts
            )
            # pylint: disable=E1102
            edge_distance = torch.linalg.norm(edge_distance_vec, dim=-1, keepdim=False)
            graph_dict = {
                "atomic_numbers_full": data_dict["atomic_numbers_full"],
                "batch_full": data_dict["batch_full"],
                "edge_index": data_dict["edge_index"],
                "edge_distance": edge_distance,
                "edge_distance_vec": edge_distance_vec,
                "node_offset": 0,
            }

        _, wigner, wigner_inv = self.get_rotmat_and_wigner(
            graph_dict["edge_distance_vec"]
        )

        ###############################################################
        # Initialize node embeddings
        ###############################################################

        x_message = torch.zeros(
            data_dict["pos"].shape[0],
            self.sph_feature_size,
            self.sphere_channels,
            device=data_dict["pos"].device,
            dtype=data_dict["pos"].dtype,
        )
        x_message[:, 0, :] = self.sphere_embedding(data_dict["atomic_numbers"])

        # edge degree embedding
        edge_distance_embedding = self.distance_expansion(graph_dict["edge_distance"])
        source_embedding = self.source_embedding(
            data_dict["atomic_numbers"][graph_dict["edge_index"][0]]
        )
        target_embedding = self.target_embedding(
            data_dict["atomic_numbers"][graph_dict["edge_index"][1]]
        )
        x_edge = torch.cat(
            (edge_distance_embedding, source_embedding, target_embedding), dim=1
        )
        x_message = self.edge_degree_embedding(
            x_message,
            x_edge,
            graph_dict["edge_distance"],
            graph_dict["edge_index"],
            wigner_inv,
        )

        ###############################################################
        # Update spherical node embeddings
        ###############################################################
        if graph_dict["edge_index"].shape[1] != 0:
            for i in range(self.num_layers):
                if self.activation_checkpointing:
                    x_message = torch.utils.checkpoint.checkpoint(
                        self.blocks[i],
                        x_message,
                        x_edge,
                        graph_dict["edge_distance"],
                        graph_dict["edge_index"],
                        wigner,
                        wigner_inv,
                        graph_dict["node_offset"],
                        use_reentrant=False,
                    )
                else:
                    x_message = self.blocks[i](
                        x_message,
                        x_edge,
                        graph_dict["edge_distance"],
                        graph_dict["edge_index"],
                        wigner,
                        wigner_inv,
                        node_offset=graph_dict["node_offset"],
                    )

        # Final layer norm
        x_message = self.norm(x_message)

        out = {
            "node_embedding": x_message,
            "displacement": displacement,
            "orig_cell": orig_cell,
        }
        out.update(graph_dict)

        return out

    @property
    def num_params(self):
        return sum(p.numel() for p in self.parameters())

    @torch.jit.ignore
    def no_weight_decay(self) -> set:
        no_wd_list = []
        named_parameters_list = [name for name, _ in self.named_parameters()]
        for module_name, module in self.named_modules():
            if isinstance(
                module,
                (
                    torch.nn.Linear,
                    SO3_Linear,
                    torch.nn.LayerNorm,
                    EquivariantLayerNormArray,
                    EquivariantLayerNormArraySphericalHarmonics,
                    EquivariantRMSNormArraySphericalHarmonicsV2,
                ),
            ):
                for parameter_name, _ in module.named_parameters():
                    if (
                        isinstance(module, (torch.nn.Linear, SO3_Linear))
                        and "weight" in parameter_name
                    ):
                        continue
                    global_parameter_name = module_name + "." + parameter_name
                    assert global_parameter_name in named_parameters_list
                    no_wd_list.append(global_parameter_name)

        return set(no_wd_list)


@registry.register_model("esen_mlp_efs_head")
class MLP_EFS_Head(nn.Module, HeadInterface):
    def __init__(self, backbone):
        super().__init__()
        backbone.energy_block = None
        backbone.force_block = None
        self.regress_stress = backbone.regress_stress
        self.regress_forces = backbone.regress_forces

        self.sphere_channels = backbone.sphere_channels
        self.hidden_channels = backbone.hidden_channels
        self.energy_block = nn.Sequential(
            nn.Linear(self.sphere_channels, self.hidden_channels, bias=True),
            nn.SiLU(),
            nn.Linear(self.hidden_channels, self.hidden_channels, bias=True),
            nn.SiLU(),
            nn.Linear(self.hidden_channels, 1, bias=True),
        )

        backbone.direct_forces = False

    @conditional_grad(torch.enable_grad())
    def forward(self, data, emb: dict[str, torch.Tensor]) -> dict[str, torch.Tensor]:
        energy_key = "energy"
        forces_key = "forces"
        stress_key = "stress"

        outputs = {}

        node_energy = self.energy_block(
            emb["node_embedding"].narrow(1, 0, 1).squeeze()
        ).view(-1, 1, 1)

        energy = torch.zeros(
            len(data["natoms"]), device=data["pos"].device, dtype=node_energy.dtype
        )
        energy.index_add_(0, data["batch"], node_energy.view(-1))
        outputs[energy_key] = energy

        if self.regress_stress:
            grads = torch.autograd.grad(
                [energy.sum()],
                [data["pos"], emb["displacement"]],
                create_graph=self.training,
            )
            forces = torch.neg(grads[0])
            virial = grads[1].view(-1, 3, 3)
            volume = torch.det(data["cell"]).abs().unsqueeze(-1)
            stress = virial / volume.view(-1, 1, 1)
            virial = torch.neg(virial)
            outputs[forces_key] = forces
            outputs[stress_key] = stress.view(-1, 9)
            data["cell"] = emb["orig_cell"]
        elif self.regress_forces:
            forces = (
                -1
                * torch.autograd.grad(
                    energy.sum(), data["pos"], create_graph=self.training
                )[0]
            )
            outputs[forces_key] = forces
        return outputs


@registry.register_model("esen_mlp_energy_head")
class MLP_Energy_Head(nn.Module, HeadInterface):
    def __init__(self, backbone, reduce: str = "sum"):
        super().__init__()
        self.reduce = reduce

        self.sphere_channels = backbone.sphere_channels
        self.hidden_channels = backbone.hidden_channels
        self.energy_block = nn.Sequential(
            nn.Linear(self.sphere_channels, self.hidden_channels, bias=True),
            nn.SiLU(),
            nn.Linear(self.hidden_channels, self.hidden_channels, bias=True),
            nn.SiLU(),
            nn.Linear(self.hidden_channels, 1, bias=True),
        )

    def forward(self, data_dict, emb: dict[str, torch.Tensor]):
        node_energy = self.energy_block(
            emb["node_embedding"].narrow(1, 0, 1).squeeze()
        ).view(-1, 1, 1)

        energy = torch.zeros(
            len(data_dict["natoms"]),
            device=node_energy.device,
            dtype=node_energy.dtype,
        )

        energy.index_add_(0, data_dict["batch"], node_energy.view(-1))
        if self.reduce == "sum":
            return {"energy": energy}
        elif self.reduce == "mean":
            return {"energy": energy / data_dict["natoms"]}
        else:
            raise ValueError(
                f"reduce can only be sum or mean, user provided: {self.reduce}"
            )


@registry.register_model("esen_linear_force_head")
class Linear_Force_Head(nn.Module, HeadInterface):
    def __init__(self, backbone):
        super().__init__()
        self.linear = SO3_Linear(backbone.sphere_channels, 1, lmax=1)

    def forward(self, data_dict, emb: dict[str, torch.Tensor]):
        forces = self.linear(emb["node_embedding"].narrow(1, 0, 4))
        forces = forces.narrow(1, 1, 3)
        forces = forces.view(-1, 3).contiguous()
        return {"forces": forces}