# Copyright (c) Facebook, Inc. and its affiliates.

# pyre-unsafe

from abc import ABC, abstractmethod
from dataclasses import dataclass
from typing import Any, Dict, List, Optional, Tuple
import torch
from torch.nn import functional as F

from detectron2.structures import BoxMode, Instances

from densepose import DensePoseDataRelative

LossDict = Dict[str, torch.Tensor]


def _linear_interpolation_utilities(v_norm, v0_src, size_src, v0_dst, size_dst, size_z):
    """
    Computes utility values for linear interpolation at points v.
    The points are given as normalized offsets in the source interval
    (v0_src, v0_src + size_src), more precisely:
        v = v0_src + v_norm * size_src / 256.0
    The computed utilities include lower points v_lo, upper points v_hi,
    interpolation weights v_w and flags j_valid indicating whether the
    points falls into the destination interval (v0_dst, v0_dst + size_dst).

    Args:
        v_norm (:obj: `torch.Tensor`): tensor of size N containing
            normalized point offsets
        v0_src (:obj: `torch.Tensor`): tensor of size N containing
            left bounds of source intervals for normalized points
        size_src (:obj: `torch.Tensor`): tensor of size N containing
            source interval sizes for normalized points
        v0_dst (:obj: `torch.Tensor`): tensor of size N containing
            left bounds of destination intervals
        size_dst (:obj: `torch.Tensor`): tensor of size N containing
            destination interval sizes
        size_z (int): interval size for data to be interpolated

    Returns:
        v_lo (:obj: `torch.Tensor`): int tensor of size N containing
            indices of lower values used for interpolation, all values are
            integers from [0, size_z - 1]
        v_hi (:obj: `torch.Tensor`): int tensor of size N containing
            indices of upper values used for interpolation, all values are
            integers from [0, size_z - 1]
        v_w (:obj: `torch.Tensor`): float tensor of size N containing
            interpolation weights
        j_valid (:obj: `torch.Tensor`): uint8 tensor of size N containing
            0 for points outside the estimation interval
            (v0_est, v0_est + size_est) and 1 otherwise
    """
    v = v0_src + v_norm * size_src / 256.0
    j_valid = (v - v0_dst >= 0) * (v - v0_dst < size_dst)
    v_grid = (v - v0_dst) * size_z / size_dst
    v_lo = v_grid.floor().long().clamp(min=0, max=size_z - 1)
    v_hi = (v_lo + 1).clamp(max=size_z - 1)
    v_grid = torch.min(v_hi.float(), v_grid)
    v_w = v_grid - v_lo.float()
    return v_lo, v_hi, v_w, j_valid


class BilinearInterpolationHelper:
    """
    Args:
        packed_annotations: object that contains packed annotations
        j_valid (:obj: `torch.Tensor`): uint8 tensor of size M containing
            0 for points to be discarded and 1 for points to be selected
        y_lo (:obj: `torch.Tensor`): int tensor of indices of upper values
            in z_est for each point
        y_hi (:obj: `torch.Tensor`): int tensor of indices of lower values
            in z_est for each point
        x_lo (:obj: `torch.Tensor`): int tensor of indices of left values
            in z_est for each point
        x_hi (:obj: `torch.Tensor`): int tensor of indices of right values
            in z_est for each point
        w_ylo_xlo (:obj: `torch.Tensor`): float tensor of size M;
            contains upper-left value weight for each point
        w_ylo_xhi (:obj: `torch.Tensor`): float tensor of size M;
            contains upper-right value weight for each point
        w_yhi_xlo (:obj: `torch.Tensor`): float tensor of size M;
            contains lower-left value weight for each point
        w_yhi_xhi (:obj: `torch.Tensor`): float tensor of size M;
            contains lower-right value weight for each point
    """

    def __init__(
        self,
        packed_annotations: Any,
        j_valid: torch.Tensor,
        y_lo: torch.Tensor,
        y_hi: torch.Tensor,
        x_lo: torch.Tensor,
        x_hi: torch.Tensor,
        w_ylo_xlo: torch.Tensor,
        w_ylo_xhi: torch.Tensor,
        w_yhi_xlo: torch.Tensor,
        w_yhi_xhi: torch.Tensor,
    ):
        for k, v in locals().items():
            if k != "self":
                setattr(self, k, v)

    @staticmethod
    def from_matches(
        packed_annotations: Any, densepose_outputs_size_hw: Tuple[int, int]
    ) -> "BilinearInterpolationHelper":
        """
        Args:
            packed_annotations: annotations packed into tensors, the following
                attributes are required:
                 - bbox_xywh_gt
                 - bbox_xywh_est
                 - x_gt
                 - y_gt
                 - point_bbox_with_dp_indices
                 - point_bbox_indices
            densepose_outputs_size_hw (tuple [int, int]): resolution of
                DensePose predictor outputs (H, W)
        Return:
            An instance of `BilinearInterpolationHelper` used to perform
            interpolation for the given annotation points and output resolution
        """

        zh, zw = densepose_outputs_size_hw
        x0_gt, y0_gt, w_gt, h_gt = packed_annotations.bbox_xywh_gt[
            packed_annotations.point_bbox_with_dp_indices
        ].unbind(dim=1)
        x0_est, y0_est, w_est, h_est = packed_annotations.bbox_xywh_est[
            packed_annotations.point_bbox_with_dp_indices
        ].unbind(dim=1)
        x_lo, x_hi, x_w, jx_valid = _linear_interpolation_utilities(
            packed_annotations.x_gt, x0_gt, w_gt, x0_est, w_est, zw
        )
        y_lo, y_hi, y_w, jy_valid = _linear_interpolation_utilities(
            packed_annotations.y_gt, y0_gt, h_gt, y0_est, h_est, zh
        )
        j_valid = jx_valid * jy_valid

        w_ylo_xlo = (1.0 - x_w) * (1.0 - y_w)
        w_ylo_xhi = x_w * (1.0 - y_w)
        w_yhi_xlo = (1.0 - x_w) * y_w
        w_yhi_xhi = x_w * y_w

        return BilinearInterpolationHelper(
            packed_annotations,
            j_valid,
            y_lo,
            y_hi,
            x_lo,
            x_hi,
            w_ylo_xlo,  # pyre-ignore[6]
            w_ylo_xhi,
            # pyre-fixme[6]: Expected `Tensor` for 9th param but got `float`.
            w_yhi_xlo,
            w_yhi_xhi,
        )

    def extract_at_points(
        self,
        z_est,
        slice_fine_segm=None,
        w_ylo_xlo=None,
        w_ylo_xhi=None,
        w_yhi_xlo=None,
        w_yhi_xhi=None,
    ):
        """
        Extract ground truth values z_gt for valid point indices and estimated
        values z_est using bilinear interpolation over top-left (y_lo, x_lo),
        top-right (y_lo, x_hi), bottom-left (y_hi, x_lo) and bottom-right
        (y_hi, x_hi) values in z_est with corresponding weights:
        w_ylo_xlo, w_ylo_xhi, w_yhi_xlo and w_yhi_xhi.
        Use slice_fine_segm to slice dim=1 in z_est
        """
        slice_fine_segm = (
            self.packed_annotations.fine_segm_labels_gt
            if slice_fine_segm is None
            else slice_fine_segm
        )
        w_ylo_xlo = self.w_ylo_xlo if w_ylo_xlo is None else w_ylo_xlo
        w_ylo_xhi = self.w_ylo_xhi if w_ylo_xhi is None else w_ylo_xhi
        w_yhi_xlo = self.w_yhi_xlo if w_yhi_xlo is None else w_yhi_xlo
        w_yhi_xhi = self.w_yhi_xhi if w_yhi_xhi is None else w_yhi_xhi

        index_bbox = self.packed_annotations.point_bbox_indices
        z_est_sampled = (
            z_est[index_bbox, slice_fine_segm, self.y_lo, self.x_lo] * w_ylo_xlo
            + z_est[index_bbox, slice_fine_segm, self.y_lo, self.x_hi] * w_ylo_xhi
            + z_est[index_bbox, slice_fine_segm, self.y_hi, self.x_lo] * w_yhi_xlo
            + z_est[index_bbox, slice_fine_segm, self.y_hi, self.x_hi] * w_yhi_xhi
        )
        return z_est_sampled


def resample_data(
    z, bbox_xywh_src, bbox_xywh_dst, wout, hout, mode: str = "nearest", padding_mode: str = "zeros"
):
    """
    Args:
        z (:obj: `torch.Tensor`): tensor of size (N,C,H,W) with data to be
            resampled
        bbox_xywh_src (:obj: `torch.Tensor`): tensor of size (N,4) containing
            source bounding boxes in format XYWH
        bbox_xywh_dst (:obj: `torch.Tensor`): tensor of size (N,4) containing
            destination bounding boxes in format XYWH
    Return:
        zresampled (:obj: `torch.Tensor`): tensor of size (N, C, Hout, Wout)
            with resampled values of z, where D is the discretization size
    """
    n = bbox_xywh_src.size(0)
    assert n == bbox_xywh_dst.size(0), (
        "The number of "
        "source ROIs for resampling ({}) should be equal to the number "
        "of destination ROIs ({})".format(bbox_xywh_src.size(0), bbox_xywh_dst.size(0))
    )
    x0src, y0src, wsrc, hsrc = bbox_xywh_src.unbind(dim=1)
    x0dst, y0dst, wdst, hdst = bbox_xywh_dst.unbind(dim=1)
    x0dst_norm = 2 * (x0dst - x0src) / wsrc - 1
    y0dst_norm = 2 * (y0dst - y0src) / hsrc - 1
    x1dst_norm = 2 * (x0dst + wdst - x0src) / wsrc - 1
    y1dst_norm = 2 * (y0dst + hdst - y0src) / hsrc - 1
    grid_w = torch.arange(wout, device=z.device, dtype=torch.float) / wout
    grid_h = torch.arange(hout, device=z.device, dtype=torch.float) / hout
    grid_w_expanded = grid_w[None, None, :].expand(n, hout, wout)
    grid_h_expanded = grid_h[None, :, None].expand(n, hout, wout)
    dx_expanded = (x1dst_norm - x0dst_norm)[:, None, None].expand(n, hout, wout)
    dy_expanded = (y1dst_norm - y0dst_norm)[:, None, None].expand(n, hout, wout)
    x0_expanded = x0dst_norm[:, None, None].expand(n, hout, wout)
    y0_expanded = y0dst_norm[:, None, None].expand(n, hout, wout)
    grid_x = grid_w_expanded * dx_expanded + x0_expanded
    grid_y = grid_h_expanded * dy_expanded + y0_expanded
    grid = torch.stack((grid_x, grid_y), dim=3)
    # resample Z from (N, C, H, W) into (N, C, Hout, Wout)
    zresampled = F.grid_sample(z, grid, mode=mode, padding_mode=padding_mode, align_corners=True)
    return zresampled


class AnnotationsAccumulator(ABC):
    """
    Abstract class for an accumulator for annotations that can produce
    dense annotations packed into tensors.
    """

    @abstractmethod
    def accumulate(self, instances_one_image: Instances):
        """
        Accumulate instances data for one image

        Args:
            instances_one_image (Instances): instances data to accumulate
        """
        pass

    @abstractmethod
    def pack(self) -> Any:
        """
        Pack data into tensors
        """
        pass


@dataclass
class PackedChartBasedAnnotations:
    """
    Packed annotations for chart-based model training. The following attributes
    are defined:
     - fine_segm_labels_gt (tensor [K] of `int64`): GT fine segmentation point labels
     - x_gt (tensor [K] of `float32`): GT normalized X point coordinates
     - y_gt (tensor [K] of `float32`): GT normalized Y point coordinates
     - u_gt (tensor [K] of `float32`): GT point U values
     - v_gt (tensor [K] of `float32`): GT point V values
     - coarse_segm_gt (tensor [N, S, S] of `float32`): GT segmentation for bounding boxes
     - bbox_xywh_gt (tensor [N, 4] of `float32`): selected GT bounding boxes in
         XYWH format
     - bbox_xywh_est (tensor [N, 4] of `float32`): selected matching estimated
         bounding boxes in XYWH format
     - point_bbox_with_dp_indices (tensor [K] of `int64`): indices of bounding boxes
         with DensePose annotations that correspond to the point data
     - point_bbox_indices (tensor [K] of `int64`): indices of bounding boxes
         (not necessarily the selected ones with DensePose data) that correspond
         to the point data
     - bbox_indices (tensor [N] of `int64`): global indices of selected bounding
         boxes with DensePose annotations; these indices could be used to access
         features that are computed for all bounding boxes, not only the ones with
         DensePose annotations.
    Here K is the total number of points and N is the total number of instances
    with DensePose annotations.
    """

    fine_segm_labels_gt: torch.Tensor
    x_gt: torch.Tensor
    y_gt: torch.Tensor
    u_gt: torch.Tensor
    v_gt: torch.Tensor
    coarse_segm_gt: Optional[torch.Tensor]
    bbox_xywh_gt: torch.Tensor
    bbox_xywh_est: torch.Tensor
    point_bbox_with_dp_indices: torch.Tensor
    point_bbox_indices: torch.Tensor
    bbox_indices: torch.Tensor


class ChartBasedAnnotationsAccumulator(AnnotationsAccumulator):
    """
    Accumulates annotations by batches that correspond to objects detected on
    individual images. Can pack them together into single tensors.
    """

    def __init__(self):
        self.i_gt = []
        self.x_gt = []
        self.y_gt = []
        self.u_gt = []
        self.v_gt = []
        self.s_gt = []
        self.bbox_xywh_gt = []
        self.bbox_xywh_est = []
        self.point_bbox_with_dp_indices = []
        self.point_bbox_indices = []
        self.bbox_indices = []
        self.nxt_bbox_with_dp_index = 0
        self.nxt_bbox_index = 0

    def accumulate(self, instances_one_image: Instances):
        """
        Accumulate instances data for one image

        Args:
            instances_one_image (Instances): instances data to accumulate
        """
        boxes_xywh_est = BoxMode.convert(
            instances_one_image.proposal_boxes.tensor.clone(), BoxMode.XYXY_ABS, BoxMode.XYWH_ABS
        )
        boxes_xywh_gt = BoxMode.convert(
            instances_one_image.gt_boxes.tensor.clone(), BoxMode.XYXY_ABS, BoxMode.XYWH_ABS
        )
        n_matches = len(boxes_xywh_gt)
        assert n_matches == len(
            boxes_xywh_est
        ), f"Got {len(boxes_xywh_est)} proposal boxes and {len(boxes_xywh_gt)} GT boxes"
        if not n_matches:
            # no detection - GT matches
            return
        if (
            not hasattr(instances_one_image, "gt_densepose")
            or instances_one_image.gt_densepose is None
        ):
            # no densepose GT for the detections, just increase the bbox index
            self.nxt_bbox_index += n_matches
            return
        for box_xywh_est, box_xywh_gt, dp_gt in zip(
            boxes_xywh_est, boxes_xywh_gt, instances_one_image.gt_densepose
        ):
            if (dp_gt is not None) and (len(dp_gt.x) > 0):
                # pyre-fixme[6]: For 1st argument expected `Tensor` but got `float`.
                # pyre-fixme[6]: For 2nd argument expected `Tensor` but got `float`.
                self._do_accumulate(box_xywh_gt, box_xywh_est, dp_gt)
            self.nxt_bbox_index += 1

    def _do_accumulate(
        self, box_xywh_gt: torch.Tensor, box_xywh_est: torch.Tensor, dp_gt: DensePoseDataRelative
    ):
        """
        Accumulate instances data for one image, given that the data is not empty

        Args:
            box_xywh_gt (tensor): GT bounding box
            box_xywh_est (tensor): estimated bounding box
            dp_gt (DensePoseDataRelative): GT densepose data
        """
        self.i_gt.append(dp_gt.i)
        self.x_gt.append(dp_gt.x)
        self.y_gt.append(dp_gt.y)
        self.u_gt.append(dp_gt.u)
        self.v_gt.append(dp_gt.v)
        if hasattr(dp_gt, "segm"):
            self.s_gt.append(dp_gt.segm.unsqueeze(0))
        self.bbox_xywh_gt.append(box_xywh_gt.view(-1, 4))
        self.bbox_xywh_est.append(box_xywh_est.view(-1, 4))
        self.point_bbox_with_dp_indices.append(
            torch.full_like(dp_gt.i, self.nxt_bbox_with_dp_index)
        )
        self.point_bbox_indices.append(torch.full_like(dp_gt.i, self.nxt_bbox_index))
        self.bbox_indices.append(self.nxt_bbox_index)
        self.nxt_bbox_with_dp_index += 1

    def pack(self) -> Optional[PackedChartBasedAnnotations]:
        """
        Pack data into tensors
        """
        if not len(self.i_gt):
            # TODO:
            # returning proper empty annotations would require
            # creating empty tensors of appropriate shape and
            # type on an appropriate device;
            # we return None so far to indicate empty annotations
            return None
        return PackedChartBasedAnnotations(
            fine_segm_labels_gt=torch.cat(self.i_gt, 0).long(),
            x_gt=torch.cat(self.x_gt, 0),
            y_gt=torch.cat(self.y_gt, 0),
            u_gt=torch.cat(self.u_gt, 0),
            v_gt=torch.cat(self.v_gt, 0),
            # ignore segmentation annotations, if not all the instances contain those
            coarse_segm_gt=torch.cat(self.s_gt, 0)
            if len(self.s_gt) == len(self.bbox_xywh_gt)
            else None,
            bbox_xywh_gt=torch.cat(self.bbox_xywh_gt, 0),
            bbox_xywh_est=torch.cat(self.bbox_xywh_est, 0),
            point_bbox_with_dp_indices=torch.cat(self.point_bbox_with_dp_indices, 0).long(),
            point_bbox_indices=torch.cat(self.point_bbox_indices, 0).long(),
            bbox_indices=torch.as_tensor(
                self.bbox_indices, dtype=torch.long, device=self.x_gt[0].device
            ).long(),
        )


def extract_packed_annotations_from_matches(
    proposals_with_targets: List[Instances], accumulator: AnnotationsAccumulator
) -> Any:
    for proposals_targets_per_image in proposals_with_targets:
        accumulator.accumulate(proposals_targets_per_image)
    return accumulator.pack()


def sample_random_indices(
    n_indices: int, n_samples: int, device: Optional[torch.device] = None
) -> Optional[torch.Tensor]:
    """
    Samples `n_samples` random indices from range `[0..n_indices - 1]`.
    If `n_indices` is smaller than `n_samples`, returns `None` meaning that all indices
    are selected.
    Args:
        n_indices (int): total number of indices
        n_samples (int): number of indices to sample
        device (torch.device): the desired device of returned tensor
    Return:
        Tensor of selected vertex indices, or `None`, if all vertices are selected
    """
    if (n_samples <= 0) or (n_indices <= n_samples):
        return None
    indices = torch.randperm(n_indices, device=device)[:n_samples]
    return indices
