import torch
import torch.nn as nn
import torch.nn.functional as F



class SmoothStep(nn.Module):
    def __init__(self, kstep=10.0):
        super(SmoothStep, self).__init__()
        self.kstep = kstep
    
    def forward(self, inputs):
        outputs = torch.pow(1-inputs, self.kstep) / (torch.pow(1-inputs, self.kstep) + torch.pow(inputs, self.kstep))
        return outputs
  

def _gather_feat(feat, ind, mask=None):
    dim = feat.size(2)
    ind = ind.unsqueeze(2).expand(ind.size(0), ind.size(1), dim)
    feat = feat.gather(1, ind)
    if mask is not None:
        mask = mask.unsqueeze(2).expand_as(feat)
        feat = feat[mask]
        feat = feat.view(-1, dim)
    return feat


def _transpose_and_gather_feat(feat, ind):
    feat = feat.permute(0, 2, 3, 1).contiguous()
    feat = feat.view(feat.size(0), -1, feat.size(3))
    feat = _gather_feat(feat, ind)
    return feat


def _slow_neg_loss(pred, gt):
    '''focal loss from CornerNet'''
    pos_inds = gt.eq(1)
    neg_inds = gt.lt(1)

    neg_weights = torch.pow(1 - gt[neg_inds], 4)

    loss = 0
    pos_pred = pred[pos_inds]
    neg_pred = pred[neg_inds]

    pos_loss = torch.log(pos_pred) * torch.pow(1 - pos_pred, 2)
    neg_loss = torch.log(1 - neg_pred) * torch.pow(neg_pred, 2) * neg_weights

    num_pos = pos_inds.float().sum()
    pos_loss = pos_loss.sum()
    neg_loss = neg_loss.sum()

    if pos_pred.nelement() == 0:
        loss = loss - neg_loss
    else:
        loss = loss - (pos_loss + neg_loss) / num_pos
    return loss


def _neg_loss(pred, gt):
    ''' Modified focal loss. Exactly the same as CornerNet.
        Runs faster and costs a little bit more memory
      Arguments:
        pred (batch x c x h x w)
        gt_regr (batch x c x h x w)
    '''
    pos_inds = gt.eq(1).float()
    neg_inds = gt.lt(1).float()

    neg_weights = torch.pow(1 - gt, 4)

    loss = 0

    pos_loss = torch.log(pred) * torch.pow(1 - pred, 2) * pos_inds
    neg_loss = torch.log(1 - pred) * torch.pow(pred, 2) * \
        neg_weights * neg_inds

    num_pos = pos_inds.float().sum()
    pos_loss = pos_loss.sum()
    neg_loss = neg_loss.sum()

    if num_pos == 0:
        loss = loss - neg_loss
    else:
        loss = loss - (pos_loss + neg_loss) / num_pos
    return loss


def _not_faster_neg_loss(pred, gt):
    pos_inds = gt.eq(1).float()
    neg_inds = gt.lt(1).float()
    num_pos = pos_inds.float().sum()
    neg_weights = torch.pow(1 - gt, 4)

    loss = 0
    trans_pred = pred * neg_inds + (1 - pred) * pos_inds
    weight = neg_weights * neg_inds + pos_inds
    all_loss = torch.log(1 - trans_pred) * torch.pow(trans_pred, 2) * weight
    all_loss = all_loss.sum()

    if num_pos > 0:
        all_loss /= num_pos
    loss -= all_loss
    return loss


def _slow_reg_loss(regr, gt_regr, mask):
    num = mask.float().sum()
    mask = mask.unsqueeze(2).expand_as(gt_regr)

    regr = regr[mask]
    gt_regr = gt_regr[mask]

    regr_loss = nn.functional.smooth_l1_loss(regr, gt_regr, size_average=False)
    regr_loss = regr_loss / (num + 1e-4)
    return regr_loss


def _reg_loss(regr, gt_regr, mask):
    ''' L1 regression loss
      Arguments:
        regr (batch x max_objects x dim)
        gt_regr (batch x max_objects x dim)
        mask (batch x max_objects)
    '''
    num = mask.float().sum()
    mask = mask.unsqueeze(2).expand_as(gt_regr).float()

    regr = regr * mask
    gt_regr = gt_regr * mask

    regr_loss = nn.functional.smooth_l1_loss(regr, gt_regr, size_average=False)
    regr_loss = regr_loss / (num + 1e-4)
    return regr_loss


class FocalLoss(nn.Module):
    '''nn.Module warpper for focal loss'''

    def __init__(self):
        super(FocalLoss, self).__init__()
        self.neg_loss = _neg_loss

    def forward(self, out, target):
        return self.neg_loss(out, target)


class RegLoss(nn.Module):
    '''Regression loss for an output tensor
      Arguments:
        output (batch x dim x h x w)
        mask (batch x max_objects)
        ind (batch x max_objects)
        target (batch x max_objects x dim)
    '''

    def __init__(self):
        super(RegLoss, self).__init__()

    def forward(self, output, mask, ind, target):
        pred = _transpose_and_gather_feat(output, ind)
        loss = _reg_loss(pred, target, mask)
        return loss


class RegL1Loss(nn.Module):
    def __init__(self):
        super(RegL1Loss, self).__init__()

    def forward(self, output, mask, ind, target):
        pred = _transpose_and_gather_feat(output, ind)
        mask = mask.unsqueeze(2).expand_as(pred).float()
        # loss = F.l1_loss(pred * mask, target * mask, reduction='elementwise_mean')
        loss = F.l1_loss(pred * mask, target * mask, size_average=False)
        loss = loss / (mask.sum() + 1e-4)
        return loss


class NormRegL1Loss(nn.Module):
    def __init__(self):
        super(NormRegL1Loss, self).__init__()

    def forward(self, output, mask, ind, target):
        pred = _transpose_and_gather_feat(output, ind)
        mask = mask.unsqueeze(2).expand_as(pred).float()
        # loss = F.l1_loss(pred * mask, target * mask, reduction='elementwise_mean')
        pred = pred / (target + 1e-4)
        target = target * 0 + 1
        loss = F.l1_loss(pred * mask, target * mask, size_average=False)
        loss = loss / (mask.sum() + 1e-4)
        return loss


class RegWeightedL1Loss(nn.Module):
    def __init__(self):
        super(RegWeightedL1Loss, self).__init__()

    def forward(self, output, mask, ind, target):
        pred = _transpose_and_gather_feat(output, ind)
        mask = mask.float()
        # loss = F.l1_loss(pred * mask, target * mask, reduction='elementwise_mean')
        loss = F.l1_loss(pred * mask, target * mask, size_average=False)
        loss = loss / (mask.sum() + 1e-4)
        return loss


class L1Loss(nn.Module):
    def __init__(self):
        super(L1Loss, self).__init__()

    def forward(self, output, mask, ind, target):
        pred = _transpose_and_gather_feat(output, ind)
        mask = mask.unsqueeze(2).expand_as(pred).float()
        loss = F.l1_loss(pred * mask, target * mask,
                         reduction='elementwise_mean')
        return loss


class BinRotLoss(nn.Module):
    def __init__(self):
        super(BinRotLoss, self).__init__()

    def forward(self, output, mask, ind, rotbin, rotres):
        pred = _transpose_and_gather_feat(output, ind)
        loss = compute_rot_loss(pred, rotbin, rotres, mask)
        return loss


def compute_res_loss(output, target):
    return F.smooth_l1_loss(output, target, reduction='elementwise_mean')

# TODO: weight


def compute_bin_loss(output, target, mask):
    mask = mask.expand_as(output)
    output = output * mask.float()
    return F.cross_entropy(output, target, reduction='elementwise_mean')


def compute_rot_loss(output, target_bin, target_res, mask):
    # output: (B, 128, 8) [bin1_cls[0], bin1_cls[1], bin1_sin, bin1_cos,
    #                 bin2_cls[0], bin2_cls[1], bin2_sin, bin2_cos]
    # target_bin: (B, 128, 2) [bin1_cls, bin2_cls]
    # target_res: (B, 128, 2) [bin1_res, bin2_res]
    # mask: (B, 128, 1)
    # import pdb; pdb.set_trace()
    output = output.view(-1, 8)
    target_bin = target_bin.view(-1, 2)
    target_res = target_res.view(-1, 2)
    mask = mask.view(-1, 1)
    loss_bin1 = compute_bin_loss(output[:, 0:2], target_bin[:, 0], mask)
    loss_bin2 = compute_bin_loss(output[:, 4:6], target_bin[:, 1], mask)
    loss_res = torch.zeros_like(loss_bin1)
    if target_bin[:, 0].nonzero().shape[0] > 0:
        idx1 = target_bin[:, 0].nonzero()[:, 0]
        valid_output1 = torch.index_select(output, 0, idx1.long())
        valid_target_res1 = torch.index_select(target_res, 0, idx1.long())
        loss_sin1 = compute_res_loss(
            valid_output1[:, 2], torch.sin(valid_target_res1[:, 0]))
        loss_cos1 = compute_res_loss(
            valid_output1[:, 3], torch.cos(valid_target_res1[:, 0]))
        loss_res += loss_sin1 + loss_cos1
    if target_bin[:, 1].nonzero().shape[0] > 0:
        idx2 = target_bin[:, 1].nonzero()[:, 0]
        valid_output2 = torch.index_select(output, 0, idx2.long())
        valid_target_res2 = torch.index_select(target_res, 0, idx2.long())
        loss_sin2 = compute_res_loss(
            valid_output2[:, 6], torch.sin(valid_target_res2[:, 1]))
        loss_cos2 = compute_res_loss(
            valid_output2[:, 7], torch.cos(valid_target_res2[:, 1]))
        loss_res += loss_sin2 + loss_cos2
    return loss_bin1 + loss_bin2 + loss_res
