from .base_regularizer import BaseRegularizer
import torch
from ..utils import common_functions as c_f
from ..distances import CosineSimilarity
from ..reducers import DivisorReducer

class SparseCentersRegularizer(BaseRegularizer):
    def __init__(self, num_classes, centers_per_class, **kwargs):
        super().__init__(**kwargs)
        assert centers_per_class > 1
        c_f.assert_distance_type(self, CosineSimilarity)
        self.set_class_masks(num_classes, centers_per_class)
        self.add_to_recordable_attributes(list_of_names=["num_classes", "centers_per_class"], is_stat=False)
        self.add_to_recordable_attributes(list_of_names=["same_class_center_sim", "diff_class_center_sim"], is_stat=True)

    def compute_loss(self, weights):
        center_similarities = self.distance(weights)
        small_val = c_f.small_val(weights.dtype)
        center_similarities_masked = torch.clamp(2.*center_similarities[self.same_class_mask], max=2)
        divisor = 2*torch.sum(self.same_class_mask)
        reg = torch.sqrt(2.0 + small_val - center_similarities_masked)
        self.set_stats(center_similarities)
        return {"loss": {"losses": reg, 
                        "indices": c_f.torch_arange_from_size(reg), 
                        "reduction_type": "element", 
                        "divisor_summands": {"two_times_num_comparisons": divisor}}}

    def set_class_masks(self, num_classes, centers_per_class):
        total_num_centers = num_classes * centers_per_class
        self.diff_class_mask = torch.ones(total_num_centers, total_num_centers, dtype=torch.bool)
        self.same_class_mask = torch.zeros(total_num_centers, total_num_centers, dtype=torch.bool)
        for i in range(num_classes):
            s, e = i*centers_per_class, (i+1)*centers_per_class
            curr_block = torch.ones(centers_per_class, centers_per_class)
            curr_block = torch.triu(curr_block, diagonal=1)
            self.same_class_mask[s:e, s:e] = curr_block
            self.diff_class_mask[s:e, s:e] = 0

    def set_stats(self, center_similarities):
        with torch.no_grad():
            self.same_class_center_sim = torch.mean(center_similarities[self.same_class_mask])
            self.diff_class_center_sim = torch.mean(center_similarities[self.diff_class_mask])

    def get_default_distance(self):
        return CosineSimilarity()

    def get_default_reducer(self):
        return DivisorReducer()
    