from typing import TYPE_CHECKING
from .batch_chooser import BatchChooser
import numpy as np
if TYPE_CHECKING:
    from ..data_loader import DataLoader


class SequentialBatchChooser(BatchChooser):

    def __init__(self, data_loader: 'DataLoader', batch_size: int):
        super().__init__(data_loader, batch_size)

        self.cursor = 0
        self.desired_samples_inds = None

    def reset(self):
        super(SequentialBatchChooser, self).reset()
        self.cursor = 0
        self.desired_samples_inds = None

    def get_next_batch_sample_indices(self):
        """ Returns a list containing the indices of the samples chosen for the next batch."""

        if self.desired_samples_inds is None:
            self.desired_samples_inds = \
                np.arange(self.data_loader.get_number_of_samples())

        next_cursor = min(
                len(self.desired_samples_inds),
                self.cursor + self.batch_size)

        next_sample_inds = self.desired_samples_inds[
            self.cursor:next_cursor]
        
        self.cursor = next_cursor

        return next_sample_inds