from .model import Model
from .batch import Batcher


class TrainLoop(object):
    def __init__(self, model: Model,
        pos_batcher: Batcher,
        neg_batcher: Batcher,
        max_epochs: int = 50) -> None:

        if not isinstance(model, Model):
            raise TypeError('model must be an instance of Model')

        if not isinstance(pos_batcher, Batcher):
            raise TypeError('pos_batcher must be an instance of Batcher')

        if not isinstance(neg_batcher, Batcher):
            raise TypeError('neg_batcher must be an instance of Batcher')

        self.model = model
        self.pos_batcher = pos_batcher
        self.neg_batcher = neg_batcher
        self.max_epochs = int(num_epochs)

    def run_epoch(self) -> None:
        pos_it = iter(self.pos_batcher)
        neg_it = iter(self.neg_batcher)

        while True:
            try:
                pos_batch = next(pos_it)
                neg_batch = next(neg_it)
            except StopIteration:
                break
            if len(pos_batch.edges) != len(neg_batch.edges):
                raise ValueError('Positive and negative batch should have same length')

    def run(self) -> None:
        for epoch in range(self.max_epochs):
            self.run_epoch()