import functools
import seqio
import tensorflow as tf
import t5.data
from datasets import load_dataset
from t5.data import postprocessors
from t5.data import preprocessors
from t5.evaluation import metrics
from seqio import FunctionDataSource, utils

TaskRegistry = seqio.TaskRegistry
vocabulary=seqio.SentencePieceVocabulary('gs://t5-data/vocabs/cc_all.32000.100extra/sentencepiece.model', extra_ids=0)

DEFAULT_OUTPUT_FEATURES = {
    "inputs": seqio.Feature(
        vocabulary=vocabulary, add_eos=True,
        required=False),
    "targets": seqio.Feature(
        vocabulary=vocabulary, add_eos=True)
}


def gen_dataset(split, shuffle=False, seed=None, column="text", dataset_params=None):
    dataset = load_dataset(**dataset_params)
    if shuffle:
        if seed:
            dataset = dataset.shuffle(seed=seed)
        else:
            dataset = dataset.shuffle()
    while True:
        for item in dataset[str(split)]:
            yield item[column]


def dataset_fn(split, shuffle_files, seed=None, dataset_params=None):
    return tf.data.Dataset.from_generator(
        functools.partial(gen_dataset, split, shuffle_files, seed, dataset_params=dataset_params),
        output_signature=tf.TensorSpec(shape=(), dtype=tf.string, name=dataset_name)
    )



@utils.map_over_dataset
def target_to_key(x, key_map, target_key):
    """Assign the value from the dataset to target_key in key_map"""
    return {**key_map, target_key: x}



# Final pretraining task used in Raffel et al., 2019 adaptated to NCC
dataset_name = 'NbAiLab/scandinavian'
dataset_params = {"path": dataset_name, "use_auth_token": True, "streaming": True}
dataset_shapes = None
TaskRegistry.add(
    "ncc_scandinavian_span_corruption_stream",
    source=seqio.FunctionDataSource(
        dataset_fn=functools.partial(dataset_fn, dataset_params=dataset_params),
        splits=("train", "validation"),
        caching_permitted=False,
        num_input_examples=dataset_shapes,
        ),
    preprocessors=[
        functools.partial(
            target_to_key, key_map={
                "inputs": None,
                "targets": None,
            }, target_key="targets"),
        seqio.preprocessors.tokenize,
        # seqio.CacheDatasetPlaceholder(),
        preprocessors.span_corruption,
        seqio.preprocessors.append_eos_after_trim,
    ],
    output_features={"targets": DEFAULT_OUTPUT_FEATURES["targets"]},
    metric_fns=[]
)