import json
from typing import List

import datasets
import numpy as np
import fortepyan as ff
from tqdm import tqdm
from datasets import (
    Split,
    Dataset,
    DatasetInfo,
    BuilderConfig,
    GeneratorBasedBuilder,
    load_dataset,
    concatenate_datasets,
)

_DESC = """
Dataset of midi pieces sliced to records of fixed number of notes.
"""


class TokenizedMidiDatasetConfig(BuilderConfig):
    def __init__(
        self,
        base_dataset_name: str = "roszcz/maestro-v1-sustain",
        extra_datasets: list[str] = [],
        sequence_length: int = 64,
        sequence_step: int = 42,
        **kwargs,
    ):
        super().__init__()
        # Version history:
        # 0.0.1: Initial version.
        super().__init__(version=datasets.Version("0.0.2"), **kwargs)

        self.base_dataset_name: str = base_dataset_name
        self.extra_datasets: list[str] = extra_datasets
        self.sequence_length: int = sequence_length
        self.sequence_step: int = sequence_step


class TokenizedMidiDataset(GeneratorBasedBuilder):
    def _info(self) -> DatasetInfo:
        return datasets.DatasetInfo(description=_DESC)

    BUILDER_CONFIG_CLASS = TokenizedMidiDatasetConfig
    BUILDER_CONFIGS = [
        TokenizedMidiDatasetConfig(
            base_dataset_name="roszcz/maestro-sustain-v2",
            extra_datasets=["roszcz/giant-midi-sustain-v2"],
            sequence_length=32,
            sequence_step=16,
            name="giant-short",
        ),
        TokenizedMidiDatasetConfig(
            base_dataset_name="roszcz/maestro-sustain-v2",
            extra_datasets=[],
            sequence_length=32,
            sequence_step=16,
            name="basic-short",
        ),
        TokenizedMidiDatasetConfig(
            base_dataset_name="roszcz/maestro-sustain-v2",
            extra_datasets=["roszcz/giant-midi-sustain-v2"],
            sequence_length=64,
            sequence_step=16,
            name="giant-mid",
        ),
        TokenizedMidiDatasetConfig(
            base_dataset_name="roszcz/maestro-sustain-v2",
            extra_datasets=[],
            sequence_length=64,
            sequence_step=16,
            name="basic-mid",
        ),
        TokenizedMidiDatasetConfig(
            base_dataset_name="roszcz/maestro-sustain-v2",
            extra_datasets=["roszcz/giant-midi-sustain-v2"],
            sequence_length=128,
            sequence_step=16,
            name="giant-long",
        ),
        TokenizedMidiDatasetConfig(
            base_dataset_name="roszcz/maestro-sustain-v2",
            extra_datasets=[],
            sequence_length=128,
            sequence_step=16,
            name="basic-long",
        ),
    ]
    DEFAULT_CONFIG_NAME = "basic-mid"

    def _split_generators(self, dl_manager: datasets.DownloadManager) -> List[datasets.SplitGenerator]:
        base = load_dataset(self.config.base_dataset_name)

        other_datasets = [load_dataset(path, split="train") for path in self.config.extra_datasets]
        other_datasets.append(base["train"])

        dataset = concatenate_datasets(other_datasets)

        # This will enable multiprocessing in load_dataset()
        n_shards = 12
        train_shards = [dataset.shard(n_shards, it) for it in range(n_shards)]

        return [
            datasets.SplitGenerator(name=Split.TRAIN, gen_kwargs={"dataset_shards": train_shards}),
            datasets.SplitGenerator(name=Split.TEST, gen_kwargs={"dataset_shards": [base["test"]]}),
            datasets.SplitGenerator(name=Split.VALIDATION, gen_kwargs={"dataset_shards": [base["validation"]]}),
        ]

    def piece_to_records(self, piece: ff.MidiPiece) -> list[dict]:
        # better practice than setting a global random state
        rs = np.random.RandomState(np.random.MT19937(np.random.SeedSequence(4)))

        n_samples = 1 + (piece.size - self.config.sequence_length) // self.config.sequence_step
        # uniform distribution, piece should be covered almost entirely
        piece_idxs = range(piece.size - self.config.sequence_length)
        start_points = rs.choice(piece_idxs, size=n_samples, replace=False)

        chopped_sequences = []
        for start in start_points:
            start = int(start)
            finish = start + self.config.sequence_length
            part = piece[start:finish]

            sequence = {
                "notes": {
                    "pitch": part.df.pitch.astype("int16").values.T,
                    "start": part.df.start.values,
                    "end": part.df.end.values,
                    "duration": part.df.duration.values,
                    "velocity": part.df.velocity.values,
                },
                "source": json.dumps(part.source),
            }
            chopped_sequences.append(sequence)

        return chopped_sequences

    def filter_pauses(self, piece: ff.MidiPiece) -> list[ff.MidiPiece]:
        next_start = piece.df.start.shift(-1)
        silent_distance = next_start - piece.df.end

        # Seconds
        distance_threshold = 4

        ids = silent_distance > distance_threshold

        break_idxs = np.where(ids)[0]

        pieces = []

        start = 0
        for break_idx in break_idxs:
            finish = break_idx.item() + 1
            piece_part = piece[start:finish]

            if piece_part.size <= self.config.sequence_length:
                continue

            pieces.append(piece_part)
            start = finish

        return pieces

    def _generate_examples(self, dataset_shards: list[Dataset]):
        # ~10min for giant midi
        for dataset in dataset_shards:
            for it, record in tqdm(enumerate(dataset), total=len(dataset)):
                piece = ff.MidiPiece.from_huggingface(dict(record))

                pieces = self.filter_pauses(piece)
                chopped_sequences = sum([self.piece_to_records(piece) for piece in pieces], [])

                for jt, sequence in enumerate(chopped_sequences):
                    # NOTE I don't really understand how this works :(
                    # When using jt as the key I started getting
                    # duplicate key errors when doing load_dataset(num_proc=8)
                    key = f"{it}_{jt}"
                    yield key, sequence