import time
from typing import Any, Dict, List, Optional

from ray.data._internal.execution.interfaces import (
    AllToAllTransformFn,
    RefBundle,
    TaskContext,
)
from ray.data._internal.execution.interfaces.transform_fn import (
    AllToAllTransformFnResult,
)
from ray.data._internal.execution.operators.map_transformer import MapTransformer
from ray.data._internal.planner.exchange.pull_based_shuffle_task_scheduler import (
    PullBasedShuffleTaskScheduler,
)
from ray.data._internal.planner.exchange.push_based_shuffle_task_scheduler import (
    PushBasedShuffleTaskScheduler,
)
from ray.data._internal.planner.exchange.shuffle_task_spec import ShuffleTaskSpec
from ray.data.context import DataContext, ShuffleStrategy
from ray.util.common import INT32_MAX


def generate_random_shuffle_fn(
    data_context: DataContext,
    seed: Optional[int],
    num_outputs: Optional[int] = None,
    ray_remote_args: Optional[Dict[str, Any]] = None,
    _debug_limit_shuffle_execution_to_num_blocks: Optional[int] = None,
) -> AllToAllTransformFn:
    """Generate function to randomly shuffle each records of blocks."""

    # If no seed has been specified, pin timestamp based one
    # so that task could be safely retried (w/o changing their output)
    seed = seed if seed is not None else (time.time_ns() % INT32_MAX)

    def fn(
        refs: List[RefBundle],
        ctx: TaskContext,
    ) -> AllToAllTransformFnResult:
        num_input_blocks = sum(len(r.blocks) for r in refs)

        # If map_transformer is specified (e.g. from fusing
        # MapOperator->AllToAllOperator), we pass a map function which
        # is applied to each block before shuffling.
        map_transformer: Optional[MapTransformer] = ctx.upstream_map_transformer
        upstream_map_fn = None
        nonlocal ray_remote_args
        if map_transformer:
            # NOTE: We override target max-block sizing of the previous
            #       transformation to avoid unnecessary block shaping (if any)
            map_transformer.override_target_max_block_size(None)

            def upstream_map_fn(blocks):
                return map_transformer.apply_transform(blocks, ctx)

            # If there is a fused upstream operator,
            # also use the ray_remote_args from the fused upstream operator.
            ray_remote_args = ctx.upstream_map_ray_remote_args

        shuffle_spec = ShuffleTaskSpec(
            target_shuffle_max_block_size=(
                ctx.target_max_block_size_override or data_context.target_max_block_size
            ),
            random_shuffle=True,
            random_seed=seed,
            upstream_map_fn=upstream_map_fn,
        )

        if data_context.shuffle_strategy == ShuffleStrategy.SORT_SHUFFLE_PUSH_BASED:
            if num_outputs is not None:
                raise NotImplementedError(
                    "Push-based shuffle doesn't support setting num_blocks yet."
                )
            scheduler = PushBasedShuffleTaskScheduler(shuffle_spec)
        else:
            scheduler = PullBasedShuffleTaskScheduler(shuffle_spec)

        return scheduler.execute(
            refs,
            num_outputs or num_input_blocks,
            task_ctx=ctx,
            map_ray_remote_args=ray_remote_args,
            reduce_ray_remote_args=ray_remote_args,
            _debug_limit_execution_to_num_blocks=(
                _debug_limit_shuffle_execution_to_num_blocks
            ),
        )

    return fn