"""Batching file prepare requests to our API."""

from __future__ import annotations

import queue
import threading
import time
from collections.abc import Mapping, Sequence
from typing import TYPE_CHECKING, Callable, NamedTuple, Union

if TYPE_CHECKING:
    from wandb.sdk.internal.internal_api import (
        Api,
        CreateArtifactFileSpecInput,
        CreateArtifactFilesResponseFile,
    )


# Request for a file to be prepared.
class RequestPrepare(NamedTuple):
    file_spec: CreateArtifactFileSpecInput
    response_channel: queue.Queue[ResponsePrepare]


class RequestFinish(NamedTuple):
    pass


class ResponsePrepare(NamedTuple):
    birth_artifact_id: str
    upload_url: str | None
    upload_headers: Sequence[str]
    upload_id: str | None
    storage_path: str | None
    multipart_upload_urls: dict[int, str] | None


Request = Union[RequestPrepare, RequestFinish]


def _clamp(x: float, low: float, high: float) -> float:
    return max(low, min(x, high))


def gather_batch(
    request_queue: queue.Queue[Request],
    batch_time: float,
    inter_event_time: float,
    max_batch_size: int,
    clock: Callable[[], float] = time.monotonic,
) -> tuple[bool, Sequence[RequestPrepare]]:
    batch_start_time = clock()
    remaining_time = batch_time

    first_request = request_queue.get()
    if isinstance(first_request, RequestFinish):
        return True, []

    batch: list[RequestPrepare] = [first_request]

    while remaining_time > 0 and len(batch) < max_batch_size:
        try:
            request = request_queue.get(
                timeout=_clamp(
                    x=inter_event_time,
                    low=1e-12,  # 0 = "block forever", so just use something tiny
                    high=remaining_time,
                ),
            )
            if isinstance(request, RequestFinish):
                return True, batch

            batch.append(request)
            remaining_time = batch_time - (clock() - batch_start_time)

        except queue.Empty:
            break

    return False, batch


def prepare_response(response: CreateArtifactFilesResponseFile) -> ResponsePrepare:
    multipart_resp = response.get("uploadMultipartUrls")
    part_list = multipart_resp["uploadUrlParts"] if multipart_resp else []
    multipart_parts = {u["partNumber"]: u["uploadUrl"] for u in part_list} or None

    return ResponsePrepare(
        birth_artifact_id=response["artifact"]["id"],
        upload_url=response["uploadUrl"],
        upload_headers=response["uploadHeaders"],
        upload_id=multipart_resp and multipart_resp.get("uploadID"),
        storage_path=response.get("storagePath"),
        multipart_upload_urls=multipart_parts,
    )


class StepPrepare:
    """A thread that batches requests to our file prepare API.

    Any number of threads may call prepare() in parallel. The PrepareBatcher thread
    will batch requests up and send them all to the backend at once.
    """

    def __init__(
        self,
        api: Api,
        batch_time: float,
        inter_event_time: float,
        max_batch_size: int,
        request_queue: queue.Queue[Request] | None = None,
    ) -> None:
        self._api = api
        self._inter_event_time = inter_event_time
        self._batch_time = batch_time
        self._max_batch_size = max_batch_size
        self._request_queue: queue.Queue[Request] = request_queue or queue.Queue()
        self._thread = threading.Thread(target=self._thread_body)
        self._thread.daemon = True

    def _thread_body(self) -> None:
        while True:
            finish, batch = gather_batch(
                request_queue=self._request_queue,
                batch_time=self._batch_time,
                inter_event_time=self._inter_event_time,
                max_batch_size=self._max_batch_size,
            )
            if batch:
                batch_response = self._prepare_batch(batch)
                # send responses
                for prepare_request in batch:
                    name = prepare_request.file_spec["name"]
                    response_file = batch_response[name]
                    response = prepare_response(response_file)
                    prepare_request.response_channel.put(response)
            if finish:
                break

    def _prepare_batch(
        self, batch: Sequence[RequestPrepare]
    ) -> Mapping[str, CreateArtifactFilesResponseFile]:
        """Execute the prepareFiles API call.

        Args:
            batch: List of RequestPrepare objects
        Returns:
            dict of (save_name: ResponseFile) pairs where ResponseFile is a dict with
                an uploadUrl key. The value of the uploadUrl key is None if the file
                already exists, or a url string if the file should be uploaded.
        """
        return self._api.create_artifact_files([req.file_spec for req in batch])

    def prepare(
        self, file_spec: CreateArtifactFileSpecInput
    ) -> queue.Queue[ResponsePrepare]:
        response_queue: queue.Queue[ResponsePrepare] = queue.Queue()
        self._request_queue.put(RequestPrepare(file_spec, response_queue))
        return response_queue

    def start(self) -> None:
        self._thread.start()

    def finish(self) -> None:
        self._request_queue.put(RequestFinish())

    def is_alive(self) -> bool:
        return self._thread.is_alive()

    def shutdown(self) -> None:
        self.finish()
        self._thread.join()