# ALL imports MUST be at the beginning - no imports in the middle of function
from typing import ...
from dataclasses import dataclass
# for HTTP IO
import urllib.request
import urllib.error

from .lib import Connection as _Connection
from ._turso import ( ... )

class ConnectionSync(_Connection):
    def __init__(...): ...

    def pull(self) -> bool: ... # returns True of new updates were pulled; False if no new updates were fetched; determine changes by inspecting .empty() method of changes
    def push(self) -> None: ...
    def checkpoint(self) -> None: ...
    def stats(self) -> None: ...

@dataclass
class PartialSyncPrefixBootstrap:
    # Bootstraps DB by fetching first N bytes/pages; enables partial sync
    length: int


@dataclass
class PartialSyncQueryBootstrap:
    # Bootstraps DB by fetching pages touched by given SQL query on server
    query: str

@dataclass
class PartialSyncOpts:
    bootstrap_strategy: Union[PartialSyncPrefixBootstrap, PartialSyncQueryBootstrap]
    segment_size: Optional[int] = None
    prefetch: Optional[bool] = None

def connect_sync(
    path: str, # path to the main database file locally
    # remote url for the sync - can be lambda which will be evaluated on every http request; if lambda returns None - internal http processing must return error which will bubble-up in the sync engine
    # remote_url MUST be used in all sync engine operations: during bootstrap and all further operations
    # remote_url must accept either http://, https:// or libsql:// protocol, where later must be just replaced with https:// under the hood for now
    remote_url: Union[str, Callable[[], Optional[str]]],
    *,
    # token for remote authentication - can be lambda which will be evaluted on every http request; if lambda returns None - internal http processing must return error which will bubble-up in the sync engine
    # auth token value ("fixed" or got from lambda) WILL not have any prefix and must be used as "Authorization" header prepended with "Bearer " prefix
    auth_token: Optional[Union[str, Callable[[], Optional[str]]]],
    client_name: Optional[str], # optional unique client name (library MUST use `turso-sync-py` if omitted)
    long_poll_timeout_ms: Optional[number], # long polling timeout
    bootstrap_if_empty: bool = True, # if not set, initial bootstrap phase will be skipped and caller must call .pull(...) explicitly in order to get initial state from remote
    partial_sync_experimental: Optional[PartialSyncOpts] = None, # EXPERIMENTAL partial sync configuration
    experimental_features: Optional[str] = None, # pass it as-is to the underlying connection
    isolation_level: Optional[str] = "DEFERRED", # pass it as-is to the underlying connection
) -> ConnectionSync: ...

# event loop for async operation "op"
while True:
    chunk = e.read(CHUNK_SIZE)
    if not chunk:
        break
    io_item.push_buffer(chunk)
    op.resume() # assert that None is returned