"""Shared inbound frame dispatch + inbound rate limit.

Extracted from the (now-removed) WS server so the HTTP transport has a
single home for the transport-agnostic dispatch chain and the per-device
token bucket. The HTTP leg (``http_server.py``) is the only transport;
this module is transport-neutral.
"""

from __future__ import annotations

import time
from typing import Any

from . import protocol

# Inbound JSON control-frame rate limit (per device, token bucket).
# A legitimate app sends occasional user-initiated requests — far below
# 20/s sustained. Media uploads are exempt (they travel via
# ``POST /v1/media``, not the frame endpoint).
INBOUND_RATE_PER_S = 20.0
INBOUND_BURST = 40

# Max length of a client-supplied device_id.
MAX_DEVICE_ID_LEN = 128


async def dispatch_frame(adapter: Any, frame: protocol.Frame, device_id: str) -> None:  # noqa: PLR0912
    """Shared inbound frame dispatch (docs/19 §19.4). Unknown types are
    ignored (forward-compat)."""
    if frame.type == protocol.TYPE_MESSAGE_SEND:
        await adapter.on_message_send(frame, device_id)
    elif frame.type == protocol.TYPE_CHANNEL_CREATE:
        await adapter.on_channel_create(frame, device_id)
    elif frame.type == protocol.TYPE_CHANNEL_RENAME:
        await adapter.on_channel_rename(frame, device_id)
    elif frame.type == protocol.TYPE_CHANNEL_SET_DEFAULT:
        await adapter.on_channel_set_default(frame, device_id)
    elif frame.type == protocol.TYPE_CHANNEL_FAVORITE:
        await adapter.on_channel_favorite(frame, device_id)
    elif frame.type == protocol.TYPE_CHANNEL_ICON:
        await adapter.on_channel_icon(frame, device_id)
    elif frame.type == protocol.TYPE_CHANNEL_SET_AUTOMATION:
        await adapter.on_channel_set_automation(frame, device_id)
    elif frame.type == protocol.TYPE_CHANNEL_DELETE:
        await adapter.on_channel_delete(frame, device_id)
    elif frame.type == protocol.TYPE_CHANNEL_LIST:
        await adapter.on_channel_list(frame, device_id)
    elif frame.type == protocol.TYPE_COMMANDS_CATALOG:
        await adapter.on_commands_catalog(frame, device_id)
    elif frame.type == protocol.TYPE_SEARCH:
        await adapter.on_search(frame, device_id)
    elif frame.type == protocol.TYPE_SYNC:
        await adapter.on_sync(frame, device_id)
    elif frame.type == protocol.TYPE_HISTORY:
        await adapter.on_history(frame, device_id)
    elif frame.type == protocol.TYPE_MESSAGE_DELETE:
        await adapter.on_message_delete(frame, device_id)
    elif frame.type == protocol.TYPE_FCM_REGISTER:
        await adapter.on_fcm_register(frame, device_id)
    elif frame.type == protocol.TYPE_PICKER_SELECT:
        await adapter.on_picker_select(frame, device_id)
    # Unknown types are ignored (forward-compat).


class _TokenBucket:
    """Minimal token bucket (stdlib only). One instance per device."""

    __slots__ = ("rate", "burst", "tokens", "updated_at")

    def __init__(self, rate: float, burst: int):
        self.rate = rate
        self.burst = burst
        self.tokens = float(burst)
        self.updated_at = time.monotonic()

    def consume(self) -> bool:
        """Try to take one token. Refills at ``rate``/s up to ``burst``."""
        now = time.monotonic()
        elapsed = now - self.updated_at
        if elapsed > 0:
            self.tokens = min(self.burst, self.tokens + elapsed * self.rate)
            self.updated_at = now
        if self.tokens >= 1.0:
            self.tokens -= 1.0
            return True
        return False