# Copyright (C) 2024–present  Loren Eteval & contributors <loren.eteval@proton.me>
#
# This file is part of Furious.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

"""Sample plugin-provided traffic counters without blocking the Qt UI."""

from __future__ import annotations

from Furious.Frozenlib import (
    APP,
    AppConnectionController,
    AppBinarySettings,
    AppSettings,
    Mixins,
    registerAppSettings,
)
from Furious.Plugins import TrafficCounters, getPluginRegistry

from PySide6 import QtCore

from concurrent.futures import Future, ThreadPoolExecutor
from dataclasses import dataclass
from typing import Optional, Tuple

import time
import logging
import operator
import weakref
import functools

__all__ = [
    'CLEAR_TRAFFIC_USAGE_ON_RECONNECT_SETTING',
    'METRICS_COLLECTION_SETTING',
    'TrafficStatsSample',
    'TrafficStatsManager',
    'formatTrafficSpeed',
    'formatTrafficUsage',
]

logger = logging.getLogger(__name__)

KIBIBYTE = 1024
MEBIBYTE = KIBIBYTE * KIBIBYTE
TRAFFIC_STATS_SAMPLE_INTERVAL = 2000
CLEAR_TRAFFIC_USAGE_ON_RECONNECT_SETTING = 'ClearTrafficUsageOnReconnect'
METRICS_COLLECTION_SETTING = 'EnableMetricsCollection'

registerAppSettings(CLEAR_TRAFFIC_USAGE_ON_RECONNECT_SETTING, isBinary=True)
registerAppSettings(
    METRICS_COLLECTION_SETTING,
    isBinary=True,
    default=AppBinarySettings.ON_,
)


@dataclass(frozen=True)
class TrafficStatsSample:
    """Describe one timestamped traffic-rate and counter observation."""

    sampledAt: float
    uploadSpeed: float
    downloadSpeed: float
    uploadUsage: int
    downloadUsage: int


@dataclass
class _TrafficUsageAccumulator:
    """Convert per-core counters into monotonic application-session totals."""

    uploadTotal: int = 0
    downloadTotal: int = 0
    previousCounters: Optional[TrafficCounters] = None

    def beginConnection(self):
        """Start a new raw-counter lifetime without discarding session totals."""
        self.previousCounters = None

    def clear(self):
        """Discard application totals and the current raw-counter baseline."""
        self.uploadTotal = 0
        self.downloadTotal = 0
        self.previousCounters = None

    def update(
        self,
        counters: TrafficCounters,
        *,
        clearOnReset=False,
    ) -> Tuple[TrafficCounters, bool]:
        """Accumulate deltas and report whether a configured reset occurred."""
        previousCounters = self.previousCounters

        counterReset = previousCounters is not None and (
            counters.uplink < previousCounters.uplink
            or counters.downlink < previousCounters.downlink
        )

        if counterReset and clearOnReset:
            self.clear()

            previousCounters = None

        self.previousCounters = counters

        if previousCounters is not None:
            self.uploadTotal += max(counters.uplink - previousCounters.uplink, 0)
            self.downloadTotal += max(
                counters.downlink - previousCounters.downlink,
                0,
            )

        return (
            TrafficCounters(
                uplink=self.uploadTotal,
                downlink=self.downloadTotal,
            ),
            counterReset and clearOnReset,
        )


def formatTrafficSpeed(bytesPerSecond: float) -> str:
    """Format a byte rate using compact binary units."""
    try:
        value = max(float(bytesPerSecond), 0.0)
    except (TypeError, ValueError):
        value = 0.0

    if value < KIBIBYTE:
        return '< 1 KiB/s'

    if value >= MEBIBYTE:
        amount = value / MEBIBYTE
        unit = 'MiB/s'
    else:
        amount = value / KIBIBYTE
        unit = 'KiB/s'

    formatted = f'{amount:.2f}'.rstrip('0').rstrip('.')

    return f'{formatted} {unit}'


def formatTrafficUsage(bytesUsed: int) -> str:
    """Format cumulative traffic using compact binary units."""
    try:
        value = max(int(bytesUsed), 0)
    except (TypeError, ValueError, OverflowError):
        value = 0

    if value < KIBIBYTE:
        return f'{value} B'

    amount = float(value)
    units = ('KiB', 'MiB', 'GiB', 'TiB', 'PiB')

    for unit in units:
        amount /= KIBIBYTE

        if amount < KIBIBYTE or unit == units[-1]:
            formatted = f'{amount:.2f}'.rstrip('0').rstrip('.')

            return f'{formatted} {unit}'

    return f'{value} B'


def _queryTrafficStats(monitor):
    """Query counters in a worker thread and timestamp the result."""
    try:
        counters = monitor.query(monitor.target)
    except Exception:
        # Any non-exit exceptions

        counters = None

    return counters, time.monotonic()


def _forwardTrafficQueryResult(managerReference, generation, future):
    """Forward completion without retaining the manager from a worker future."""
    manager = managerReference()

    if isinstance(manager, TrafficStatsManager):
        manager._futureCompleted(generation, future)


class TrafficStatsManager(
    Mixins.ConnectionAware,
    Mixins.CleanupOnExit,
    QtCore.QObject,
):
    """Publish plugin traffic usage and rates independently from presentation."""

    speedChanged = QtCore.Signal(float, float)
    usageChanged = QtCore.Signal(object, object)
    sampleChanged = QtCore.Signal(object)
    usageHistoryReset = QtCore.Signal()
    statisticsUnavailable = QtCore.Signal()
    _sampleReady = QtCore.Signal(int, object, float)

    def __init__(self, parent=None):
        """Initialize the timer and lazy worker-thread state."""
        super().__init__(parent)

        self._executor = None
        self._future = None
        self._monitor = None
        self._generation = 0
        self._queryInFlight = False
        self._previousCounters = None
        self._previousSampleTime = None
        self._usageAccumulator = _TrafficUsageAccumulator()
        self._hasConnected = False
        self._connected = False
        self._collectionEnabled = AppSettings.isStateON_(METRICS_COLLECTION_SETTING)

        self._sampleTimer = QtCore.QTimer(self)
        self._sampleTimer.setInterval(TRAFFIC_STATS_SAMPLE_INTERVAL)
        self._sampleTimer.timeout.connect(self._requestSample)
        self._sampleReady.connect(self._consumeResult)

    def _resumeSampling(self):
        """Resume polling whenever a statistics monitor is available."""
        if not self._collectionEnabled or self._monitor is None:
            return

        if not self._ensureExecutor():
            self.statisticsUnavailable.emit()

            return

        self._sampleTimer.start()
        self._requestSample()

    @staticmethod
    def _activeRuntimes():
        """Return the runtimes owned by the active connection controller."""
        try:
            return AppConnectionController().runtimes
        except (AttributeError, RuntimeError):
            return tuple()

    def _closeExecutor(self):
        """Cancel queued work and release the background query executor."""
        executor = self._executor

        self._cancelCurrentQuery()
        self._executor = None

        if executor is not None:
            executor.shutdown(wait=False, cancel_futures=True)

    def _cancelCurrentQuery(self):
        """Forget the active generation and cancel it when still queued."""
        future = self._future

        self._future = None
        self._queryInFlight = False

        if future is not None:
            future.cancel()

    def _ensureExecutor(self) -> bool:
        """Create the single background query thread when needed."""
        if self._executor is not None:
            return True

        try:
            self._executor = ThreadPoolExecutor(max_workers=1)
        except Exception as ex:
            # Any non-exit exceptions

            logger.error(f'failed to start traffic statistics worker: {ex}')

            self._closeExecutor()

            return False

        return True

    def _futureCompleted(self, generation: int, future: Future):
        """Forward a worker result to the manager's Qt thread."""
        try:
            counters, sampledAt = future.result()
        except Exception:
            # Any non-exit exceptions

            counters, sampledAt = None, time.monotonic()

        try:
            self._sampleReady.emit(generation, counters, sampledAt)
        except RuntimeError:
            # The application may be closing after the query completed.
            pass

    def _resetSamples(self):
        """Discard the speed baseline and in-flight marker."""
        self._queryInFlight = False
        self._previousCounters = None
        self._previousSampleTime = None

    def _beginConnectionUsage(self):
        """Reset only the raw usage baseline for a new core lifetime."""
        self._usageAccumulator.beginConnection()

    def _clearSessionUsage(self):
        """Clear accumulated totals and notify history consumers."""
        self._usageAccumulator.clear()
        self.usageHistoryReset.emit()

    @staticmethod
    def _clearUsageOnReconnectEnabled() -> bool:
        """Return the current persistent reconnect-reset preference."""
        return AppSettings.isStateON_(CLEAR_TRAFFIC_USAGE_ON_RECONNECT_SETTING)

    def _activateMonitor(self, monitor):
        """Begin sampling one plugin-provided monitor."""
        self._sampleTimer.stop()
        self._generation += 1
        self._cancelCurrentQuery()

        self._monitor = monitor
        self._resetSamples()
        self._beginConnectionUsage()

        if monitor is None:
            self.statisticsUnavailable.emit()

            return

        self._resumeSampling()

    def _deactivateMonitor(self):
        """Stop statistics work without changing the connection lifecycle."""
        self._sampleTimer.stop()
        self._generation += 1

        self._cancelCurrentQuery()
        self._monitor = None

        self._resetSamples()
        self._beginConnectionUsage()

        self.statisticsUnavailable.emit()

    @QtCore.Slot(bool)
    def setCollectionEnabled(self, enabled: bool):
        """Apply the metrics preference immediately to the active connection."""
        enabled = bool(enabled)

        if enabled == self._collectionEnabled:
            return

        self._collectionEnabled = enabled

        if not enabled:
            self._deactivateMonitor()

            return

        if self._connected:
            monitor = getPluginRegistry().trafficStatsMonitorForRuntimes(
                self._activeRuntimes()
            )

            self._activateMonitor(monitor)

    @QtCore.Slot()
    def _requestSample(self):
        """Queue one statistics query unless another query is still running."""
        if not self._collectionEnabled or self._monitor is None or self._queryInFlight:
            return

        if not self._ensureExecutor():
            self.statisticsUnavailable.emit()

            return

        try:
            future = self._executor.submit(_queryTrafficStats, self._monitor)
        except Exception as ex:
            # Any non-exit exceptions

            logger.error(f'failed to queue traffic statistics query: {ex}')

            return

        self._future = future
        self._queryInFlight = True

        future.add_done_callback(
            functools.partial(
                _forwardTrafficQueryResult,
                weakref.ref(self),
                self._generation,
            )
        )

    def _updateSpeeds(self, counters: TrafficCounters, sampledAt: float):
        """Calculate and emit rates from one cumulative counter sample."""
        sessionCounters, usageWasReset = self._usageAccumulator.update(
            counters,
            clearOnReset=self._clearUsageOnReconnectEnabled(),
        )

        if usageWasReset:
            self.usageHistoryReset.emit()

        self.usageChanged.emit(sessionCounters.uplink, sessionCounters.downlink)

        previousCounters = self._previousCounters
        previousSampleTime = self._previousSampleTime

        self._previousCounters = counters
        self._previousSampleTime = sampledAt

        if previousCounters is None or previousSampleTime is None:
            uploadSpeed, downloadSpeed = 0.0, 0.0
        else:
            elapsed = sampledAt - previousSampleTime

            if elapsed <= 0:
                uploadSpeed, downloadSpeed = 0.0, 0.0
            else:
                uplinkDelta = max(counters.uplink - previousCounters.uplink, 0)
                downlinkDelta = max(counters.downlink - previousCounters.downlink, 0)
                uploadSpeed = uplinkDelta / elapsed
                downloadSpeed = downlinkDelta / elapsed

        self.speedChanged.emit(uploadSpeed, downloadSpeed)
        self.sampleChanged.emit(
            TrafficStatsSample(
                sampledAt=sampledAt,
                uploadSpeed=uploadSpeed,
                downloadSpeed=downloadSpeed,
                uploadUsage=sessionCounters.uplink,
                downloadUsage=sessionCounters.downlink,
            )
        )

    @staticmethod
    def _validatedCounters(counters) -> Optional[TrafficCounters]:
        """Return integral, non-negative provider counters or ``None``."""
        if not isinstance(counters, TrafficCounters):
            return None

        values = []

        for value in (counters.uplink, counters.downlink):
            if isinstance(value, bool):
                return None

            try:
                normalized = operator.index(value)
            except TypeError:
                return None

            if normalized < 0:
                return None

            values.append(normalized)

        return TrafficCounters(uplink=values[0], downlink=values[1])

    @QtCore.Slot(int, object, float)
    def _consumeResult(self, generation, counters, sampledAt):
        """Consume one worker result on Qt's GUI thread."""
        if generation != self._generation:
            return

        self._future = None
        self._queryInFlight = False

        counters = self._validatedCounters(counters)

        if counters is None:
            self._previousCounters = None
            self._previousSampleTime = None

            self.statisticsUnavailable.emit()

            return

        self._updateSpeeds(counters, sampledAt)

    def connectedCallback(self):
        """Discover and activate statistics for the connected runtime."""
        if self._hasConnected and self._clearUsageOnReconnectEnabled():
            self._clearSessionUsage()

        self._hasConnected = True
        self._connected = True

        if not self._collectionEnabled:
            self._deactivateMonitor()

            return

        monitor = getPluginRegistry().trafficStatsMonitorForRuntimes(
            self._activeRuntimes()
        )

        self._activateMonitor(monitor)

    def disconnectedCallback(self):
        """Stop sampling and clear traffic speeds after disconnecting."""
        self._connected = False
        self._sampleTimer.stop()
        self._generation += 1

        self._cancelCurrentQuery()
        self._monitor = None

        self._resetSamples()
        self._beginConnectionUsage()

        self.statisticsUnavailable.emit()

    def cleanup(self):
        """Release the timer and background query executor."""
        self.disconnectedCallback()
        self._closeExecutor()