# -*- coding: utf-8 -*-

# Copyright © Cloud Linux GmbH & Cloud Linux Software, Inc 2010-2021 All Rights Reserved
#
# Licensed under CLOUD LINUX LICENSE AGREEMENT
# http://cloudlinux.com/docs/LICENSE.TXT

"""
This module contains Autotracer class
"""

__package__ = "ssa.modules"

import heapq
import json
import logging
import os
from collections import defaultdict
from dataclasses import dataclass, field, asdict
from datetime import datetime, timedelta
from fnmatch import fnmatchcase
from typing import Dict, Iterator, Optional, NamedTuple, List, Iterable
from urllib.parse import urlparse

import numpy as np

from ssa.db import setup_database
from ssa.internal.exceptions import SSAError
from ssa.modules.common import Common
from ssa.modules.storage import iter_domains_data, iter_domain_url_data
from ssa.autotracing import status, disabled_users, misconfiguration_checks
from ssa.configuration import load_tunables
from ssa.configuration.schemes import autotracing_tunables_schema
from ssa.internal.constants import autotracing_log, autotracing_stats_file
from ssa.internal.utils import sentry_init

xray_import_error = None
try:
    import xray.shared_library as xray_lib
except ImportError as e:
    xray_import_error = e
    xray_lib = None


@dataclass
class URL:
    """URL data container"""

    uri: str  # full URL including domain and URI
    avg_duration: int  # average duration during the day
    max_duration: int  # maximum duration during the day
    total_slow_reqs: int  # total SLOW request count during the day
    total_reqs: int  # total request count during the day
    belongs_to: str  # domain
    belongs_to_user: str  # domain owner


@dataclass
class RulesRejects:
    """Rejects counters container"""

    non_wp: int = 0  # number of URLs, skipped due to non-WP site
    throttled: int = 0  # number of URLs, skipped due to throttling
    density: int = 0  # number of URLs, skipped due to low density
    slowness: int = 0  # number of URLs, skipped because they are considered fast
    max_slowness: int = 0  # number of URLs, skipped because they are considered too slow
    disabled: int = 0  # number of URLs, skipped due to disabled autotracing
    nginx: int = 0  # number of URLs, skipped due to nginx caching
    frequency: int = 0  # number of URLs, skipped due to min_retracing_interval
    server_limit: int = 0  # number of URLs, skipped due to per-server limit
    domain_limit: int = 0  # number of URLs, skipped due to per-domain limit
    no_domain: int = 0  # number of URLs, skipped due to unavailable domain info (e.g. no domain)


@dataclass
class Stats:
    """AutoTracer statistics container"""

    rules_version: str  # version of rules applied from autotracing.json
    urls_processed: int = 0  # number of URLs, processed within the latest iteration
    urls_selected: int = 0  # number of URLs, selected to launch autotracing tasks
    rejects: RulesRejects = field(default_factory=RulesRejects)  # rejects counters


class URLS(NamedTuple):
    """
    Representation of an URL
    """

    domain_name: str
    uri_path: str


def url_split(url: str) -> URLS:
    """
    Split URL into domain_name and uripath including query string
    :param url: URL of format protocol://domain/path;parameters?query#fragment
    :return: namedtuple URL(domain_name, uripath)
    """
    fragments = urlparse(url)
    qs = f"?{fragments.query}" if fragments.query else ""
    uri = f"{fragments.path}{qs}" if fragments.path else "/"
    _no_www_netloc = fragments.netloc.replace("www.", "")
    _no_port_netloc = _no_www_netloc.split(":")[0]
    return URLS(_no_port_netloc, uri)


class AutoTracer(Common):
    """
    SSA autotracing module implementation.
    """

    def __init__(self, engine=None):
        super().__init__()
        self.logger = logging.getLogger("auto_tracer")
        self.logger.info("AutoTracer enabled: %s", __package__)
        self.disabled_users = list()
        self.tasks_list = list()
        self.stats = None  # initial value for an iteration statistics

        self.engine = engine if engine else setup_database()

    def __call__(self):
        try:
            misconfiguration_checks()
        except SSAError as exc:
            self.logger.info("AutoTracer skipped: %s", exc.reason)
            return

        if xray_lib is None:
            # to send sentry event only if x-ray really not installed
            if os.path.exists("/usr/sbin/cloudlinux-xray-agent"):
                self.logger.error(
                    "AutoTracer skipped: X-ray module import error: %s",
                    str(xray_import_error),
                )
            else:
                self.logger.info("AutoTracer skipped: X-Ray not installed")
            return

        start_tool = xray_lib.start_autotracing

        if start_tool is not None:
            self.logger.info("AutoTracer started")
            # reload config
            super().__init__()
            self.logger.debug("AutoTracer loaded config: %s", self.config)
            # start gather own statistics for a current iteration
            self.stats = Stats(self.rules_version)
            for url in self.urls_scheduled():
                self.logger.info("Starting auto task for %s", url.uri)
                self.stats.urls_selected += 1
                try:
                    start_tool(url=url.uri, tracing_count=self.request_number)
                except Exception as e:
                    # most likely XRayError
                    self.logger.error("Failed to start task: %s", str(e))
        self.save_iteration_stats()

    @staticmethod
    def load_conf() -> dict:
        """
        Load configuration
        """
        return load_tunables("autotracing.json", autotracing_tunables_schema)

    @staticmethod
    def gets_domaininfo(domain_name: str) -> Optional[object]:
        """
        Gets domain info for the specified domain
        """
        if xray_lib is None:
            return None
        return xray_lib.domain_info(domain_name)

    def nginx_is_enabled(self, user_name: str) -> bool:
        """
        Says if nginx is enabled for a specific user
        """
        if self.skip_nginx:
            if xray_lib is None:
                return False
            return xray_lib.NginxUserCache(user_name).is_enabled
        return False

    def per_server_limit_recalculated(self) -> int:
        """Recalculate limit per server taking into account running tasks"""
        running_count = len(
            [task for task in self.tasks_list if task["status"] == "running" and task["user"] == "*autotracing*"]
        )
        self.logger.debug("Number of running autotracing tasks %s", running_count)
        return self.per_server_limit - running_count

    def excludes_old_tasks(self, full_list: Optional[list] = None) -> list:
        """
        Excludes tasks older than N days from the general list of tasks
        """
        if full_list is None:
            full_list = xray_lib.tasks_list()
            self.logger.debug("Task list loaded %s", full_list)

        n_days_ago = datetime.now() - timedelta(days=self.min_retracing_interval)
        return [
            task
            for task in full_list
            if (task.get("createtime") if task.get("createtime") is not None else 0) > int(n_days_ago.timestamp())
        ]

    def exclude_thesame_urls(self, current_url: str) -> bool:
        """
        Excludes url from the list if it completely matches the current url
        or if domain names match and "*" follows the domain name in the list
        """
        # c - current parsed url
        c = url_split(current_url)
        for task_data in self.tasks_list:
            # t - task parsed url
            t = url_split(task_data["url"])
            direct_match = c.domain_name == t.domain_name and c.uri_path == t.uri_path
            wildcard_match = fnmatchcase(c.domain_name, t.domain_name) and fnmatchcase(c.uri_path, t.uri_path)
            if direct_match or wildcard_match:
                self.logger.debug(
                    "Skipped: URL %s was traced recently. Matched by %s",
                    current_url,
                    task_data["url"],
                )
                return True
        return False

    def pass_by_density(self, url_total_reqs: list, domain_total_reqs: list) -> bool:
        """Check that URL density passes given threshold"""
        if self.density:
            url_density = np.amin(np.corrcoef(url_total_reqs, domain_total_reqs))
            self.logger.debug("Calculated density %s", url_density)
            return url_density > self.density_threshold
        return True

    def pass_by_slowness_percentile(self, url_durations: Iterable[int]) -> bool:
        """
        The measure of "slowness" for URL is:
        at least N% of its requests take more than X seconds.
        N% -- self.slow_duration_percentage
        X -- self.slow_duration_threshold
        """
        reversed_percentile = 100 - self.slow_duration_percentage
        reversed_percentile_value = np.percentile(url_durations, reversed_percentile)
        self.logger.debug(
            "Calculated %sth percentile %s for min duration",
            reversed_percentile,
            reversed_percentile_value,
        )
        return reversed_percentile_value >= self.slow_duration_threshold

    def pass_by_max_slowness_percentile(self, url_durations: Iterable[int]) -> bool:
        """
        The opposite to pass_by_slowness_percentile method.
        The measure of "much slowness" for URL is:
        at least N% of its requests must take less than X seconds.
        N% -- self.max_slow_duration_percentage
        X -- self.max_slow_duration_threshold
        """
        percentile_value = np.percentile(url_durations, self.max_slow_duration_percentage)
        self.logger.debug(
            "Calculated %sth percentile %s for max duration",
            self.max_slow_duration_percentage,
            percentile_value,
        )
        return percentile_value <= self.max_slow_duration_threshold

    def pass_by_allowed_throttling(self, url_throttled_reqs: Optional[list], url_total_reqs: list) -> bool:
        """
        Check that percent of throttled requests per URL passes given threshold
        """
        if url_throttled_reqs is None:
            # skip URL with unavailable throttling info
            return False
        throttled_percent = (sum(url_throttled_reqs) / sum(url_total_reqs)) * 100
        self.logger.debug("Calculated throttled percent %s", throttled_percent)
        return throttled_percent <= self.allowed_throttling_percentage

    def pass_by_engine(self, wp_status: Optional[bool]) -> bool:
        """
        Check that URLs of a particular domain should be analyzed.
        For now we skip non-wordpress sites
        """
        if self.only_wp:
            # turn unavailable wp_status, aka None, into False
            return bool(wp_status)
        return True

    def urls_computationally_filtered(self) -> Iterator[URL]:
        """
        Select all URLs suitable for auto tracing by very basic rules:
         - WP site
         - suitable throttling
         - suitable density
         - measure of "slow" URL
         ORDER OF RULES MUST NOT BE CHANGED: IT AFFECTS STATISTICS COUNTERS
        """
        for domain_data in iter_domains_data(self.engine):
            domain_owner = None
            if not self.pass_by_engine(domain_data.is_a_wordpress_domain):
                # rule ordering #1: skip non-wordpress sites
                # corresponds to non_wp RulesRejects counter
                self.logger.debug("Skipped by engine: non-wordpress")
                # all URLs of non-WP site are skipped then,
                # thus counters (reject abd total) are to be increased
                # on number of these URLs ignoring non-URL data fields
                skipped_count = domain_data.urls_number
                self.stats.rejects.non_wp += skipped_count
                self.stats.urls_processed += skipped_count
                continue

            # stream per-URL durations + aggregates one path at a time
            # (merge-join in storage) so the whole per-domain
            # {path: [durations...]} working set never lives in memory at
            # once; bounds peak RSS to a single URL for the cgroup ceiling
            for url, durations, data in iter_domain_url_data(self.engine, domain_data.domain_name):
                if url in self.non_url_fields:
                    # skip entry of domain requests counter
                    continue

                self.logger.debug("Processing URL %s", url)
                self.stats.urls_processed += 1
                if not self.pass_by_allowed_throttling(data.get("url_throttled_reqs"), data["url_total_reqs"]):
                    # rule ordering #2: percent of throttled requests
                    # corresponds to throttled RulesRejects counter
                    self.logger.debug("Skipped by throttled percent")
                    self.stats.rejects.throttled += 1
                    continue

                if not self.pass_by_density(data["url_total_reqs"], domain_data.domain_total_reqs):
                    # rule ordering #3: density threshold
                    # corresponds to density RulesRejects counter
                    self.logger.debug("Skipped by density")
                    self.stats.rejects.density += 1
                    continue

                if not self.pass_by_slowness_percentile(durations):
                    # rule ordering #4: slowness assessment
                    # corresponds to slowness RulesRejects counter
                    self.logger.debug("Skipped by slowness percentile")
                    self.stats.rejects.slowness += 1
                    continue

                if not self.pass_by_max_slowness_percentile(durations):
                    # rule ordering #5: maximum allowed slowness assessment
                    # corresponds to max_slowness RulesRejects counter
                    self.logger.debug("Skipped by max slowness percentile")
                    self.stats.rejects.max_slowness += 1
                    continue

                # the URL has passed all computational checks
                # from here we already need username
                if domain_owner is None:
                    domain_info = self.gets_domaininfo(domain_data.domain_name)
                    if domain_info is None:
                        # this generally indicates "Domain does not exist"
                        # error, we should skip such URLs
                        self.logger.debug("Skipped by unavailable domain info")
                        self.stats.rejects.no_domain += 1
                        continue
                    else:
                        domain_owner = domain_info.user

                yield URL(
                    url,
                    avg_duration=int(np.mean(durations)),
                    total_slow_reqs=sum(data["url_slow_reqs"]),
                    total_reqs=sum(data["url_total_reqs"]),
                    max_duration=max(durations),
                    belongs_to=domain_data.domain_name,
                    belongs_to_user=domain_owner,
                )

    def urls_selected(self, stats_collected: Optional[dict] = None) -> Iterator[URL]:
        """
        From selected by computed thresholds URLs take those for which:
         - autotracing enabled
         - nginx disabled
        ORDER OF RULES MUST NOT BE CHANGED: IT AFFECTS STATISTICS COUNTERS
        """
        # fill disabled users list, initially empty
        self.fill_in_disabled_users()

        for url in self.urls_computationally_filtered():
            if url.belongs_to_user in self.disabled_users:
                # rule ordering #6: skip users for whom autotracing is disabled
                # corresponds to disabled RulesRejects counter
                self.logger.debug("Skipped: autotracing is disabled for %s", url.belongs_to_user)
                self.stats.rejects.disabled += 1
                continue
            if self.nginx_is_enabled(url.belongs_to_user):
                # rule ordering #7: skip url the owner of which uses nginx
                # corresponds to nginx RulesRejects counter
                self.logger.debug("Skipped: nginx is enabled for %s", url.belongs_to_user)
                self.stats.rejects.nginx += 1
                continue
            yield url

    def urls_scheduled(self) -> Iterator[URL]:
        """
        Schedule autotracing by sorted list taking into account the limits:
         - no same task for 10 days
         - limit per server
         - limit per domain
        Rule ordering still affects statistics counters, but the counting for
        rules #8 (frequency) and #9 (domain_limit) now happens during candidate
        selection in urls_sorted() (which bounds the candidate list to the best
        per_domain_limit URLs per domain). Only server_limit (#10) is counted
        here. Keep this attribution in sync with urls_sorted() and
        docs/design/autotracer-and-decision-maker.md.
        Return resulting list of URLs scheduled for auto tracing
        """
        # initial limit counters
        general_tasks_counter = 0
        tasks_counter_per_domain = defaultdict(int)
        # get task list and filter out all old tasks in one turn
        # (urls_sorted() consults it to drop frequency-excluded candidates)
        self.tasks_list = self.excludes_old_tasks()
        per_server_smart_limit = self.per_server_limit_recalculated()
        # select and sort candidate URLs (bounded to the best per_domain_limit
        # candidates per domain, so the full candidate list is never
        # materialized/sorted)
        sorted_urls = self.urls_sorted()
        self.logger.debug("Sorted scheduled list %s", sorted_urls)
        for url in sorted_urls:
            if self.exclude_thesame_urls(url.uri):
                # rule ordering #8: limit of days for url (min_retracing_interval)
                # corresponds to frequency RulesRejects counter
                self.stats.rejects.frequency += 1
                continue
            if general_tasks_counter < per_server_smart_limit:
                if tasks_counter_per_domain[url.belongs_to] < self.per_domain_limit:
                    general_tasks_counter += 1
                    tasks_counter_per_domain[url.belongs_to] += 1
                    yield url
                else:
                    # rule ordering #9: domain limit is hit
                    # corresponds to domain_limit RulesRejects counter
                    self.logger.debug(
                        "Skipped URL %s by domain limit (%s)",
                        url.uri,
                        self.per_domain_limit,
                    )
                    self.stats.rejects.domain_limit += 1
            else:
                # rule ordering #10: server limit is hit
                # corresponds to server_limit RulesRejects counter
                self.logger.debug(
                    "Skipped URL %s by server limit (%s)",
                    url.uri,
                    per_server_smart_limit,
                )
                self.stats.rejects.server_limit += 1

    def urls_sorted(self) -> List[URL]:
        """
        Select candidate URLs for scheduling, sorted by total number of
        requests first and by average duration second.

        Only the best ``per_domain_limit`` candidates per domain are retained:
        a domain can never schedule more than that (see urls_scheduled), so
        lower-ranked same-domain candidates are unschedulable. Frequency
        excluded URLs (min_retracing_interval) are dropped up front as well,
        since they never consume a schedule slot. This bounds peak memory to
        O(domains * per_domain_limit) instead of materializing and fully
        sorting every candidate — an attacker can inflate the candidate count
        with distinct cache-busting query strings, but they all collapse onto
        their own domain's small per-domain cap (CLPRO-3310 F-09).
        """
        per_domain_limit = self.per_domain_limit
        # per-domain bounded selection: each domain keeps a min-heap of its
        # best per_domain_limit candidates. `order` is a per-survivor sequence
        # number: negating it in the sort key reproduces the previous stable
        # double-sort tie-break (earlier candidate wins on equal metrics) and
        # keeps heap entries totally ordered so URL objects are never compared.
        per_domain_best: Dict[str, list] = defaultdict(list)
        order = 0
        for url in self.urls_selected():
            if self.exclude_thesame_urls(url.uri):
                # rule ordering #8: limit of days for url (min_retracing_interval)
                # corresponds to frequency RulesRejects counter
                self.stats.rejects.frequency += 1
                continue
            order += 1
            entry = ((url.total_reqs, url.avg_duration, -order), url)
            heap = per_domain_best[url.belongs_to]
            if len(heap) < per_domain_limit:
                heapq.heappush(heap, entry)
            elif per_domain_limit > 0 and entry[0] > heap[0][0]:
                # better than the weakest kept candidate for this domain;
                # the evicted one is unschedulable by the per-domain cap
                heapq.heapreplace(heap, entry)
                self.stats.rejects.domain_limit += 1
            else:
                # rule ordering #9: domain limit is hit
                # corresponds to domain_limit RulesRejects counter
                self.stats.rejects.domain_limit += 1
        candidates = [entry for heap in per_domain_best.values() for entry in heap]
        candidates.sort(key=lambda entry: entry[0], reverse=True)
        return [url for _, url in candidates]

    def fill_in_disabled_users(self) -> None:
        """
        Fill internal list of disabled users
        """
        self.disabled_users = disabled_users()

    def save_iteration_stats(self) -> None:
        """
        Save collected statistics for current iteration to file
        """
        if self.stats is not None:
            try:
                with open(autotracing_stats_file, "w") as stats_file:
                    json.dump(asdict(self.stats), stats_file)
            except OSError as e:
                self.logger.warning("Unable to save iteration stats to file: %s", str(e))

    def load_iteration_stats(self) -> dict:
        """
        Load statistics for latest iteration from file
        """
        try:
            with open(autotracing_stats_file) as stats_file:
                _data = json.load(stats_file)
                stat_data = Stats(
                    _data["rules_version"],
                    _data["urls_processed"],
                    _data["urls_selected"],
                    RulesRejects(**_data["rejects"]),
                )
        except (OSError, json.JSONDecodeError, KeyError):
            stat_data = Stats(self.rules_version)
        return asdict(stat_data)

    def get_stats(self) -> dict:
        """"""
        # load saved stats
        stats_loaded = self.load_iteration_stats()
        stats_loaded.update(dict(status=status()[0], disabled_users_quantity=len(disabled_users())))
        return stats_loaded


def standalone_log_path() -> str:
    """Absolute path of the standalone auto-tracer log.

    Always resolves inside the fixed, root-owned clos_ssa log directory
    (derived from ``autotracing_log``) rather than against the caller's cwd,
    so the destination cannot be redirected by the directory the dev entry
    point happens to be launched from.
    """
    return os.path.join(os.path.dirname(autotracing_log), "auto_tracer_standalone.log")


def open_standalone_log(log_path: str):
    """Open ``log_path`` for appending and return the file object.

    Uses ``O_NOFOLLOW`` so a symlink pre-planted at the target is refused
    rather than followed: the open raises instead of appending through the
    link to an arbitrary root-owned file.
    """
    log_fd = os.open(log_path, os.O_WRONLY | os.O_CREAT | os.O_APPEND | os.O_NOFOLLOW, 0o640)
    return os.fdopen(log_fd, "a")


if __name__ == "__main__":
    sentry_init()
    # Log to the fixed, root-owned clos_ssa log dir, never a relative path
    # resolved against the caller's cwd, and refuse to follow a symlink
    # planted at the target (O_NOFOLLOW).
    logging.basicConfig(stream=open_standalone_log(standalone_log_path()), level=logging.DEBUG)
    t = AutoTracer()
    t()