#!/usr/bin/env python3

"""A check plugin for Nagios/Icinga/etc. that queries Home Assistant for the current state of entities."""

import argparse
import dataclasses
import logging
import re
import sys
from urllib.parse import urljoin
from typing import Optional
from pathlib import Path

import requests
import nagiosplugin

_log = logging.getLogger("nagiosplugin")


@dataclasses.dataclass
class Entities(nagiosplugin.Resource):
    url: str
    token: str
    device_class: str
    numeric: bool
    filters: list[str]
    attribute: Optional[str]
    friendly_name: bool
    min: Optional[float] = None
    max: Optional[float] = None

    def hass_get(self, endpoint: str) -> requests.Response:
        headers = {
            "Authorization": "Bearer " + self.token,
            "Content-Type": "application/json",
        }

        r = requests.get(urljoin(self.url, endpoint), headers=headers)
        if not r.ok:
            raise Exception("Failed to query Home Assistant API: " + r.text)

        return r.json()

    def check_api(self):
        message = self.hass_get("/api/").get("message")
        if message != "API running.":
            print("ERROR: " + message)
            sys.exit(1)
        else:
            print("OK: " + message)

    def probe(self):
        response = self.hass_get("/api/states")
        for state in response:
            if state["attributes"].get("device_class") == self.device_class and all(
                state["attributes"].get(k) == v for k, v in self.filters
            ):
                if self.attribute is not None:
                    value = state["attributes"].get(
                        self.attribute, -1 if self.numeric else "attribute missing"
                    )
                    uom = None
                else:
                    if self.numeric:
                        value = (
                            float(state["state"]) if state["state"].isnumeric() else -1
                        )
                    else:
                        value = state["state"]
                    uom = state["attributes"].get("unit_of_measurement")

                if self.friendly_name:
                    name = (
                        state["attributes"]
                        .get("friendly_name", state["entity_id"])
                        .translate({ord(c): "_" for c in "'="})
                    )
                else:
                    name = state["entity_id"]

                if state["state"] == "unavailable":
                    _log.info(f"{state['entity_id']} unavailable")
                yield nagiosplugin.Metric(
                    name,
                    value,
                    uom,
                    context=self.device_class,
                    min=self.min,
                    max=self.max,
                )


class RegexContext(nagiosplugin.Context):
    def __init__(
        self,
        name: str,
        ok: str = None,
        warning: str = None,
        critical: str = None,
        fmt_metric=None,
        result_cls=nagiosplugin.Result,
    ):
        super().__init__(name, fmt_metric=fmt_metric, result_cls=result_cls)
        # '.^' should match nothing
        self.ok = re.compile(ok or ".^")
        self.warning = re.compile(warning or ".^")
        self.critical = re.compile(critical or ".^")

    def fmt_reason(self, regex: re.Pattern, metric: nagiosplugin.Metric) -> str:
        return f"{metric.name} matched regex '{regex.pattern}' ({metric.value})"

    def evaluate(self, metric: nagiosplugin.Metric, resource):
        if self.critical.match(metric.value):
            return self.result_cls(
                nagiosplugin.Critical, self.fmt_reason(self.critical, metric), metric
            )
        elif self.warning.match(metric.value):
            return self.result_cls(
                nagiosplugin.Warn, self.fmt_reason(self.warning, metric), metric
            )
        elif self.ok.match(metric.value):
            return self.result_cls(
                nagiosplugin.Ok, self.fmt_reason(self.ok, metric), metric
            )
        else:
            return self.result_cls(
                nagiosplugin.Unknown,
                f"{metric.name} did not match any defined patterns ({metric.value})",
                metric,
            )


def key_value(arg: str):
    k, _, v = arg.partition("=")
    return k, v


class Icinga2ConfAction(argparse.Action):
    def __init__(
        self,
        option_strings,
        dest=argparse.SUPPRESS,
        default=argparse.SUPPRESS,
        help="Generate conf file for icinga2 CheckCommand",
    ):
        super().__init__(
            option_strings=option_strings,
            dest=dest,
            default=default,
            nargs=0,
            help=help,
        )

    def _format_actions(self, param_prefix: str, parser: argparse.ArgumentParser):
        for action in parser._actions:
            if action.dest in [self.dest, "help", "version"] or isinstance(
                action, argparse._SubParsersAction
            ):
                continue

            arg_str = action.option_strings[-1]
            icinga2_var = arg_str.lstrip("-").replace("-", "_")
            print(f'    "{arg_str}" = {{')

            if action.required:
                print("      required = true")

            if isinstance(
                action,
                (
                    argparse._StoreConstAction,
                    argparse._CountAction,
                    argparse._AppendConstAction,
                ),
            ):
                print(f'      set_if = "${param_prefix}_{icinga2_var}$"')
            else:
                print(f'      value = "${param_prefix}_{icinga2_var}$"')

            print(f'      description = "{action.help}"')
            print("    }")

    def __call__(
        self, parser: argparse.ArgumentParser, namespace, values, option_string=None
    ):
        filename = Path(__file__).absolute()
        command_name = filename.stem.removeprefix("check_")
        # FIXME: assumes that script will be in a subdirectory of PluginContribDir
        command_path = filename.relative_to(filename.parents[1])

        if parser._subparsers:
            # TODO: this seems a bit more hacky than it needs to be
            choices = parser._subparsers._group_actions[0].choices
            for subname, subparser in choices.items():
                print(f'object CheckCommand "{command_name}" {{')
                print(
                    f'  command = [ PluginContribDir + "/{command_path}", "{subname}" ]'
                )

                print("  arguments = {")

                self._format_actions(command_name, parser)
                self._format_actions(f"{command_name}_{subname}", subparser)

                print("  }\n}")
        else:
            print(f'object CheckCommand "{command_name}" {{')
            print(f'  command = [ PluginContribDir + "/{command_path}" ]')

            print("  arguments = {")

            self._format_actions(command_name, parser)

            print("  }\n}")

        parser.exit()


@nagiosplugin.guarded
def main():
    argp = argparse.ArgumentParser(description=__doc__)

    argp.add_argument("--version", action="version", version="0.1.0")
    argp.add_argument("-v", "--verbose", action="count", default=0)
    argp.add_argument("--make-icinga-conf", action=Icinga2ConfAction)

    argp.add_argument(
        "-t",
        "--token",
        required=True,
        type=str,
        help="token for Home Assistant REST API (see https://developers.home-assistant.io/docs/api/rest/)",
    )
    argp.add_argument(
        "-u", "--url", required=True, type=str, help="URL for Home Assistant"
    )

    shared_parser = argparse.ArgumentParser(add_help=False)
    common_args = shared_parser.add_argument_group(
        "Common Arguments", "Arguments shared between metric types"
    )
    common_args.add_argument(
        "-d",
        "--device-class",
        type=str,
        required=True,
        help="device class of entities to monitor",
    )
    common_args.add_argument(
        "-a", "--attribute", type=str, help="check attribute instead of value"
    )
    common_args.add_argument(
        "-f",
        "--filter",
        type=key_value,
        default=[],
        nargs="*",
        help="filter by 'attribute=value' (may be specified multiple times)",
    )
    common_args.add_argument(
        "--friendly",
        action="store_true",
        help="use friendly name, when available",
    )

    subparsers = argp.add_subparsers(
        title="Query type", required=True, dest="subparser_name"
    )

    scalar_parser = subparsers.add_parser(
        "scalar", help="Numeric metrics", parents=[shared_parser]
    )
    scalar_parser.add_argument(
        "-w",
        "--warning",
        metavar="RANGE",
        required=True,
        help="return warning if value is outside %(metavar)s",
    )
    scalar_parser.add_argument(
        "-c",
        "--critical",
        metavar="RANGE",
        required=True,
        help="return critical if value is outside %(metavar)s",
    )
    scalar_parser.add_argument(
        "--min",
        type=float,
        help="min for performance data",
    )
    scalar_parser.add_argument(
        "--max",
        type=float,
        help="max for performance data",
    )

    text_parser = subparsers.add_parser(
        "text", help="Textual metrics", parents=[shared_parser]
    )
    text_parser.add_argument(
        "-o",
        "--ok",
        metavar="REGEX",
        help="return ok if value matches %(metavar)s",
    )
    text_parser.add_argument(
        "-w",
        "--warning",
        metavar="REGEX",
        help="return warning if value matches %(metavar)s",
    )
    text_parser.add_argument(
        "-c",
        "--critical",
        metavar="REGEX",
        help="return critical if value matches %(metavar)s",
    )

    args = argp.parse_args()
    if args.subparser_name == "scalar":
        check = nagiosplugin.Check(
            Entities(
                url=args.url,
                token=args.token,
                device_class=args.device_class,
                numeric=True,
                min=args.min,
                max=args.max,
                filters=args.filter,
                attribute=args.attribute,
                friendly_name=args.friendly,
            ),
            nagiosplugin.ScalarContext(args.device_class, args.warning, args.critical),
        )
    elif args.subparser_name == "text":
        check = nagiosplugin.Check(
            Entities(
                url=args.url,
                token=args.token,
                device_class=args.device_class,
                numeric=False,
                filters=args.filter,
                attribute=args.attribute,
                friendly_name=args.friendly,
            ),
            RegexContext(args.device_class, args.ok, args.warning, args.critical),
        )

    check.main(args.verbose)


if __name__ == "__main__":
    main()