from __future__ import annotations

import logging
from collections.abc import Mapping
from dataclasses import dataclass, field
from datetime import datetime, timedelta
from typing import Any

from blackout_notifier.clients import ExternalServiceError, Notifier, SaapaClient
from blackout_notifier.messages import (
    cancelled_outage_message,
    new_outage_message,
    reactivated_outage_message,
    updated_outage_message,
)
from blackout_notifier.models import Outage, OutageDataError, jalali_query_window
from blackout_notifier.state import StateRepository

LOGGER = logging.getLogger(__name__)


@dataclass(slots=True)
class RunResult:
    sent: int = 0
    state_changed: bool = False
    errors: list[str] = field(default_factory=list)


class OutageService:
    def __init__(
        self,
        *,
        bill_chat_ids: Mapping[str, tuple[str, ...]],
        lookahead_days: int,
        saapa: SaapaClient,
        notifier: Notifier,
        state_repository: StateRepository,
    ) -> None:
        self._bill_chat_ids = dict(bill_chat_ids)
        self._lookahead_days = lookahead_days
        self._saapa = saapa
        self._notifier = notifier
        self._state_repository = state_repository

    def run(self, now: datetime, *, persist: bool = True) -> RunResult:
        state = self._state_repository.load()
        result = RunResult()
        from_date, to_date = jalali_query_window(now, self._lookahead_days)

        for bill_id, chat_ids in self._bill_chat_ids.items():
            try:
                outages = self._saapa.fetch(bill_id, from_date, to_date)
            except ExternalServiceError as error:
                result.errors.append(str(error))
                LOGGER.error("%s", error)
                continue
            self._process_bill(state, bill_id, chat_ids, outages, now, result)

        if self._prune_expired(state, now):
            result.state_changed = True
        if result.state_changed and persist:
            state["updated_at"] = now.isoformat()
            self._state_repository.save(state)
        return result

    def _process_bill(
        self,
        state: dict[str, Any],
        bill_id: str,
        chat_ids: tuple[str, ...],
        outages: list[Outage],
        now: datetime,
        result: RunResult,
    ) -> None:
        bills = state["bills"]
        bill_state = bills.get(bill_id)
        if bill_state is None:
            bill_state = {"events": {}}
        records: dict[str, dict[str, Any]] = bill_state["events"]
        current = {
            outage.outage_number: outage for outage in outages if outage.stop_datetime() > now
        }

        for event_id, outage in current.items():
            record = records.get(event_id)
            if record is None:
                if self._notify(chat_ids, new_outage_message(bill_id, outage, now), result):
                    records[event_id] = _record(outage, now)
                    result.state_changed = True
                continue

            previous = Outage.from_dict(record["snapshot"])
            if record["status"] == "cancelled":
                if self._notify(chat_ids, reactivated_outage_message(bill_id, outage, now), result):
                    records[event_id] = _record(outage, now)
                    result.state_changed = True
                continue

            if outage.fingerprint() != record["notified_hash"]:
                if self._notify(
                    chat_ids,
                    updated_outage_message(bill_id, previous, outage, now),
                    result,
                ):
                    records[event_id] = _record(outage, now)
                    result.state_changed = True
                continue

            if record["missing_checks"]:
                record["missing_checks"] = 0
                record["last_seen_at"] = now.isoformat()
                result.state_changed = True

        for event_id, record in list(records.items()):
            if event_id in current or record["status"] != "active":
                continue
            try:
                previous = Outage.from_dict(record["snapshot"])
            except OutageDataError as error:
                result.errors.append(f"Invalid stored outage for bill {bill_id}: {error}")
                continue
            if previous.start_datetime() <= now:
                continue
            if record["missing_checks"] == 0:
                record["missing_checks"] = 1
                result.state_changed = True
            elif self._notify(chat_ids, cancelled_outage_message(bill_id, previous, now), result):
                record["status"] = "cancelled"
                record["missing_checks"] = 2
                record["notified_at"] = now.isoformat()
                result.state_changed = True

        if records and bill_id not in bills:
            bills[bill_id] = bill_state

    def _notify(self, chat_ids: tuple[str, ...], message: str, result: RunResult) -> bool:
        delivered_to_all = True
        for chat_id in chat_ids:
            try:
                self._notifier.send(chat_id, message)
            except ExternalServiceError as error:
                result.errors.append(str(error))
                LOGGER.error("%s", error)
                delivered_to_all = False
                continue
            result.sent += 1
        return delivered_to_all

    @staticmethod
    def _prune_expired(state: dict[str, Any], now: datetime) -> bool:
        changed = False
        cutoff = now - timedelta(days=30)
        for bill_id, bill_state in list(state["bills"].items()):
            records = bill_state["events"]
            for event_id, record in list(records.items()):
                outage = Outage.from_dict(record["snapshot"])
                if outage.stop_datetime() < cutoff:
                    del records[event_id]
                    changed = True
            if not records:
                del state["bills"][bill_id]
                changed = True
        return changed


def _record(outage: Outage, now: datetime) -> dict[str, Any]:
    return {
        "snapshot": outage.to_dict(),
        "notified_hash": outage.fingerprint(),
        "status": "active",
        "missing_checks": 0,
        "last_seen_at": now.isoformat(),
        "notified_at": now.isoformat(),
    }