import { IMonitorStatsRepository } from "@/domain/monitor-stats/monitor-stats.repository.interface.js";
import { IMonitorsRepository } from "@/domain/monitors/monitor.repository.interface.js";
import type { Check, CheckDiskInfo } from "@/domain/checks/check.type.js";
import {
	HardwareMetricKeys,
	MonitorStatuses,
	type HardwareBreaches,
	type HardwareCounters,
	type Monitor,
	type MonitorStatus,
} from "@/domain/monitors/monitor.type.js";
import type { StatusChangeResult } from "@/types/network.js";
import { AppError } from "@/utils/AppError.js";
import { ILogger } from "@/utils/logger.js";
import type { HardwareStatusMetrics } from "@/types/network.js";
import { MAX_RECENT_CHECKS } from "@/domain/monitors/monitor.type.js";
import { toCheckSnapshot } from "@/domain/checks/check.snapshot.js";
import { findContainerBreaches } from "@/domain/docker/docker-alert.js";

const SERVICE_NAME = "StatusService";
const HARDWARE_ALERT_COUNTER_START = 5;

export interface IStatusService {
	updateRunningStats(check: Check, monitor: Monitor): Promise<boolean>;
	updateMonitorStatus(check: Check, monitor: Monitor): Promise<StatusChangeResult>;
}

export class StatusService implements IStatusService {
	static SERVICE_NAME = SERVICE_NAME;
	private logger: ILogger;
	private monitorsRepository: IMonitorsRepository;
	private monitorStatsRepository: IMonitorStatsRepository;

	constructor(logger: ILogger, monitorsRepository: IMonitorsRepository, monitorStatsRepository: IMonitorStatsRepository) {
		this.logger = logger;
		this.monitorsRepository = monitorsRepository;
		this.monitorStatsRepository = monitorStatsRepository;
	}

	async updateRunningStats(check: Check, monitor: Monitor) {
		try {
			await this.monitorStatsRepository.updateByMonitorId(monitor.id, {
				status: check.status === true,
				responseTime: check.responseTime ?? 0,
				now: Date.now(),
			});
			return true;
		} catch (error: unknown) {
			this.logger.error({
				service: SERVICE_NAME,
				message: error instanceof Error ? error.message : "Unknown error",
				method: "updateRunningStats",
				stack: error instanceof Error ? error.stack : undefined,
			});
			return false;
		}
	}

	private tryUpdateRunningStats = async (check: Check, monitor: Monitor) => {
		const statsOk = await this.updateRunningStats(check, monitor);
		if (!statsOk) {
			this.logger.warn({
				service: SERVICE_NAME,
				method: "updateMonitorStatus",
				message: `Stats update failed for monitor ${monitor.id}`,
			});
		}
	};

	private computeReachability = (
		currentStatus: MonitorStatus,
		window: Array<boolean>,
		threshold: number
	): { nextStatus: "up" | "down"; transitioned: boolean } => {
		const failures = window.filter((status) => status === false).length;
		const failureRate = (failures / window.length) * 100;

		if (failureRate >= threshold && currentStatus !== "down") {
			return { nextStatus: "down", transitioned: true };
		}

		if (failureRate < threshold && currentStatus === "down") {
			return { nextStatus: "up", transitioned: true };
		}
		return { nextStatus: "up", transitioned: false };
	};

	private computeHardwareStatus = (params: {
		currentStatus: MonitorStatus;
		reachabilityDown: boolean;
		metrics: HardwareStatusMetrics;
		thresholds: { cpu: number; memory: number; disk: number; temp: number };
		counters: HardwareCounters;
	}): {
		nextStatus: MonitorStatus;
		transitioned: boolean;
		breaches: HardwareBreaches;
		nextCounters: HardwareCounters;
	} => {
		const { metrics, thresholds, counters, currentStatus, reachabilityDown } = params;

		const cpuUsage = metrics.cpu?.usage_percent ?? -1;
		const memoryUsage = metrics.memory?.usage_percent ?? -1;
		const temps = metrics.cpu?.temperature ?? [];

		const breaches: HardwareBreaches = {
			cpu: cpuUsage !== -1 && cpuUsage > thresholds.cpu / 100,
			memory: memoryUsage !== -1 && memoryUsage > thresholds.memory / 100,
			disk: metrics.disk
				? metrics.disk.some((d: CheckDiskInfo) => d != null && typeof d.usage_percent === "number" && d.usage_percent > thresholds.disk / 100)
				: false,
			temp: temps.some((temp: number) => temp > thresholds.temp),
		};

		// Update counters: decrement (floored at 0) if breached, reset to start otherwise.
		const nextCounters = { ...counters };
		for (const key of HardwareMetricKeys) {
			nextCounters[key] = breaches[key] ? Math.max(0, counters[key] - 1) : HARDWARE_ALERT_COUNTER_START;
		}

		// Status transition: reachability "down" takes precedence; hardware can only drive
		// transitions into "breached" and back out to "up". Any other case leaves status untouched.
		let nextStatus: MonitorStatus = currentStatus;
		let transitioned = false;

		if (!reachabilityDown) {
			// A counter can only reach zero via the decrement path, which only runs when that
			// metric is currently breaching — so anyCounterZero already implies anyBreached.
			const anyCounterZero = HardwareMetricKeys.some((k) => nextCounters[k] === 0);
			const allNormal = HardwareMetricKeys.every((k) => !breaches[k]);

			if (anyCounterZero && currentStatus !== "breached") {
				nextStatus = "breached";
				transitioned = true;
			} else if (allNormal && currentStatus === "breached") {
				nextStatus = "up";
				transitioned = true;
			}
		}

		return { nextStatus, transitioned, breaches, nextCounters };
	};

	private computeDockerStatus = (params: { currentStatus: MonitorStatus; reachabilityDown: boolean; breaching: boolean }) => {
		const { currentStatus, reachabilityDown, breaching } = params;
		let nextStatus: MonitorStatus = currentStatus;
		let transitioned = false;

		if (!reachabilityDown) {
			if (breaching && currentStatus !== "breached") {
				nextStatus = "breached";
				transitioned = true;
			} else if (!breaching && currentStatus === "breached") {
				nextStatus = "up";
				transitioned = true;
			}
		}
		return { nextStatus, transitioned };
	};

	updateMonitorStatus = async (check: Check, monitor: Monitor): Promise<StatusChangeResult> => {
		try {
			const { status } = check;

			// Update running stats
			await this.tryUpdateRunningStats(check, monitor);

			const prevStatus = monitor.status;
			const checkSnapshot = toCheckSnapshot(check);

			// Project the window as it will look after updating DB
			// This is done because we need the updated status window to compute new status, but we don't
			// want an an extra DB write just to get the window.
			const projectedWindow = [...(monitor.statusWindow || []), check.status].slice(-monitor.statusWindowSize);

			// Build the status patch — computed against the projected window
			const patch: Partial<Monitor> = {};

			// Resolve "initializing" and "maintenance" up front, incidents should be created on initialization && down
			// Unknown values (e.g. legacy boolean statuses from old versions) are resolved the same way,
			// otherwise computeReachability can never transition them and they stay stuck forever.
			const isUnknownStatus = !MonitorStatuses.includes(monitor.status);
			let newStatus: MonitorStatus = monitor.status;
			let statusChanged = false;
			if (monitor.status === "initializing" || monitor.status === "maintenance" || isUnknownStatus) {
				newStatus = status ? "up" : "down";
				patch.status = newStatus;
				statusChanged = newStatus === "down";
			}

			let thresholdBreaches: HardwareBreaches | undefined;

			if (projectedWindow.length >= monitor.statusWindowSize) {
				// First evaluate reachability status changes, which apply to all monitor types
				// and take precedence over hardware breaches.
				const reachabilityResult = this.computeReachability(newStatus, projectedWindow, monitor.statusWindowThreshold);
				if (reachabilityResult.transitioned) {
					newStatus = reachabilityResult.nextStatus;
					statusChanged = true;
				}

				// Evaluate hardware threshold breaches
				if (monitor.type === "hardware") {
					const hardware = this.computeHardwareStatus({
						currentStatus: newStatus,
						reachabilityDown: newStatus === "down",
						metrics: check,
						thresholds: {
							cpu: monitor.cpuAlertThreshold,
							memory: monitor.memoryAlertThreshold,
							disk: monitor.diskAlertThreshold,
							temp: monitor.tempAlertThreshold,
						},
						counters: {
							cpu: monitor.cpuAlertCounter,
							memory: monitor.memoryAlertCounter,
							disk: monitor.diskAlertCounter,
							temp: monitor.tempAlertCounter,
						},
					});

					patch.cpuAlertCounter = hardware.nextCounters.cpu;
					patch.memoryAlertCounter = hardware.nextCounters.memory;
					patch.diskAlertCounter = hardware.nextCounters.disk;
					patch.tempAlertCounter = hardware.nextCounters.temp;
					thresholdBreaches = hardware.breaches;
					if (hardware.transitioned) {
						newStatus = hardware.nextStatus;
						statusChanged = true;
					}
				}

				if (monitor.type === "docker" && check.containers) {
					const breaches = findContainerBreaches(monitor, check.containers);
					const docker = this.computeDockerStatus({
						currentStatus: newStatus,
						reachabilityDown: newStatus === "down",
						breaching: breaches.length > 0,
					});
					if (docker.transitioned) {
						newStatus = docker.nextStatus;
						statusChanged = true;
					}
				}
				patch.status = newStatus;
			}

			// Single atomic write: push arrays + set status/counters
			const updated = await this.monitorsRepository.updateStatusWindowAndChecks(
				monitor.id,
				monitor.teamId,
				check.status,
				checkSnapshot,
				monitor.statusWindowSize,
				MAX_RECENT_CHECKS,
				patch
			);

			return {
				monitor: updated,
				statusChanged,
				prevStatus,
				thresholdBreaches,
			};
		} catch (error: unknown) {
			throw new AppError({
				message: `Failed to update monitor with id ${check.metadata.monitorId} with status: ${error instanceof Error ? error.message : "Unknown error"}`,
				service: SERVICE_NAME,
				method: "updateMonitorStatus",
			});
		}
	};
}