import { FastifyInstance } from "fastify"
import { HeadBucketCommand } from "@aws-sdk/client-s3"
import { s3 } from "../utils/s3"
import { secrets } from "../utils/secrets"

type MetricSample = {
    labels: Record<string, string>
    value: number
}

const metricLinePattern = /^([a-zA-Z_:][a-zA-Z0-9_:]*)(?:\{([^}]*)\})?\s+(-?(?:\d+(?:\.\d+)?|\.\d+)(?:e[+-]?\d+)?|-?Inf|NaN)$/i

const nodeExporterUrl = () =>
    (process.env.NODE_EXPORTER_URL || "http://node-exporter:9100").replace(/\/+$/, "")

const parseLabels = (value = "") => {
    const labels: Record<string, string> = {}
    const labelPattern = /(\w+)="((?:\\"|[^"])*)"/g
    let match: RegExpExecArray | null

    while ((match = labelPattern.exec(value))) {
        labels[match[1]] = match[2].replace(/\\"/g, "\"")
    }

    return labels
}

const parsePrometheusMetrics = (text: string) => {
    const metrics = new Map<string, MetricSample[]>()

    for (const line of text.split("\n")) {
        if (!line || line.startsWith("#")) continue

        const match = line.match(metricLinePattern)
        if (!match) continue

        const value = Number(match[3])
        if (!Number.isFinite(value)) continue

        const samples = metrics.get(match[1]) || []
        samples.push({
            labels: parseLabels(match[2]),
            value,
        })
        metrics.set(match[1], samples)
    }

    return metrics
}

const firstMetricValue = (metrics: Map<string, MetricSample[]>, name: string) =>
    metrics.get(name)?.[0]?.value ?? null

const findMetricValue = (
    metrics: Map<string, MetricSample[]>,
    name: string,
    predicate: (sample: MetricSample) => boolean
) => metrics.get(name)?.find(predicate)?.value ?? null

const serviceState = (ok: boolean, detail?: Record<string, any>) => ({
    ok,
    status: ok ? "ok" : "error",
    ...detail,
})

export const checkFileStorage = async (client = s3, bucket = secrets.S3_BUCKET, timeoutMs = 3000) => {
    const controller = new AbortController()
    const timeout = setTimeout(() => controller.abort(), timeoutMs)

    try {
        if (!client || !bucket) return serviceState(false, { error: "S3-Dateispeicher ist nicht eingerichtet" })
        await client.send(new HeadBucketCommand({ Bucket: bucket }), { abortSignal: controller.signal })
        return serviceState(true, { provider: process.env.FEDEO_STORAGE_PROVIDER === "seaweedfs" ? "seaweedfs" : "s3" })
    } catch {
        return serviceState(false, {
            error: controller.signal.aborted ? "S3-Prüfung hat das Zeitlimit überschritten" : "S3-Bucket nicht erreichbar oder Zugriff verweigert",
        })
    } finally {
        clearTimeout(timeout)
    }
}

export const buildSystemStatus = async (server: FastifyInstance) => {
    const checkedAt = new Date()
    const nodeExporterMetricsUrl = `${nodeExporterUrl()}/metrics`
    let nodeMetrics: Map<string, MetricSample[]> | null = null
    let nodeExporterError: string | null = null

    try {
        const response = await fetch(nodeExporterMetricsUrl)
        if (!response.ok) {
            throw new Error(`Node Exporter antwortet mit ${response.status}`)
        }
        nodeMetrics = parsePrometheusMetrics(await response.text())
    } catch (err: any) {
        nodeExporterError = err?.message || "Node Exporter nicht erreichbar"
    }

    const memoryTotal = nodeMetrics ? firstMetricValue(nodeMetrics, "node_memory_MemTotal_bytes") : null
    const memoryAvailable = nodeMetrics ? firstMetricValue(nodeMetrics, "node_memory_MemAvailable_bytes") : null
    const rootSize = nodeMetrics
        ? findMetricValue(nodeMetrics, "node_filesystem_size_bytes", (sample) => sample.labels.mountpoint === "/")
        : null
    const rootAvailable = nodeMetrics
        ? findMetricValue(nodeMetrics, "node_filesystem_avail_bytes", (sample) => sample.labels.mountpoint === "/")
        : null
    const bootTime = nodeMetrics ? firstMetricValue(nodeMetrics, "node_boot_time_seconds") : null
    const cpuCount = nodeMetrics
        ? new Set((nodeMetrics.get("node_cpu_seconds_total") || [])
            .filter((sample) => sample.labels.mode === "idle")
            .map((sample) => sample.labels.cpu)).size
        : null
    const uname = nodeMetrics?.get("node_uname_info")?.[0]?.labels || null

    const databaseCheck = await server.db.execute("SELECT NOW() as now")

    return {
        checkedAt: checkedAt.toISOString(),
        backend: {
            status: "ok",
            uptimeSeconds: Math.round(process.uptime()),
            nodeVersion: process.version,
            environment: process.env.NODE_ENV || "development",
        },
        server: {
            status: nodeMetrics ? "ok" : "unavailable",
            nodeExporterUrl: nodeExporterMetricsUrl,
            error: nodeExporterError,
            hostname: uname?.nodename || null,
            kernel: uname?.release || null,
            cpuCount,
            load: {
                one: nodeMetrics ? firstMetricValue(nodeMetrics, "node_load1") : null,
                five: nodeMetrics ? firstMetricValue(nodeMetrics, "node_load5") : null,
                fifteen: nodeMetrics ? firstMetricValue(nodeMetrics, "node_load15") : null,
            },
            memory: {
                totalBytes: memoryTotal,
                availableBytes: memoryAvailable,
                usedBytes: memoryTotal !== null && memoryAvailable !== null ? memoryTotal - memoryAvailable : null,
                usedPercent: memoryTotal ? Math.round(((memoryTotal - (memoryAvailable || 0)) / memoryTotal) * 1000) / 10 : null,
            },
            disk: {
                rootTotalBytes: rootSize,
                rootAvailableBytes: rootAvailable,
                rootUsedBytes: rootSize !== null && rootAvailable !== null ? rootSize - rootAvailable : null,
                rootUsedPercent: rootSize ? Math.round(((rootSize - (rootAvailable || 0)) / rootSize) * 1000) / 10 : null,
            },
            uptimeSeconds: bootTime ? Math.max(0, Math.round(Date.now() / 1000 - bootTime)) : null,
        },
        services: {
            database: serviceState(true, {
                checkedAt: String(databaseCheck.rows?.[0]?.now || checkedAt.toISOString()),
            }),
            nodeExporter: serviceState(Boolean(nodeMetrics), {
                url: nodeExporterMetricsUrl,
                error: nodeExporterError,
            }),
            // Preserve the response key for older clients; check the authenticated S3 API for every provider.
            minio: await checkFileStorage(),
        },
    }
}