export const HOST_TELEMETRY_SCHEMA =
  "nodedc.infrastructure.host-telemetry.v1";

export const HOST_TELEMETRY_PROFILE = "linux-host-telegraf-v1";

const REF_RE = /^[A-Za-z0-9][A-Za-z0-9._:-]{0,127}$/;
const ISO_TIMESTAMP_RE = /^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(?:\.\d{3})?Z$/;

export function telegrafBatchToHostTelemetry(input, context = {}) {
  const metrics = telegrafMetrics(input);
  const observedAt = latestMetricTimestamp(metrics) ?? normalizeTimestamp(
    context.observedAt ?? new Date().toISOString(),
    "observed_at",
  );
  const byName = new Map();
  for (const metric of metrics) {
    const values = byName.get(metric.name) ?? [];
    values.push(metric);
    byName.set(metric.name, values);
  }

  const cpu = metricWithTag(byName.get("cpu"), "cpu", "cpu-total")
    ?? firstMetric(byName.get("cpu"));
  const memory = firstMetric(byName.get("mem"));
  const swap = firstMetric(byName.get("swap"));
  const system = firstMetric(byName.get("system"));
  const processes = firstMetric(byName.get("processes"));
  const systemCpu = firstMetric(byName.get("system_cpu"));

  return normalizeHostTelemetrySnapshot({
    schemaVersion: HOST_TELEMETRY_SCHEMA,
    profile: HOST_TELEMETRY_PROFILE,
    hostKey: context.hostKey,
    observedAt,
    source: {
      agent: "telegraf",
      agentVersion: context.agentVersion ?? "1.38.4",
      collectorRef: context.collectorRef ?? "service:nodedc-host-telemetry-agent",
    },
    hardware: {
      hostname: context.hostname ?? metricHost(metrics),
      architecture: context.architecture ?? null,
      platform: context.platform ?? "linux",
      kernelRelease: context.kernelRelease ?? null,
      cpuModel: context.cpuModel ?? null,
      logicalProcessors: finiteInteger(
        context.logicalProcessors ?? systemCpu?.fields.cpu_count,
      ),
    },
    cpu: {
      usagePercent: finiteNumber(cpu?.fields.usage_active)
        ?? percentFromIdle(cpu?.fields.usage_idle),
      load1: finiteNumber(system?.fields.load1),
      load5: finiteNumber(system?.fields.load5),
      load15: finiteNumber(system?.fields.load15),
    },
    memory: {
      totalBytes: finiteInteger(memory?.fields.total),
      availableBytes: finiteInteger(memory?.fields.available),
      usedBytes: finiteInteger(memory?.fields.used),
      usedPercent: finiteNumber(memory?.fields.used_percent),
    },
    swap: {
      totalBytes: finiteInteger(swap?.fields.total),
      freeBytes: finiteInteger(swap?.fields.free),
      usedBytes: finiteInteger(swap?.fields.used),
      usedPercent: finiteNumber(swap?.fields.used_percent),
    },
    system: {
      uptimeSeconds: finiteInteger(system?.fields.uptime),
      users: finiteInteger(system?.fields.n_users),
      processes: {
        total: finiteInteger(processes?.fields.total),
        running: finiteInteger(processes?.fields.running),
        sleeping: finiteInteger(processes?.fields.sleeping),
        blocked: finiteInteger(processes?.fields.blocked),
        zombies: finiteInteger(processes?.fields.zombies),
      },
    },
    disks: (byName.get("disk") ?? []).map((metric) => ({
      device: textOrNull(metric.tags.device),
      mount: textOrNull(metric.tags.path),
      filesystem: textOrNull(metric.tags.fstype),
      totalBytes: finiteInteger(metric.fields.total),
      freeBytes: finiteInteger(metric.fields.free),
      usedBytes: finiteInteger(metric.fields.used),
      usedPercent: finiteNumber(metric.fields.used_percent),
    })),
    network: (byName.get("net") ?? []).map((metric) => ({
      interface: textOrNull(metric.tags.interface),
      bytesReceived: finiteInteger(metric.fields.bytes_recv),
      bytesSent: finiteInteger(metric.fields.bytes_sent),
      packetsReceived: finiteInteger(metric.fields.packets_recv),
      packetsSent: finiteInteger(metric.fields.packets_sent),
      errorsReceived: finiteInteger(metric.fields.err_in),
      errorsSent: finiteInteger(metric.fields.err_out),
      droppedReceived: finiteInteger(metric.fields.drop_in),
      droppedSent: finiteInteger(metric.fields.drop_out),
    })),
    services: (byName.get("systemd_units") ?? []).map((metric) => ({
      name: textOrNull(metric.tags.name),
      loadState: textOrNull(metric.tags.load),
      activeState: textOrNull(metric.tags.active),
      subState: textOrNull(metric.tags.sub),
      memoryBytes: finiteInteger(metric.fields.mem_current),
      restarts: finiteInteger(metric.fields.restarts),
      pid: finiteInteger(metric.fields.pid),
    })),
  });
}

export function normalizeHostTelemetrySnapshot(input) {
  assertPlainObject(input, "host_telemetry");
  if (input.schemaVersion !== HOST_TELEMETRY_SCHEMA) {
    throw new TypeError("host_telemetry_schema_invalid");
  }
  if (input.profile !== HOST_TELEMETRY_PROFILE) {
    throw new TypeError("host_telemetry_profile_invalid");
  }
  const snapshot = {
    schemaVersion: HOST_TELEMETRY_SCHEMA,
    profile: HOST_TELEMETRY_PROFILE,
    hostKey: normalizeRef(input.hostKey, "host_key"),
    observedAt: normalizeTimestamp(input.observedAt, "observed_at"),
    source: normalizeSource(input.source),
    hardware: normalizeHardware(input.hardware),
    cpu: normalizeCpu(input.cpu),
    memory: normalizeMemory(input.memory, "memory"),
    swap: normalizeMemory(input.swap, "swap"),
    system: normalizeSystem(input.system),
    disks: normalizeArray(input.disks, normalizeDisk, 32),
    network: normalizeArray(input.network, normalizeNetwork, 64),
    services: normalizeArray(input.services, normalizeService, 64),
  };
  return deepFreeze(snapshot);
}

function telegrafMetrics(input) {
  const candidate = Array.isArray(input)
    ? input
    : input && typeof input === "object" && Array.isArray(input.metrics)
      ? input.metrics
      : input && typeof input === "object"
        ? [input]
        : null;
  if (!candidate || candidate.length < 1 || candidate.length > 512) {
    throw new TypeError("host_telemetry_telegraf_batch_invalid");
  }
  return candidate.map((metric) => {
    assertPlainObject(metric, "host_telemetry_telegraf_metric");
    assertPlainObject(metric.fields, "host_telemetry_telegraf_fields");
    const name = text(metric.name, 1, 80, "host_telemetry_telegraf_name_invalid");
    const tags = metric.tags == null ? {} : metric.tags;
    assertPlainObject(tags, "host_telemetry_telegraf_tags");
    return { name, fields: { ...metric.fields }, tags: { ...tags }, timestamp: metric.timestamp };
  });
}

function latestMetricTimestamp(metrics) {
  let latest = null;
  for (const metric of metrics) {
    const raw = Number(metric.timestamp);
    if (!Number.isFinite(raw) || raw <= 0) continue;
    const milliseconds = raw > 10_000_000_000 ? raw / 1_000_000 : raw * 1000;
    if (!Number.isFinite(milliseconds)) continue;
    const value = new Date(milliseconds).toISOString();
    if (!latest || value > latest) latest = value;
  }
  return latest;
}

function metricWithTag(metrics = [], key, value) {
  return metrics.find((metric) => metric.tags[key] === value) ?? null;
}

function firstMetric(metrics = []) {
  return metrics[0] ?? null;
}

function metricHost(metrics) {
  for (const metric of metrics) {
    if (typeof metric.tags.host === "string" && metric.tags.host.trim()) {
      return metric.tags.host.trim().slice(0, 160);
    }
  }
  return null;
}

function normalizeSource(input) {
  assertPlainObject(input, "host_telemetry_source");
  return {
    agent: text(input.agent, 1, 64, "host_telemetry_agent_invalid"),
    agentVersion: text(input.agentVersion, 1, 64, "host_telemetry_agent_version_invalid"),
    collectorRef: normalizeRef(input.collectorRef, "collector_ref"),
  };
}

function normalizeHardware(input) {
  assertPlainObject(input, "host_telemetry_hardware");
  return {
    hostname: optionalText(input.hostname, 160),
    architecture: optionalText(input.architecture, 64),
    platform: optionalText(input.platform, 64),
    kernelRelease: optionalText(input.kernelRelease, 160),
    cpuModel: optionalText(input.cpuModel, 256),
    logicalProcessors: optionalInteger(input.logicalProcessors, 1_024),
  };
}

function normalizeCpu(input) {
  assertPlainObject(input, "host_telemetry_cpu");
  return {
    usagePercent: optionalPercent(input.usagePercent),
    load1: optionalNumber(input.load1, 0, 100_000),
    load5: optionalNumber(input.load5, 0, 100_000),
    load15: optionalNumber(input.load15, 0, 100_000),
  };
}

function normalizeMemory(input, field) {
  assertPlainObject(input, `host_telemetry_${field}`);
  return {
    totalBytes: optionalInteger(input.totalBytes, Number.MAX_SAFE_INTEGER),
    availableBytes: optionalInteger(input.availableBytes, Number.MAX_SAFE_INTEGER),
    freeBytes: optionalInteger(input.freeBytes, Number.MAX_SAFE_INTEGER),
    usedBytes: optionalInteger(input.usedBytes, Number.MAX_SAFE_INTEGER),
    usedPercent: optionalPercent(input.usedPercent),
  };
}

function normalizeSystem(input) {
  assertPlainObject(input, "host_telemetry_system");
  assertPlainObject(input.processes, "host_telemetry_processes");
  return {
    uptimeSeconds: optionalInteger(input.uptimeSeconds, Number.MAX_SAFE_INTEGER),
    users: optionalInteger(input.users, 1_000_000),
    processes: {
      total: optionalInteger(input.processes.total, 1_000_000),
      running: optionalInteger(input.processes.running, 1_000_000),
      sleeping: optionalInteger(input.processes.sleeping, 1_000_000),
      blocked: optionalInteger(input.processes.blocked, 1_000_000),
      zombies: optionalInteger(input.processes.zombies, 1_000_000),
    },
  };
}

function normalizeDisk(input) {
  assertPlainObject(input, "host_telemetry_disk");
  return {
    device: optionalText(input.device, 256),
    mount: optionalText(input.mount, 512),
    filesystem: optionalText(input.filesystem, 64),
    totalBytes: optionalInteger(input.totalBytes, Number.MAX_SAFE_INTEGER),
    freeBytes: optionalInteger(input.freeBytes, Number.MAX_SAFE_INTEGER),
    usedBytes: optionalInteger(input.usedBytes, Number.MAX_SAFE_INTEGER),
    usedPercent: optionalPercent(input.usedPercent),
  };
}

function normalizeNetwork(input) {
  assertPlainObject(input, "host_telemetry_network");
  return {
    interface: optionalText(input.interface, 64),
    bytesReceived: optionalInteger(input.bytesReceived, Number.MAX_SAFE_INTEGER),
    bytesSent: optionalInteger(input.bytesSent, Number.MAX_SAFE_INTEGER),
    packetsReceived: optionalInteger(input.packetsReceived, Number.MAX_SAFE_INTEGER),
    packetsSent: optionalInteger(input.packetsSent, Number.MAX_SAFE_INTEGER),
    errorsReceived: optionalInteger(input.errorsReceived, Number.MAX_SAFE_INTEGER),
    errorsSent: optionalInteger(input.errorsSent, Number.MAX_SAFE_INTEGER),
    droppedReceived: optionalInteger(input.droppedReceived, Number.MAX_SAFE_INTEGER),
    droppedSent: optionalInteger(input.droppedSent, Number.MAX_SAFE_INTEGER),
  };
}

function normalizeService(input) {
  assertPlainObject(input, "host_telemetry_service");
  return {
    name: optionalText(input.name, 160),
    loadState: optionalText(input.loadState, 64),
    activeState: optionalText(input.activeState, 64),
    subState: optionalText(input.subState, 64),
    memoryBytes: optionalInteger(input.memoryBytes, Number.MAX_SAFE_INTEGER),
    restarts: optionalInteger(input.restarts, Number.MAX_SAFE_INTEGER),
    pid: optionalInteger(input.pid, Number.MAX_SAFE_INTEGER),
  };
}

function normalizeArray(value, mapper, maximum) {
  if (!Array.isArray(value) || value.length > maximum) {
    throw new TypeError("host_telemetry_collection_invalid");
  }
  return value.map(mapper);
}

function normalizeRef(value, field) {
  if (typeof value !== "string" || !REF_RE.test(value)) {
    throw new TypeError(`host_telemetry_${field}_invalid`);
  }
  return value;
}

function normalizeTimestamp(value, field) {
  if (typeof value !== "string" || !ISO_TIMESTAMP_RE.test(value)) {
    throw new TypeError(`host_telemetry_${field}_invalid`);
  }
  const timestamp = new Date(value);
  if (!Number.isFinite(timestamp.valueOf())) {
    throw new TypeError(`host_telemetry_${field}_invalid`);
  }
  return timestamp.toISOString();
}

function text(value, minimum, maximum, errorCode) {
  if (typeof value !== "string") throw new TypeError(errorCode);
  const normalized = value.trim();
  if (normalized.length < minimum || normalized.length > maximum) {
    throw new TypeError(errorCode);
  }
  return normalized;
}

function optionalText(value, maximum) {
  if (value == null || value === "") return null;
  return text(value, 1, maximum, "host_telemetry_text_invalid");
}

function textOrNull(value) {
  return typeof value === "string" && value.trim() ? value.trim() : null;
}

function optionalInteger(value, maximum) {
  if (value == null) return null;
  const normalized = Number(value);
  if (!Number.isSafeInteger(normalized) || normalized < 0 || normalized > maximum) {
    throw new TypeError("host_telemetry_integer_invalid");
  }
  return normalized;
}

function optionalNumber(value, minimum, maximum) {
  if (value == null) return null;
  const normalized = Number(value);
  if (!Number.isFinite(normalized) || normalized < minimum || normalized > maximum) {
    throw new TypeError("host_telemetry_number_invalid");
  }
  return normalized;
}

function optionalPercent(value) {
  return optionalNumber(value, 0, 100);
}

function finiteInteger(value) {
  const normalized = Number(value);
  return Number.isSafeInteger(normalized) && normalized >= 0 ? normalized : null;
}

function finiteNumber(value) {
  const normalized = Number(value);
  return Number.isFinite(normalized) && normalized >= 0 ? normalized : null;
}

function percentFromIdle(value) {
  const idle = finiteNumber(value);
  return idle == null ? null : Math.max(0, Math.min(100, 100 - idle));
}

function assertPlainObject(value, field) {
  if (!value || typeof value !== "object" || Array.isArray(value)) {
    throw new TypeError(`${field}_invalid`);
  }
}

function deepFreeze(value) {
  if (value && typeof value === "object" && !Object.isFrozen(value)) {
    Object.freeze(value);
    for (const nested of Object.values(value)) deepFreeze(nested);
  }
  return value;
}