import { useState, useEffect, useCallback } from 'react';
import api from './lib/api.js';
import {
  IconServer,
  IconRefresh,
  IconChartBar,
  IconAlertCircle,
} from '@tabler/icons-react';
import PageHeader from './components/PageHeader.jsx';

const REQUEST_TIMEOUT_MS = 15000;

function formatBytes(bytes) {
  if (bytes == null || bytes === 0) return '0 B';
  const k = 1024;
  const sizes = ['B', 'KB', 'MB', 'GB', 'TB'];
  const i = Math.min(Math.floor(Math.log(bytes) / Math.log(k)), sizes.length - 1);
  return `${parseFloat((bytes / Math.pow(k, i)).toFixed(2))} ${sizes[i]}`;
}

/** Цвет прогресс-бара по проценту: зелёный / жёлтый / красный */
function progressVariant(percent) {
  if (percent == null) return 'secondary';
  if (percent >= 90) return 'danger';
  if (percent >= 70) return 'warning';
  return 'success';
}

/** Один KPI-блок: заголовок, значение, прогресс-бар (как на референсной карточке) */
function KpiBlock({ label, value, percent, variant }) {
  const barVariant = variant || progressVariant(percent);
  return (
    <div className="mb-3">
      <div className="text-uppercase small fw-semibold text-secondary mb-1">{label}</div>
      <div className="d-flex align-items-baseline gap-2 flex-wrap">
        <span className="h4 mb-0 fw-bold">{value}</span>
        {percent != null && (
          <span className={`small fw-medium text-${barVariant}`}>{percent}%</span>
        )}
      </div>
      {percent != null && (
        <div className="progress progress-sm mt-1" style={{ height: 6 }}>
          <div
            className={`progress-bar bg-${barVariant}`}
            role="progressbar"
            style={{ width: `${Math.min(100, percent)}%` }}
            aria-valuenow={percent}
            aria-valuemin={0}
            aria-valuemax={100}
          />
        </div>
      )}
    </div>
  );
}

/** Карточка одного роутера: иконка перед названием, сводка, KPI (RAM, CPU, HDD) */
function RouterResourceCard({ router }) {
  const { name, host, error, resource } = router;
  const hasResource = resource && !error;

  return (
    <div className="card rounded-3 shadow-sm border-0 overflow-hidden h-100">
      <div className="card-body p-4">
        <div className="d-flex align-items-center mb-3">
          <span className="avatar avatar-lg bg-primary-lt text-primary rounded-3 me-3 flex-shrink-0">
            <IconServer size={28} />
          </span>
          <div className="min-w-0">
            <h3 className="h4 fw-bold mb-0 text-body text-truncate">
              {name}
            </h3>
            <p className="text-secondary small mb-0 mt-1">
              {host}
              {resource?.version && (
                <span className="ms-1"> · RouterOS {resource.version}</span>
              )}
            </p>
          </div>
        </div>
        <div>
          {error && (
            <div className="alert alert-danger py-2 mb-3 d-flex align-items-center">
              <IconAlertCircle size={20} className="me-2 flex-shrink-0" />
              <span className="small">{error}</span>
            </div>
          )}

          {hasResource && (
            <div className="row g-3">
              {/* RAM */}
              <div className="col-12 col-md-4">
                <KpiBlock
                  label="RAM"
                  value={
                    resource.usedMemory != null && resource.totalMemory != null
                      ? `${formatBytes(resource.usedMemory)} / ${formatBytes(resource.totalMemory)}`
                      : '—'
                  }
                  percent={resource.memoryUsagePercent}
                />
              </div>
              {/* CPU */}
              <div className="col-12 col-md-4">
                <KpiBlock
                  label="CPU"
                  value={
                    resource.cpuLoad != null
                      ? `${resource.cpuLoad}%`
                      : '—'
                  }
                  percent={resource.cpuLoad}
                />
              </div>
              {/* HDD */}
              <div className="col-12 col-md-4">
                <KpiBlock
                  label="HDD"
                  value={
                    resource.usedHddSpace != null && resource.totalHddSpace != null
                      ? `${formatBytes(resource.usedHddSpace)} / ${formatBytes(resource.totalHddSpace)}`
                      : resource.totalHddSpace != null
                        ? formatBytes(resource.totalHddSpace)
                        : '—'
                  }
                  percent={resource.hddUsagePercent}
                />
              </div>
            </div>
          )}

          {hasResource && (resource.boardName || resource.uptime) && (
            <div className="mt-2 pt-2 border-top small text-muted">
              {resource.boardName && <span>{resource.boardName}</span>}
              {resource.uptime && (
                <span className="ms-2"> · Uptime: {resource.uptime}</span>
              )}
            </div>
          )}
        </div>
      </div>
    </div>
  );
}

export default function ResourceStatsPage() {
  const [routers, setRouters] = useState([]);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState(null);

  const fetchStats = useCallback(async (abortSignal) => {
    setLoading(true);
    setError(null);
    const opts = { timeout: REQUEST_TIMEOUT_MS, noRetry: true, ...(abortSignal ? { signal: abortSignal } : {}) };
    try {
      const res = await api.get('/resources/stats', opts);
      const data = res?.data;
      setRouters(Array.isArray(data?.routers) ? data.routers : []);
    } catch (e) {
      if (e?.name === 'CanceledError' || e?.name === 'AbortError' || e?.code === 'ERR_CANCELED') return;
      setError(e?.response?.data?.message || e?.message || 'Не удалось загрузить статистику');
      // Не очищаем список — пользователь видит старые данные и сообщение об ошибке
    } finally {
      setLoading(false);
    }
  }, []);

  useEffect(() => {
    const controller = new AbortController();
    fetchStats(controller.signal);
    return () => controller.abort();
  }, [fetchStats]);

  return (
    <div className="page-body">
      <PageHeader
        title="Статистика ресурсов"
        pretitle="Роутеры"
        icon={<IconChartBar size={28} />}
        meta="Потребление RAM, CPU и HDD по каждому роутеру (MikroTik)"
        actions={
          <button
            type="button"
            className="btn btn-outline-primary"
            onClick={() => fetchStats()}
            disabled={loading}
          >
            <IconRefresh size={18} className={loading ? 'spin' : ''} />
            <span className="ms-1">Обновить</span>
          </button>
        }
      />

      {error && (
        <div className="alert alert-danger d-flex align-items-center">
          <IconAlertCircle size={24} className="me-2" />
          <span>{error}</span>
        </div>
      )}

      {loading && routers.length === 0 ? (
        <div className="row">
          {[1, 2, 3].map((i) => (
            <div key={i} className="col-12 col-lg-6 col-xl-4 mb-4">
              <div className="card rounded-3 border-0 placeholder-glow">
                <div className="card-body p-4">
                  <div className="placeholder col-6 mb-2" />
                  <div className="placeholder col-8 mb-3" />
                  <div className="placeholder col-12" style={{ height: 60 }} />
                </div>
              </div>
            </div>
          ))}
        </div>
      ) : routers.length === 0 ? (
        <div className="card rounded-3 border-0">
          <div className="card-body text-center py-5 text-muted">
            <IconServer size={48} className="mb-2 opacity-50" />
            <p className="mb-0">Нет роутеров с настроенным MikroTik API (jumphost/home).</p>
          </div>
        </div>
      ) : (
        <div className="row">
          {routers.map((router) => (
            <div key={router.serverId || router.name} className="col-12 col-lg-6 col-xl-4 mb-4">
              <RouterResourceCard router={router} />
            </div>
          ))}
        </div>
      )}

      <style>{`
        .spin {
          animation: spin 0.8s linear infinite;
        }
        @keyframes spin {
          from { transform: rotate(0deg); }
          to { transform: rotate(360deg); }
        }
      `}</style>
    </div>
  );
}