import { useState, useEffect, useCallback } from 'react';
import { getDiagLog, clearDiagLog } from '../api/dns';
import ConfirmDialog from './ConfirmDialog';
import { exportCsv } from '../utils/exportCsv';

const PAGE_SIZE = 50;

function formatDate(iso) {
  if (!iso) return '—';
  const d = new Date(iso);
  return `${d.toLocaleDateString('sv-SE')} ${d.toLocaleTimeString('sv-SE', { hour: '2-digit', minute: '2-digit', second: '2-digit' })}`;
}

export default function DiagnosticsPage() {
  const [entries, setEntries]           = useState([]);
  const [total, setTotal]               = useState(0);
  const [page, setPage]                 = useState(0);
  const [loading, setLoading]           = useState(false);
  const [error, setError]               = useState('');
  const [filterProvider, setFilterProvider] = useState('');
  const [filterOk, setFilterOk]         = useState('');
  const [confirmClear, setConfirmClear] = useState(false);

  const load = useCallback((pg = 0) => {
    setLoading(true); setError('');
    getDiagLog({
      provider: filterProvider || undefined,
      ok:       filterOk !== '' ? filterOk : undefined,
      limit:    PAGE_SIZE,
      offset:   pg * PAGE_SIZE,
    })
      .then(({ entries, total }) => { setEntries(entries); setTotal(total); })
      .catch(e => setError(e.message))
      .finally(() => setLoading(false));
  }, [filterProvider, filterOk]);

  useEffect(() => { setPage(0); load(0); }, [load]);

  function goToPage(pg) { setPage(pg); load(pg); }

  async function handleClear() {
    await clearDiagLog();
    setConfirmClear(false);
    setEntries([]); setTotal(0);
  }

  const totalPages = Math.ceil(total / PAGE_SIZE);
  const errorCount = entries.filter(e => !e.ok).length;

  return (
    <div className="dashboard">
      <div className="dashboard-header" style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'flex-start' }}>
        <div>
          <h2>Provider Diagnostics</h2>
          <p className="dashboard-hint">
            Every API call made to DNS providers — last 200 entries. Use this to troubleshoot connectivity issues.
          </p>
        </div>
        <button className="btn-danger" onClick={() => setConfirmClear(true)}>Clear Log</button>
      </div>

      {error && <div className="error-banner" style={{ marginBottom: 16 }}><strong>Error:</strong> {error}</div>}

      <div className="records-actions" style={{ marginBottom: 16 }}>
        <select className="filter-input" value={filterProvider} onChange={e => setFilterProvider(e.target.value)}>
          <option value="">All providers</option>
          <option value="cloudflare">Cloudflare</option>
          <option value="loopia">Loopia</option>
          <option value="pihole">Pi-hole</option>
          <option value="azure">Azure DNS</option>
          <option value="cpanel">cPanel</option>
        </select>
        <select className="filter-input" value={filterOk} onChange={e => setFilterOk(e.target.value)}>
          <option value="">All results</option>
          <option value="false">Errors only</option>
          <option value="true">Success only</option>
        </select>
        <button className="btn-secondary" onClick={() => load(page)}>↺ Refresh</button>
        <button className="btn-export" onClick={() =>
          exportCsv(
            entries.map(e => ({ timestamp: e.timestamp, provider: e.provider, operation: e.operation, method: e.method, url: e.url, status: e.status ?? '', latency: e.latency, ok: e.ok ? 'yes' : 'no', error: e.error ?? '' })),
            ['timestamp','provider','operation','method','url','status','latency','ok','error'],
            { timestamp:'Time', provider:'Provider', operation:'Operation', method:'Method', url:'URL', status:'Status', latency:'Latency (ms)', ok:'OK', error:'Error' },
            'diagnostics.csv'
          )
        }>⬇ Export CSV</button>
        <span className="record-count">{total} entries{errorCount > 0 && <span style={{ color: '#ef4444', marginLeft: 8 }}>· {errorCount} errors on this page</span>}</span>
      </div>

      {loading ? <p className="hint">Loading…</p> : entries.length === 0 ? (
        <div className="empty-state">
          <p>No diagnostic entries yet — make a DNS operation (sync, add, delete) to populate the log.</p>
        </div>
      ) : (
        <>
          <div className="table-wrapper">
            <table className="records-table">
              <thead>
                <tr>
                  <th>Time</th>
                  <th>Provider</th>
                  <th>Operation</th>
                  <th>Status</th>
                  <th>Latency</th>
                  <th>URL</th>
                  <th>Error</th>
                </tr>
              </thead>
              <tbody>
                {entries.map(e => (
                  <tr key={e.id} className={!e.ok ? 'diag-row-error' : ''}>
                    <td style={{ fontSize: 11, color: 'var(--text-muted)', whiteSpace: 'nowrap' }}>{formatDate(e.timestamp)}</td>
                    <td style={{ textTransform: 'capitalize', fontWeight: 500 }}>{e.provider}</td>
                    <td style={{ fontFamily: 'monospace', fontSize: 12 }}>{e.operation}</td>
                    <td>
                      <span className={`health-badge ${e.ok ? 'health-ok' : 'health-error'}`}>
                        {e.status ?? 'ERR'}
                      </span>
                    </td>
                    <td style={{ fontFamily: 'monospace', fontSize: 12, color: e.latency > 2000 ? '#f59e0b' : 'var(--text-muted)' }}>
                      {e.latency}ms
                    </td>
                    <td style={{ fontFamily: 'monospace', fontSize: 11, color: 'var(--text-muted)', maxWidth: 320, overflow: 'hidden', textOverflow: 'ellipsis', whiteSpace: 'nowrap' }} title={e.url}>
                      {e.url}
                    </td>
                    <td style={{ fontSize: 12, color: '#fca5a5', maxWidth: 200, overflow: 'hidden', textOverflow: 'ellipsis', whiteSpace: 'nowrap' }} title={e.error ?? ''}>
                      {e.error ?? ''}
                    </td>
                  </tr>
                ))}
              </tbody>
            </table>
          </div>

          {totalPages > 1 && (
            <div className="audit-pagination">
              <button className="btn-secondary" onClick={() => goToPage(page - 1)} disabled={page === 0}>← Prev</button>
              <span className="record-count">Page {page + 1} of {totalPages}</span>
              <button className="btn-secondary" onClick={() => goToPage(page + 1)} disabled={page >= totalPages - 1}>Next →</button>
            </div>
          )}
        </>
      )}

      {confirmClear && (
        <ConfirmDialog
          title="Clear Diagnostic Log"
          message="This will delete all diagnostic entries. This cannot be undone."
          confirmLabel="Clear Log"
          danger
          onConfirm={handleClear}
          onCancel={() => setConfirmClear(false)}
        />
      )}
    </div>
  );
}