feat: add Missing Data module as new sidebar entry

Replaces the tab approach with a dedicated 'Missing Data' module in the
sidebar. The module has two sub-tabs: 'Missing Classification' and
'Missing Launch Date'. Shows SKU, Name, Classification, Launch Date and
Ready to Order columns. Includes a local Excel serial date formatter so
dates that slipped through the App.tsx pre-processing are rendered
correctly instead of showing as raw numbers.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/MissingDataView.tsx

@@ -0,0 +1,267 @@
+import React, { useState, useMemo } from 'react';
+import { ExcelRow, COLUMNS } from '../types';
+import { Search, ChevronDown, ChevronUp, X } from 'lucide-react';
+import { cn } from '../lib/utils';
+
+interface MissingDataViewProps {
+  data: ExcelRow[];
+  headers: string[];
+}
+
+function formatDateValue(val: any): string {
+  if (val === null || val === undefined || val === '') return '';
+  if (typeof val === 'number') {
+    if (val >= 25569 && val <= 60000) {
+      const excelEpoch = new Date(1899, 11, 30);
+      const date = new Date(excelEpoch.getTime() + val * 86400000);
+      return date.toLocaleDateString('en-GB', { day: '2-digit', month: '2-digit', year: 'numeric' });
+    }
+    return '';
+  }
+  return String(val);
+}
+
+function isEmptyOrEpoch(val: any): boolean {
+  if (val === null || val === undefined || val === '') return true;
+  if (typeof val === 'number') {
+    if (val === 0 || val === 1) return true;
+    if (val >= 25569 && val <= 60000) {
+      // valid date range — not empty
+      return false;
+    }
+    // number outside date range — treat as empty
+    return true;
+  }
+  const s = String(val).trim();
+  if (s === '' || s === '0' || s === '1') return true;
+  if (s.endsWith('/1900')) return true;
+  return false;
+}
+
+type TabType = 'missingClass' | 'missingLaunch';
+
+export function MissingDataView({ data, headers }: MissingDataViewProps) {
+  const [activeTab, setActiveTab] = useState<TabType>('missingClass');
+  const [search, setSearch] = useState('');
+  const [sortCol, setSortCol] = useState<number | null>(null);
+  const [sortDesc, setSortDesc] = useState(false);
+  const [page, setPage] = useState(1);
+  const pageSize = 100;
+
+  const launchDateCol = useMemo(() =>
+    headers.findIndex(h => h.toLowerCase().includes('launch')), [headers]);
+  const readyToOrderCol = useMemo(() =>
+    headers.findIndex(h => h.toLowerCase().includes('ready')), [headers]);
+
+  const filteredData = useMemo(() => {
+    let result = data.map((row, index) => ({ row, index }));
+
+    if (activeTab === 'missingClass') {
+      result = result.filter(r => {
+        const val = r.row[COLUMNS.CLASSIFICATION];
+        return !val || String(val).trim() === '';
+      });
+    }
+
+    if (activeTab === 'missingLaunch') {
+      result = result.filter(r => {
+        const val = launchDateCol >= 0 ? r.row[launchDateCol] : undefined;
+        return isEmptyOrEpoch(val);
+      });
+    }
+
+    if (search) {
+      const s = search.toLowerCase();
+      result = result.filter(r =>
+        String(r.row[COLUMNS.ARTICLE_NO] || '').toLowerCase().includes(s) ||
+        String(r.row[COLUMNS.ARTICLE_NAME] || '').toLowerCase().includes(s)
+      );
+    }
+
+    if (sortCol !== null) {
+      result.sort((a, b) => {
+        const valA = a.row[sortCol];
+        const valB = b.row[sortCol];
+        if (typeof valA === 'number' && typeof valB === 'number') {
+          return sortDesc ? valB - valA : valA - valB;
+        }
+        const sA = String(valA || '');
+        const sB = String(valB || '');
+        return sortDesc ? sB.localeCompare(sA) : sA.localeCompare(sB);
+      });
+    }
+
+    return result;
+  }, [data, activeTab, search, sortCol, sortDesc, launchDateCol]);
+
+  const paginatedData = useMemo(() => {
+    const start = (page - 1) * pageSize;
+    return filteredData.slice(start, start + pageSize);
+  }, [filteredData, page]);
+
+  const totalPages = Math.ceil(filteredData.length / pageSize);
+
+  const handleSort = (col: number) => {
+    if (sortCol === col) setSortDesc(d => !d);
+    else { setSortCol(col); setSortDesc(false); }
+  };
+
+  const tabs: { id: TabType; label: string }[] = [
+    { id: 'missingClass', label: 'Missing Classification' },
+    { id: 'missingLaunch', label: 'Missing Launch Date' },
+  ];
+
+  const launchHeader = launchDateCol >= 0 ? headers[launchDateCol] : 'Launch Date';
+  const readyHeader = readyToOrderCol >= 0 ? headers[readyToOrderCol] : 'Ready to Order';
+
+  const columns = [
+    { col: COLUMNS.ARTICLE_NO, label: 'SKU', width: 100 },
+    { col: COLUMNS.ARTICLE_NAME, label: 'Name', width: 220 },
+    { col: COLUMNS.CLASSIFICATION, label: 'Classification', width: 130 },
+    ...(launchDateCol >= 0 ? [{ col: launchDateCol, label: launchHeader, width: 130 }] : []),
+    ...(readyToOrderCol >= 0 ? [{ col: readyToOrderCol, label: readyHeader, width: 130 }] : []),
+  ];
+
+  return (
+    <div className="flex flex-col h-full">
+      <div className="flex flex-wrap gap-2 mb-6">
+        {tabs.map(tab => (
+          <button
+            key={tab.id}
+            onClick={() => { setActiveTab(tab.id); setPage(1); }}
+            className={cn(
+              "px-4 py-2 rounded-md text-sm font-medium transition-colors",
+              activeTab === tab.id
+                ? "bg-indigo-600 text-white shadow-md"
+                : "bg-slate-800 text-slate-400 hover:bg-slate-700 hover:text-white"
+            )}
+          >
+            {tab.label}
+          </button>
+        ))}
+      </div>
+
+      <div className="flex flex-wrap gap-4 mb-6 bg-slate-800/50 p-4 rounded-xl border border-slate-700/50">
+        <div className="flex-1 min-w-[200px] relative">
+          <Search className="absolute left-3 top-1/2 -translate-y-1/2 w-4 h-4 text-slate-500" />
+          <input
+            type="text"
+            placeholder="Search SKU or Name..."
+            value={search}
+            onChange={e => { setSearch(e.target.value); setPage(1); }}
+            className="w-full pl-9 pr-10 py-2 bg-slate-900/50 border border-slate-700 rounded-md text-sm text-white focus:outline-none focus:border-indigo-500 focus:ring-1 focus:ring-indigo-500"
+          />
+          {search && (
+            <button
+              onClick={() => { setSearch(''); setPage(1); }}
+              className="absolute right-3 top-1/2 -translate-y-1/2 text-slate-400 hover:text-white"
+            >
+              <X className="w-4 h-4" />
+            </button>
+          )}
+        </div>
+        <div className="flex items-center text-xs text-slate-500">
+          {filteredData.length} items
+        </div>
+      </div>
+
+      <div className="flex-1 bg-slate-800 rounded-xl border border-slate-700 shadow-xl overflow-hidden flex flex-col">
+        <div className="overflow-x-auto flex-1">
+          <table className="w-full text-left text-xs">
+            <thead className="bg-slate-900/80 text-slate-400 sticky top-0 z-10">
+              <tr>
+                {columns.map(({ col, label, width }) => (
+                  <th
+                    key={col}
+                    style={{ width, minWidth: width }}
+                    className="px-3 py-3 font-medium border-r border-slate-700/30 select-none cursor-pointer hover:text-white"
+                    onClick={() => handleSort(col)}
+                  >
+                    <span className="flex items-center gap-1">
+                      {label}
+                      {sortCol === col && (
+                        sortDesc ? <ChevronDown className="w-3 h-3" /> : <ChevronUp className="w-3 h-3" />
+                      )}
+                    </span>
+                  </th>
+                ))}
+              </tr>
+            </thead>
+            <tbody className="divide-y divide-slate-700/30">
+              {paginatedData.map(({ row, index }) => (
+                <tr key={index} className="hover:bg-slate-700/20 transition-colors">
+                  <td className="px-3 py-2 font-mono text-indigo-400 truncate" style={{ width: 100 }}>
+                    {row[COLUMNS.ARTICLE_NO]}
+                  </td>
+                  <td className="px-3 py-2 font-medium text-slate-200 truncate" style={{ width: 220 }} title={row[COLUMNS.ARTICLE_NAME]}>
+                    {row[COLUMNS.ARTICLE_NAME]}
+                  </td>
+                  <td className="px-3 py-2 truncate" style={{ width: 130 }}>
+                    {row[COLUMNS.CLASSIFICATION] && String(row[COLUMNS.CLASSIFICATION]).trim() !== '' ? (
+                      <span className={cn(
+                        "px-1.5 py-0.5 rounded-[4px] text-[10px] font-bold border",
+                        String(row[COLUMNS.CLASSIFICATION]).includes('OOC')
+                          ? "bg-amber-500/10 text-amber-500 border-amber-500/20"
+                          : "bg-slate-700/50 text-slate-400 border-slate-600/50"
+                      )}>
+                        {row[COLUMNS.CLASSIFICATION]}
+                      </span>
+                    ) : (
+                      <span className="inline-flex items-center px-1.5 py-0.5 rounded text-[10px] font-medium bg-red-500/10 text-red-400 border border-red-500/20">Empty</span>
+                    )}
+                  </td>
+                  {launchDateCol >= 0 && (
+                    <td className="px-3 py-2 truncate font-mono text-slate-300" style={{ width: 130 }}>
+                      {isEmptyOrEpoch(row[launchDateCol]) ? (
+                        <span className="inline-flex items-center px-1.5 py-0.5 rounded text-[10px] font-medium bg-red-500/10 text-red-400 border border-red-500/20">Empty</span>
+                      ) : (
+                        formatDateValue(row[launchDateCol]) || String(row[launchDateCol])
+                      )}
+                    </td>
+                  )}
+                  {readyToOrderCol >= 0 && (
+                    <td className="px-3 py-2 truncate font-mono text-slate-300" style={{ width: 130 }}>
+                      {row[readyToOrderCol] !== null && row[readyToOrderCol] !== undefined && row[readyToOrderCol] !== '' ? (
+                        formatDateValue(row[readyToOrderCol]) || String(row[readyToOrderCol])
+                      ) : (
+                        <span className="inline-flex items-center px-1.5 py-0.5 rounded text-[10px] font-medium bg-slate-700/50 text-slate-500 border border-slate-600/50">—</span>
+                      )}
+                    </td>
+                  )}
+                </tr>
+              ))}
+              {paginatedData.length === 0 && (
+                <tr>
+                  <td colSpan={columns.length} className="px-4 py-8 text-center text-slate-500">
+                    No items found.
+                  </td>
+                </tr>
+              )}
+            </tbody>
+          </table>
+        </div>
+
+        <div className="bg-slate-900 border-t border-slate-700 p-4 flex items-center justify-between text-xs text-slate-500">
+          <div>Showing {paginatedData.length} of {filteredData.length} items</div>
+          <div className="flex items-center gap-2">
+            <button
+              disabled={page === 1}
+              onClick={() => setPage(p => p - 1)}
+              className="px-2 py-1 rounded bg-slate-800 hover:bg-slate-700 disabled:opacity-50 transition-colors"
+            >
+              Previous
+            </button>
+            <span className="text-slate-300">Page {page} of {totalPages || 1}</span>
+            <button
+              disabled={page === totalPages || totalPages === 0}
+              onClick={() => setPage(p => p + 1)}
+              className="px-2 py-1 rounded bg-slate-800 hover:bg-slate-700 disabled:opacity-50 transition-colors"
+            >
+              Next
+            </button>
+          </div>
+        </div>
+      </div>
+    </div>
+  );
+}