refactor: refactor units tool to match calculate blueprint

Rewrites all three units components to use the same glass panel
layout, lg:grid-cols-5 two-panel split, and interactive patterns
established by the calculate tool.

- MainConverter: category sidebar (left 2/5) replaces Select dropdown;
  converter card + scrollable conversion grid (right 3/5); mobile
  'Category | Convert' tab switcher; clickable conversion cards set
  target unit; glass Grid/Chart toggle
- SearchUnits: native input with glass border, glass dropdown panel,
  compact result rows matching font selector style
- VisualComparison: polished gradient bars, tighter spacing, cleaner
  value display; all drag logic preserved

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

components/units/MainConverter.tsx

@@ -1,11 +1,7 @@
 'use client';
 
 import { useState, useEffect, useCallback } from 'react';
-import { ArrowLeftRight, BarChart3 } from 'lucide-react';
-import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card';
-import { Input } from '@/components/ui/input';
-import { Label } from '@/components/ui/label';
-import { Button } from '@/components/ui/button';
+import { ArrowLeftRight, BarChart3, Grid3X3 } from 'lucide-react';
 import {
   Select,
   SelectContent,
@@ -15,7 +11,6 @@ import {
 } from '@/components/ui/select';
 import SearchUnits from './SearchUnits';
 import VisualComparison from './VisualComparison';
-
 import {
   getAllMeasures,
   getUnitsForMeasure,
@@ -27,211 +22,313 @@ import {
 } from '@/lib/units/units';
 import { parseNumberInput, formatNumber, cn } from '@/lib/utils';
 
+type Tab = 'category' | 'convert';
+
+const CATEGORY_ICONS: Partial<Record<Measure, string>> = {
+  length: '📏', mass: '⚖️', temperature: '🌡️', speed: '⚡', time: '⏱️',
+  area: '⬛', volume: '🧊', digital: '💾', energy: '⚡', pressure: '🔵',
+  power: '🔆', frequency: '〰️', angle: '📐', current: '⚡', voltage: '🔌',
+};
+
 export default function MainConverter() {
   const [selectedMeasure, setSelectedMeasure] = useState<Measure>('length');
   const [selectedUnit, setSelectedUnit] = useState<string>('m');
   const [targetUnit, setTargetUnit] = useState<string>('ft');
   const [inputValue, setInputValue] = useState<string>('1');
   const [conversions, setConversions] = useState<ConversionResult[]>([]);
-  const [showVisualComparison, setShowVisualComparison] = useState(false);
-  const [isDragging, setIsDragging] = useState(false);
+  const [showChart, setShowChart] = useState(false);
+  const [tab, setTab] = useState<Tab>('category');
 
   const measures = getAllMeasures();
   const units = getUnitsForMeasure(selectedMeasure);
 
-  // Update conversions when input changes
   useEffect(() => {
     const numValue = parseNumberInput(inputValue);
     if (numValue !== null && selectedUnit) {
-      const results = convertToAll(numValue, selectedUnit);
-      setConversions(results);
+      setConversions(convertToAll(numValue, selectedUnit));
     } else {
       setConversions([]);
     }
   }, [inputValue, selectedUnit]);
 
-  // Update selected unit when measure changes
   useEffect(() => {
     const availableUnits = getUnitsForMeasure(selectedMeasure);
     if (availableUnits.length > 0) {
       setSelectedUnit(availableUnits[0]);
-      setTargetUnit(availableUnits[1] || availableUnits[0]);
+      setTargetUnit(availableUnits[1] ?? availableUnits[0]);
     }
   }, [selectedMeasure]);
 
-  // Swap units
   const handleSwapUnits = useCallback(() => {
-    const temp = selectedUnit;
-    setSelectedUnit(targetUnit);
-    setTargetUnit(temp);
-
-    // Convert the value
     const numValue = parseNumberInput(inputValue);
     if (numValue !== null) {
-      const converted = convertUnit(numValue, selectedUnit, targetUnit);
-      setInputValue(converted.toString());
+      setInputValue(convertUnit(numValue, selectedUnit, targetUnit).toString());
     }
+    setSelectedUnit(targetUnit);
+    setTargetUnit(selectedUnit);
   }, [selectedUnit, targetUnit, inputValue]);
 
-  // Handle search selection
   const handleSearchSelect = useCallback((unit: string, measure: Measure) => {
     setSelectedMeasure(measure);
     setSelectedUnit(unit);
+    setTab('convert');
   }, []);
 
-  // Handle value change from draggable bars
-  const handleValueChange = useCallback((value: number, unit: string, dragging: boolean) => {
-    setIsDragging(dragging);
+  const handleCategorySelect = useCallback((measure: Measure) => {
+    setSelectedMeasure(measure);
+    setTab('convert');
+  }, []);
 
-    // Convert the dragged unit's value back to the currently selected unit
-    // This keeps the source unit stable while updating the value
-    const convertedValue = convertUnit(value, unit, selectedUnit);
-    setInputValue(convertedValue.toString());
-    // Keep selectedUnit unchanged
-  }, [selectedUnit]);
+  const handleValueChange = useCallback(
+    (value: number, unit: string, _dragging: boolean) => {
+      setInputValue(convertUnit(value, unit, selectedUnit).toString());
+    },
+    [selectedUnit]
+  );
+
+  const resultValue = (() => {
+    const n = parseNumberInput(inputValue);
+    return n !== null ? convertUnit(n, selectedUnit, targetUnit) : null;
+  })();
 
   return (
-    <div className="w-full space-y-6">
+    <div className="flex flex-col gap-4">
 
-      {/* Quick Access Row */}
-      <Card>
-        <CardContent className="flex flex-col md:flex-row md:items-center gap-3 justify-between">
-          <div className="flex-1">
+      {/* ── Mobile tab switcher ────────────────────────────────── */}
+      <div className="flex lg:hidden glass rounded-xl p-1 gap-1">
+        {(['category', 'convert'] as Tab[]).map((t) => (
+          <button
+            key={t}
+            onClick={() => setTab(t)}
+            className={cn(
+              'flex-1 py-2.5 rounded-lg text-sm font-medium capitalize transition-all',
+              tab === t
+                ? 'bg-primary text-primary-foreground shadow-sm'
+                : 'text-muted-foreground hover:text-foreground'
+            )}
+          >
+            {t === 'category' ? 'Category' : 'Convert'}
+          </button>
+        ))}
+      </div>
+
+      {/* ── Main layout ────────────────────────────────────────── */}
+      <div
+        className="grid grid-cols-1 lg:grid-cols-5 gap-4"
+        style={{ height: 'calc(100svh - 220px)', minHeight: '620px' }}
+      >
+
+        {/* Left panel: search + categories */}
+        <div
+          className={cn(
+            'lg:col-span-2 flex flex-col gap-3 overflow-hidden',
+            tab !== 'category' && 'hidden lg:flex'
+          )}
+        >
+          {/* Search */}
+          <div className="glass rounded-xl p-4 shrink-0">
+            <span className="text-[10px] font-semibold text-muted-foreground uppercase tracking-widest block mb-2">
+              Search
+            </span>
             <SearchUnits onSelectUnit={handleSearchSelect} />
           </div>
-          <div className="w-full md:w-56 shrink-0">
-            <Select
-              value={selectedMeasure}
-              onValueChange={(value) => setSelectedMeasure(value as Measure)}
-            >
-              <SelectTrigger className="w-full">
-                <SelectValue placeholder="Measure" />
-              </SelectTrigger>
-              <SelectContent>
-                {measures.map((measure) => (
-                  <SelectItem key={measure} value={measure}>
-                    {formatMeasureName(measure)}
-                  </SelectItem>
-                ))}
-              </SelectContent>
-            </Select>
-          </div>
-        </CardContent>
-      </Card>
 
-      {/* Main Converter Card */}
-      <Card>
-        <CardHeader>
-          <CardTitle>Convert {formatMeasureName(selectedMeasure)}</CardTitle>
-        </CardHeader>
-        <CardContent className="space-y-4">
-          <div className="flex flex-col gap-3 md:flex-row md:items-end md:gap-2">
-            <div className="flex-1 w-full">
-              <Label className="text-xs mb-1.5">Value</Label>
-              <Input
+          {/* Category list */}
+          <div className="glass rounded-xl p-3 flex flex-col flex-1 min-h-0 overflow-hidden">
+            <div className="flex items-center justify-between mb-3 shrink-0">
+              <span className="text-[10px] font-semibold text-muted-foreground uppercase tracking-widest">
+                Categories
+              </span>
+              <span className="text-[10px] text-muted-foreground/35 font-mono tabular-nums">
+                {measures.length}
+              </span>
+            </div>
+
+            <div className="flex-1 min-h-0 overflow-y-auto scrollbar-thin scrollbar-thumb-primary/20 scrollbar-track-transparent space-y-0.5 pr-0.5">
+              {measures.map((measure) => {
+                const isSelected = selectedMeasure === measure;
+                const unitCount = getUnitsForMeasure(measure).length;
+                return (
+                  <button
+                    key={measure}
+                    onClick={() => handleCategorySelect(measure)}
+                    className={cn(
+                      'w-full flex items-center gap-2 px-2 py-1.5 rounded-lg transition-all text-left',
+                      'border-l-2',
+                      isSelected
+                        ? 'bg-primary/10 border-primary text-primary'
+                        : 'border-transparent text-foreground/65 hover:bg-primary/8 hover:text-foreground'
+                    )}
+                  >
+                    <span className="text-xs leading-none shrink-0 opacity-70">
+                      {CATEGORY_ICONS[measure] ?? '📦'}
+                    </span>
+                    <span className="flex-1 text-xs font-mono truncate">{formatMeasureName(measure)}</span>
+                    <span
+                      className={cn(
+                        'text-[10px] font-mono tabular-nums shrink-0 px-1.5 py-0.5 rounded',
+                        isSelected
+                          ? 'bg-primary/20 text-primary'
+                          : 'bg-muted/40 text-muted-foreground/40'
+                      )}
+                    >
+                      {unitCount}
+                    </span>
+                  </button>
+                );
+              })}
+            </div>
+          </div>
+        </div>
+
+        {/* Right panel: converter + results */}
+        <div
+          className={cn(
+            'lg:col-span-3 flex flex-col gap-3 overflow-hidden',
+            tab !== 'convert' && 'hidden lg:flex'
+          )}
+        >
+          {/* Converter card */}
+          <div className="glass rounded-xl p-4 shrink-0">
+            <span className="text-[10px] font-semibold text-muted-foreground uppercase tracking-widest block mb-3">
+              Convert {formatMeasureName(selectedMeasure)}
+            </span>
+
+            {/* Input row */}
+            <div className="flex items-center gap-2">
+              {/* Value input */}
+              <input
                 type="text"
                 inputMode="decimal"
                 value={inputValue}
                 onChange={(e) => setInputValue(e.target.value)}
-                placeholder="Enter value"
-                className={cn("text-lg", "w-full", "max-w-full")}
+                placeholder="0"
+                className="flex-1 min-w-0 bg-transparent border border-border/40 rounded-lg px-3 py-2 text-sm font-mono outline-none focus:border-primary/50 transition-colors placeholder:text-muted-foreground/30 tabular-nums"
               />
-            </div>
-            <div className="w-full md:w-36">
-              <Label className="text-xs mb-1.5">From</Label>
-              <Select
-                value={selectedUnit}
-                onValueChange={(value) => setSelectedUnit(value)}
-              >
-                <SelectTrigger className="w-full">
-                  <SelectValue placeholder="From" />
+
+              {/* From unit */}
+              <Select value={selectedUnit} onValueChange={setSelectedUnit}>
+                <SelectTrigger className="w-28 h-9 shrink-0 text-xs border-border/30 bg-transparent hover:border-primary/30 transition-colors font-mono">
+                  <SelectValue />
                 </SelectTrigger>
                 <SelectContent>
                   {units.map((unit) => (
-                    <SelectItem key={unit} value={unit}>
-                      {unit}
-                    </SelectItem>
-                  ))}
-                </SelectContent>
-              </Select>
-            </div>
-            <Button
-              variant="outline"
-              size="icon"
-              onClick={handleSwapUnits}
-              className="shrink-0 w-full md:w-7"
-              title="Swap units"
-            >
-              <ArrowLeftRight className="h-3.5 w-3.5" />
-            </Button>
-            <div className="w-full md:w-36">
-              <Label className="text-xs mb-1.5">To</Label>
-              <Select
-                value={targetUnit}
-                onValueChange={(value) => setTargetUnit(value)}
-              >
-                <SelectTrigger className="w-full">
-                  <SelectValue placeholder="To" />
-                </SelectTrigger>
-                <SelectContent>
-                  {units.map((unit) => (
-                    <SelectItem key={unit} value={unit}>
+                    <SelectItem key={unit} value={unit} className="font-mono text-xs">
+                      {unit}
+                    </SelectItem>
+                  ))}
+                </SelectContent>
+              </Select>
+
+              {/* Swap */}
+              <button
+                onClick={handleSwapUnits}
+                title="Swap units"
+                className="shrink-0 w-8 h-8 flex items-center justify-center glass rounded-lg border border-border/30 text-muted-foreground hover:text-primary hover:border-primary/30 hover:bg-primary/10 transition-all"
+              >
+                <ArrowLeftRight className="w-3.5 h-3.5" />
+              </button>
+
+              {/* To unit */}
+              <Select value={targetUnit} onValueChange={setTargetUnit}>
+                <SelectTrigger className="w-28 h-9 shrink-0 text-xs border-border/30 bg-transparent hover:border-primary/30 transition-colors font-mono">
+                  <SelectValue />
+                </SelectTrigger>
+                <SelectContent>
+                  {units.map((unit) => (
+                    <SelectItem key={unit} value={unit} className="font-mono text-xs">
                       {unit}
                     </SelectItem>
                   ))}
                 </SelectContent>
               </Select>
             </div>
+
+            {/* Result display */}
+            {resultValue !== null && (
+              <div className="mt-3 px-3 py-2.5 rounded-lg bg-primary/5 border border-primary/15">
+                <div className="text-[10px] text-muted-foreground/50 font-mono mb-0.5">Result</div>
+                <div className="flex items-baseline gap-2">
+                  <span className="text-xl font-bold tabular-nums font-mono bg-gradient-to-r from-primary to-pink-400 bg-clip-text text-transparent">
+                    {formatNumber(resultValue)}
+                  </span>
+                  <span className="text-sm text-muted-foreground/60 font-mono">{targetUnit}</span>
+                </div>
+              </div>
+            )}
           </div>
 
-          {parseNumberInput(inputValue) !== null && (
-            <div className="p-3 rounded-lg bg-primary/5 border border-primary/15">
-              <div className="text-xs text-muted-foreground mb-0.5">Result</div>
-              <div className="text-2xl font-bold text-primary tabular-nums">
-                {formatNumber(convertUnit(parseNumberInput(inputValue)!, selectedUnit, targetUnit))} <span className="text-base font-medium text-muted-foreground">{targetUnit}</span>
+          {/* All conversions */}
+          <div className="glass rounded-xl p-3 flex flex-col flex-1 min-h-0 overflow-hidden">
+            <div className="flex items-center justify-between mb-3 shrink-0">
+              <span className="text-[10px] font-semibold text-muted-foreground uppercase tracking-widest">
+                All Conversions
+              </span>
+              {/* Grid / Chart toggle */}
+              <div className="flex glass rounded-lg p-0.5 gap-0.5">
+                <button
+                  onClick={() => setShowChart(false)}
+                  title="Grid view"
+                  className={cn(
+                    'flex items-center gap-1 px-2 py-1 rounded-md text-xs transition-all',
+                    !showChart
+                      ? 'bg-primary text-primary-foreground shadow-sm'
+                      : 'text-muted-foreground hover:text-foreground'
+                  )}
+                >
+                  <Grid3X3 className="w-3 h-3" />
+                </button>
+                <button
+                  onClick={() => setShowChart(true)}
+                  title="Chart view"
+                  className={cn(
+                    'flex items-center gap-1 px-2 py-1 rounded-md text-xs transition-all',
+                    showChart
+                      ? 'bg-primary text-primary-foreground shadow-sm'
+                      : 'text-muted-foreground hover:text-foreground'
+                  )}
+                >
+                  <BarChart3 className="w-3 h-3" />
+                </button>
               </div>
             </div>
-          )}
-        </CardContent>
-      </Card>
 
-      {/* Results */}
-      <Card>
-        <CardHeader>
-          <div className="flex items-center justify-between">
-            <CardTitle>All Conversions</CardTitle>
-            <Button
-              variant="outline"
-              size="xs"
-              onClick={() => setShowVisualComparison(!showVisualComparison)}
-            >
-              <BarChart3 className="h-3 w-3 mr-1" />
-              {showVisualComparison ? 'Grid' : 'Chart'}
-            </Button>
-          </div>
-        </CardHeader>
-        <CardContent>
-          {showVisualComparison ? (
-            <VisualComparison
-              conversions={conversions}
-              onValueChange={handleValueChange}
-            />
-          ) : (
-            <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-3">
-              {conversions.map((conversion) => (
-                <div
-                  key={conversion.unit}
-                  className="p-3 rounded-lg border border-border/50 hover:border-primary/30 transition-colors"
-                >
-                  <div className="text-xs text-muted-foreground">{conversion.unitInfo.plural}</div>
-                  <div className="text-lg font-bold tabular-nums mt-0.5">{formatNumber(conversion.value)}</div>
-                  <div className="text-xs text-muted-foreground">{conversion.unit}</div>
+            <div className="flex-1 min-h-0 overflow-y-auto scrollbar-thin scrollbar-thumb-primary/20 scrollbar-track-transparent pr-0.5">
+              {showChart ? (
+                <VisualComparison conversions={conversions} onValueChange={handleValueChange} />
+              ) : (
+                <div className="grid grid-cols-2 lg:grid-cols-3 gap-2">
+                  {conversions.map((conversion) => {
+                    const isTarget = targetUnit === conversion.unit;
+                    return (
+                      <button
+                        key={conversion.unit}
+                        onClick={() => setTargetUnit(conversion.unit)}
+                        className={cn(
+                          'p-2.5 rounded-lg border text-left transition-all',
+                          isTarget
+                            ? 'border-primary/50 bg-primary/10 text-primary'
+                            : 'border-border/30 hover:border-primary/30 hover:bg-primary/6 text-foreground/75'
+                        )}
+                      >
+                        <div className="text-[10px] text-muted-foreground/50 font-mono truncate mb-0.5">
+                          {conversion.unitInfo.plural}
+                        </div>
+                        <div className="text-sm font-bold tabular-nums font-mono leading-none">
+                          {formatNumber(conversion.value)}
+                        </div>
+                        <div className="text-[10px] text-muted-foreground/40 font-mono mt-0.5">
+                          {conversion.unit}
+                        </div>
+                      </button>
+                    );
+                  })}
                 </div>
-              ))}
+              )}
             </div>
-          )}
-        </CardContent>
-      </Card>
+          </div>
+        </div>
+      </div>
     </div>
   );
 }