refactor(usage): modularize UsagePage into separate section components

src/components/usage/ChartLineSelector.tsx

@@ -0,0 +1,92 @@
+import { useTranslation } from 'react-i18next';
+import { Card } from '@/components/ui/Card';
+import { Button } from '@/components/ui/Button';
+import styles from '@/pages/UsagePage.module.scss';
+
+export interface ChartLineSelectorProps {
+  chartLines: string[];
+  modelNames: string[];
+  maxLines?: number;
+  onChange: (lines: string[]) => void;
+}
+
+export function ChartLineSelector({
+  chartLines,
+  modelNames,
+  maxLines = 9,
+  onChange
+}: ChartLineSelectorProps) {
+  const { t } = useTranslation();
+
+  const handleAdd = () => {
+    if (chartLines.length >= maxLines) return;
+    const unusedModel = modelNames.find((m) => !chartLines.includes(m));
+    if (unusedModel) {
+      onChange([...chartLines, unusedModel]);
+    } else {
+      onChange([...chartLines, 'all']);
+    }
+  };
+
+  const handleRemove = (index: number) => {
+    if (chartLines.length <= 1) return;
+    const newLines = [...chartLines];
+    newLines.splice(index, 1);
+    onChange(newLines);
+  };
+
+  const handleChange = (index: number, value: string) => {
+    const newLines = [...chartLines];
+    newLines[index] = value;
+    onChange(newLines);
+  };
+
+  return (
+    <Card
+      title={t('usage_stats.chart_line_actions_label')}
+      extra={
+        <div className={styles.chartLineHeader}>
+          <span className={styles.chartLineCount}>
+            {chartLines.length}/{maxLines}
+          </span>
+          <Button
+            variant="secondary"
+            size="sm"
+            onClick={handleAdd}
+            disabled={chartLines.length >= maxLines}
+          >
+            {t('usage_stats.chart_line_add')}
+          </Button>
+        </div>
+      }
+    >
+      <div className={styles.chartLineList}>
+        {chartLines.map((line, index) => (
+          <div key={index} className={styles.chartLineItem}>
+            <span className={styles.chartLineLabel}>
+              {t(`usage_stats.chart_line_label_${index + 1}`)}
+            </span>
+            <select
+              value={line}
+              onChange={(e) => handleChange(index, e.target.value)}
+              className={styles.select}
+            >
+              <option value="all">{t('usage_stats.chart_line_all')}</option>
+              {modelNames.map((name) => (
+                <option key={name} value={name}>
+                  {name}
+                </option>
+              ))}
+            </select>
+            {chartLines.length > 1 && (
+              <Button variant="danger" size="sm" onClick={() => handleRemove(index)}>
+                {t('usage_stats.chart_line_delete')}
+              </Button>
+            )}
+          </div>
+        ))}
+      </div>
+      <p className={styles.chartLineHint}>{t('usage_stats.chart_line_hint')}</p>
+    </Card>
+  );
+}