feat: add NumericStepper component and integrate into index page

src/components/index.ts

@@ -11,4 +11,5 @@ export { default as Link }         from './Link/link.astro';
 export { default as ListItem }     from './ListItem/listItem.astro';
 export { default as ListItemTitle } from './ListItem/listItemTitle.astro';
 export { default as ListItemSubtitle } from './ListItem/listItemSubtitle.astro';
-export { default as LoadingBar }    from './LoadingBar/loadingBar.astro';
+export { default as LoadingBar }    from './LoadingBar/loadingBar.astro';
+export { default as NumericStepper } from './numericStepper/numericStepper.astro';

src/components/numericStepper/_numericStepper.scss

@@ -0,0 +1,14 @@
+@use '../../styles/tokens/typography' as *;
+
+.numeric-stepper {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: var(--nds-spacing-xs);
+  width: fit-content;
+  & p {
+    @include text-xl;
+    margin: 0;
+    
+  }
+}

src/components/numericStepper/numericStepper.astro

@@ -0,0 +1,117 @@
+---
+import Button from '../Button/button.astro';
+import { Arrow2Icon } from '../Icons';
+
+export interface Props {
+  id: string;
+  min?: number;
+  max?: number;
+  value?: number;
+  step?: number;
+}
+
+const { id, min, max, value = 0, step = 1 } = Astro.props;
+---
+
+<div
+  class="numeric-stepper"
+  id={id}
+  data-numeric-stepper
+  data-min={min}
+  data-max={max}
+  data-value={value}
+  data-step={step}
+>
+  <span class="numeric-stepper__control" data-action="increment">
+    <Button type="secondary" icon={true}>
+      <Arrow2Icon size={24} orientation="up" />
+    </Button>
+  </span>
+
+  <p class="numeric-stepper__value">{value}</p>
+
+  <span class="numeric-stepper__control" data-action="decrement">
+    <Button type="secondary" icon={true}>
+      <Arrow2Icon size={24} orientation="down" />
+    </Button>
+  </span>
+</div>
+
+<script>
+  type StepperAction = 'increment' | 'decrement';
+
+  interface StepperChangeDetail {
+    value: number;
+  }
+
+  interface StepperSetDetail {
+    value: number;
+  }
+
+  interface NumericStepperElement extends HTMLElement {
+    setValue: (value: number) => void;
+    getValue: () => number;
+    getStep: () => number;
+  }
+
+  declare global {
+    interface HTMLElementEventMap {
+      'stepper:change': CustomEvent<StepperChangeDetail>;
+      'stepper:set': CustomEvent<StepperSetDetail>;
+    }
+  }
+
+  document.querySelectorAll<NumericStepperElement>('[data-numeric-stepper]').forEach((stepper) => {
+    const { min: minAttr, max: maxAttr, step: stepAttr, value: valueAttr } = stepper.dataset;
+
+    const min = minAttr !== undefined ? Number(minAttr) : -Infinity;
+    const max = maxAttr !== undefined ? Number(maxAttr) : Infinity;
+    const step = stepAttr !== undefined ? Number(stepAttr) : 1;
+
+    let current = valueAttr !== undefined ? Number(valueAttr) : 0;
+
+    const display = stepper.querySelector<HTMLParagraphElement>('.numeric-stepper__value');
+
+    function render(): void {
+      if (display) display.textContent = String(current);
+      stepper.dataset.value = String(current);
+    }
+
+    function setValue(newValue: number): void {
+      const clamped = Math.min(max, Math.max(min, newValue));
+      if (clamped === current) return;
+
+      current = clamped;
+      render();
+
+      stepper.dispatchEvent(
+        new CustomEvent<StepperChangeDetail>('stepper:change', {
+          detail: { value: current },
+          bubbles: true,
+        }),
+      );
+    }
+
+    stepper.addEventListener('click', (event: MouseEvent) => {
+      const target = event.target as HTMLElement;
+      const control = target.closest<HTMLElement>('[data-action]');
+      if (!control || !stepper.contains(control)) return;
+
+      const action = control.dataset.action as StepperAction | undefined;
+      if (action === 'increment') setValue(current + step);
+      else if (action === 'decrement') setValue(current - step);
+    });
+
+    stepper.addEventListener('stepper:set', (event) => {
+      setValue(event.detail.value);
+    });
+
+    stepper.setValue = (value: number): void => setValue(value);
+    stepper.getValue = (): number => current;
+    stepper.getStep = (): number => step;
+  });
+</script>
+
+<style lang="scss">
+@use './numericStepper';
+</style>