﻿<script setup lang="ts">
import { computed, onMounted, onUnmounted, ref, watch } from 'vue';
import { useRouter } from 'vue-router';
import { useI18n } from 'vue-i18n';
import type { BannerItem } from '../BannerCarousel.vue';
import defaultBannerImg from '../../assets/images/banner.webp';

const props = defineProps<{
  banners: BannerItem[];
  fallbackTo?: string;
}>();

const { t } = useI18n();
const router = useRouter();
const active = ref(0);
const timer = ref<ReturnType<typeof setInterval> | null>(null);
const FALLBACK_IMG = '/uploads/banners/welcome.svg';

const slideCount = computed(() => props.banners.length);
const canLoop = computed(() => slideCount.value > 1);

function imageUrl(banner: BannerItem) {
  return banner.translation?.imageUrl || defaultBannerImg || FALLBACK_IMG;
}

function onImgError(e: Event) {
  const img = e.target as HTMLImageElement;
  if (img.dataset.fallbackApplied) return;
  img.dataset.fallbackApplied = '1';
  img.src = defaultBannerImg || FALLBACK_IMG;
}

function title(banner: BannerItem) {
  return banner.translation?.title || t('home.banner_fallback');
}

function normalizeOffset(index: number) {
  const len = slideCount.value;
  if (!len) return 0;
  let offset = index - active.value;
  if (offset > len / 2) offset -= len;
  if (offset < -len / 2) offset += len;
  return offset;
}

/** Coverflow：略重叠，中间卡片置顶 */
function slideLayout(index: number) {
  const offset = normalizeOffset(index);
  const abs = Math.abs(offset);

  if (abs > 1) {
    return { hidden: true, offset, active: false };
  }

  const slotX = 50 + offset * 26;
  const scale = offset === 0 ? 1 : 0.9;
  const rotateY = offset === 0 ? 0 : offset < 0 ? 12 : -12;
  const zIndex = offset === 0 ? 10 : 5;

  return {
    hidden: false,
    offset,
    active: offset === 0,
    slotX,
    scale,
    rotateY,
    zIndex,
  };
}

function slideStyle(index: number) {
  const layout = slideLayout(index);
  if (layout.hidden) {
    return {
      left: '50%',
      transform: 'translate(-50%, -50%) scale(0.7)',
      opacity: '0',
      zIndex: '0',
      pointerEvents: 'none' as const,
    };
  }

  return {
    left: `${layout.slotX}%`,
    transform: `translate(-50%, -50%) scale(${layout.scale}) rotateY(${layout.rotateY}deg)`,
    opacity: '1',
    zIndex: String(layout.zIndex),
    pointerEvents: 'auto' as const,
  };
}

function goTo(index: number) {
  if (!slideCount.value) return;
  active.value = (index + slideCount.value) % slideCount.value;
}

function next() {
  goTo(active.value + 1);
}

function prev() {
  goTo(active.value - 1);
}

function onBannerClick(banner: BannerItem, index: number) {
  if (normalizeOffset(index) !== 0) {
    goTo(index);
    return;
  }
  if (banner.id) {
    void router.push(`/announcements/${banner.id}`);
    return;
  }
  if (props.fallbackTo) {
    void router.push(props.fallbackTo);
  }
}

function startAutoPlay() {
  stopAutoPlay();
  if (!canLoop.value) return;
  timer.value = setInterval(next, 5000);
}

function stopAutoPlay() {
  if (timer.value) {
    clearInterval(timer.value);
    timer.value = null;
  }
}

watch(
  () => props.banners.length,
  () => {
    active.value = 0;
    startAutoPlay();
  },
);

onMounted(startAutoPlay);
onUnmounted(stopAutoPlay);
</script>

<template>
  <section
    v-if="banners.length"
    class="banner-coverflow"
    @mouseenter="stopAutoPlay"
    @mouseleave="startAutoPlay"
  >
    <div class="coverflow-stage">
      <button
        v-for="(banner, i) in banners"
        :key="banner.id ?? i"
        type="button"
        class="coverflow-slide"
        :class="{ 'is-active': slideLayout(i).active, 'is-side': Math.abs(slideLayout(i).offset) === 1 }"
        :style="slideStyle(i)"
        :aria-label="title(banner)"
        @click="onBannerClick(banner, i)"
      >
        <div class="slide-card">
          <img
            v-if="imageUrl(banner)"
            :src="imageUrl(banner)"
            :alt="''"
            class="slide-img"
            :loading="i === 0 ? 'eager' : 'lazy'"
            @error="onImgError"
          />
          <div v-else class="slide-fallback" aria-hidden="true">
            <svg class="fallback-icon" viewBox="0 0 24 24" aria-hidden="true">
              <path fill="currentColor" d="M21 19V5c0-1.1-.9-2-2-2H5c-1.1 0-2 .9-2 2v14c0 1.1.9 2 2 2h14c1.1 0 2-.9 2-2zM8.5 13.5l2.5 3.01L14.5 12l4.5 6H5l3.5-4.5z"/>
            </svg>
          </div>
          <div v-if="slideLayout(i).active" class="click-hint" aria-hidden="true">
            <span class="click-ring" />
            <svg class="click-icon" viewBox="0 0 24 24" aria-hidden="true">
              <path
                fill="currentColor"
                d="M9 11.24V7.5a2.5 2.5 0 0 1 5 0v3.74c1.21-.81 2-2.18 2-3.74C16 5.01 13.99 3 11.5 3S7 5.01 7 7.5c0 1.56.79 2.93 2 3.74zm9.84 4.63-4.54-2.26a1.5 1.5 0 0 0-.54-.11H13v-6c0-.83-.67-1.5-1.5-1.5S10 6.67 10 7.5v10.74l-3.43-.72a1 1 0 0 0-.24-.03c-.31 0-.59.13-.79.33l-.79.8 4.94 4.94c.27.27.65.44 1.06.44h6.79c.75 0 1.33-.55 1.44-1.28l.75-5.27a1.5 1.5 0 0 0-.91-1.38z"
              />
            </svg>
          </div>
        </div>
      </button>

      <button
        v-if="canLoop"
        type="button"
        class="nav-btn prev"
        :aria-label="t('home.banner_prev')"
        @click.stop="prev"
      >
        <svg viewBox="0 0 24 24" aria-hidden="true"><path fill="currentColor" d="M15.41 7.41 14 6l-6 6 6 6 1.41-1.41L10.83 12z"/></svg>
      </button>
      <button
        v-if="canLoop"
        type="button"
        class="nav-btn next"
        :aria-label="t('home.banner_next')"
        @click.stop="next"
      >
        <svg viewBox="0 0 24 24" aria-hidden="true"><path fill="currentColor" d="M10 6 8.59 7.41 13.17 12l-4.58 4.59L10 18l6-6z"/></svg>
      </button>
    </div>

    <div v-if="canLoop" class="coverflow-dots">
      <button
        v-for="(_, i) in banners"
        :key="i"
        type="button"
        class="dot"
        :class="{ active: i === active }"
        :aria-label="t('home.banner_slide', { n: i + 1 })"
        @click.stop="goTo(i)"
      />
    </div>
  </section>
</template>

<style scoped>
.banner-coverflow {
  width: 100%;
  padding: 4px 0 0;
}

.coverflow-stage {
  position: relative;
  height: clamp(260px, 28vw, 360px);
  perspective: 1000px;
}

.coverflow-slide {
  position: absolute;
  top: 50%;
  width: 42%;
  max-width: 560px;
  height: 90%;
  padding: 0;
  border: none;
  background: transparent;
  cursor: pointer;
  transition:
    left 0.55s cubic-bezier(0.25, 0.8, 0.25, 1),
    transform 0.55s cubic-bezier(0.25, 0.8, 0.25, 1),
    opacity 0.4s ease;
  transform-style: preserve-3d;
  will-change: left, transform;
}

.slide-card {
  position: relative;
  width: 100%;
  height: 100%;
  border-radius: 14px;
  overflow: hidden;
  background: linear-gradient(180deg, #141414 0%, #0a0a0a 100%);
  box-shadow: 0 10px 32px rgba(0, 0, 0, 0.45);
  transition: box-shadow 0.35s ease, filter 0.35s ease, transform 0.25s ease;
  display: flex;
  align-items: center;
  justify-content: center;
}

.coverflow-slide.is-side .slide-card {
  filter: brightness(0.72) saturate(0.9);
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.35);
}

.coverflow-slide.is-side:hover .slide-card {
  filter: brightness(0.88) saturate(1);
}

.coverflow-slide.is-active .slide-card {
  filter: none;
  box-shadow:
    0 16px 40px rgba(0, 0, 0, 0.5),
    0 0 28px rgba(0, 102, 204, 0.22),
    0 0 56px rgba(0, 102, 204, 0.1);
  animation: banner-breathe 3s ease-in-out infinite;
}

.coverflow-slide.is-active:hover .slide-card {
  animation: none;
  transform: scale(1.018);
}

@keyframes banner-breathe {
  0%,
  100% {
    transform: scale(1);
    box-shadow:
      0 16px 40px rgba(0, 0, 0, 0.5),
      0 0 22px rgba(0, 102, 204, 0.16),
      0 0 48px rgba(0, 102, 204, 0.08);
  }

  50% {
    transform: scale(1.008);
    box-shadow:
      0 18px 44px rgba(0, 0, 0, 0.52),
      0 0 32px rgba(0, 102, 204, 0.26),
      0 0 60px rgba(0, 102, 204, 0.12);
  }
}

.slide-img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  object-position: center;
  display: block;
}

.slide-fallback {
  width: 100%;
  height: 100%;
  min-height: 120px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(135deg, rgba(0, 102, 204, 0.12), #1a1a1a);
}

.fallback-icon {
  width: 40px;
  height: 40px;
  color: rgba(0, 102, 204, 0.35);
}

.click-hint {
  position: absolute;
  right: 10px;
  bottom: 10px;
  width: 28px;
  height: 28px;
  display: flex;
  align-items: center;
  justify-content: center;
  pointer-events: none;
  z-index: 2;
  background: rgba(0, 0, 0, 0.35);
  border-radius: 50%;
}

.click-ring {
  position: absolute;
  inset: 0;
  border-radius: 50%;
  border: 1px solid rgba(0, 102, 204, 0.45);
  animation: click-ring-pulse 2.8s ease-out infinite;
}

.click-icon {
  position: relative;
  width: 15px;
  height: 15px;
  color: rgba(0, 102, 204, 0.88);
  animation: click-icon-bob 2.8s ease-in-out infinite;
}

@keyframes click-ring-pulse {
  0% {
    transform: scale(0.9);
    opacity: 0.55;
  }

  70% {
    transform: scale(1.35);
    opacity: 0;
  }

  100% {
    transform: scale(1.35);
    opacity: 0;
  }
}

@keyframes click-icon-bob {
  0%,
  100% {
    transform: translateY(1px) scale(1);
    opacity: 0.65;
  }

  50% {
    transform: translateY(-1px) scale(1.06);
    opacity: 1;
  }
}

.coverflow-slide.is-active:hover .click-hint {
  opacity: 0;
  transition: opacity 0.2s ease;
}

@media (prefers-reduced-motion: reduce) {
  .coverflow-slide.is-active .slide-card,
  .click-ring,
  .click-icon {
    animation: none;
  }
}

.nav-btn {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  width: 36px;
  height: 36px;
  border-radius: 50%;
  border: 1px solid rgba(0, 102, 204, 0.4);
  background: rgba(10, 10, 10, 0.75);
  color: var(--primary-light);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 20;
  transition: background 0.2s, border-color 0.2s;
}

.nav-btn svg {
  width: 20px;
  height: 20px;
}

.nav-btn:hover {
  background: rgba(0, 102, 204, 0.2);
  border-color: var(--primary);
}

.nav-btn.prev {
  left: 4px;
}

.nav-btn.next {
  right: 4px;
}

.coverflow-dots {
  display: flex;
  justify-content: center;
  gap: 8px;
  margin-top: 14px;
}

.dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.25);
  border: none;
  padding: 0;
  cursor: pointer;
  transition: all 0.25s ease;
}

.dot.active {
  width: 22px;
  border-radius: 4px;
  background: var(--primary);
}

.dot:hover:not(.active) {
  background: rgba(255, 255, 255, 0.45);
}
</style>
