<template>
  <div v-if="chapter">
    <BookChapterHeader
      :title="chapter.title"
      :description="chapter.description"
      :order="chapter.order"
      :reading-time="chapter.readingTime"
      :chapter-slug="slug"
    />

    <BookChapterContent :content="chapter" />

    <!-- Prev / Next navigation -->
    <nav class="mt-16 flex items-center justify-between border-t border-white/8 pt-8">
      <NuxtLink
        v-if="prevChapter"
        :to="`/economique/modele-eco/${prevChapter.stem?.split('/').pop()}`"
        class="btn-ghost gap-2"
      >
        <div class="i-lucide-arrow-left h-4 w-4" />
        <span class="text-sm">{{ prevChapter.title }}</span>
      </NuxtLink>
      <div v-else />

      <NuxtLink
        v-if="nextChapter"
        :to="`/economique/modele-eco/${nextChapter.stem?.split('/').pop()}`"
        class="btn-ghost gap-2"
      >
        <span class="text-sm">{{ nextChapter.title }}</span>
        <div class="i-lucide-arrow-right h-4 w-4" />
      </NuxtLink>
      <div v-else />
    </nav>
  </div>
</template>

<script setup lang="ts">
definePageMeta({
  layout: 'reading',
})

const route = useRoute()
const slug = route.params.slug as string

// Scroll to top when navigating between chapters (component reused by Vue Router)
watch(() => slug, () => {
  if (import.meta.client) window.scrollTo({ top: 0, behavior: 'instant' })
})

// Initialize guided mode
useGuidedMode()

const { data: chapter } = await useAsyncData(`chapter-${slug}`, () =>
  queryCollection('book').path(`/book/${slug}`).first(),
)

if (!chapter.value) {
  throw createError({ statusCode: 404, statusMessage: 'Chapitre non trouvé' })
}

useSeoPage({
  title: chapter.value?.title ?? slug,
  description: chapter.value?.description as string ?? `Chapitre « ${chapter.value?.title} » — Une économie du don, enfin concevable.`,
  image: '/images/Couv-Economie-du-don.jpg',
  type: 'article',
})

// Get adjacent chapters for navigation
const { data: allChapters } = await useAsyncData('book-nav', () =>
  queryCollection('book').order('order', 'ASC').all(),
)

const currentIndex = computed(() =>
  allChapters.value?.findIndex(c => c.stem?.split('/').pop() === slug) ?? -1,
)

const prevChapter = computed(() => {
  const idx = currentIndex.value
  if (idx <= 0 || !allChapters.value) return null
  return allChapters.value[idx - 1]
})

const nextChapter = computed(() => {
  const idx = currentIndex.value
  if (!allChapters.value || idx >= allChapters.value.length - 1) return null
  return allChapters.value[idx + 1]
})
</script>
