import { defineStore } from 'pinia'
import { ref, computed } from 'vue'
import { useApi } from '../composables/useApi.js'

export const useGalleryStore = defineStore('gallery', () => {
  const api = useApi()

  const images = ref([])
  const dateGroups = ref([])  // [{year, month, image_ids}]
  const nextCursor = ref(null)
  const loading = ref(false)
  const error = ref(null)
  const filter = ref({ tag_id: null })

  const timelineBuckets = ref([])
  const timelineLoading = ref(false)

  let inflightId = 0

  async function loadInitial() {
    images.value = []
    dateGroups.value = []
    nextCursor.value = null
    await loadMore()
  }

  async function loadMore() {
    if (loading.value) return
    loading.value = true
    error.value = null
    const myId = ++inflightId
    try {
      const params = { limit: 50 }
      if (filter.value.tag_id) params.tag_id = filter.value.tag_id
      if (nextCursor.value) params.cursor = nextCursor.value
      const body = await api.get('/api/gallery/scroll', { params })
      if (myId !== inflightId) return  // stale response
      images.value.push(...body.images)
      dateGroups.value = mergeGroups(dateGroups.value, body.date_groups)
      nextCursor.value = body.next_cursor
    } catch (e) {
      error.value = e.message
    } finally {
      if (myId === inflightId) loading.value = false
    }
  }

  async function loadTimeline() {
    timelineLoading.value = true
    try {
      const params = filter.value.tag_id ? { tag_id: filter.value.tag_id } : {}
      timelineBuckets.value = await api.get('/api/gallery/timeline', { params })
    } finally {
      timelineLoading.value = false
    }
  }

  async function jumpTo(year, month) {
    const params = { year, month }
    if (filter.value.tag_id) params.tag_id = filter.value.tag_id
    const body = await api.get('/api/gallery/jump', { params })
    if (body.cursor) {
      images.value = []
      dateGroups.value = []
      nextCursor.value = body.cursor
      await loadMore()
    }
  }

  function setTagFilter(tagId) {
    filter.value.tag_id = tagId
    loadInitial()
    loadTimeline()
  }

  const hasMore = computed(() => nextCursor.value !== null)
  const isEmpty = computed(() => !loading.value && images.value.length === 0 && error.value === null)

  return {
    images, dateGroups, hasMore, isEmpty, loading, error,
    filter, timelineBuckets, timelineLoading,
    loadInitial, loadMore, loadTimeline, jumpTo, setTagFilter
  }
})

function mergeGroups(existing, incoming) {
  // Merge sequential groups with the same (year, month) instead of duplicating.
  const merged = [...existing]
  for (const g of incoming) {
    const tail = merged[merged.length - 1]
    if (tail && tail.year === g.year && tail.month === g.month) {
      tail.image_ids = [...tail.image_ids, ...g.image_ids]
    } else {
      merged.push({ ...g, image_ids: [...g.image_ids] })
    }
  }
  return merged
}