import { defineStore } from "pinia";
import { computed, ref, watch } from "vue";
import { loadGalleryAssets } from "@/data";
import type { Collection, GalleryAsset } from "@/types/gallery";

export const BATCH = 12;

function assetMatchesFilters(
  asset: GalleryAsset,
  collection: Collection | "all",
  selectedTags: Set<string>,
): boolean {
  if (collection !== "all" && asset.collection !== collection) {
    return false;
  }
  if (selectedTags.size === 0) {
    return true;
  }
  return [...selectedTags].some((t) => asset.tags.includes(t));
}

export const useGalleryStore = defineStore("gallery", () => {
  const allAssets = ref<GalleryAsset[]>([]);
  const isLoading = ref(false);
  const loadError = ref<string | null>(null);

  const activeCollection = ref<Collection | "all">("all");
  const selectedTags = ref<Set<string>>(new Set());
  const visibleCount = ref(BATCH);
  const lightboxAssetId = ref<string | null>(null);

  const filteredAssets = computed(() =>
    allAssets.value.filter((a) =>
      assetMatchesFilters(a, activeCollection.value, selectedTags.value),
    ),
  );

  const visibleAssets = computed(() =>
    filteredAssets.value.slice(0, visibleCount.value),
  );

  const hasMore = computed(
    () => visibleCount.value < filteredAssets.value.length,
  );

  const allTags = computed(() => {
    const s = new Set<string>();
    for (const a of allAssets.value) {
      for (const t of a.tags) {
        s.add(t);
      }
    }
    return [...s].sort((a, b) => a.localeCompare(b));
  });

  function setCollection(c: Collection | "all") {
    activeCollection.value = c;
  }

  async function init() {
    if (isLoading.value) {
      return;
    }
    isLoading.value = true;
    loadError.value = null;
    try {
      allAssets.value = await loadGalleryAssets();
      resetPagination();
    } catch (error) {
      loadError.value = "Unable to load gallery assets.";
      allAssets.value = [];
      resetPagination();
      console.error(error);
    } finally {
      isLoading.value = false;
    }
  }

  function toggleTag(tag: string) {
    const next = new Set(selectedTags.value);
    if (next.has(tag)) {
      next.delete(tag);
    } else {
      next.add(tag);
    }
    selectedTags.value = next;
  }

  function clearTags() {
    selectedTags.value = new Set();
  }

  function loadMore() {
    if (!hasMore.value) {
      return;
    }
    visibleCount.value = Math.min(
      visibleCount.value + BATCH,
      filteredAssets.value.length,
    );
  }

  function resetPagination() {
    visibleCount.value = Math.min(BATCH, filteredAssets.value.length);
  }

  watch([activeCollection, selectedTags], () => {
    resetPagination();
  });

  function openLightbox(assetId: string) {
    lightboxAssetId.value = assetId;
  }

  function closeLightbox() {
    lightboxAssetId.value = null;
  }

  const lightboxAsset = computed(() => {
    const id = lightboxAssetId.value;
    if (!id) {
      return null;
    }
    return filteredAssets.value.find((a) => a.id === id) ?? null;
  });

  const lightboxIndex = computed(() => {
    const id = lightboxAssetId.value;
    if (!id) {
      return -1;
    }
    return filteredAssets.value.findIndex((a) => a.id === id);
  });

  function stepLightbox(delta: number) {
    const list = filteredAssets.value;
    if (list.length === 0) {
      return;
    }
    let i = lightboxIndex.value;
    if (i < 0) {
      i = 0;
    }
    const next = (i + delta + list.length) % list.length;
    lightboxAssetId.value = list[next]!.id;
  }

  return {
    allAssets,
    isLoading,
    loadError,
    activeCollection,
    selectedTags,
    visibleAssets,
    filteredAssets,
    hasMore,
    allTags,
    setCollection,
    init,
    toggleTag,
    clearTags,
    loadMore,
    resetPagination,
    lightboxAssetId,
    lightboxAsset,
    lightboxIndex,
    openLightbox,
    closeLightbox,
    stepLightbox,
  };
});