<script>
import { GlLoadingIcon, GlIntersectionObserver } from '@gitlab/ui';
import Draggable from 'vuedraggable';
import { mapActions, mapGetters, mapState } from 'vuex';
import { sortableStart, sortableEnd } from '~/boards/mixins/sortable_default_options';
import { sprintf, __ } from '~/locale';
import defaultSortableConfig from '~/sortable/sortable_config';
import Tracking from '~/tracking';
import { toggleFormEventPrefix, DraggableItemTypes } from '../constants';
import eventHub from '../eventhub';
import BoardCard from './board_card.vue';
import BoardNewIssue from './board_new_issue.vue';

export default {
  draggableItemTypes: DraggableItemTypes,
  name: 'BoardList',
  i18n: {
    loading: __('Loading'),
    loadingMoreboardItems: __('Loading more'),
    showingAllIssues: __('Showing all issues'),
    showingAllEpics: __('Showing all epics'),
  },
  components: {
    BoardCard,
    BoardNewIssue,
    BoardNewEpic: () => import('ee_component/boards/components/board_new_epic.vue'),
    GlLoadingIcon,
    GlIntersectionObserver,
  },
  mixins: [Tracking.mixin()],
  props: {
    disabled: {
      type: Boolean,
      required: true,
    },
    list: {
      type: Object,
      required: true,
    },
    boardItems: {
      type: Array,
      required: true,
    },
  },
  data() {
    return {
      scrollOffset: 250,
      showCount: false,
      showIssueForm: false,
      showEpicForm: false,
    };
  },
  computed: {
    ...mapState(['pageInfoByListId', 'listsFlags']),
    ...mapGetters(['isEpicBoard']),
    listItemsCount() {
      return this.isEpicBoard ? this.list.epicsCount : this.list.issuesCount;
    },
    paginatedIssueText() {
      return sprintf(__('Showing %{pageSize} of %{total} %{issuableType}'), {
        pageSize: this.boardItems.length,
        total: this.listItemsCount,
        issuableType: this.isEpicBoard ? 'epics' : 'issues',
      });
    },
    toggleFormEventPrefix() {
      return this.isEpicBoard ? toggleFormEventPrefix.epic : toggleFormEventPrefix.issue;
    },
    boardItemsSizeExceedsMax() {
      return this.list.maxIssueCount > 0 && this.listItemsCount > this.list.maxIssueCount;
    },
    hasNextPage() {
      return this.pageInfoByListId[this.list.id]?.hasNextPage;
    },
    loading() {
      return this.listsFlags[this.list.id]?.isLoading;
    },
    loadingMore() {
      return this.listsFlags[this.list.id]?.isLoadingMore;
    },
    epicCreateFormVisible() {
      return this.isEpicBoard && this.list.listType !== 'closed' && this.showEpicForm;
    },
    issueCreateFormVisible() {
      return !this.isEpicBoard && this.list.listType !== 'closed' && this.showIssueForm;
    },
    listRef() {
      // When list is draggable, the reference to the list needs to be accessed differently
      return this.canMoveIssue ? this.$refs.list.$el : this.$refs.list;
    },
    showingAllItems() {
      return this.boardItems.length === this.listItemsCount;
    },
    showingAllItemsText() {
      return this.isEpicBoard
        ? this.$options.i18n.showingAllEpics
        : this.$options.i18n.showingAllIssues;
    },
    canMoveIssue() {
      return !this.disabled;
    },
    treeRootWrapper() {
      return this.canMoveIssue && !this.listsFlags[this.list.id]?.addItemToListInProgress
        ? Draggable
        : 'ul';
    },
    treeRootOptions() {
      const options = {
        ...defaultSortableConfig,
        fallbackOnBody: false,
        group: 'board-list',
        tag: 'ul',
        'ghost-class': 'board-card-drag-active',
        'data-list-id': this.list.id,
        value: this.boardItems,
      };

      return this.canMoveIssue ? options : {};
    },
  },
  watch: {
    boardItems() {
      this.$nextTick(() => {
        this.showCount = this.scrollHeight() > Math.ceil(this.listHeight());
      });
    },
    'list.id': {
      handler(id, oldVal) {
        if (id) {
          eventHub.$on(`${this.toggleFormEventPrefix}${this.list.id}`, this.toggleForm);
          eventHub.$on(`scroll-board-list-${this.list.id}`, this.scrollToTop);

          eventHub.$off(`${this.toggleFormEventPrefix}${oldVal}`, this.toggleForm);
          eventHub.$off(`scroll-board-list-${oldVal}`, this.scrollToTop);
        }
      },
      immediate: true,
    },
  },
  beforeDestroy() {
    eventHub.$off(`${this.toggleFormEventPrefix}${this.list.id}`, this.toggleForm);
    eventHub.$off(`scroll-board-list-${this.list.id}`, this.scrollToTop);
  },
  methods: {
    ...mapActions(['fetchItemsForList', 'moveItem']),
    listHeight() {
      return this.listRef.getBoundingClientRect().height;
    },
    scrollHeight() {
      return this.listRef.scrollHeight;
    },
    scrollTop() {
      return this.listRef.scrollTop + this.listHeight();
    },
    scrollToTop() {
      this.listRef.scrollTop = 0;
    },
    loadNextPage() {
      this.fetchItemsForList({ listId: this.list.id, fetchNext: true });
    },
    toggleForm() {
      if (this.isEpicBoard) {
        this.showEpicForm = !this.showEpicForm;
      } else {
        this.showIssueForm = !this.showIssueForm;
      }
    },
    onReachingListBottom() {
      if (!this.loadingMore && this.hasNextPage) {
        this.showCount = true;
        this.loadNextPage();
      }
    },
    handleDragOnStart({
      item: {
        dataset: { draggableItemType },
      },
    }) {
      if (draggableItemType !== DraggableItemTypes.card) {
        return;
      }

      sortableStart();
      this.track('drag_card', { label: 'board' });
    },
    handleDragOnEnd({
      newIndex: originalNewIndex,
      oldIndex,
      from,
      to,
      item: {
        dataset: { draggableItemType, itemId, itemIid, itemPath },
      },
    }) {
      if (draggableItemType !== DraggableItemTypes.card) {
        return;
      }

      sortableEnd();
      let newIndex = originalNewIndex;
      let { children } = to;
      let moveBeforeId;
      let moveAfterId;

      children = Array.from(children).filter((card) => card.classList.contains('board-card'));

      if (newIndex > children.length) {
        newIndex = children.length;
      }

      const getItemId = (el) => el.dataset.itemId;

      // If item is being moved within the same list
      if (from === to) {
        if (newIndex > oldIndex && children.length > 1) {
          // If item is being moved down we look for the item that ends up before
          moveBeforeId = getItemId(children[newIndex]);
        } else if (newIndex < oldIndex && children.length > 1) {
          // If item is being moved up we look for the item that ends up after
          moveAfterId = getItemId(children[newIndex]);
        } else {
          // If item remains in the same list at the same position we do nothing
          return;
        }
      } else {
        // We look for the item that ends up before the moved item if it exists
        if (children[newIndex - 1]) {
          moveBeforeId = getItemId(children[newIndex - 1]);
        }
        // We look for the item that ends up after the moved item if it exists
        if (children[newIndex]) {
          moveAfterId = getItemId(children[newIndex]);
        }
      }

      this.moveItem({
        itemId,
        itemIid,
        itemPath,
        fromListId: from.dataset.listId,
        toListId: to.dataset.listId,
        moveBeforeId,
        moveAfterId,
      });
    },
  },
};
</script>

<template>
  <div
    v-show="!list.collapsed"
    class="board-list-component gl-relative gl-h-full gl-display-flex gl-flex-direction-column"
    data-qa-selector="board_list_cards_area"
  >
    <div
      v-if="loading"
      class="gl-mt-4 gl-text-center"
      :aria-label="$options.i18n.loading"
      data-testid="board_list_loading"
    >
      <gl-loading-icon size="sm" />
    </div>
    <board-new-issue v-if="issueCreateFormVisible" :list="list" />
    <board-new-epic v-if="epicCreateFormVisible" :list="list" />
    <component
      :is="treeRootWrapper"
      v-show="!loading"
      ref="list"
      v-bind="treeRootOptions"
      :data-board="list.id"
      :data-board-type="list.listType"
      :class="{ 'bg-danger-100': boardItemsSizeExceedsMax }"
      draggable=".board-card"
      class="board-list gl-w-full gl-h-full gl-list-style-none gl-mb-0 gl-p-2 js-board-list"
      data-testid="tree-root-wrapper"
      @start="handleDragOnStart"
      @end="handleDragOnEnd"
    >
      <board-card
        v-for="(item, index) in boardItems"
        ref="issue"
        :key="item.id"
        :index="index"
        :list="list"
        :item="item"
        :data-draggable-item-type="$options.draggableItemTypes.card"
        :disabled="disabled"
      />
      <gl-intersection-observer @appear="onReachingListBottom">
        <li v-if="showCount" class="board-list-count gl-text-center" data-issue-id="-1">
          <gl-loading-icon
            v-if="loadingMore"
            size="sm"
            :label="$options.i18n.loadingMoreboardItems"
            data-testid="count-loading-icon"
          />
          <span v-if="showingAllItems">{{ showingAllItemsText }}</span>
          <span v-else>{{ paginatedIssueText }}</span>
        </li>
      </gl-intersection-observer>
    </component>
  </div>
</template>
