<template>
  <div v-if="isDrawerOpen" class="drawer-overlay" @click="closeDrawer">
    <div class="drawer-content" :class="{ 'drawer-open': isDrawerOpen }" @click.stop>
      <div class="drawer-header sidebar-logo">
        <div class="drawer-header-content">
          <router-link to="/" @click="closeDrawer">
            <img :src="Logo" alt="Logo" class="drawer-logo" />
          </router-link>

          <button class="icon-button" aria-label="Close" @click="closeDrawer">
            <i class="pi pi-times"></i>
          </button>
        </div>
      </div>

      <div class="drawer-body">
        <div class="categories-container">
          <Category
            v-for="cat in CATEGORIES"
            :key="cat.name"
            :category="cat"
            :location="route"
            :pending-active-path="pendingActivePath ?? undefined"
            :handle-click="onNavClick"
            :handle-transition-navigation="handleMobileTransitionNavigation"
            :on-item-mouse-enter="() => {}"
            :on-item-mouse-leave="() => {}"
            :is-transitioning="isTransitioning"
          />
        </div>

        <div class="separator"></div>

        <div class="useful-links">
          <p class="useful-links-title">Useful Links</p>

          <div class="links-container">
            <a href="https://github.com/DavidHDev/vue-bits" target="_blank" @click="closeDrawer" class="useful-link">
              <span>GitHub</span>

              <i class="pi pi-arrow-up-right arrow-icon"></i>
            </a>

            <router-link to="/text-animations/split-text" @click="closeDrawer" class="useful-link">
              <span>Docs</span>

              <i class="pi pi-arrow-up-right arrow-icon"></i>
            </router-link>

            <a href="https://davidhaz.com/" target="_blank" @click="closeDrawer" class="useful-link">
              <span>Who made this?</span>

              <i class="pi pi-arrow-up-right arrow-icon"></i>
            </a>
          </div>
        </div>
      </div>
    </div>
  </div>

  <nav
    ref="sidebarContainerRef"
    class="sidebar"
    :class="{ 'sidebar-no-fade': isScrolledToBottom }"
    @scroll="handleScroll"
  >
    <div ref="sidebarRef" class="sidebar-content">
      <div
        class="active-line"
        :style="{
          transform:
            isLineVisible && linePosition !== null ? `translateY(${linePosition - 8}px)` : 'translateY(-100px)',
          opacity: isLineVisible ? 1 : 0
        }"
      ></div>

      <div
        class="hover-line"
        :style="{
          transform: hoverLinePosition !== null ? `translateY(${hoverLinePosition - 8}px)` : 'translateY(-100px)',
          opacity: isHoverLineVisible ? 1 : 0
        }"
      ></div>

      <div class="categories-list">
        <Category
          v-for="cat in CATEGORIES"
          :key="cat.name"
          :category="cat"
          :location="route"
          :pending-active-path="pendingActivePath ?? undefined"
          :handle-click="scrollToTop"
          :handle-transition-navigation="handleTransitionNavigation"
          :on-item-mouse-enter="onItemEnter"
          :on-item-mouse-leave="onItemLeave"
          :is-transitioning="isTransitioning"
        />
      </div>
    </div>
  </nav>
</template>

<script setup lang="ts">
import { ref, onMounted, onUnmounted, nextTick, watch, defineComponent, h, computed, useTemplateRef } from 'vue';
import { useRoute, useRouter } from 'vue-router';
import { CATEGORIES, NEW, UPDATED } from '../../constants/Categories';
import Logo from '../../assets/logos/vue-bits-logo.svg';
import '../../css/sidebar.css';

const HOVER_TIMEOUT_DELAY = 150;

const isDrawerOpen = ref(false);
const linePosition = ref<number | null>(null);
const isLineVisible = ref(false);
const hoverLinePosition = ref<number | null>(null);
const isHoverLineVisible = ref(false);
const pendingActivePath = ref<string | null>(null);
const isScrolledToBottom = ref(false);
const isTransitioning = ref(false);

const sidebarRef = useTemplateRef<HTMLDivElement>('sidebarRef');
const sidebarContainerRef = useTemplateRef<HTMLDivElement>('sidebarContainerRef');

let hoverTimeoutRef: number | null = null;
let hoverDelayTimeoutRef: number | null = null;

const route = useRoute();
const router = useRouter();

const scrollToTop = () => window.scrollTo(0, 0);
const slug = (str: string) => str.replace(/\s+/g, '-').toLowerCase();

const findActiveElement = () => {
  const activePath = pendingActivePath.value || route.path;

  for (const category of CATEGORIES) {
    const activeItem = category.subcategories.find((sub: string) => {
      const expectedPath = `/${slug(category.name)}/${slug(sub)}`;
      return activePath === expectedPath;
    });
    if (activeItem) {
      const selector = `.sidebar a[href="${activePath}"]`;
      const element = document.querySelector(selector) as HTMLElement;
      return element;
    }
  }
  return null;
};

const updateLinePosition = (el: HTMLElement | null) => {
  if (!el || !sidebarRef.value || !sidebarRef.value.offsetParent) return null;
  const sidebarRect = sidebarRef.value.getBoundingClientRect();
  const elRect = el.getBoundingClientRect();
  return elRect.top - sidebarRect.top + elRect.height / 2;
};

const closeDrawer = () => {
  isDrawerOpen.value = false;
};

const onNavClick = () => {
  closeDrawer();
  scrollToTop();
};

const handleTransitionNavigation = async (path: string) => {
  if (isTransitioning.value || route.path === path) return;

  pendingActivePath.value = path;

  // TODO: Implement transition when available
  await router.push(path);
  scrollToTop();
  pendingActivePath.value = null;
};

const handleMobileTransitionNavigation = async (path: string) => {
  if (isTransitioning.value || route.path === path) return;

  closeDrawer();
  pendingActivePath.value = path;

  // TODO: Implement transition when available
  await router.push(path);
  scrollToTop();
  pendingActivePath.value = null;
};

const onItemEnter = (path: string, e: Event) => {
  if (hoverTimeoutRef) clearTimeout(hoverTimeoutRef);
  if (hoverDelayTimeoutRef) clearTimeout(hoverDelayTimeoutRef);

  const targetElement = e.currentTarget as HTMLElement;
  const pos = updateLinePosition(targetElement);

  if (pos !== null) {
    hoverLinePosition.value = pos;
  }

  hoverDelayTimeoutRef = setTimeout(() => {
    isHoverLineVisible.value = true;
  }, 200);
};

const onItemLeave = () => {
  if (hoverDelayTimeoutRef) clearTimeout(hoverDelayTimeoutRef);

  hoverTimeoutRef = setTimeout(() => {
    isHoverLineVisible.value = false;
  }, HOVER_TIMEOUT_DELAY);
};

const handleScroll = () => {
  const sidebarElement = sidebarContainerRef.value;
  if (!sidebarElement) return;

  const { scrollTop, scrollHeight, clientHeight } = sidebarElement;
  const isAtBottom = scrollTop + clientHeight >= scrollHeight - 10;
  isScrolledToBottom.value = isAtBottom;
};

const updateActiveLine = async () => {
  await nextTick();

  setTimeout(() => {
    const activeEl = findActiveElement();

    if (!activeEl) {
      isLineVisible.value = false;
      return;
    }

    const pos = updateLinePosition(activeEl);
    if (pos !== null) {
      linePosition.value = pos;
      isLineVisible.value = true;
    } else {
      isLineVisible.value = false;
    }
  }, 100);
};

const Category = defineComponent({
  name: 'Category',
  props: {
    category: {
      type: Object,
      required: true
    },
    location: {
      type: Object,
      required: true
    },
    pendingActivePath: {
      type: String,
      default: null
    },
    handleClick: {
      type: Function,
      required: true
    },
    handleTransitionNavigation: {
      type: Function,
      required: true
    },
    onItemMouseEnter: {
      type: Function,
      required: true
    },
    onItemMouseLeave: {
      type: Function,
      required: true
    },
    isTransitioning: {
      type: Boolean,
      default: false
    }
  },
  setup(props) {
    interface ItemType {
      sub: string;
      path: string;
      isActive: boolean;
      isNew: boolean;
      isUpdated: boolean;
    }

    const items = computed(() =>
      props.category.subcategories.map((sub: string): ItemType => {
        const path = `/${slug(props.category.name)}/${slug(sub)}`;
        const activePath = props.pendingActivePath || props.location.path;
        return {
          sub,
          path,
          isActive: activePath === path,
          isNew: (NEW as string[]).includes(sub),
          isUpdated: (UPDATED as string[]).includes(sub)
        };
      })
    );

    return () =>
      h('div', { class: 'category' }, [
        h('p', { class: 'category-name' }, props.category.name),
        h(
          'div',
          { class: 'category-items' },
          items.value.map(({ sub, path, isActive, isNew, isUpdated }: ItemType) => {
            return h(
              'router-link',
              {
                key: path,
                to: path,
                class: ['sidebar-item', { 'active-sidebar-item': isActive }, { transitioning: props.isTransitioning }],
                onClick: (e: Event) => {
                  e.preventDefault();
                  props.handleTransitionNavigation(path);
                },
                onMouseenter: (e: Event) => props.onItemMouseEnter(path, e),
                onMouseleave: props.onItemMouseLeave
              },
              {
                default: () =>
                  [
                    sub,
                    isNew ? h('span', { class: 'new-tag' }, 'New') : null,
                    isUpdated ? h('span', { class: 'updated-tag' }, 'Updated') : null
                  ].filter(Boolean)
              }
            );
          })
        )
      ]);
  }
});

watch(() => route.path, updateActiveLine);
watch(pendingActivePath, updateActiveLine);

onMounted(() => {
  updateActiveLine();
  if (sidebarContainerRef.value) {
    sidebarContainerRef.value.addEventListener('scroll', handleScroll);
    handleScroll();
  }
});

onUnmounted(() => {
  if (hoverTimeoutRef) clearTimeout(hoverTimeoutRef);
  if (hoverDelayTimeoutRef) clearTimeout(hoverDelayTimeoutRef);
  if (sidebarContainerRef.value) {
    sidebarContainerRef.value.removeEventListener('scroll', handleScroll);
  }
});
</script>
