import { ref, nextTick } from 'vue';
import axios from 'axios';
import { Readability } from '@mozilla/readability';

// Module-level state — declared outside useFeeds() so every caller shares the
// same singleton refs (a Pinia-free "store" for the feed list and its UI state).
const showMessage = ref(false)
const feeds = ref([]);
const message = ref('')
const showModal = ref(false)
const viewMode = ref('list') // 'list' | 'article' — toggled from the hamburger menu
const currentIndex = ref(0)
const layout = ref(localStorage.getItem('layout') || 'list') // 'list' | 'cards' — list-view display style, toggled from the hamburger menu

let observer; // Declare observer outside the setup function
let initialLoad = false

export function authHeaders() {
  return {
    headers: {
      'Content-Type': 'application/json',
      'user-token': localStorage.getItem("user-token")
    }
  }
}

// Tells the server to revoke the current token (bumps token_version, so any
// other outstanding tokens for this account are invalidated too) before
// clearing the local session. Best-effort: if the request fails (e.g. the
// token already expired) the local session is cleared regardless.
export async function logout() {
  try {
    await axios.post('/api/v1/auth/logout', null, authHeaders())
  } catch (error) {
    console.error('Error logging out', error)
  }
  localStorage.removeItem('user-token')
  localStorage.removeItem('user-id')
}

// Some feeds (e.g. Deutsche Welle) ship <img> tags whose `src` and various
// lazy-load attributes (`data-url`, `data-src`, `srcset`, ...) contain an
// unresolved `${placeholderName}` template — or its URL-encoded `%7B...%7D`
// form — that their own frontend fills in from the sibling `data-format`
// attribute before loading; verbatim they 404. Resolve every such attribute
// the same way (so Readability's own lazy-image handling can't resurrect a
// stale template into `src`), preferring `data-url` as the source of truth
// for `src`, and drop the <img> entirely if a template still remains.
const TEMPLATE_PATTERN = /\$\{[^}]+\}|%7[bB][^%]*%7[dD]/
const TEMPLATE_PATTERN_GLOBAL = /\$\{[^}]+\}|%7[bB][^%]*%7[dD]/g

// `data-format` holds a symbolic name from DW's CMS (e.g. "MASTER_LANDSCAPE"),
// but their image CDN only accepts numeric format ids in the URL — the
// template's `${formatId}` literally means a number. Substituting the
// symbolic name verbatim produces a 400 (image fails to load). DW generates
// the same fixed set of numeric variants for every image, so map the
// symbolic names we've seen to their numeric equivalent.
const DW_FORMAT_IDS = {
  MASTER_LANDSCAPE: '6', // 940x529, 16:9 — matches DW's `16/9` aspect ratio
}

function resolveTemplatedImage(img) {
  const rawFormat = img.getAttribute('data-format')
  const format = rawFormat && (DW_FORMAT_IDS[rawFormat] ?? (/^\d+$/.test(rawFormat) ? rawFormat : null))
  const dataUrl = img.getAttribute('data-url')

  if (format) {
    if (dataUrl && TEMPLATE_PATTERN.test(dataUrl)) {
      img.setAttribute('src', dataUrl.replace(TEMPLATE_PATTERN_GLOBAL, format))
    }
    for (const attr of [...img.attributes]) {
      if (attr.name !== 'src' && TEMPLATE_PATTERN.test(attr.value)) {
        img.setAttribute(attr.name, attr.value.replace(TEMPLATE_PATTERN_GLOBAL, format))
      }
    }
  }

  if (TEMPLATE_PATTERN.test(img.getAttribute('src') ?? '')) {
    img.remove()
  }
}

function showMessageForXSeconds(text, seconds) {
  message.value = text;
  showMessage.value = true;

  // Set a timeout to hide the message after x seconds
  setTimeout(() => {
    showMessage.value = false;
    message.value = '';
  }, seconds * 1000); // Convert seconds to milliseconds
}

async function getReadable(feed, index) {
  try {
    const response = await axios.post("/api/v1/article/read", {
      url: feed.url
    }, authHeaders())

    const doc = new DOMParser().parseFromString(response.data.content, 'text/html');
    // Scraped articles often contain image/link URLs that are relative to the
    // source site. A <base> tag makes the browser (and Readability) resolve
    // them against the article's original URL instead of our own origin.
    const base = doc.createElement('base');
    base.setAttribute('href', feed.url);
    doc.head.prepend(base);
    doc.querySelectorAll('img').forEach(resolveTemplatedImage);
    doc.querySelectorAll('video, audio').forEach(el => el.remove());
    // Some feeds (e.g. Stuttgarter Nachrichten) embed a social-sharing widget
    // (WhatsApp/Email/Facebook/... links plus a "Link kopiert" tooltip) in the
    // article body. It's not part of the article, so strip it before Readability
    // pulls it into the parsed content.
    doc.querySelectorAll('#article-social-bar').forEach(el => el.remove())
    // Some feeds (e.g. Deutsche Welle) leave behind a heading + play-icon SVG
    // for an embedded video/audio player whose actual <video>/<audio>/<iframe>
    // we already stripped — without it, the heading is just a giant orphaned
    // icon that takes up space and links nowhere.
    doc.querySelectorAll('[aria-label]').forEach(el => {
      if (/^(Eingebettete[rs]?|Embedded) (Video|Audio)/i.test(el.getAttribute('aria-label'))) {
        el.remove()
      }
    })
    // Alpine.js widget overlays: x-cloak marks elements that should be hidden
    // until Alpine.js initialises (prevents FOUC). These are always widget
    // containers (e.g. taz's "taz schneller googeln" promo), never article
    // content, so they're safe to remove unconditionally.
    doc.querySelectorAll('[x-cloak]').forEach(el => el.remove())
    // taz subscription promo blocks: a standalone <section> whose link(s) point
    // to an /abo/ subscription page. Only climb to <section>, not <article>,
    // to avoid accidentally removing the main article body.
    doc.querySelectorAll('a[href*="/abo/"]').forEach(el => {
      const container = el.closest('section')
      if (container) container.remove()
    })
    // taz "Mehr zum Thema" related-articles teaser section.
    doc.querySelectorAll('#articleTeaser').forEach(el => el.remove())
    // taz subsidiary magazine promo blocks (e.g. taz FUTURZWEI): either the
    // <article> itself or its direct <a> child carries an aria-label containing "Abo".
    doc.querySelectorAll('article[aria-label*="Abo"]').forEach(el => {
      const container = el.closest('section') ?? el
      container.remove()
    })
    doc.querySelectorAll('article > a[aria-label*="Abo"]').forEach(el => {
      const container = el.closest('section') ?? el.closest('article')
      if (container) container.remove()
    })
    const article = new Readability(doc).parse();
    if (!article) {
      showMessageForXSeconds('Could not extract readable content.', 5)
      return
    }
    feeds.value[index].content = article.content;
    feeds.value[index].readable = true;
  } catch (error) {
    console.error('Error fetching data:', error)
    showMessageForXSeconds(error, 5)
  }
}

async function markRead(id) {
  try {
    const response = await axios.put("/api/v1/article/read/" + id, null, authHeaders())
    console.log(response.status)
  } catch (error) {
    console.log(error)
  }
}

const fetchData = async () => {
  const user_id = localStorage.getItem("user-id")
  try {
    const response = await axios.get("/api/v1/article/get/" + user_id, authHeaders());
    const items = [];
    response.data.feeds.forEach(feed => {
      feed.items.forEach(item => items.push({ ...item, feedTitle: feed.title }));
    });
    // timestamps are zero-padded "YYYY-MM-DD HH:MM:SS" strings, so a plain
    // lexicographic comparison sorts them chronologically.
    items.sort((a, b) => b.timestamp.localeCompare(a.timestamp));
    feeds.value = items;
    await nextTick();
    setupIntersectionObserver();
  } catch (error) {
    console.error('Error fetching data:', error)
    showMessageForXSeconds(error, 5)
  }
};

async function sync(silent = false) {
  try {
    const response = await axios.post('/api/v1/article/sync', {
      user_id: parseInt(localStorage.getItem("user-id"))
    }, authHeaders())

    if (response.status == 200 && !silent) {
      showMessageForXSeconds('Sync successful.', 5)
    }
    fetchData();
  } catch (error) {
    console.error('Error sync', error)
    if (!silent) {
      showMessageForXSeconds(error, 5)
    }
  }
}

function setupIntersectionObserver() {
  if (observer) {
    observer.disconnect();
  }

  // The sticky topbar overlays the top of the viewport, so an article fully
  // hidden behind it should already count as "scrolled past" — shrink the
  // observer's root by that height so it stops intersecting at that point.
  const topbarHeight = document.querySelector('.app-nav')?.getBoundingClientRect().height ?? 0;

  observer = new IntersectionObserver((entries) => handleIntersection(entries, topbarHeight), {
    root: null, // Use the viewport as the root
    rootMargin: `-${topbarHeight}px 0px 0px 0px`,
    // threshold: 0.5, // Fire the callback when at least 50% of the element is visible
  });

  const observedDivs = document.querySelectorAll(".observe");
  if (observedDivs.length > 0) {
    observedDivs.forEach(observedDiv => {
      observer.observe(observedDiv);
    })
  }
}

function handleIntersection(entries, topbarHeight = 0) {
  // Resolve all affected feeds before touching feeds.value — the target.id
  // indices are render-time positions that shift once we splice the array.
  const readFeeds = entries
    .filter(entry => initialLoad === true && !entry.isIntersecting && entry.boundingClientRect.y < topbarHeight)
    .map(entry => feeds.value[entry.target.id])
    .filter(Boolean)

  if (readFeeds.length === 0) return

  // Disconnect before the DOM mutation. In card layout the cards are short
  // enough that the shift caused by removing one can push the next card above
  // the header, which the observer would immediately treat as another read —
  // cascading until many articles disappear at once.
  if (observer) {
    observer.disconnect()
    observer = null
  }

  const readIds = new Set(readFeeds.map(feed => feed.id))
  feeds.value = feeds.value.filter(feed => !readIds.has(feed.id))

  for (const feed of readFeeds) {
    markRead(feed.id)
  }

  nextTick().then(() => {
    // If scroll anchoring didn't compensate for the removed content (common
    // with position:fixed headers and overflow-x:hidden on body), the first
    // remaining article will have drifted above the header. Correct the scroll
    // position so it sits exactly at the header bottom before reconnecting —
    // otherwise the initial observation would immediately mark everything above
    // the topbar as read and cascade until the list is empty.
    const first = document.querySelector('.observe')
    if (first) {
      const top = first.getBoundingClientRect().top
      if (top < topbarHeight) {
        window.scrollBy(0, top - topbarHeight)
      }
    }
    setupIntersectionObserver()
  })
}

function disconnectObserver() {
  if (observer) {
    observer.disconnect()
    observer = null
  }
}

function setInitialLoad(value) {
  initialLoad = value
}

async function markAllRead() {
  if (feeds.value.length === 0) return
  if (!window.confirm('Mark all articles as read?')) return

  const ids = feeds.value.map(feed => feed.id)
  feeds.value = []
  currentIndex.value = 0
  // markRead swallows its own errors, so Promise.all can't reject here.
  await Promise.all(ids.map(id => markRead(id)))
  showMessageForXSeconds('All articles marked as read.', 5)
}

function markCurrentArticleRead() {
  const feed = feeds.value[currentIndex.value]
  // Marking read here (rather than via removeFeed, as the scroll-based list
  // view does) keeps the array stable so currentIndex stays valid while paging.
  // The local `read` flag lets leaveArticleView() drop these once we're done.
  if (feed) {
    feed.read = true
    markRead(feed.id)
  }
}

async function leaveArticleView() {
  // Articles paged past in article view were marked read but deliberately kept
  // in place so currentIndex stayed valid — drop them now so they don't keep
  // showing up in the list view.
  feeds.value = feeds.value.filter(feed => !feed.read)
  currentIndex.value = 0
  viewMode.value = 'list'
  // The v-if on the list container tears down and recreates all .observe DOM
  // nodes when switching views, so the intersection observer must be
  // re-pointed at the new elements after Vue has finished rendering.
  await nextTick()
  setupIntersectionObserver()
}

function toggleViewMode() {
  if (viewMode.value === 'article') {
    leaveArticleView()
  } else {
    // Disconnect first: the v-if switch is about to unmount all .observe
    // elements, which would otherwise fire intersection callbacks reporting
    // them as no-longer-intersecting and mark every visible article read.
    if (observer) {
      observer.disconnect()
      observer = null
    }
    viewMode.value = 'article'
    currentIndex.value = 0
    markCurrentArticleRead()
  }
}

async function toggleLayout() {
  if (observer) {
    observer.disconnect()
    observer = null
  }
  window.scrollTo(0, 0)
  layout.value = layout.value === 'list' ? 'cards' : 'list'
  localStorage.setItem('layout', layout.value)
  await nextTick()
  setupIntersectionObserver()
}

function nextArticle() {
  if (currentIndex.value < feeds.value.length - 1) {
    currentIndex.value += 1
    markCurrentArticleRead()
    window.scrollTo(0, 0)
  }
}

function prevArticle() {
  if (currentIndex.value > 0) {
    currentIndex.value -= 1
    markCurrentArticleRead()
    window.scrollTo(0, 0)
  }
}

export function useFeeds() {
  return {
    feeds,
    showMessage,
    message,
    showModal,
    viewMode,
    currentIndex,
    toggleViewMode,
    leaveArticleView,
    layout,
    toggleLayout,
    nextArticle,
    prevArticle,
    fetchData,
    sync,
    getReadable,
    markRead,
    markAllRead,
    showMessageForXSeconds,
    setupIntersectionObserver,
    disconnectObserver,
    setInitialLoad,
    handleIntersection,
  }
}