"use strict";

// ── state ──────────────────────────────────────────────────────────────────
let images = [];
let current_idx = 0;
let current_query = "";
let current_page = 0;
let is_loading = false;
let is_fetching_more = false;

// ── elements ───────────────────────────────────────────────────────────────
const search_screen  = document.getElementById("search_screen");
const gallery_screen = document.getElementById("gallery_screen");
const search_input   = document.getElementById("search_input");
const search_btn     = document.getElementById("search_btn");
const recents_section= document.getElementById("recents_section");
const recents_list   = document.getElementById("recents_list");
const img_track      = document.getElementById("img_track");
const img_counter    = document.getElementById("img_counter");
const back_btn       = document.getElementById("back_btn");
const arrow_left     = document.getElementById("arrow_left");
const arrow_right    = document.getElementById("arrow_right");
const loading_bar    = document.getElementById("loading_bar");
const toast_el       = document.getElementById("toast");

// ── recents ────────────────────────────────────────────────────────────────
function load_recents() {
  return JSON.parse(localStorage.getItem("diashow_recents") || "[]");
}

function save_recent(q) {
  let recents = load_recents().filter(r => r !== q);
  recents.unshift(q);
  recents = recents.slice(0, 8);
  localStorage.setItem("diashow_recents", JSON.stringify(recents));
}

function render_recents() {
  const recents = load_recents();
  if (!recents.length) { recents_section.style.display = "none"; return; }
  recents_section.style.display = "block";
  recents_list.innerHTML = recents
    .map(r => `<button class="recent_chip" data-q="${escape_html(r)}">${escape_html(r)}</button>`)
    .join("");
}

function escape_html(s) {
  return s.replace(/&/g, "&amp;").replace(/</g, "&lt;").replace(/>/g, "&gt;").replace(/"/g, "&quot;");
}

// ── loading bar ────────────────────────────────────────────────────────────
let bar_timer = null;

function show_loading() {
  loading_bar.style.width = "0%";
  loading_bar.classList.add("active");
  loading_bar.style.transition = "none";
  requestAnimationFrame(() => {
    loading_bar.style.transition = "width 1.5s ease-out";
    loading_bar.style.width = "75%";
  });
}

function hide_loading() {
  loading_bar.style.transition = "width 0.2s ease";
  loading_bar.style.width = "100%";
  clearTimeout(bar_timer);
  bar_timer = setTimeout(() => {
    loading_bar.classList.remove("active");
    loading_bar.style.width = "0%";
  }, 250);
}

// ── toast ──────────────────────────────────────────────────────────────────
let toast_timer = null;

function show_toast(msg) {
  toast_el.textContent = msg;
  toast_el.classList.add("show");
  clearTimeout(toast_timer);
  toast_timer = setTimeout(() => toast_el.classList.remove("show"), 3000);
}

// ── API ────────────────────────────────────────────────────────────────────
async function fetch_images(query, page = 0) {
  const res = await fetch(`/api/search?q=${encodeURIComponent(query)}&page=${page}`);
  if (!res.ok) throw new Error(`HTTP ${res.status}`);
  const data = await res.json();
  if (data.error) throw new Error(data.error);
  return data.images || [];
}

// ── search ─────────────────────────────────────────────────────────────────
async function do_search(q) {
  if (!q.trim() || is_loading) return;
  q = q.trim();
  is_loading = true;
  show_loading();
  search_btn.disabled = true;

  try {
    const results = await fetch_images(q);
    if (!results.length) {
      show_toast("no images found :/");
      return;
    }
    save_recent(q);
    current_query = q;
    current_page = 0;
    images = results;
    current_idx = 0;
    open_gallery();
  } catch (e) {
    show_toast("fetch failed — " + e.message);
  } finally {
    is_loading = false;
    hide_loading();
    search_btn.disabled = false;
  }
}

// ── gallery ────────────────────────────────────────────────────────────────
function make_slide(img_data, idx) {
  const slide = document.createElement("div");
  slide.className = "img_slide";
  slide.dataset.idx = idx;

  const el = document.createElement("img");
  el.alt = "";
  el.loading = "lazy";
  el.src = img_data.url;
  el.onerror = () => {
    slide.innerHTML = `<div class="img_err">image failed to load</div>`;
  };
  slide.appendChild(el);
  return slide;
}

function open_gallery() {
  img_track.innerHTML = "";
  images.forEach((img, i) => img_track.appendChild(make_slide(img, i)));

  search_screen.style.display = "none";
  gallery_screen.classList.add("active");

  go_to(0, false);
  document.body.style.overflow = "hidden";
}

function close_gallery() {
  gallery_screen.classList.remove("active");
  search_screen.style.display = "";
  document.body.style.overflow = "";
  render_recents();
}

function update_counter() {
  img_counter.textContent = `${current_idx + 1} / ${images.length}`;
}

function go_to(idx, animate = true) {
  if (!animate) img_track.style.transition = "none";
  else img_track.style.transition = "";

  current_idx = Math.max(0, Math.min(idx, images.length - 1));
  img_track.style.transform = `translateX(-${current_idx * 100}%)`;
  update_counter();

  // reset transition after instant move
  if (!animate) requestAnimationFrame(() => img_track.style.transition = "");

  // load more when 3 images from the end
  if (current_idx >= images.length - 3) load_more();
}

async function load_more() {
  if (is_fetching_more) return;
  is_fetching_more = true;
  try {
    const next_page = current_page + 1;
    const more = await fetch_images(current_query, next_page);
    if (more.length) {
      current_page = next_page;
      more.forEach(img => {
        const slide = make_slide(img, images.length);
        img_track.appendChild(slide);
        images.push(img);
      });
      update_counter();
    }
  } catch (_) {
    // silently ignore load-more failures
  } finally {
    is_fetching_more = false;
  }
}

function next_image() { if (current_idx < images.length - 1) go_to(current_idx + 1); }
function prev_image() { if (current_idx > 0) go_to(current_idx - 1); }

// ── touch / swipe ──────────────────────────────────────────────────────────
let touch_start_x = 0;
let touch_start_y = 0;
let touch_dx = 0;
let is_swiping = false;

gallery_screen.addEventListener("touchstart", e => {
  touch_start_x = e.touches[0].clientX;
  touch_start_y = e.touches[0].clientY;
  touch_dx = 0;
  is_swiping = false;
}, { passive: true });

gallery_screen.addEventListener("touchmove", e => {
  const dx = e.touches[0].clientX - touch_start_x;
  const dy = e.touches[0].clientY - touch_start_y;

  if (!is_swiping) {
    // lock to horizontal if angle is mostly horizontal
    if (Math.abs(dx) < Math.abs(dy)) return;
    is_swiping = true;
  }

  e.preventDefault();
  touch_dx = dx;
  // live drag feel
  const base = -current_idx * 100;
  const drag = (dx / window.innerWidth) * 100;
  img_track.style.transition = "none";
  img_track.style.transform = `translateX(calc(${base}% + ${dx}px))`;
}, { passive: false });

gallery_screen.addEventListener("touchend", () => {
  if (!is_swiping) return;
  const threshold = window.innerWidth * 0.2;
  if (touch_dx < -threshold) next_image();
  else if (touch_dx > threshold) prev_image();
  else go_to(current_idx); // snap back
  is_swiping = false;
  touch_dx = 0;
}, { passive: true });

// ── keyboard ───────────────────────────────────────────────────────────────
document.addEventListener("keydown", e => {
  if (!gallery_screen.classList.contains("active")) return;
  if (e.key === "ArrowRight") next_image();
  else if (e.key === "ArrowLeft") prev_image();
  else if (e.key === "Escape") close_gallery();
});

// ── event listeners ────────────────────────────────────────────────────────
search_btn.addEventListener("click", () => do_search(search_input.value));

search_input.addEventListener("keydown", e => {
  if (e.key === "Enter") do_search(search_input.value);
});

back_btn.addEventListener("click", close_gallery);
arrow_left.addEventListener("click", prev_image);
arrow_right.addEventListener("click", next_image);

recents_list.addEventListener("click", e => {
  const chip = e.target.closest(".recent_chip");
  if (!chip) return;
  const q = chip.dataset.q;
  search_input.value = q;
  do_search(q);
});

// ── init ───────────────────────────────────────────────────────────────────
render_recents();
search_input.focus();