(() => {
  'use strict';

  // Every message from the interest form and email links goes to all of these addresses.
  const CONTACT_EMAILS = ['zli12321@terpmail.umd.edu', 'zl22754@uga.edu'];
  const CONTACT_TEXT = CONTACT_EMAILS.join(' and ');

  const $ = (sel, root = document) => root.querySelector(sel);
  const $$ = (sel, root = document) => Array.from(root.querySelectorAll(sel));
  const reduceMotion = window.matchMedia('(prefers-reduced-motion: reduce)').matches;

  const mailto = (subject, body) => {
    const params = [`subject=${encodeURIComponent(subject)}`];
    if (body) params.push(`body=${encodeURIComponent(body)}`);
    return `mailto:${CONTACT_EMAILS.join(',')}?${params.join('&')}`;
  };

  function initContact() {
    $$('[data-contact]').forEach((link) => {
      link.href = mailto(link.dataset.subject || 'AI for Science collaboration');
      if (link.hasAttribute('data-show-address')) link.textContent = CONTACT_TEXT;
    });
    $$('[data-year]').forEach((el) => {
      el.textContent = String(new Date().getFullYear());
    });
  }

  function initNav() {
    const nav = $('.nav');
    const onScroll = () => nav.classList.toggle('is-scrolled', window.scrollY > 8);
    onScroll();
    window.addEventListener('scroll', onScroll, { passive: true });

    const toggle = $('.nav-toggle');
    const menu = $('#mobile-menu');
    const setOpen = (open) => {
      toggle.setAttribute('aria-expanded', String(open));
      toggle.setAttribute('aria-label', open ? 'Close menu' : 'Open menu');
      menu.hidden = !open;
      document.body.classList.toggle('menu-open', open);
    };
    toggle.addEventListener('click', () => setOpen(toggle.getAttribute('aria-expanded') !== 'true'));
    $$('a', menu).forEach((a) => a.addEventListener('click', () => setOpen(false)));
    window.addEventListener('keydown', (e) => {
      if (e.key === 'Escape') setOpen(false);
    });
    window.matchMedia('(min-width: 1101px)').addEventListener('change', (e) => {
      if (e.matches) setOpen(false);
    });

    if (!('IntersectionObserver' in window)) return;
    const links = new Map($$('.nav-links a').map((a) => [a.getAttribute('href').slice(1), a]));
    const observer = new IntersectionObserver((entries) => {
      entries.forEach((entry) => {
        if (!entry.isIntersecting) return;
        links.forEach((a) => a.classList.remove('is-active'));
        const active = links.get(entry.target.dataset.nav || entry.target.id);
        if (active) active.classList.add('is-active');
      });
    }, { rootMargin: '-45% 0px -50% 0px' });
    $$('main > section[id]').forEach((section) => observer.observe(section));
  }

  function initReveal() {
    const items = $$('.reveal');
    if (reduceMotion || !('IntersectionObserver' in window)) {
      items.forEach((el) => el.classList.add('is-visible'));
      return;
    }
    const observer = new IntersectionObserver((entries) => {
      entries.forEach((entry) => {
        if (!entry.isIntersecting) return;
        entry.target.classList.add('is-visible');
        observer.unobserve(entry.target);
      });
    }, { rootMargin: '0px 0px -8% 0px', threshold: 0.12 });
    items.forEach((el) => observer.observe(el));
  }

  function initExplorer() {
    const root = $('#explorer');
    if (!root) return;
    root.classList.add('is-enhanced');
    const panels = $$('.explorer-panel', root);

    panels.forEach((panel) => {
      const stages = $$('.stage', panel);
      if (!stages.length) return;
      const tabs = document.createElement('div');
      tabs.className = 'stage-tabs';
      tabs.setAttribute('role', 'group');
      tabs.setAttribute('aria-label', 'Project stages');
      const buttons = stages.map((stage, i) => {
        const button = document.createElement('button');
        button.type = 'button';
        button.className = 'stage-btn';
        const num = document.createElement('span');
        num.className = 'sb-num';
        num.textContent = String(i + 1);
        const name = document.createElement('span');
        name.textContent = $('.stage-title', stage).textContent;
        button.append(num, name);
        return button;
      });
      const select = (index) => {
        buttons.forEach((b, i) => b.setAttribute('aria-pressed', String(i === index)));
        stages.forEach((s, i) => {
          s.hidden = i !== index;
        });
      };
      buttons.forEach((b, i) => b.addEventListener('click', () => select(i)));
      tabs.append(...buttons);
      panel.insertBefore(tabs, stages[0]);
      select(0);
    });

    const toggles = $$('.ft-btn', root);
    const setField = (field) => {
      root.dataset.field = field;
      toggles.forEach((b) => b.setAttribute('aria-pressed', String(b.dataset.field === field)));
      panels.forEach((p) => {
        p.hidden = p.dataset.field !== field;
      });
    };
    toggles.forEach((b) => b.addEventListener('click', () => setField(b.dataset.field)));
    setField('bio');
  }

  function initExamples() {
    const grid = $('#ex-grid');
    const modal = $('#ex-modal');
    const source = $('#examples-data');
    if (!grid || !modal || !source) return;
    let examples;
    try {
      examples = JSON.parse(source.textContent);
    } catch (err) {
      return;
    }
    const cards = $$('.ex-card', grid);

    const more = $('#ex-more');
    const extras = cards.filter((card) => card.classList.contains('is-extra'));
    if (more) {
      if (!extras.length) more.hidden = true;
      more.textContent = `Show ${extras.length} more demos`;
      more.addEventListener('click', () => {
        grid.classList.add('show-all');
        more.setAttribute('aria-expanded', 'true');
        if (extras[0]) extras[0].focus({ preventScroll: true });
      });
    }

    const sheet = $('.ex-sheet', modal);
    const closeButton = $('.icon-btn[data-ex-close]', modal);
    const field = (id) => document.getElementById(id);
    const fields = {
      domain: field('exm-domain'),
      title: field('exm-title'),
      tracks: field('exm-tracks'),
      img: field('exm-img'),
      desc: field('exm-desc'),
      why: field('exm-why'),
      software: field('exm-software'),
      artifacts: field('exm-artifacts'),
      axes: field('exm-axes'),
      outputs: field('exm-outputs'),
      cta: field('exm-cta'),
      live: field('exm-live'),
    };
    let current = 0;
    let lastFocus = null;
    let liveView = null;

    const mountLive = (ex) => {
      if (liveView) {
        liveView.dispose();
        liveView = null;
      }
      const live = window.ILLive;
      if (!fields.live || !live || !live.ready) {
        if (fields.live) fields.live.hidden = true;
        return;
      }
      fields.live.hidden = false;
      fields.live.style.setProperty('--dc', ex.color);
      liveView = live.mount(fields.live, ex.kind, { color: ex.color, hero: true });
      if (!liveView) fields.live.hidden = true;
    };

    const listItems = (ul, items, cls) => {
      ul.replaceChildren(...items.map((text) => {
        const li = document.createElement('li');
        li.textContent = text;
        if (cls) li.className = cls;
        return li;
      }));
    };

    const render = (index) => {
      current = (index + examples.length) % examples.length;
      const ex = examples[current];
      sheet.style.setProperty('--dc', ex.color);
      fields.domain.textContent = ex.domain;
      fields.title.textContent = ex.title;
      listItems(fields.tracks, ex.tags, 'trk trk-rel');
      fields.img.src = ex.img;
      fields.img.alt = ex.alt;
      fields.desc.textContent = ex.description;
      const lead = document.createElement('strong');
      lead.textContent = 'In your research: ';
      fields.why.replaceChildren(lead, document.createTextNode(ex.why));
      listItems(fields.software, ex.software);
      listItems(fields.artifacts, ex.artifacts);
      listItems(fields.axes, ex.axes);
      listItems(fields.outputs, ex.outputs);
      sheet.scrollTop = 0;
      if (!modal.hidden) mountLive(ex);
    };

    const open = (index) => {
      lastFocus = document.activeElement;
      render(index);
      modal.hidden = false;
      mountLive(examples[current]);
      document.body.classList.add('modal-open');
      closeButton.focus();
    };
    const close = () => {
      modal.hidden = true;
      if (liveView) {
        liveView.dispose();
        liveView = null;
      }
      document.body.classList.remove('modal-open');
      if (lastFocus) lastFocus.focus({ preventScroll: true });
    };
    document.addEventListener('il-live-ready', () => {
      if (!modal.hidden) mountLive(examples[current]);
    });

    fields.cta.addEventListener('click', (e) => {
      e.preventDefault();
      const form = $('#join-form');
      if (form) form.elements.namedItem('interest').value = examples[current].title;
      close();
      $('#join').scrollIntoView({ behavior: reduceMotion ? 'auto' : 'smooth' });
      const name = form && form.elements.namedItem('name');
      if (name) setTimeout(() => name.focus({ preventScroll: true }), reduceMotion ? 0 : 600);
    });

    cards.forEach((card) => {
      const index = Number(card.dataset.index);
      card.addEventListener('click', () => open(index));
      card.addEventListener('keydown', (e) => {
        if (e.key === 'Enter' || e.key === ' ') {
          e.preventDefault();
          open(index);
        }
      });
    });
    $$('[data-ex-close]', modal).forEach((el) => el.addEventListener('click', close));
    $('[data-ex-prev]', modal).addEventListener('click', () => render(current - 1));
    $('[data-ex-next]', modal).addEventListener('click', () => render(current + 1));

    document.addEventListener('keydown', (e) => {
      if (modal.hidden) return;
      if (e.key === 'Escape') {
        e.preventDefault();
        close();
      } else if (e.key === 'ArrowRight') {
        render(current + 1);
      } else if (e.key === 'ArrowLeft') {
        render(current - 1);
      } else if (e.key === 'Tab') {
        const focusables = $$('button, a[href]', sheet);
        const first = focusables[0];
        const last = focusables[focusables.length - 1];
        if (e.shiftKey && document.activeElement === first) {
          e.preventDefault();
          last.focus();
        } else if (!e.shiftKey && document.activeElement === last) {
          e.preventDefault();
          first.focus();
        }
      }
    });
  }

  function initForm() {
    const form = $('#join-form');
    if (!form) return;
    const note = $('#form-note');
    const nameInput = form.elements.namedItem('name');
    nameInput.addEventListener('input', () => nameInput.removeAttribute('aria-invalid'));

    form.addEventListener('submit', (e) => {
      e.preventDefault();
      const data = new FormData(form);
      const value = (key) => String(data.get(key) || '').trim();
      const name = value('name');
      if (!name) {
        nameInput.setAttribute('aria-invalid', 'true');
        note.textContent = 'Please add your name so we know who to reply to.';
        nameInput.focus();
        return;
      }
      const field = value('field') || 'Not specified';
      const lines = [
        `Name: ${name}`,
        `University & program: ${value('program') || '-'}`,
        `Field: ${field}`,
        `Research: ${value('topic') || '-'}`,
        '',
        'How I use AI in my research today:',
        value('ai_use') || '-',
        '',
        `How I'd like to take part: ${data.getAll('involve').join(', ') || 'Not sure yet'}`,
      ];
      if (value('interest')) lines.push(`Demo that caught my eye: ${value('interest')}`);

      const link = document.createElement('a');
      link.href = mailto(`AI for Science collaboration: ${name} (${field})`, lines.join('\r\n'));
      link.hidden = true;
      document.body.append(link);
      link.click();
      link.remove();
      note.textContent = `Your email app should open with your message ready to send. If it doesn't, write to ${CONTACT_TEXT}.`;
    });
  }

  function initMorph() {
    const canvas = $('#morph');
    if (!canvas || !canvas.getContext) return;
    const ctx = canvas.getContext('2d');
    const labels = $$('.morph-labels .ml');

    // Rock-salt lattice: 5 x 5 x 5 sites, two alternating species.
    const SPACING = 0.42;
    const lattice = [];
    for (let i = 0; i < 5; i += 1) {
      for (let j = 0; j < 5; j += 1) {
        for (let k = 0; k < 5; k += 1) {
          lattice.push({ x: (i - 2) * SPACING, y: (j - 2) * SPACING, z: (k - 2) * SPACING, c: (i + j + k) % 2, r: 3.3 });
        }
      }
    }
    const latticeEdges = [];
    for (let a = 0; a < lattice.length; a += 1) {
      for (let b = a + 1; b < lattice.length; b += 1) {
        const p = lattice[a];
        const q = lattice[b];
        const d = Math.abs(p.x - q.x) + Math.abs(p.y - q.y) + Math.abs(p.z - q.z);
        if (Math.abs(d - SPACING) < 1e-6) latticeEdges.push([a, b]);
      }
    }

    // Double helix: two backbones of 50 points plus 25 base pairs on the axis.
    const PER_STRAND = 50;
    const helix = [];
    const helixEdges = [];
    for (let s = 0; s < 2; s += 1) {
      for (let i = 0; i < PER_STRAND; i += 1) {
        const t = i / (PER_STRAND - 1);
        const angle = t * 2.1 * Math.PI * 2 + s * Math.PI;
        helix.push({ x: 0.6 * Math.cos(angle), y: (t - 0.5) * 2.1, z: 0.6 * Math.sin(angle), c: 2 + s, r: 3.4 });
        if (i > 0) helixEdges.push([s * PER_STRAND + i - 1, s * PER_STRAND + i]);
      }
    }
    for (let i = 0; i < PER_STRAND; i += 2) {
      const a = helix[i];
      const b = helix[PER_STRAND + i];
      const mid = helix.length;
      helix.push({ x: (a.x + b.x) / 2, y: (a.y + b.y) / 2, z: (a.z + b.z) / 2, c: 4, r: 2.3 });
      helixEdges.push([i, mid], [mid, PER_STRAND + i]);
    }

    // Pair points by height so the morph flows within horizontal bands.
    const byHeight = (pts) => pts.map((_, i) => i).sort((a, b) =>
      (pts[a].y - pts[b].y) || (Math.atan2(pts[a].z, pts[a].x) - Math.atan2(pts[b].z, pts[b].x)));
    const orderA = byHeight(lattice);
    const orderB = byHeight(helix);
    const slotA = [];
    const slotB = [];
    orderA.forEach((orig, k) => { slotA[orig] = k; });
    orderB.forEach((orig, k) => { slotB[orig] = k; });
    const points = orderA.map((orig, k) => ({ a: lattice[orig], b: helix[orderB[k]] }));
    const edgesA = latticeEdges.map(([p, q]) => [slotA[p], slotA[q]]);
    const edgesB = helixEdges.map(([p, q]) => [slotB[p], slotB[q]]);

    const RGB = [[15, 159, 117], [79, 70, 229], [15, 159, 117], [20, 184, 166], [245, 158, 11]];
    const projected = points.map(() => ({ sx: 0, sy: 0, z: 0, p: 1 }));
    const depthOrder = points.map((_, i) => i);
    const smooth = (x) => x * x * (3 - 2 * x);
    const morphAt = (ms) => {
      const s = (ms / 1000) % 12;
      if (s < 3.6) return 0;
      if (s < 6) return smooth((s - 3.6) / 2.4);
      if (s < 9.6) return 1;
      return 1 - smooth((s - 9.6) / 2.4);
    };

    let w = 0;
    let h = 0;
    let dpr = 1;
    let shown = -1;
    const resize = () => {
      const rect = canvas.getBoundingClientRect();
      dpr = Math.min(window.devicePixelRatio || 1, 2);
      w = rect.width;
      h = rect.height;
      canvas.width = Math.max(1, Math.round(w * dpr));
      canvas.height = Math.max(1, Math.round(h * dpr));
    };

    const draw = (now) => {
      if (w < 8 || h < 8) return;
      const m = reduceMotion ? 0 : morphAt(now);
      const rot = reduceMotion ? 0.6 : now * 0.00022;
      const tilt = 0.32;
      const cosR = Math.cos(rot);
      const sinR = Math.sin(rot);
      const cosT = Math.cos(tilt);
      const sinT = Math.sin(tilt);
      const size = Math.min(w, h);
      const scale = size * 0.34;
      const cx = w / 2;
      const cy = h * 0.47;
      const camera = 3.6;

      ctx.setTransform(dpr, 0, 0, dpr, 0, 0);
      ctx.clearRect(0, 0, w, h);
      for (let k = 0; k < points.length; k += 1) {
        const { a, b } = points[k];
        const x = a.x + (b.x - a.x) * m;
        const y = a.y + (b.y - a.y) * m;
        const z = a.z + (b.z - a.z) * m;
        const x1 = x * cosR + z * sinR;
        const z1 = -x * sinR + z * cosR;
        const y2 = y * cosT - z1 * sinT;
        const z2 = y * sinT + z1 * cosT;
        const persp = camera / (camera - z2);
        const pr = projected[k];
        pr.sx = cx + x1 * scale * persp;
        pr.sy = cy - y2 * scale * persp;
        pr.z = z2;
        pr.p = persp;
      }

      const drawEdges = (edges, alpha, rgb) => {
        if (alpha < 0.02) return;
        ctx.lineWidth = 1.2;
        for (const [i, j] of edges) {
          const p = projected[i];
          const q = projected[j];
          const depth = Math.min(1, Math.max(0, ((p.z + q.z) / 2 + 1.2) / 2.4));
          ctx.strokeStyle = `rgba(${rgb}, ${(alpha * (0.1 + 0.4 * depth)).toFixed(3)})`;
          ctx.beginPath();
          ctx.moveTo(p.sx, p.sy);
          ctx.lineTo(q.sx, q.sy);
          ctx.stroke();
        }
      };
      drawEdges(edgesA, 1 - m, '79, 70, 229');
      drawEdges(edgesB, m, '15, 159, 117');

      depthOrder.sort((i, j) => projected[i].z - projected[j].z);
      const unit = size / 440;
      for (const k of depthOrder) {
        const pr = projected[k];
        const { a, b } = points[k];
        const ca = RGB[a.c];
        const cb = RGB[b.c];
        const depth = Math.min(1, Math.max(0, (pr.z + 1.2) / 2.4));
        const radius = (a.r + (b.r - a.r) * m) * pr.p * unit;
        ctx.fillStyle = `rgba(${Math.round(ca[0] + (cb[0] - ca[0]) * m)}, ${Math.round(ca[1] + (cb[1] - ca[1]) * m)}, ${Math.round(ca[2] + (cb[2] - ca[2]) * m)}, ${(0.42 + 0.58 * depth).toFixed(3)})`;
        ctx.beginPath();
        ctx.arc(pr.sx, pr.sy, radius, 0, Math.PI * 2);
        ctx.fill();
      }

      const shape = m >= 0.5 ? 1 : 0;
      if (shape !== shown) {
        shown = shape;
        labels.forEach((label) => label.classList.toggle('is-on', Number(label.dataset.shape) === shape));
      }
    };

    let raf = 0;
    let inView = true;
    const loop = (now) => {
      draw(now);
      raf = requestAnimationFrame(loop);
    };
    const start = () => {
      if (!raf && inView && !document.hidden && !reduceMotion) raf = requestAnimationFrame(loop);
    };
    const stop = () => {
      cancelAnimationFrame(raf);
      raf = 0;
    };

    resize();
    draw(performance.now());
    if ('ResizeObserver' in window) {
      new ResizeObserver(() => {
        resize();
        if (!raf) draw(performance.now());
      }).observe(canvas);
    }
    if (reduceMotion) return;
    if ('IntersectionObserver' in window) {
      new IntersectionObserver((entries) => {
        inView = entries[0].isIntersecting;
        if (inView) start();
        else stop();
      }).observe(canvas);
    }
    document.addEventListener('visibilitychange', () => {
      if (document.hidden) stop();
      else start();
    });
    start();
  }

  initContact();
  initNav();
  initReveal();
  initExplorer();
  initExamples();
  initForm();
  initMorph();
})();