(() => {
  const fileInput = document.getElementById('file-input');
  const cameraInput = document.getElementById('camera-input');
  const cameraBtn = document.getElementById('camera-btn');
  const libraryBtn = document.getElementById('library-btn');
  const dropZone = document.getElementById('drop-zone');
  const dropCard = document.getElementById('drop-card');
  const editorCard = document.getElementById('editor-card');
  const canvas = document.getElementById('canvas');
  const ctx = canvas.getContext('2d');

  const templateRow = document.getElementById('template-row');
  const captionInput = document.getElementById('caption-input');
  const captionStatus = document.getElementById('caption-status');
  const redraftBtn = document.getElementById('redraft-btn');

  const newPhotoBtn = document.getElementById('new-photo-btn');
  const downloadBtn = document.getElementById('download-btn');
  const shareBtn = document.getElementById('share-btn');
  const resultPanel = document.getElementById('result-panel');

  const source = document.createElement('canvas'); // original photo, cover-cropped into the photo area
  const sourceCtx = source.getContext('2d');

  let originalImg = null;
  let photoDate = new Date();
  let locationLabel = null; // "City, Country" from EXIF GPS + server-side reverse geocode, or null

  // Slack the fixed 3:2 crop leaves to pan within, in original-photo pixel
  // space — recomputed every rebuildSource(), read by the drag handler.
  let cropBounds = { iw: 0, ih: 0, cropW: 0, cropH: 0, outW: 0, outH: 0 };
  const panHint = document.getElementById('pan-hint');

  const params = {
    template: 'cream',
    // Normalized 0-1 position of the crop window within whatever slack the
    // fixed 3:2 aspect leaves — 0.5/0.5 is centered.
    cropOffsetX: 0.5,
    cropOffsetY: 0.5,
    caption: '',
  };

  // Registered via CSS @font-face but canvas fillText won't wait for a
  // lazily-loaded webfont on its own — load it explicitly once up front.
  let fontReady = false;
  document.fonts.load('700 40px Caveat').catch(() => {}).finally(() => {
    fontReady = true;
    if (originalImg) render();
  });

  // Small seeded PRNG so a template's jagged/faded look stays fixed per
  // photo instead of jittering every redraw.
  function mulberry32(seed) {
    let a = Math.floor(seed * 0xffffffff);
    return function () {
      a |= 0; a = (a + 0x6d2b79f5) | 0;
      let t = Math.imul(a ^ (a >>> 15), 1 | a);
      t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
      return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
    };
  }
  let torSeed = Math.random();

  async function loadFile(file) {
    if (!file || !file.type.startsWith('image/')) return;

    // Read EXIF before the image element even loads — DateTimeOriginal
    // backdates the caption/postmark to when the photo was actually taken,
    // not when it happened to be uploaded; GPS (if present) drives the
    // location line. Both are optional: parse failures/missing tags just
    // mean "fall back to upload date, no location," per PROPOSAL.md.
    const exif = window.PostcardExif ? await window.PostcardExif.read(file) : null;
    photoDate = exif?.date || new Date();
    locationLabel = null;

    const url = URL.createObjectURL(file);
    const img = new Image();
    img.onload = () => {
      originalImg = img;
      URL.revokeObjectURL(url);
      dropCard.hidden = true;
      editorCard.hidden = false;
      resultPanel.hidden = true;
      torSeed = Math.random();
      params.cropOffsetX = 0.5;
      params.cropOffsetY = 0.5;
      rebuildSource();
      render();
      draftCaption();
      if (exif && exif.lat != null && exif.lon != null) lookupLocation(exif.lat, exif.lon);
    };
    img.src = url;
  }

  async function lookupLocation(lat, lon) {
    try {
      const res = await fetch(`/api/geocode?lat=${lat}&lon=${lon}`);
      const data = await res.json();
      if (data.label) {
        locationLabel = data.label;
        render();
      }
    } catch {
      // No location line — never invents one, per PROPOSAL.md.
    }
  }

  // Builds `source`: the photo cover-cropped to a fixed postcard photo-area
  // aspect (3:2, classic postcard proportions), capped so a raw phone photo
  // doesn't choke canvas ops.
  function rebuildSource() {
    if (!originalImg) return;
    const iw = originalImg.naturalWidth;
    const ih = originalImg.naturalHeight;
    const targetAspect = 3 / 2;

    let cropW = iw, cropH = ih, cropX = 0, cropY = 0;
    const currentAspect = iw / ih;
    if (currentAspect > targetAspect) {
      cropW = Math.round(ih * targetAspect);
      cropX = Math.round((iw - cropW) * params.cropOffsetX);
    } else {
      cropH = Math.round(iw / targetAspect);
      cropY = Math.round((ih - cropH) * params.cropOffsetY);
    }

    const maxDim = 1800;
    let outW = cropW, outH = cropH;
    if (Math.max(outW, outH) > maxDim) {
      const scale = maxDim / Math.max(outW, outH);
      outW = Math.round(outW * scale);
      outH = Math.round(outH * scale);
    }

    source.width = outW;
    source.height = outH;
    sourceCtx.clearRect(0, 0, outW, outH);
    sourceCtx.drawImage(originalImg, cropX, cropY, cropW, cropH, 0, 0, outW, outH);

    cropBounds = { iw, ih, cropW, cropH, outW, outH };
    updatePanAffordance();

    // Full card = photo area + a border margin all around, matching a
    // physical postcard's white/cream frame.
    const margin = Math.round(outW * 0.06);
    canvas.width = outW + margin * 2;
    canvas.height = outH + margin * 2;
  }

  function hasPanSlack() {
    return cropBounds.iw > cropBounds.cropW || cropBounds.ih > cropBounds.cropH;
  }

  function updatePanAffordance() {
    const pannable = hasPanSlack();
    canvas.classList.toggle('pannable', pannable);
    if (panHint) panHint.hidden = !pannable;
  }

  // Drag-to-reposition, same trick as latent: convert pointer movement in
  // CSS pixels to original-photo pixels via crop-width/display-width,
  // through the outW downscale (canvas's own pixel space === outW/outH,
  // not cropW/cropH) and the canvas's CSS scaling, so it stays 1:1
  // regardless of either. Dragging from anywhere on the canvas is fine
  // even though the border margin isn't photo -- the gesture still reads
  // as "drag the photo," and the margin is only ~6% per side.
  let dragState = null;
  let panRaf = null;

  canvas.addEventListener('pointerdown', (e) => {
    if (!hasPanSlack()) return;
    const { iw, ih, cropW, cropH } = cropBounds;
    dragState = {
      pointerId: e.pointerId,
      startX: e.clientX,
      startY: e.clientY,
      cropX0: Math.round((iw - cropW) * params.cropOffsetX),
      cropY0: Math.round((ih - cropH) * params.cropOffsetY),
    };
    canvas.setPointerCapture(e.pointerId);
    canvas.classList.add('panning');
  });

  canvas.addEventListener('pointermove', (e) => {
    if (!dragState || e.pointerId !== dragState.pointerId) return;
    const rect = canvas.getBoundingClientRect();
    const { iw, ih, cropW, cropH, outW, outH } = cropBounds;
    const cropPxPerCssPxX = (canvas.width / rect.width) * (cropW / outW);
    const cropPxPerCssPxY = (canvas.height / rect.height) * (cropH / outH);
    const deltaX = (e.clientX - dragState.startX) * cropPxPerCssPxX;
    const deltaY = (e.clientY - dragState.startY) * cropPxPerCssPxY;

    const slackX = iw - cropW;
    const slackY = ih - cropH;
    const newCropX = Math.min(Math.max(dragState.cropX0 - deltaX, 0), slackX);
    const newCropY = Math.min(Math.max(dragState.cropY0 - deltaY, 0), slackY);
    params.cropOffsetX = slackX > 0 ? newCropX / slackX : 0.5;
    params.cropOffsetY = slackY > 0 ? newCropY / slackY : 0.5;

    if (panRaf) return;
    panRaf = requestAnimationFrame(() => {
      panRaf = null;
      rebuildSource();
      render();
    });
  });

  function endPan(e) {
    if (!dragState || (e && e.pointerId !== dragState.pointerId)) return;
    canvas.classList.remove('panning');
    dragState = null;
  }
  canvas.addEventListener('pointerup', endPan);
  canvas.addEventListener('pointercancel', endPan);

  function render() {
    if (!originalImg) return;
    const w = canvas.width;
    const h = canvas.height;
    const margin = Math.round(source.width * 0.06);

    ctx.clearRect(0, 0, w, h);

    // Border background per template.
    if (params.template === 'faded') {
      ctx.fillStyle = '#e9dfc8';
    } else {
      ctx.fillStyle = '#f7f2e6';
    }
    ctx.fillRect(0, 0, w, h);

    // Photo, with a per-template filter applied at draw time.
    ctx.save();
    ctx.filter = params.template === 'faded'
      ? 'sepia(0.25) saturate(0.55) contrast(0.85) brightness(1.1)'
      : 'none';
    if (params.template === 'torn') {
      clipTornRect(margin, margin, source.width, source.height, torSeed);
    }
    ctx.drawImage(source, margin, margin);
    ctx.restore();

    if (params.template !== 'torn') {
      ctx.strokeStyle = 'rgba(0,0,0,0.15)';
      ctx.lineWidth = 1;
      ctx.strokeRect(margin + 0.5, margin + 0.5, source.width - 1, source.height - 1);
    }

    drawStampCorner(w, h, margin);
    drawCaption(w, h, margin);
  }

  // Clips the current path to a rectangle with a hand-torn edge — jagged
  // teeth along each side, seeded so it's stable per photo.
  function clipTornRect(x, y, w, h, seed) {
    const rng = mulberry32(seed);
    const tooth = Math.max(2, Math.round(Math.min(w, h) * 0.006));
    const step = tooth * 3;

    ctx.beginPath();
    let px = x, py = y;
    ctx.moveTo(px, py);
    for (; px < x + w; px += step) ctx.lineTo(px, y + (rng() - 0.5) * tooth);
    ctx.lineTo(x + w, y + (rng() - 0.5) * tooth);
    for (; py < y + h; py += step) ctx.lineTo(x + w + (rng() - 0.5) * tooth, py);
    ctx.lineTo(x + w + (rng() - 0.5) * tooth, y + h);
    for (px = x + w; px > x; px -= step) ctx.lineTo(px, y + h + (rng() - 0.5) * tooth);
    ctx.lineTo(x, y + h + (rng() - 0.5) * tooth);
    for (py = y + h; py > y; py -= step) ctx.lineTo(x + (rng() - 0.5) * tooth, py);
    ctx.closePath();
    ctx.clip();
  }

  // Postmark stamp — date always, plus a location line only when the photo
  // had EXIF GPS and reverse geocoding succeeded. Never an invented
  // location, per PROPOSAL.md's fallback for "no EXIF GPS."
  function drawStampCorner(w, h, margin) {
    const size = margin * 1.6;
    // Right edge of the (rotated) box must stay inside the card, not just
    // inside the photo area — the border margin is the only safe zone.
    const x = w - margin - size;
    const y = margin * 0.15;

    ctx.save();
    ctx.translate(x, y);
    ctx.rotate((6 * Math.PI) / 180);
    ctx.strokeStyle = 'rgba(0,0,0,0.35)';
    ctx.lineWidth = Math.max(1, size * 0.02);
    ctx.setLineDash([size * 0.04, size * 0.03]);
    ctx.strokeRect(0, 0, size, size * 0.8);
    ctx.setLineDash([]);

    ctx.fillStyle = 'rgba(0,0,0,0.55)';
    ctx.textAlign = 'center';
    const dateStr = photoDate.toLocaleDateString(undefined, { year: 'numeric', month: 'short', day: 'numeric' });

    if (locationLabel) {
      ctx.font = `${Math.round(size * 0.1)}px ui-monospace, 'JetBrains Mono', 'Fira Code', monospace`;
      ctx.fillText(truncate(locationLabel, 18), size / 2, size * 0.3);
      ctx.font = `${Math.round(size * 0.11)}px ui-monospace, 'JetBrains Mono', 'Fira Code', monospace`;
      ctx.fillText(dateStr, size / 2, size * 0.52);
      ctx.font = `${Math.round(size * 0.08)}px ui-monospace, 'JetBrains Mono', 'Fira Code', monospace`;
      ctx.fillText('postcard', size / 2, size * 0.7);
    } else {
      ctx.font = `${Math.round(size * 0.13)}px ui-monospace, 'JetBrains Mono', 'Fira Code', monospace`;
      ctx.fillText(dateStr, size / 2, size * 0.45);
      ctx.font = `${Math.round(size * 0.09)}px ui-monospace, 'JetBrains Mono', 'Fira Code', monospace`;
      ctx.fillText('postcard', size / 2, size * 0.65);
    }
    ctx.restore();
  }

  function truncate(str, maxLen) {
    return str.length > maxLen ? `${str.slice(0, maxLen - 1)}…` : str;
  }

  function drawCaption(w, h, margin) {
    if (!params.caption) return;
    ctx.save();
    ctx.fillStyle = 'rgba(30,25,15,0.85)';
    ctx.textAlign = 'left';
    ctx.textBaseline = 'alphabetic';
    // Caveat reads smaller than a sans face at the same px size (thin
    // connected strokes), so it gets a bigger multiplier and bolder weight
    // than a plain cursive fallback would need.
    const fontSize = Math.max(16, Math.round(margin * 0.55));
    ctx.font = fontReady
      ? `700 ${fontSize}px "Caveat", cursive`
      : `${Math.round(fontSize * 0.75)}px "Segoe Script", "Bradley Hand", cursive`;
    wrapText(params.caption, margin, h - margin * 0.35, w - margin * 2, fontSize * 1.15);
    ctx.restore();
  }

  function wrapText(text, x, bottomY, maxWidth, lineHeight) {
    const words = text.split(/\s+/);
    const lines = [];
    let line = '';
    for (const word of words) {
      const test = line ? `${line} ${word}` : word;
      if (ctx.measureText(test).width > maxWidth && line) {
        lines.push(line);
        line = word;
      } else {
        line = test;
      }
    }
    if (line) lines.push(line);
    const clipped = lines.slice(-3); // at most 3 lines, bottom-anchored
    const startY = bottomY - (clipped.length - 1) * lineHeight;
    clipped.forEach((l, i) => ctx.fillText(l, x, startY + i * lineHeight));
  }

  async function draftCaption() {
    captionStatus.textContent = 'drafting…';
    try {
      const dateStr = photoDate.toISOString().slice(0, 10);
      const res = await fetch(`/api/caption?date=${dateStr}`);
      const data = await res.json();
      captionInput.value = data.caption || '';
      params.caption = captionInput.value;
      captionStatus.textContent = '';
      render();
    } catch {
      captionStatus.textContent = '';
    }
  }

  function showResult(html, isError) {
    resultPanel.innerHTML = html;
    resultPanel.classList.toggle('error', !!isError);
    resultPanel.hidden = false;
  }

  function canvasToBlob() {
    return new Promise(resolve => canvas.toBlob(resolve, 'image/jpeg', 0.92));
  }

  async function upload() {
    shareBtn.disabled = true;
    showResult('uploading&hellip;');
    try {
      const blob = await canvasToBlob();
      const res = await fetch('/api/upload', {
        method: 'POST',
        headers: { 'Content-Type': 'image/jpeg' },
        body: blob,
      });
      if (!res.ok) {
        const body = await res.json().catch(() => ({}));
        throw new Error(body.error || `upload failed (${res.status})`);
      }
      const data = await res.json();
      const link = `${location.origin}${data.url}`;
      showResult(`share link: <a href="${link}">${link}</a>`);
    } catch (err) {
      showResult(err.message || 'something went wrong', true);
    } finally {
      shareBtn.disabled = false;
    }
  }

  fileInput.addEventListener('change', () => loadFile(fileInput.files[0]));
  cameraInput.addEventListener('change', () => loadFile(cameraInput.files[0]));
  cameraBtn.addEventListener('click', () => cameraInput.click());
  libraryBtn.addEventListener('click', () => fileInput.click());

  ['dragover', 'dragenter'].forEach(evt =>
    dropZone.addEventListener(evt, e => {
      e.preventDefault();
      dropZone.classList.add('drag-over');
    })
  );
  ['dragleave', 'dragend', 'drop'].forEach(evt =>
    dropZone.addEventListener(evt, () => dropZone.classList.remove('drag-over'))
  );
  dropZone.addEventListener('drop', e => {
    e.preventDefault();
    loadFile(e.dataTransfer.files[0]);
  });

  [...templateRow.children].forEach(btn => {
    btn.addEventListener('click', () => {
      params.template = btn.dataset.template;
      [...templateRow.children].forEach(b => b.classList.toggle('active', b === btn));
      render();
    });
  });

  captionInput.addEventListener('input', () => {
    params.caption = captionInput.value;
    render();
  });
  redraftBtn.addEventListener('click', draftCaption);

  newPhotoBtn.addEventListener('click', () => {
    originalImg = null;
    locationLabel = null;
    fileInput.value = '';
    cameraInput.value = '';
    editorCard.hidden = true;
    dropCard.hidden = false;
    resultPanel.hidden = true;
  });

  downloadBtn.addEventListener('click', async () => {
    const blob = await canvasToBlob();
    const url = URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.href = url;
    a.download = `postcard-${Date.now()}.jpg`;
    a.click();
    URL.revokeObjectURL(url);
  });

  shareBtn.addEventListener('click', upload);
})();