const fs = require('fs');
const path = require('path');
const NodeStl = require('node-stl');
const AdmZip = require('adm-zip');

const THUMBNAIL_DIR = './thumbnails';

const MODEL_FORMATS = ['stl', '3mf', 'obj', 'fbx', 'step', 'stp', '3dm', 'gcode', 'gco'];
const ARCHIVE_FORMATS = ['zip', '7z', 'rar', 'tar', 'tgz'];
const IMAGE_FORMATS = ['jpg', 'jpeg', 'png', 'gif', 'webp', 'bmp', 'svg'];
// Kept with a model and viewable, but never matched as duplicates.
const COMPANION_FORMATS = [...IMAGE_FORMATS, 'pdf', 'txt', 'md', 'mtl'];
const ALLOWED_FORMATS = [...MODEL_FORMATS, ...ARCHIVE_FORMATS, ...COMPANION_FORMATS];

function ensureThumbnailDir() {
  if (!fs.existsSync(THUMBNAIL_DIR)) fs.mkdirSync(THUMBNAIL_DIR, { recursive: true });
}

function formatOf(filename) {
  const lower = filename.toLowerCase();
  if (lower.endsWith('.tar.gz')) return 'tgz';
  return path.extname(lower).slice(1);
}

function isAllowed(filename) {
  return ALLOWED_FORMATS.includes(formatOf(filename));
}

// Geometry metadata. Only STL is computed natively today; others return nulls
// (3MF/OBJ/STEP volume can be added later via a Python/trimesh sidecar).
function extractMetadata(filePath, format) {
  if (format !== 'stl') return { volume: null, bbox: null, facets: null };
  try {
    const stl = new NodeStl(filePath);
    const bb = stl.boundingBox; // [x, y, z]
    return {
      volume: Number.isFinite(stl.volume) ? stl.volume : null,
      bbox: Array.isArray(bb) ? { x: bb[0], y: bb[1], z: bb[2] } : null,
      facets: null, // node-stl does not expose facet count
    };
  } catch (err) {
    console.error('STL metadata extraction failed:', err.message);
    return { volume: null, bbox: null, facets: null };
  }
}

// Which embedded PNG makes the best card image: the project thumbnail, then the
// first plate render. Slicer pick maps, top views and small/unlit variants last.
function thumbnailRank(name) {
  if (name === 'metadata/thumbnail.png') return 0;
  if (/metadata\/plate_1\.png$/.test(name)) return 1;
  if (/metadata\/plate_\d+\.png$/.test(name)) return 2;
  if (/(pick_|top_|no_light|_small)/.test(name)) return 9;
  return 5;
}

// A .3mf is a zip; slicers embed a PNG preview under /Metadata/. If present,
// pull it out as the model thumbnail. Returns a path under thumbnails/ or null.
function extract3mfThumbnail(filePath, baseName) {
  try {
    ensureThumbnailDir();
    const zip = new AdmZip(filePath);
    const entry = zip.getEntries()
      .filter((e) => {
        const n = e.entryName.toLowerCase();
        return n.endsWith('.png') && (n.includes('thumbnail') || n.includes('metadata/'));
      })
      .sort((a, b) => thumbnailRank(a.entryName.toLowerCase()) - thumbnailRank(b.entryName.toLowerCase()))[0];
    if (!entry) return null;
    const out = path.join(THUMBNAIL_DIR, `${baseName}.png`);
    fs.writeFileSync(out, entry.getData());
    return out;
  } catch (err) {
    console.error('3MF thumbnail extraction failed:', err.message);
    return null;
  }
}

// Copy a picture that came with a model into thumbnails/ (a copy, so replacing
// the thumbnail later never deletes the model's own file).
function copyAsThumbnail(filePath, baseName) {
  try {
    ensureThumbnailDir();
    const out = path.join(THUMBNAIL_DIR, `${baseName}-image${path.extname(filePath).toLowerCase()}`);
    fs.copyFileSync(filePath, out);
    return out;
  } catch (err) {
    console.error('Image thumbnail copy failed:', err.message);
    return null;
  }
}

module.exports = {
  MODEL_FORMATS, ARCHIVE_FORMATS, IMAGE_FORMATS, COMPANION_FORMATS, ALLOWED_FORMATS,
  formatOf, isAllowed, extractMetadata, extract3mfThumbnail, copyAsThumbnail,
};