// What each model asks for, and what you have on hand.
//
// A Bambu Studio / OrcaSlicer 3MF names the filaments its plates use. Reading
// that means shelling out to Python, so it is done once per model in the
// background — like thumbnails and fingerprints — and kept in models.filaments.
// With that stored, "what can I print right now" is a plain query rather than
// hundreds of subprocesses.
const db = require('./db');
const converter = require('./converter');

const BATCH = 25;

// Models that have never been looked at, paired with their first loose 3MF.
// A model whose only 3MF sits inside an archive is left for a later pass rather
// than paying an extraction for each one.
const PENDING = `
  FROM models m
  LEFT JOIN LATERAL (
    SELECT f.file_path FROM files f
    WHERE f.model_id = m.id AND f.format = '3mf'
    ORDER BY f.id LIMIT 1
  ) f3 ON true
  WHERE m.deleted_at IS NULL AND m.filaments_status IS NULL`;

// "PLA Basic" and "pla basic" are the same filament; "PLA-CF" is not.
const normalise = (s) => String(s || '').trim().toUpperCase().replace(/\s+/g, ' ');

// Bambu writes #RRGGBB and #RRGGBBAA; the alpha channel is not a colour.
function rgb(hex) {
  const m = /^#?([0-9a-f]{6})(?:[0-9a-f]{2})?$/i.exec(String(hex || '').trim());
  if (!m) return null;
  const n = parseInt(m[1], 16);
  return { r: (n >> 16) & 255, g: (n >> 8) & 255, b: n & 255 };
}

// Redmean distance: closer to how an eye judges two colours than plain RGB.
// 0 is identical, black to white is about 765. Null when either is unknown.
function colourDistance(a, b) {
  const x = rgb(a);
  const y = rgb(b);
  if (!x || !y) return null;
  const rm = (x.r + y.r) / 2;
  const dr = x.r - y.r;
  const dg = x.g - y.g;
  const db = x.b - y.b;
  return Math.sqrt((2 + rm / 256) * dr * dr + 4 * dg * dg + (2 + (255 - rm) / 256) * db * db);
}

// How close counts as the same colour. 50 keeps #000000 and #161616 apart (~66)
// while allowing genuinely near shades to stand in for each other.
const COLOUR_TOLERANCE = 50;

// Which spool fills which slot. One spool cannot fill two slots, so the best
// colour matches are assigned first. A slot whose project gives no colour is
// satisfied by any spool of the right material.
function assignSpools(filaments, spools) {
  const slots = (filaments || []).map((f, i) => ({
    index: i, material: normalise(f.type), colour: f.colour || null,
  }));
  const shelf = (spools || [])
    .filter((s) => s.remaining_g === null || s.remaining_g === undefined || Number(s.remaining_g) > 0)
    .map((s, i) => ({
      key: s.id == null ? `i${i}` : `s${s.id}`, material: normalise(s.material),
      colour: s.colour_hex || null, name: s.colour || s.material,
    }));

  const pairs = [];
  for (const slot of slots) {
    for (const spool of shelf) {
      if (spool.material !== slot.material) continue;
      if (slot.colour === null) { pairs.push({ slot: slot.index, spool: spool.key, d: 0 }); continue; }
      const d = colourDistance(slot.colour, spool.colour);
      if (d !== null && d <= COLOUR_TOLERANCE) pairs.push({ slot: slot.index, spool: spool.key, d });
    }
  }
  pairs.sort((a, b) => a.d - b.d);

  const filledBy = new Map();
  const usedSpools = new Set();
  for (const p of pairs) {
    if (filledBy.has(p.slot) || usedSpools.has(p.spool)) continue;
    filledBy.set(p.slot, p.spool);
    usedSpools.add(p.spool);
  }

  return slots.map((slot) => {
    const key = filledBy.get(slot.index);
    const by = key ? shelf.find((s) => s.key === key) : null;
    let nearest = null;
    if (!by && slot.colour) {
      for (const spool of shelf) {
        if (spool.material !== slot.material) continue;
        const d = colourDistance(slot.colour, spool.colour);
        if (d !== null && (!nearest || d < nearest.distance)) nearest = { name: spool.name, distance: Math.round(d) };
      }
    }
    return { ...slot, filled: Boolean(by), by: by ? by.name : null, nearest };
  });
}

// The slots you can't fill from the shelf.
function shortfall(filaments, spools) {
  return assignSpools(filaments, spools).filter((s) => !s.filled);
}

// True when every slot has a spool. A model we know nothing about is not
// claimed to be printable.
function isPrintable(filaments, spools) {
  if (!filaments || !filaments.length) return false;
  return shortfall(filaments, spools).length === 0;
}

// One pass. Returns whether it did any work, so it fits the background worker
// loop in fingerprint.js.
async function run() {
  const { rows } = await db.query(
    `SELECT m.id, f3.file_path ${PENDING} ORDER BY m.id LIMIT ${BATCH}`);
  if (!rows.length) return false;

  for (const row of rows) {
    if (!row.file_path) {
      await mark(row.id, 'none', null);
      continue;
    }
    try {
      const filaments = await converter.readFilaments(row.file_path);
      // A plain 3MF mesh names no filaments — that is an answer, not a failure.
      await mark(row.id, filaments.length ? 'done' : 'none', filaments.length ? filaments : null);
    } catch (err) {
      console.warn(`Could not read filaments for model ${row.id}:`, err.message);
      await mark(row.id, 'error', null);
    }
  }
  return true;
}

async function mark(modelId, status, filaments) {
  await db.query('UPDATE models SET filaments = $2, filaments_status = $3 WHERE id = $1',
    [modelId, filaments ? JSON.stringify(filaments) : null, status]);
}

async function pendingCount() {
  const { rows } = await db.query(`SELECT COUNT(*)::int AS n ${PENDING}`);
  return rows[0].n;
}

// Look at every model again — after adding files, say.
async function reread() {
  await db.query('UPDATE models SET filaments_status = NULL');
}

module.exports = {
  run, pendingCount, reread,
  assignSpools, shortfall, isPrintable, normalise, colourDistance, rgb, COLOUR_TOLERANCE,
};