// Keeps the Filament page in step with what a printer has loaded.
//
// planSync() works out, without touching the database, what a printer's report
// means for your spools; applySync() carries that out. Only spools with an RFID
// tag are handled automatically: an untagged spool looks identical to any other
// of its colour, so there's no way to tell it from one you already have.
const db = require('./db');
const { colourDistance, normalise, paletteMatch } = require('./filaments');

// How close a hand-added spool's colour must be for it to adopt a printer's tag.
const ADOPT_TOLERANCE = 12;

// Where a tray is, as stored on a spool: "<printer serial>/<unit>/<slot>", with
// "ext" as the unit for the external spool holder.
const slotKey = (printerSerial, tray) =>
  `${printerSerial}/${tray.unit == null ? 'ext' : tray.unit}/${tray.slot == null ? 0 : tray.slot}`;

function planSync(existing, trays, printerSerial, palette, { measures = false } = {}) {
  const actions = [];
  // Grams left, only when this printer's AMS actually measures it. An AMS lite
  // reports full or empty, which is not a weight.
  const gramsLeft = (tray) => (measures && tray.remain != null && tray.weight
    ? Math.round((tray.weight * tray.remain) / 100)
    : null);
  const untracked = [];
  const byUuid = new Map(existing.filter((s) => s.rfid_uuid).map((s) => [s.rfid_uuid, s]));
  const adopted = new Set(); // hand-added spools already matched in this report
  const seen = new Set();    // existing spools this report accounts for

  for (const tray of trays || []) {
    if (!tray || tray.empty) continue;
    const slot = slotKey(printerSerial, tray);
    if (!tray.uuid) {
      untracked.push({ slot, material: tray.material, colour: tray.colour });
      continue;
    }

    const known = byUuid.get(tray.uuid);
    if (known) {
      seen.add(known.id);
      actions.push({ op: 'update', id: known.id, slot, printerSerial, remaining: gramsLeft(tray) });
      continue;
    }

    const named = paletteMatch(palette, tray.material, tray.type, tray.colour);

    // A spool you added by hand before the printer reported it: take it over
    // rather than adding a second copy.
    const adopt = existing.find((s) => {
      if (s.rfid_uuid || adopted.has(s.id)) return false;
      if (normalise(s.material) !== normalise(tray.material)) return false;
      const d = colourDistance(s.colour_hex, tray.colour);
      return d !== null && d <= ADOPT_TOLERANCE;
    });
    if (adopt) {
      adopted.add(adopt.id);
      seen.add(adopt.id);
      actions.push({
        op: 'adopt', id: adopt.id, slot, printerSerial,
        uuid: tray.uuid, tagUid: tray.tagUid, productCode: tray.idName,
        code: named ? named.code : null, totalG: tray.weight, remaining: gramsLeft(tray),
      });
      continue;
    }

    actions.push({
      op: 'create', slot, printerSerial,
      spool: {
        material: tray.material,
        colour: named ? named.name : (tray.idName || tray.colour || tray.material),
        colour_hex: tray.colour,
        brand: 'Bambu Lab',
        code: named ? named.code : null,
        total_g: tray.weight,
        remaining_g: gramsLeft(tray), // blank unless this printer's AMS measures it
        rfid_uuid: tray.uuid,
        tag_uid: tray.tagUid,
        product_code: tray.idName,
      },
    });
  }

  // Anything this printer used to hold that it no longer reports has come out.
  for (const s of existing) {
    if (s.printer_serial === printerSerial && s.ams_slot && !seen.has(s.id)) {
      actions.push({ op: 'unload', id: s.id });
    }
  }
  return { actions, untracked };
}

async function applySync({ actions }) {
  const summary = { created: 0, adopted: 0, updated: 0, unloaded: 0 };
  for (const a of actions) {
    if (a.op === 'create') {
      const s = a.spool;
      const { rowCount } = await db.query(
        `INSERT INTO filament_spools (material, colour, colour_hex, brand, code, total_g, remaining_g,
           rfid_uuid, tag_uid, product_code, ams_slot, printer_serial, last_seen_at)
         VALUES ($1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12, now())
         ON CONFLICT (rfid_uuid) WHERE rfid_uuid IS NOT NULL DO NOTHING`,
        [s.material, s.colour, s.colour_hex, s.brand, s.code, s.total_g, s.remaining_g,
          s.rfid_uuid, s.tag_uid, s.product_code, a.slot, a.printerSerial]);
      summary.created += rowCount;
    } else if (a.op === 'adopt') {
      const { rowCount } = await db.query(
        `UPDATE filament_spools SET rfid_uuid = $2, tag_uid = $3, product_code = $4,
           code = COALESCE(code, $5), total_g = COALESCE(total_g, $6),
           ams_slot = $7, printer_serial = $8, remaining_g = COALESCE($9, remaining_g),
           last_seen_at = now(), date_modified = now()
         WHERE id = $1 AND rfid_uuid IS NULL`,
        [a.id, a.uuid, a.tagUid, a.productCode, a.code, a.totalG, a.slot, a.printerSerial, a.remaining ?? null]);
      summary.adopted += rowCount;
    } else if (a.op === 'update') {
      // A measured weight replaces the stored one; no reading leaves it alone.
      await db.query(
        `UPDATE filament_spools SET ams_slot = $2, printer_serial = $3, last_seen_at = now(),
           remaining_g = COALESCE($4, remaining_g)
         WHERE id = $1`,
        [a.id, a.slot, a.printerSerial, a.remaining ?? null]);
      summary.updated += 1;
    } else if (a.op === 'unload') {
      await db.query('UPDATE filament_spools SET ams_slot = NULL WHERE id = $1', [a.id]);
      summary.unloaded += 1;
    }
  }
  return summary;
}

// Reads the shelf, plans against one printer's trays, and applies it.
async function syncPrinter(printerSerial, trays, palette, options = {}) {
  const { rows: existing } = await db.query('SELECT * FROM filament_spools');
  const plan = planSync(existing, trays, printerSerial, palette, options);
  const summary = await applySync(plan);
  return { ...summary, untracked: plan.untracked };
}

module.exports = { planSync, syncPrinter, slotKey };