forskjeller.naiv.no/public/sparing/app.js

// Formateringshjelpere — norsk locale
function fmtKr(n) {
  return Math.round(n).toLocaleString('nb-NO') + '\u202fkr';
}

function fmtShort(n) {
  if (n >= 1e6) return (n / 1e6).toFixed(1).replace('.', ',') + '\u202fM';
  if (n >= 1e3) return Math.round(n / 1e3) + '\u202fk';
  return Math.round(n);
}

// Fremtidig verdi av annuitet med månedlig compounding
// FV = P × ((1+r)^n - 1) / r  der r = årsrate/12, n = år×12
// Spesialtilfelle: r=0 → FV = P × n
function futureValue(P, annualRate, years) {
  const n = years * 12;
  if (annualRate === 0) return P * n;
  const r = annualRate / 12;
  return P * (Math.pow(1 + r, n) - 1) / r;
}

function getData() {
  const P = +document.getElementById('monthly').value;
  const rA = +document.getElementById('rateA').value / 100;
  const rB = +document.getElementById('rateB').value / 100;
  const Y = +document.getElementById('yrs').value;

  const labels = [], valA = [], valB = [], gaps = [];
  const deposits = [], interestA = [], interestB = [];

  for (let y = 0; y <= Y; y++) {
    labels.push(y === 0 ? 'I dag' : (y % 5 === 0 || Y <= 10 || y === Y) ? 'År ' + y : '');
    const a = futureValue(P, rA, y);
    const b = futureValue(P, rB, y);
    const dep = P * 12 * y;
    valA.push(a);
    valB.push(b);
    gaps.push(b - a);
    deposits.push(dep);
    interestA.push(a - dep);
    interestB.push(b - dep);
  }

  return { P, rA, rB, Y, labels, valA, valB, gaps, deposits, interestA, interestB };
}

const GRID_COLOR = 'rgba(0,0,0,0.06)';
const TICK_COLOR = '#8a857e';

function baseOpts() {
  return {
    responsive: true, maintainAspectRatio: false,
    plugins: {
      legend: { display: false },
      tooltip: {
        callbacks: { label: c => ' ' + fmtKr(c.parsed.y) },
        backgroundColor: '#1a1714',
        titleColor: '#f5f2eb',
        bodyColor: 'rgba(245,242,235,0.7)',
        padding: 10,
        cornerRadius: 4,
        titleFont: { family: 'DM Sans', size: 12 },
        bodyFont: { family: 'DM Sans', size: 12 }
      }
    },
    scales: {
      x: {
        ticks: { color: TICK_COLOR, font: { size: 11, family: 'DM Sans' }, autoSkip: false, maxRotation: 0 },
        grid: { display: false },
        border: { color: 'rgba(0,0,0,0.1)' }
      },
      y: {
        ticks: { color: TICK_COLOR, font: { size: 11, family: 'DM Sans' }, callback: v => fmtShort(v) },
        grid: { color: GRID_COLOR },
        border: { dash: [3, 3], color: 'transparent' }
      }
    }
  };
}

// Diagram 1: Formue over tid (to linjer)
const chart1 = new Chart(document.getElementById('chart1'), {
  type: 'line',
  data: { labels: [], datasets: [
    { data: [], borderColor: '#1a4a8a', backgroundColor: 'rgba(26,74,138,0.07)', fill: true, tension: 0.35, pointRadius: 0, borderWidth: 2 },
    { data: [], borderColor: '#c0392b', backgroundColor: 'rgba(192,57,43,0.07)', fill: true, tension: 0.35, pointRadius: 0, borderWidth: 2 }
  ]},
  options: baseOpts()
});

// Diagram 2: Forskjell i formue (gap)
const chart2 = new Chart(document.getElementById('chart2'), {
  type: 'line',
  data: { labels: [], datasets: [
    { data: [], borderColor: '#4a3a8a', backgroundColor: 'rgba(74,58,138,0.1)', fill: true, tension: 0.35, pointRadius: 0, borderWidth: 2 }
  ]},
  options: baseOpts()
});

// Diagram 3: Stacked bar — innskudd + renter for A og B
const chart3Opts = baseOpts();
chart3Opts.scales.x.stacked = true;
chart3Opts.scales.y.stacked = true;
const chart3 = new Chart(document.getElementById('chart3'), {
  type: 'bar',
  data: { labels: [], datasets: [
    { label: 'Innskudd', data: [], backgroundColor: '#1a4a8a', stack: 'A' },
    { label: 'Renter A', data: [], backgroundColor: 'rgba(26,74,138,0.35)', stack: 'A' },
    { label: 'Innskudd', data: [], backgroundColor: '#c0392b', stack: 'B' },
    { label: 'Renter B', data: [], backgroundColor: 'rgba(192,57,43,0.35)', stack: 'B' }
  ]},
  options: chart3Opts
});

// SIKKERHETSNOTAT: Alle verdier i innerHTML-kall er utelukkende beregnet fra
// numeriske slider-verdier (range inputs). Ingen bruker-tekstinput brukes.
function update() {
  const { P, rA, rB, Y, labels, valA, valB, gaps, deposits, interestA, interestB } = getData();

  // Oppdater slider-visning
  document.querySelectorAll('.yr-lbl').forEach(el => el.textContent = Y);
  document.getElementById('monthly-out').textContent = Math.round(P).toLocaleString('nb-NO') + '\u202fkr';
  document.getElementById('rateA-out').textContent = (rA * 100).toLocaleString('nb-NO', { minimumFractionDigits: 1 }) + '\u202f%';
  document.getElementById('rateB-out').textContent = (rB * 100).toLocaleString('nb-NO', { minimumFractionDigits: 1 }) + '\u202f%';
  document.getElementById('yrs-out').textContent = Y + '\u202får';

  const totalPaid = P * 12 * Y;

  // Statistikkort
  document.getElementById('st-valA').textContent = fmtKr(valA[Y]);
  document.getElementById('st-subA').textContent = 'herav ' + fmtKr(interestA[Y]) + ' i renter';
  document.getElementById('st-valB').textContent = fmtKr(valB[Y]);
  document.getElementById('st-subB').textContent = 'herav ' + fmtKr(interestB[Y]) + ' i renter';
  document.getElementById('st-diff').textContent = fmtKr(gaps[Y]);
  const ppDiff = Math.abs(rB * 100 - rA * 100);
  document.getElementById('st-diff-sub').textContent = 'pga. ' + ppDiff.toLocaleString('nb-NO', { minimumFractionDigits: 1 }) + ' pp forskjell';
  document.getElementById('st-paid').textContent = fmtKr(totalPaid);

  // Banner
  document.getElementById('banner-gap').textContent = fmtKr(gaps[Y]);

  // Innsikt
  const insightEl = document.getElementById('insight');
  insightEl.textContent = '';
  const parts = [
    { text: 'Dere betalte inn like mye: ' },
    { text: fmtKr(totalPaid), bold: true },
    { text: '. Men B har ' },
    { text: fmtKr(gaps[Y]), bold: true },
    { text: ' mer — kun pga. ' + ppDiff.toLocaleString('nb-NO', { minimumFractionDigits: 1 }) + ' prosentpoeng høyere avkastning.' }
  ];
  parts.forEach(p => {
    if (p.bold) {
      const strong = document.createElement('strong');
      strong.textContent = p.text;
      insightEl.appendChild(strong);
    } else {
      insightEl.appendChild(document.createTextNode(p.text));
    }
  });

  // Diagram 1: Formue over tid
  chart1.data.labels = labels;
  chart1.data.datasets[0].data = valA;
  chart1.data.datasets[1].data = valB;
  chart1.update('none');

  // Diagram 2: Gap
  chart2.data.labels = labels;
  chart2.data.datasets[0].data = gaps;
  chart2.update('none');

  // Diagram 3: Stacked bar — sample hvert 5. år for lesbarhet
  const barLabels = [], barDep = [], barIntA = [], barDepB = [], barIntB = [];
  for (let y = 0; y <= Y; y++) {
    if (y === 0 || y % 5 === 0 || y === Y) {
      barLabels.push(y === 0 ? 'I dag' : 'År ' + y);
      barDep.push(deposits[y]);
      barIntA.push(interestA[y]);
      barDepB.push(deposits[y]);
      barIntB.push(interestB[y]);
    }
  }
  chart3.data.labels = barLabels;
  chart3.data.datasets[0].data = barDep;
  chart3.data.datasets[1].data = barIntA;
  chart3.data.datasets[2].data = barDepB;
  chart3.data.datasets[3].data = barIntB;
  chart3.update('none');
}

['monthly', 'rateA', 'rateB', 'yrs'].forEach(id =>
  document.getElementById(id).addEventListener('input', update)
);
update();