// 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
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 inheritance = +document.getElementById('inheritance').value;
  const P = +document.getElementById('monthly').value;
  const rate = +document.getElementById('rate').value / 100;
  const Y = +document.getElementById('yrs').value;

  const labels = [], wealthA = [], wealthB = [], gaps = [], arvPct = [];

  for (let y = 0; y <= Y; y++) {
    labels.push(y === 0 ? 'I dag' : (y % 5 === 0 || Y <= 10 || y === Y) ? 'År ' + y : '');

    // A = ren annuitet (starter fra null)
    const a = futureValue(P, rate, y);

    // B = arv med rentes rente + samme annuitet
    const arvGrown = inheritance * Math.pow(1 + rate, y);
    const b = arvGrown + futureValue(P, rate, y);

    // Gap = Arv × (1+r)^n — vokser alltid
    const gap = arvGrown;

    wealthA.push(a);
    wealthB.push(b);
    gaps.push(gap);

    // Arvens andel av Bs formue (prosent)
    arvPct.push(b > 0 ? (arvGrown / b) * 100 : 0);
  }

  return { inheritance, P, rate, Y, labels, wealthA, wealthB, gaps, arvPct };
}

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' }
      }
    }
  };
}

// Tilpasset y-akse for prosentdiagram
function pctOpts() {
  const opts = baseOpts();
  opts.scales.y.min = 0;
  opts.scales.y.max = 100;
  opts.scales.y.ticks = {
    color: TICK_COLOR,
    font: { size: 11, family: 'DM Sans' },
    callback: v => v + ' %'
  };
  opts.plugins.tooltip.callbacks = {
    label: c => ' ' + c.parsed.y.toFixed(1) + ' %'
  };
  return opts;
}

// Diagram 1: Formue over tid
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: Absolutt forskjell (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: Arvens andel av Bs formue (prosent — tilpasset y-akse)
const chart3 = new Chart(document.getElementById('chart3'), {
  type: 'line',
  data: { labels: [], datasets: [
    { data: [], borderColor: '#b5620a', backgroundColor: 'rgba(181,98,10,0.1)', fill: true, tension: 0.35, pointRadius: 0, borderWidth: 2 }
  ]},
  options: pctOpts()
});

// SIKKERHETSNOTAT: Alle verdier er beregnet fra numeriske slider-verdier.
// Ingen bruker-tekstinput brukes i DOM-oppdateringer.
function update() {
  const { inheritance, P, rate, Y, labels, wealthA, wealthB, gaps, arvPct } = getData();

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

  // Statistikkort
  document.getElementById('st-valA').textContent = fmtKr(wealthA[Y]);
  document.getElementById('st-valB').textContent = fmtKr(wealthB[Y]);
  document.getElementById('st-subB').textContent = 'herav ' + fmtKr(gaps[Y]) + ' fra arv';
  document.getElementById('st-gap').textContent = fmtKr(gaps[Y]);
  const multiplier = (gaps[Y] / inheritance).toFixed(1).replace('.', ',');
  document.getElementById('st-gap-sub').textContent = multiplier + '× opprinnelig arv';
  document.getElementById('st-grown').textContent = fmtKr(gaps[Y]);
  document.getElementById('st-grown-sub').textContent = 'fra ' + fmtKr(inheritance);

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

  // Innsikt — bruker DOM-metoder for sikkerhet
  const insightEl = document.getElementById('insight');
  insightEl.textContent = '';
  const parts = [
    { text: 'A sparte like mye som B i ' + Y + ' år. Men arven på ' },
    { text: fmtKr(inheritance), bold: true },
    { text: ' har vokst til ' },
    { text: fmtKr(gaps[Y]), bold: true },
    { text: ' — og gapet kan aldri lukkes.' }
  ];
  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
  chart1.data.labels = labels;
  chart1.data.datasets[0].data = wealthA;
  chart1.data.datasets[1].data = wealthB;
  chart1.update('none');

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

  // Diagram 3: Arvens prosentandel
  chart3.data.labels = labels;
  chart3.data.datasets[0].data = arvPct;
  chart3.update('none');
}

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