(function(){
  'use strict';
  const $ = id => document.getElementById(id);
  const form = $('topsoil-form');
  if (!form || !window.SCT) return;

  const projectDefaults = {
    'lawn-leveling': {depth:1, tip:'A 1-inch layer is common for light lawn leveling.'},
    'new-lawn': {depth:4, tip:'New lawns often use 4–6 inches over poor subsoil.'},
    'garden-bed': {depth:6, tip:'Garden and flower beds commonly use about 6–8 inches.'},
    'raised-bed': {depth:12, tip:'Use the actual interior depth of the raised bed.'},
    'custom': {depth:3, tip:'Enter the depth needed for your specific project.'}
  };

  function updateShape(){
    const shape = $('shape').value;
    document.querySelectorAll('.shape-rectangle,.shape-triangle,.shape-circle,.shape-custom').forEach(el => { el.hidden = true; });
    document.querySelectorAll(`.shape-${shape}`).forEach(el => { el.hidden = false; });
    $('length-label').textContent = shape === 'triangle' ? 'Triangle base' : 'Length';
    $('width-label').textContent = shape === 'triangle' ? 'Triangle height' : 'Width';
  }

  function updateDensity(){
    $('custom-density-wrap').hidden = $('density').value !== 'custom';
  }

  function updateProject(setDepth){
    const item = projectDefaults[$('project-type').value];
    $('project-tip').textContent = item.tip;
    if (setDepth) $('depth').value = item.depth;
  }

  function calculate(event){
    if (event) event.preventDefault();
    SCT.showError($('topsoil-error'), '');

    const shape = $('shape').value;
    const quantity = Math.max(1, SCT.integer($('quantity').value, 1));
    const length = SCT.positive($('length').value);
    const width = SCT.positive($('width').value);
    const diameter = SCT.positive($('diameter').value);
    const knownArea = SCT.positive($('known-area').value);
    const depth = SCT.positive($('depth').value);
    const waste = SCT.positive($('waste').value);
    const density = $('density').value === 'custom' ? SCT.positive($('custom-density').value) : Number($('density').value);
    const bagType = $('bag-type').value;
    const bagPrice = SCT.positive($('bag-price').value);
    const yardPrice = SCT.positive($('yard-price').value);
    const delivery = SCT.positive($('delivery').value);
    const pickupCapacity = SCT.positive($('pickup-capacity').value, 1);
    const dumpCapacity = SCT.positive($('dump-capacity').value, 10);

    let areaSingle = 0;
    if (shape === 'circle') {
      if (!diameter) return SCT.showError($('topsoil-error'), 'Enter a positive diameter.');
      areaSingle = Math.PI * Math.pow(diameter / 2, 2);
    } else if (shape === 'custom') {
      if (!knownArea) return SCT.showError($('topsoil-error'), 'Enter a positive square footage.');
      areaSingle = knownArea;
    } else {
      if (!length || !width) return SCT.showError($('topsoil-error'), 'Enter positive area dimensions.');
      areaSingle = shape === 'triangle' ? (length * width) / 2 : length * width;
    }
    if (!depth || !density) return SCT.showError($('topsoil-error'), 'Enter a positive depth and soil density.');

    const area = areaSingle * quantity;
    const baseFeet = area * (depth / 12);
    const cubicFeet = baseFeet * (1 + waste / 100);
    const exactYards = cubicFeet / 27;
    const bulkYards = Math.ceil(exactYards * 4) / 4;
    const pounds = exactYards * density;
    const tons = pounds / 2000;

    let bagVolume = 0;
    let bagLabel = '';
    if (bagType === '40lb') {
      bagVolume = 40 / (density / 27);
      bagLabel = '40 lb bags';
    } else {
      bagVolume = Number(bagType);
      bagLabel = `${bagType} cu ft bags`;
    }
    const bags = Math.ceil(cubicFeet / bagVolume);
    const bagCost = bags * bagPrice;
    const bulkCost = bulkYards * yardPrice + delivery;
    const pickupExact = exactYards / pickupCapacity;
    const dumpExact = exactYards / dumpCapacity;
    const pickupLoads = Math.ceil(pickupExact);
    const dumpLoads = Math.ceil(dumpExact);

    let bestCost = '—';
    let guidance = `Plan to buy about ${SCT.format(bulkYards, 2)} cubic yards, or ${SCT.plural(bags, 'bag')} if purchasing ${bagLabel}.`;
    if (bagPrice && yardPrice) {
      const useBags = bagCost <= bulkCost;
      bestCost = SCT.money(Math.min(bagCost, bulkCost));
      guidance += ` Based on the entered prices, ${useBags ? 'bagged topsoil' : 'bulk topsoil including delivery'} is less expensive.`;
    } else if (bagPrice) bestCost = SCT.money(bagCost);
    else if (yardPrice) bestCost = SCT.money(bulkCost);
    if (pickupLoads > 1) guidance += ' Verify your vehicle payload before hauling; topsoil is heavy.';

    SCT.setText('topsoil-main-result', `${SCT.format(bulkYards, 2)} cubic yards`);
    SCT.setText('shopping-list', `${SCT.format(tons, 2)} tons estimated, or ${SCT.plural(bags, 'bag')}.`);
    SCT.setText('cubic-yards', `${SCT.format(bulkYards, 2)} yd³`);
    SCT.setText('tons-needed', `${SCT.format(tons, 2)} tons`);
    SCT.setText('bags-needed', SCT.plural(bags, 'bag'));
    SCT.setText('best-cost', bestCost);
    SCT.setText('buying-guidance', guidance);
    SCT.setText('area-result', `${SCT.format(area, 1)} ft²`);
    SCT.setText('cubic-feet', `${SCT.format(cubicFeet, 1)} ft³`);
    SCT.setText('exact-yards', `${SCT.format(exactYards, 2)} yd³`);
    SCT.setText('weight-result', `${SCT.format(pounds, 0)} lb`);
    SCT.setText('bag-cost', bagPrice ? SCT.money(bagCost) : '—');
    SCT.setText('bulk-cost', yardPrice ? SCT.money(bulkCost) : '—');
    SCT.setText('pickup-loads', `${SCT.plural(pickupLoads, 'load')} (${SCT.format(pickupExact, 2)} exact)`);
    SCT.setText('dump-loads', `${SCT.plural(dumpLoads, 'load')} (${SCT.format(dumpExact, 2)} exact)`);
  }

  function loadExample(){
    const values = {
      'project-type':'lawn-leveling', shape:'rectangle', quantity:'1', length:'30', width:'20', diameter:'20', 'known-area':'600', depth:'1', waste:'10', density:'2200', 'custom-density':'2200', 'bag-type':'40lb', 'bag-price':'3.98', 'yard-price':'38', delivery:'65', 'pickup-capacity':'1', 'dump-capacity':'10'
    };
    Object.entries(values).forEach(([id,value]) => { $(id).value = value; });
    updateProject(false); updateShape(); updateDensity(); calculate();
  }

  form.addEventListener('submit', calculate);
  $('shape').addEventListener('change', () => { updateShape(); calculate(); });
  $('density').addEventListener('change', () => { updateDensity(); calculate(); });
  $('project-type').addEventListener('change', () => { updateProject(true); calculate(); });
  $('bag-type').addEventListener('change', calculate);
  $('example-btn').addEventListener('click', loadExample);
  $('reset-btn').addEventListener('click', () => SCT.reset(form, () => { updateProject(false); updateShape(); updateDensity(); calculate(); }));
  $('print-btn').addEventListener('click', SCT.print);
  updateProject(false); updateShape(); updateDensity(); calculate();
})();