dickloads/src/routes/+page.svelte

<script lang="ts">
  import { browser } from '$app/environment';
  import { goto } from '$app/navigation';
  import { page } from '$app/state';
  import { florpUnits } from '$lib/units/definitions';
  import { convertById } from '$lib/convert';
  import { FRACTIONAL_DIGITS } from '$lib/config';
  import { formatBig } from '$lib/format';
  import Big from 'big.js';
  import type { Unit, ResultItem } from '$lib/types';
  import ConverterCard from '../components/ConverterCard.svelte';

  /**
   * Converter page — owns all reactive state.
   * Phase 2: live conversion, URL state, highlight interaction.
   * Phase 3 will add NL input.
   */

  const units: Unit[] = florpUnits;

  // ── Reactive state ──────────────────────────────────────────────────────────
  let inputValue = $state<number>(1);
  let fromUnitId = $state<string>(units[0].id);
  let highlightedUnitId = $state<string | null>(null);

  // ── Initialize from URL params on first client-side load ───────────────────
  if (browser) {
    const params = page.url.searchParams;
    const pValue = params.get('value');
    const pFrom = params.get('from');
    const pHighlight = params.get('highlight');

    if (pValue !== null) {
      const n = parseFloat(pValue);
      if (!isNaN(n)) inputValue = n;
    }
    if (pFrom !== null && units.some((u) => u.id === pFrom)) {
      fromUnitId = pFrom;
    }
    if (pHighlight !== null && units.some((u) => u.id === pHighlight)) {
      highlightedUnitId = pHighlight;
    }
  }

  // ── Derived: results for ALL units in definition order ─────────────────────
  // convert.ts already handles the same-unit identity (from.id === to.id → return value),
  // so no special-casing needed here for the from-unit.
  let results = $derived<ResultItem[]>(
    units.map((u) => ({
      unit: u,
      convertedValue: convertById(inputValue, fromUnitId, u.id, units)
    }))
  );

  // ── Derived: highlighted result (unit + value) sourced from full results ────
  // Results now includes all units, so from-unit can be highlighted too.
  let highlightedResult = $derived(
    highlightedUnitId !== null
      ? (results.find((r) => r.unit.id === highlightedUnitId) ?? null)
      : null
  );

  let fromUnit = $derived(units.find(u => u.id === fromUnitId) ?? units[0]);

  // ── URL sync: update URL only when serialized params actually change ────────
  $effect(() => {
    if (!browser) return;
    const params = new URLSearchParams();
    params.set('value', String(inputValue));
    params.set('from', fromUnitId);
    if (highlightedUnitId !== null) {
      params.set('highlight', highlightedUnitId);
    }
    const next = params.toString();
    if (next !== window.location.search.slice(1)) {
      goto(`?${next}`, { replaceState: true, noScroll: true });
    }
  });

  // ── Event handlers ──────────────────────────────────────────────────────────
  function handleUnitChange(id: string) {
    fromUnitId = id;
    // Clear highlight if the selected unit becomes the new from-unit.
    if (highlightedUnitId === id) {
      highlightedUnitId = null;
    }
  }

  function handleHighlight(id: string) {
    highlightedUnitId = id === highlightedUnitId ? null : id;
  }

  function handleSetInput(id: string) {
    // Shift+click: promote result unit to from-unit.
    // inputValue is NOT changed — outputs recalculate from the same inputValue with the new fromUnitId.
    // highlightedUnitId is NOT cleared — the two states are independent.
    fromUnitId = id;
  }

  function handleCtrlClick(id: string, convertedValue: Big) {
    // Ctrl+click: adopt this tile's displayed value as the new inputValue and promote it to from-unit.
    // This is the "pivot" gesture.
    inputValue = parseFloat(convertedValue.toFixed(FRACTIONAL_DIGITS));
    fromUnitId = id;
  }
</script>

<svelte:head>
  <title>Humor Units — Converter</title>
</svelte:head>

<div class="highlighted-result" class:has-highlight={highlightedResult !== null} aria-live="polite">
  {#if highlightedResult !== null}
    <button class="highlight-dismiss" onclick={() => (highlightedUnitId = null)} aria-label="Remove highlight">×</button>
    <div class="highlighted-equation">
      <span class="highlighted-eq-from">{formatBig(new Big(inputValue))} {fromUnit.labelPlural}</span>
      <span class="highlighted-eq-sep">=</span>
      <span class="highlighted-eq-to">{formatBig(highlightedResult.convertedValue)} {highlightedResult.unit.labelPlural}</span>
    </div>
    <span class="highlighted-symbol">{highlightedResult.unit.symbol}</span>
  {:else}
    <span class="highlighted-placeholder">Click a result to highlight it</span>
  {/if}
</div>

<ConverterCard
  {units}
  {inputValue}
  {fromUnitId}
  {highlightedUnitId}
  {results}
  oninputchange={(v) => (inputValue = v)}
  onunitchange={handleUnitChange}
  onhighlight={handleHighlight}
  onsetinput={handleSetInput}
  onctrlclick={handleCtrlClick}
/>