mpckit/frontend/src/App.svelte

<script lang="ts">
  import { onMount } from "svelte";
  import AboutModal from "./lib/AboutModal.svelte";
  import BankBar from "./lib/BankBar.svelte";
  import PadPanel from "./lib/PadPanel.svelte";
  import SequencePanel from "./lib/SequencePanel.svelte";
  import SlotGrid, { type Cell } from "./lib/SlotGrid.svelte";
  import { app, newProject, refresh, ui, type Tab } from "./lib/store.svelte";
  import { BANKS, PER_BANK, bars, gridSlots, tuneText } from "./lib/slots";

  onMount(refresh);

  const st = $derived(app.state);
  // The bindings type Go slices as `T[] | null`; Go always sends arrays.
  const pads = $derived(st?.pads ?? []);

  // Sequences by slot, for the grid and the panel.
  const seqBySlot = $derived(new Map((st?.sequences ?? []).map((q) => [q.slot, q])));

  function perBank(filled: (slot: number) => boolean): number[] {
    return Array.from({ length: BANKS.length }, (_, b) => {
      let n = 0;
      for (let i = 0; i < PER_BANK; i++) if (filled(b * PER_BANK + i)) n++;
      return n;
    });
  }

  const padCounts = $derived(perBank((s) => (pads[s]?.file ?? "") !== ""));
  const seqCounts = $derived(perBank((s) => seqBySlot.has(s)));

  const padCells: Cell[] = $derived(
    st
      ? gridSlots(ui.padBank).map((slot) => {
          const p = pads[slot];
          const badges = [tuneText(p.coarse, p.fine), p.muteGroup ? "M" + p.muteGroup : ""].filter(Boolean);
          return {
            slot,
            label: p.label,
            name: p.name,
            meta: p.file ? badges.join(" · ") : "",
            aria: `Pad ${p.label}, ${p.file || "empty"}`,
          };
        })
      : [],
  );

  const seqCells: Cell[] = $derived(
    st
      ? gridSlots(ui.seqBank).map((slot) => {
          const q = seqBySlot.get(slot);
          const label = pads[slot].label; // pad and sequence slots share labels
          return {
            slot,
            label,
            name: q?.name ?? "",
            meta: q ? `${q.bpm} · ${bars(q.bars)}` : "",
            aria: `Sequence slot ${label}, ${q?.name ?? "empty"}`,
          };
        })
      : [],
  );

  function pickTab(t: Tab) {
    ui.tab = t;
  }

  // Arrow keys move between the two tabs, as in the WAI-ARIA tabs pattern.
  function tabKey(e: KeyboardEvent) {
    if (e.key === "ArrowLeft" || e.key === "ArrowRight") {
      ui.tab = ui.tab === "pads" ? "sequences" : "pads";
      document.getElementById("tab-" + ui.tab)?.focus();
    }
  }
</script>

<div class="page">
  <header>
    <h1>mpckit</h1>
    <div class="name">
      <label class="eyebrow" for="project-name">Project name</label>
      <input id="project-name" type="text" value={st?.name ?? ""} readonly />
    </div>
    <div class="actions">
      <button type="button" class="btn" onclick={newProject}>New</button>
      <button type="button" class="btn" disabled>Load</button>
      <button type="button" class="btn" disabled>Export zip</button>
      <button type="button" class="btn primary" disabled>Export to folder</button>
    </div>
    <button type="button" class="about-link" onclick={() => (ui.aboutOpen = true)}>About</button>
  </header>

  {#if app.error}
    <p class="error" role="alert">{app.error}</p>
  {/if}

  <div class="tabs" role="tablist" aria-label="Views">
    <button id="tab-pads" type="button" role="tab" aria-selected={ui.tab === "pads"} aria-controls="view-pads" tabindex={ui.tab === "pads" ? 0 : -1} onclick={() => pickTab("pads")} onkeydown={tabKey}>Pads</button>
    <button id="tab-sequences" type="button" role="tab" aria-selected={ui.tab === "sequences"} aria-controls="view-sequences" tabindex={ui.tab === "sequences" ? 0 : -1} onclick={() => pickTab("sequences")} onkeydown={tabKey}>Sequences</button>
  </div>

  {#if st}
    {#if ui.tab === "pads"}
      <div id="view-pads" class="panels" role="tabpanel" aria-labelledby="tab-pads">
        <section class="panel grid-panel" aria-label="Pads">
          <div class="grid-head">
            <h2 class="eyebrow">Pad bank</h2>
            <span class="mono summary">Bank {BANKS[ui.padBank]} · {padCounts[ui.padBank]} of 16 filled</span>
          </div>
          <BankBar
            bank={ui.padBank}
            counts={padCounts}
            what="pads filled"
            onpick={(b) => {
              ui.padBank = b;
              ui.padSlot = b * PER_BANK;
            }}
          />
          <SlotGrid cells={padCells} selected={ui.padSlot} onpick={(s) => (ui.padSlot = s)} />
          <p class="hint grid-hint">Click a pad to select and hear it. Drag a pad to move it, drag onto a filled pad to swap, hold Alt while dragging to copy. Drop a WAV file on any pad to assign it.</p>
        </section>
        <PadPanel pad={pads[ui.padSlot]} limits={st.limits} />
      </div>
    {:else}
      <div id="view-sequences" class="panels" role="tabpanel" aria-labelledby="tab-sequences">
        <section class="panel grid-panel" aria-label="Sequence slots">
          <div class="grid-head">
            <h2 class="eyebrow">Sequence bank</h2>
            <span class="mono summary">Bank {BANKS[ui.seqBank]} · {seqCounts[ui.seqBank]} of 16 used</span>
          </div>
          <BankBar
            bank={ui.seqBank}
            counts={seqCounts}
            what="slots used"
            onpick={(b) => {
              ui.seqBank = b;
              ui.seqSlot = b * PER_BANK;
            }}
          />
          <SlotGrid cells={seqCells} selected={ui.seqSlot} onpick={(s) => (ui.seqSlot = s)} />
          <p class="hint grid-hint">Each pad is one sequence slot, {st.limits.maxSequences} in total. Click an empty slot to add a sequence there.</p>
        </section>
        <SequencePanel slot={ui.seqSlot} seq={seqBySlot.get(ui.seqSlot)} limits={st.limits} />
      </div>
    {/if}

    <footer class="mono">
      <span>{st.sampleCount} of {st.limits.maxSamples} samples</span>
      <span>{st.sequenceCount} of {st.limits.maxSequences} sequences</span>
      <span>WAV files only</span>
    </footer>
  {:else if !app.error}
    <p class="hint">Loading…</p>
  {/if}

  {#if ui.aboutOpen}
    <AboutModal onclose={() => (ui.aboutOpen = false)} />
  {/if}
</div>

<style>
  /* Exactly the window's height: header, tabs, panels (which take the rest)
     and footer. Nothing scrolls at the page level. */
  .page {
    height: 100%;
    max-width: 1440px;
    margin: 0 auto;
    padding: 12px 20px;
    display: flex;
    flex-direction: column;
    gap: 12px;
  }
  h1 {
    margin: 0;
    font-family: var(--display);
    font-weight: 700;
    font-size: 24px;
    letter-spacing: 0.02em;
  }
  .about-link {
    min-height: 40px;
    padding: 0 8px;
    background: transparent;
    color: var(--accent);
    border: 0;
    font: inherit;
    font-weight: 500;
    text-decoration: underline;
    text-underline-offset: 3px;
    cursor: pointer;
  }
  header {
    flex: none;
    display: flex;
    align-items: center;
    gap: 16px;
    padding-bottom: 12px;
    border-bottom: 1px solid var(--line);
  }
  .name {
    display: flex;
    align-items: center;
    gap: 10px;
    flex: 1 1 auto;
    min-width: 0;
    max-width: 380px;
  }
  .name label {
    white-space: nowrap;
  }
  .name input {
    height: 40px;
    min-width: 120px;
    padding: 0 12px;
    background: var(--surface);
    color: var(--text);
    border: 1px solid var(--edge);
    border-radius: 6px;
    font: inherit;
    font-weight: 600;
    width: 100%;
  }
  .actions {
    display: flex;
    gap: 8px;
    margin-left: auto;
  }
  .tabs {
    flex: none;
    display: flex;
    gap: 4px;
    border-bottom: 1px solid var(--line);
  }
  .tabs button {
    height: 40px;
    padding: 0 22px;
    background: transparent;
    color: var(--muted);
    border: 0;
    border-bottom: 3px solid transparent;
    font-family: var(--display);
    font-size: 16px;
    font-weight: 700;
    cursor: pointer;
  }
  .tabs button[aria-selected="true"] {
    color: var(--text);
    border-bottom-color: var(--accent);
  }
  .grid-head {
    display: flex;
    align-items: baseline;
    justify-content: space-between;
    gap: 12px;
  }
  .summary {
    font-size: 12px;
    color: var(--muted);
  }
  footer {
    flex: none;
    display: flex;
    flex-wrap: wrap;
    gap: 8px 24px;
    font-size: 12px;
    color: var(--muted);
  }
  /* Narrow window: drop the visible name label (the input keeps it). */
  @media (max-width: 1100px) {
    .name label {
      position: absolute;
      width: 1px;
      height: 1px;
      overflow: hidden;
      clip-path: inset(50%);
    }
  }
  /* Short window: give the grid the hint's lines. */
  @media (max-height: 600px) {
    .grid-hint {
      display: none;
    }
  }
  .error {
    flex: none;
    margin: 0;
    padding: 10px 12px;
    border: 1px solid #e5484d;
    border-radius: 6px;
    color: #ffb4b4;
  }
</style>