refactor: isolate Radio controls and tuner presentation

src/ui/radioTunerModel.js

@@ -0,0 +1,87 @@
+/** Map an integer tuner slot directly to one available directory station. */
+export function radioTunerSlot(value, stationCount) {
+  const count = Math.max(0, Math.floor(Number(stationCount) || 0));
+  if (!count) return { slot: 0, max: 0, locked: false, stationIndex: -1, leftIndex: -1, rightIndex: -1 };
+  const max = Math.max(0, count - 1);
+  const slot = Math.min(max, Math.max(0, Math.round(Number(value) || 0)));
+  return {
+    slot,
+    max,
+    locked: true,
+    stationIndex: slot,
+    leftIndex: slot,
+    rightIndex: slot,
+  };
+}
+
+/** Snap a tuner release to the nearest available directory station. */
+export function radioTunerCommitSlot(value, stationCount) {
+  return radioTunerSlot(value, stationCount);
+}
+
+/** Map one pointer coordinate to continuous absolute directory progress. */
+export function radioTunerPointerPosition(clientX, left, width, stationCount, insetPx = 7) {
+  const count = Math.max(0, Math.floor(Number(stationCount) || 0));
+  if (!count) return { ratio: 0, coordinate: 0, stationIndex: -1 };
+  if (count === 1) return { ratio: 0.5, coordinate: 0, stationIndex: 0 };
+  const inset = Math.max(0, Number(insetPx) || 0);
+  const usableWidth = Math.max(1, (Number(width) || 0) - inset * 2);
+  const ratio = Math.min(1, Math.max(0, ((Number(clientX) || 0) - (Number(left) || 0) - inset) / usableWidth));
+  const coordinate = ratio * (count - 1);
+  return {
+    ratio,
+    coordinate,
+    stationIndex: Math.min(count - 1, Math.max(0, Math.floor(coordinate + 0.5))),
+  };
+}
+
+/** Build a bounded virtual tuner tape around one continuous directory coordinate. */
+export function buildRadioTunerTicks(coordinate, stationCount, width, {
+  insetPx = 7,
+  minPitchPx = 14,
+  speedFactor = 5,
+  overscan = 2,
+  labelStep = 6,
+} = {}) {
+  const count = Math.max(0, Math.floor(Number(stationCount) || 0));
+  const dialWidth = Math.max(0, Number(width) || 0);
+  const inset = Math.max(0, Number(insetPx) || 0);
+  const usableWidth = Math.max(0, dialWidth - inset * 2);
+  if (!count) return { ticks: [], needleX: inset, pitchPx: 0, ratio: 0 };
+  const value = Math.min(count - 1, Math.max(0, Number(coordinate) || 0));
+  if (count === 1) {
+    return {
+      ticks: [{ stationIndex: 0, channel: 1, xPx: inset + usableWidth / 2, current: true, label: '01' }],
+      needleX: inset + usableWidth / 2,
+      pitchPx: Math.max(1, Number(minPitchPx) || 14),
+      ratio: 0.5,
+    };
+  }
+  const directoryStep = usableWidth / (count - 1);
+  const pitchPx = Math.max(
+    Math.max(1, Number(minPitchPx) || 14),
+    directoryStep * Math.max(1, Number(speedFactor) || 5),
+  );
+  const needleX = inset + directoryStep * value;
+  const overscanPx = pitchPx * Math.max(0, Number(overscan) || 0);
+  const first = Math.max(0, Math.ceil(value + (-overscanPx - needleX) / pitchPx));
+  const last = Math.min(count - 1, Math.floor(value + (dialWidth + overscanPx - needleX) / pitchPx));
+  const currentIndex = Math.min(count - 1, Math.max(0, Math.floor(value + 0.5)));
+  const majorEvery = Math.max(1, Math.floor(Number(labelStep) || 6));
+  const labelWidth = Math.max(2, String(count).length);
+  const ticks = [];
+  for (let stationIndex = first; stationIndex <= last; stationIndex += 1) {
+    const channel = stationIndex + 1;
+    const current = stationIndex === currentIndex;
+    const labelled = current || stationIndex === 0 || stationIndex === count - 1 || channel % majorEvery === 0;
+    ticks.push({
+      stationIndex,
+      channel,
+      xPx: needleX + pitchPx * (stationIndex - value),
+      current,
+      label: labelled ? String(channel).padStart(labelWidth, '0') : '',
+    });
+  }
+  return { ticks, needleX, pitchPx, ratio: value / (count - 1) };
+}
+