1 files changed, 144 insertions, 0 deletions
diff --git a/src/modules/game/sight_line.js b/src/modules/game/sight_line.js
new file mode 100644
index 0000000..411faa8
--- /dev/null
+++ b/src/modules/game/sight_line.js
@@ -0,0 +1,144 @@
+const targetClassName = 'sight-line-target',
+  activeClassName = 'active';
+
+function evenr_to_axial(x, y) {
+  return { q: x - (y + (y & 1)) / 2, r: y };
+}
+
+function axial_to_evenr(q, r) {
+  return { x: q + (r + (r & 1)) / 2, y: r };
+}
+
+function axial_distance(q1, r1, q2, r2) {
+  return (Math.abs(q1 - q2) + Math.abs(q1 + r1 - q2 - r2) + Math.abs(r1 - r2)) / 2;
+}
+
+function offset_distance(x1, y1, x2, y2) {
+  const { q: q1, r: r1 } = evenr_to_axial(x1, y1),
+    { q: q2, r: r2 } = evenr_to_axial(x2, y2);
+
+  return axial_distance(q1, r1, q2, r2);
+}
+
+function cube_to_axial(q, r, _) {
+  return { q, r };
+}
+
+function axial_to_cube(q, r) {
+  return { q, r, s: -q - r };
+}
+
+function cube_round(q, r, s) {
+  let rQ = Math.round(q),
+    rR = Math.round(r),
+    rS = Math.round(s);
+
+  const q_diff = Math.abs(rQ - q),
+    r_diff = Math.abs(rR - r),
+    s_diff = Math.abs(rS - s);
+
+  if (q_diff > r_diff && q_diff > s_diff) {
+    rQ = -rR - rS;
+  } else if (r_diff > s_diff) {
+    rR = -rQ - rS;
+  } else {
+    rS = -rQ - rR;
+  }
+
+  return { q: rQ, r: rR, s: rS };
+}
+
+function axial_round(q, r) {
+  const cube = axial_to_cube(q, r),
+    round = cube_round(cube.q, cube.r, cube.s),
+    axial = cube_to_axial(round.q, round.r, round.s);
+
+  return { q: axial.q, r: axial.r };
+}
+
+function lerp(a, b, t) {
+  return a + (b - a) * t;
+}
+
+function axial_lerp(q1, r1, q2, r2, t) {
+  return { q: lerp(q1, q2, t), r: lerp(r1, r2, t) };
+}
+
+function lock(sightLine, cell) {
+  sightLine.classList.remove(activeClassName);
+  cell.classList.add(targetClassName);
+
+  return cell;
+}
+
+function unlock(sightLine, lockTarget) {
+  sightLine.classList.add(activeClassName);
+  lockTarget.classList.remove(targetClassName);
+
+  return null;
+}
+
+let sightLine, lockTarget,
+  activeHexes = [];
+
+export function create({ x: x1, y: y1 }, { x: x2, y: y2 }) {
+  const line = document.createElementNS(svgns, 'line');
+  sightLine = line;
+
+  line.classList.add('sight-line');
+  line.classList.add(activeClassName);
+  line.setAttributeNS(null, 'x1', x1);
+  line.setAttributeNS(null, 'y1', y1);
+  line.setAttributeNS(null, 'x2', x2);
+  line.setAttributeNS(null, 'y2', y2);
+
+  return line;
+}
+
+export function calcIndexes(x1, y1, x2, y2) {
+  const axial1 = evenr_to_axial(x1, y1),
+    axial2 = evenr_to_axial(x2, y2),
+    n = offset_distance(x1, y1, x2, y2),
+    results = [];
+
+  for (let i = 0; i <= n; i++) {
+    const lerp = axial_lerp(axial1.q, axial1.r, axial2.q, axial2.r, 1.0 / n * i),
+      round = axial_round(lerp.q, lerp.r),
+      { x, y } = axial_to_evenr(round.q, round.r);
+
+    results.push([x, y]);
+  }
+
+  return results;
+}
+
+export function clear() {
+  sightLine && sightLine.remove();
+  sightLine = null;
+
+  lockTarget && lockTarget.classList.remove(targetClassName);
+  lockTarget = null;
+}
+
+export function update({ x, y }) {
+  sightLine.setAttributeNS(null, 'x1', x);
+  sightLine.setAttributeNS(null, 'y1', y);
+}
+
+export function toggleLock(cell) {
+  lockTarget = lockTarget ? unlock(sightLine, lockTarget) : lock(sightLine, cell);
+}
+
+export function getSightLine() {
+  return sightLine;
+}
+
+export function getLockTarget() {
+  return lockTarget;
+}
+
+export function setHexes(hexes) {
+  activeHexes.forEach(h => h.classList.remove(activeClassName));
+  hexes.forEach(h => h.classList.add(activeClassName));
+  activeHexes = hexes;
+}