refactor the whole damn thing

src/Util/relativePosition.js

@@ -0,0 +1,45 @@
+import ID from './ID'
+
+export function getRelativePosition (type, offset) {
+  if (offset === 0) {
+    return ['startof', type._id.user, type._id.clock]
+  } else {
+    let t = type.start
+    while (t !== null && t.length < offset) {
+      if (!t._deleted) {
+        offset -= t.length
+      }
+      t = t._right
+    }
+    return [t._id.user, t._id.clock + offset - 1]
+  }
+}
+
+export function fromRelativePosition (y, rpos) {
+  if (rpos[0] === 'startof') {
+    return {
+      type: y.os.get(new ID(rpos[1], rpos[2])),
+      offset: 0
+    }
+  } else {
+    let offset = 0
+    let struct = y.os.findNodeWithUpperBound(new ID(rpos[0], rpos[1]))
+    let parent = struct._parent
+    if (parent._deleted) {
+      return null
+    }
+    if (!struct.deleted) {
+      offset = rpos[1] - struct._id.clock
+    }
+    while (struct.left !== null) {
+      struct = struct.left
+      if (!struct.deleted) {
+        offset += struct._length
+      }
+    }
+    return {
+      type: parent,
+      offset: offset
+    }
+  }
+}