Initial commit

server/api/helpers/insert-to-positionables.js

@@ -0,0 +1,131 @@
+const GAP = 2 ** 14;
+const MIN_GAP = 0.125;
+const MAX_POSITION = 2 ** 40; // 2 ** 50
+
+const findBeginnings = positions => {
+  positions.unshift(0);
+
+  let prevPosition = positions.pop();
+  const beginnings = [prevPosition];
+
+  _.forEachRight(positions, position => {
+    if (prevPosition - MIN_GAP >= position) {
+      return false;
+    }
+
+    prevPosition = position;
+    beginnings.unshift(prevPosition);
+  });
+
+  return beginnings;
+};
+
+const getRepositionsMap = positions => {
+  const repositionsMap = {};
+
+  if (positions.length <= 1) {
+    if (!_.isUndefined(positions[0]) && positions[0] > MAX_POSITION) {
+      return null;
+    }
+
+    return repositionsMap;
+  }
+
+  let prevPosition = positions.shift();
+
+  for (let i = 0; i < positions.length; i++) {
+    const position = positions[i];
+    const nextPosition = positions[i + 1];
+
+    if (prevPosition + MIN_GAP <= position) {
+      break;
+    }
+
+    if (
+      !_.isUndefined(nextPosition) &&
+      prevPosition + MIN_GAP * 2 <= nextPosition
+    ) {
+      (repositionsMap[position] || (repositionsMap[position] = [])).push(
+        prevPosition + (nextPosition - prevPosition) / 2
+      );
+
+      break;
+    }
+
+    prevPosition += GAP;
+
+    if (prevPosition > MAX_POSITION) {
+      return null;
+    }
+
+    (repositionsMap[position] || (repositionsMap[position] = [])).push(
+      prevPosition
+    );
+  }
+
+  return repositionsMap;
+};
+
+const getFullRepositionsMap = positions => {
+  const repositionsMap = {};
+
+  _.forEach(positions, (position, index) => {
+    (repositionsMap[position] || (repositionsMap[position] = [])).push(
+      GAP * (index + 1)
+    );
+  });
+
+  return repositionsMap;
+};
+
+module.exports = {
+  sync: true,
+
+  inputs: {
+    position: {
+      type: 'number',
+      required: true
+    },
+    records: {
+      type: 'ref',
+      required: true
+    }
+  },
+
+  fn: function(inputs, exits) {
+    const lowers = [];
+    const uppers = [];
+
+    inputs.records.forEach(({ position }) => {
+      (position <= inputs.position ? lowers : uppers).push(position);
+    });
+
+    const beginnings = findBeginnings([...lowers, inputs.position]);
+
+    const repositionsMap =
+      getRepositionsMap([...beginnings, ...uppers]) ||
+      getFullRepositionsMap([...lowers, inputs.position, ...uppers]);
+
+    let position = repositionsMap[inputs.position]
+      ? repositionsMap[inputs.position].pop()
+      : inputs.position;
+
+    const repositions = [];
+
+    _.forEachRight(inputs.records, ({ id, position }) => {
+      if (_.isEmpty(repositionsMap[position])) {
+        return;
+      }
+
+      repositions.unshift({
+        id,
+        position: repositionsMap[position].pop()
+      });
+    });
+
+    return exits.success({
+      position,
+      repositions
+    });
+  }
+};