import {createSelector} from "reselect";

function calculateSpocs(component, spocs) {
  let spocIndex = 0;
  return component.spocs.positions.map(position => {
    const rickRoll = Math.random();
    if (spocs.data.spocs[spocIndex] && rickRoll <= component.spocs.probability) {
      return {
        ...position,
        result: spocs.data.spocs[spocIndex++],
      };
    }
    return position;
  });
}

export const selectLayoutRender = createSelector(
  // Selects layout, feeds, spocs so that we only recompute if
  // any of these values change.
  [
    state => state.DiscoveryStream.layout,
    state => state.DiscoveryStream.feeds,
    state => state.DiscoveryStream.spocs,
  ],

  // Adds data to each component from feeds. This function only re-runs if one of the inputs change.
  // TODO: calculate spocs
  function layoutRender(layout, feeds, spocs) {
    return layout.map(row => ({
      ...row,

      // Loops through all the components and adds a .data property
      // containing data from feeds
      components: row.components.map(component => {
        if (!component.feed || !feeds[component.feed.url]) {
          return component;
        }

        // Calculate if we should display a spoc or not.
        if (component.spocs && spocs.data.spocs && spocs.data.spocs.length) {
          component.spocs = {
            ...component.spocs,
            positions: calculateSpocs(component, spocs),
          };
        }

        return {...component, data: feeds[component.feed.url].data};
      }),
    }));
  }
);