// @flow
import { createSelector } from 'reselect';

const selectState = state => state.comments || {};

export const selectCommentsById = createSelector(selectState, state => state.commentById || {});

export const selectIsFetchingComments = createSelector(selectState, state => state.isLoading);

export const selectCommentsByClaimId = createSelector(selectState, selectCommentsById, (state, byId) => {
  const byClaimId = state.byId || {};
  const comments = {};

  // replace every comment_id in the list with the actual comment object
  Object.keys(byClaimId).forEach(claimId => {
    const commentIds = byClaimId[claimId];

    comments[claimId] = Array(commentIds === null ? 0 : commentIds.length);
    for (let i = 0; i < commentIds.length; i++) {
      comments[claimId][i] = byId[commentIds[i]];
    }
  });

  return comments;
});

// previously this used a mapping from claimId -> Array<Comments>
/* export const selectCommentsById = createSelector(
  selectState,
  state => state.byId || {}
); */
export const selectCommentsByUri = createSelector(selectState, state => {
  const byUri = state.commentsByUri || {};
  const comments = {};
  Object.keys(byUri).forEach(uri => {
    const claimId = byUri[uri];
    if (claimId === null) {
      comments[uri] = null;
    } else {
      comments[uri] = claimId;
    }
  });

  return comments;
});

export const makeSelectCommentsForUri = (uri: string) =>
  createSelector(selectCommentsByClaimId, selectCommentsByUri, (byClaimId, byUri) => {
    const claimId = byUri[uri];
    return byClaimId && byClaimId[claimId];
  });

// todo: allow SDK to retrieve user comments through comment_list
// todo: implement selectors for selecting comments owned by user