talk/migrations/1510174676_user_status.js

const UserModel = require('../models/user');
const merge = require('lodash/merge');

const getUserBatch = async () => {
  let query = {
    status: {
      $in: [
        'ACTIVE',
        'BANNED',
        'PENDING',
        'APPROVED'
      ]
    }
  };

  // Find all the users that need migrating.
  return UserModel.collection.find(query);
};

module.exports = {
  async up() {

    const created_at = Date.now();

    // Get the first batch of users.
    let cursor = await getUserBatch();

    const updates = [];
    while (await cursor.hasNext()) {
      const user = await cursor.next();

      const {id, status, canEditName, suspension, disabled} = user;

      let update = {
        $unset: {
          canEditName: '',
          suspension: '',
          disabled: '',
        },
        $set: {
          status: {

            // The username status is specific to each case.
            username: {
              history: []
            },

            // The user is not banned by default.
            banned: {
              status: false,
              history: []
            },

            // The user is not suspended by default.
            suspension: {
              until: null,
              history: []
            },
          },
          updated_at: created_at
        },
      };

      if (disabled) {
        update = merge(update, {
          $set: {
            status: {
              banned: {
                status: true,
                history: [{
                  status: true,
                  created_at
                }]
              },
            }
          }
        });
      }

      // If the user has an "until" property of their suspension, then we need
      // to reflect that in the new status object.
      if (suspension && suspension.until !== null) {
        update = merge(update, {
          $set: {
            status: {
              suspension: {
                until: suspension.until,
                history: [{
                  until: suspension.until,
                  created_at,
                }]
              }
            }
          }
        });
      }

      switch (status) {
      case 'ACTIVE':
        if (canEditName) {
          update = merge(update, {
            $set: {
              status: {
                username: {
                  status: 'UNSET',
                  history: [{
                    status: 'UNSET',
                    created_at
                  }]
                }
              }
            }
          });
        } else {
          update = merge(update, {
            $set: {
              status: {
                username: {
                  status: 'SET',
                  history: [{
                    status: 'SET',
                    created_at
                  }]
                }
              }
            }
          });
        }
        break;
      case 'BANNED':
        if (canEditName) {
          update = merge(update, {
            $set: {
              status: {
                username: {
                  status: 'REJECTED',
                  history: [{
                    status: 'REJECTED',
                    created_at
                  }]
                }
              }
            }
          });
        } else {
          update = merge(update, {
            $set: {
              status: {
                banned: {
                  status: true,
                  history: [{
                    status: true,
                    created_at
                  }]
                },
                username: {
                  status: 'SET',
                  history: [{
                    status: 'SET',
                    created_at
                  }]
                }
              }
            }
          });
        }
        break;
      case 'PENDING':
        update = merge(update, {
          $set: {
            status: {
              username: {
                status: 'CHANGED',
                history: [{
                  status: 'CHANGED',
                  created_at
                }]
              }
            }
          }
        });
        break;
      case 'APPROVED':
        update = merge(update, {
          $set: {
            status: {
              username: {
                status: 'APPROVED',
                history: [{
                  status: 'APPROVED',
                  created_at
                }]
              }
            }
          }
        });
        break;
      default:
        throw new Error(`${status} is an invalid status`);
      }

      updates.push({query: {id}, update});
    }

    if (updates.length > 0) {

      // Create a new batch operation.
      let bulk = UserModel.collection.initializeUnorderedBulkOp();

      for (const {query, update} of updates) {
        bulk.find(query).updateOne(update);
      }

      // Execute the bulk update operation.
      await bulk.execute();
    }
  }
};