ddb-mock.js

class MockDynamoDB {
  constructor() {
    this.tables = {}
  }

  get(params, callback) {
    /** if table does not exist, return with an error */
    if (!this.tables[params.TableName]) callback({ message: 'no items in table', }, null)
    else {
      const key = Object.keys(params.Key)[0] // e.g.  user_id
      const hash = params.Key[key]           // e.g. user|123
      const Item = this.tables[params.TableName].filter((item) => {
        return item[key] === hash
      })[0]                                  // e.g. { user_id, org_ids, ... }

      callback(null, {
        Item,
      })
    }
  }

  put(params, callback) {
    /** if table does not exist, create it */
    if (!this.tables[params.TableName]) this.tables[params.TableName] = []
    /** then add the data to the table */
    this.tables[params.TableName].push(params.Item)
    /** then return empty object because DynamoDB does not return an id */
    callback(null, {})
  }

  query(params, callback) {
    if (!this.tables[params.TableName]) callback({ message: 'no items in table', }, null)
    else {
      // eslint-disable-next-line
      const Items = this.tables[params.TableName].filter((item) => {
        const cond = params.KeyConditionExpression
        const values = params.ExpressionAttributeValues
        const names = params.ExpressionAttributeNames

        const a = cond.replace(/( and )/g, ' && ')
        const b = a.replace(/( = )/g, ' === ')
        const c = b.replace(/( or )/g, ' || ')
        const d = cond.match(/(:\w+)/g).reduce((acc, key) => {
          const re = new RegExp(key, 'g')
          return acc.replace(re, `'${values[key]}'`)
        }, c)
        const e = cond.match(/(#\w+)/g).reduce((acc, key) => {
          const re = new RegExp(key, 'g')
          return acc.replace(re, `item.${names[key]}`)
        }, d)

        // eslint-disable-next-line
        return eval(e)
      })

      callback(null, {
        Items,
      })
    }
  }
}

export default MockDynamoDB