const AWS = require('aws-sdk');

const dynamoDbDocumentClient = new AWS.DynamoDB.DocumentClient({
  apiVersion: '2012-10-08',
  region: 'eu-west-1',
});

const openDbConnection = () => dynamoDbDocumentClient;

const getTableName = (table) => {
  const environment = process.argv[2];
  return `${table}${environment}`;
};

const scan = async ({
  dbConnection, filter, values, table,
}) => {
  const { Items } = await dbConnection.scan({
    FilterExpression: filter,
    ExpressionAttributeValues: values,
    TableName: table,
  }).promise();
  return Items;
};

const updateItem = async ({
  dbConnection,
  table,
  id,
  expression,
  values,
  names,
  condition,
  returnUpdated = false,
}) => {
  try {
    const result = await dbConnection
      .update({
        TableName: table,
        Key: { id },
        UpdateExpression: expression,
        ExpressionAttributeValues: values,
        ExpressionAttributeNames: names,
        ConditionExpression: condition,
        ReturnValues: returnUpdated ? 'ALL_NEW' : 'NONE',
      })
      .promise();
    return (returnUpdated && result.Attributes) || true;
  } catch (error) {
    if (error.code === 'ConditionalCheckFailedException') {
      log(`Item ${id} in ${table} did not pass the update condition: ${condition}`);
      return false;
    }
    throw error;
  }
};

const handler = async () => {
  const dbConnection = openDbConnection();
  const conversations = await scan({
    dbConnection,
    table: getTableName('Conversations'),
  });

  const updatedConversations = await Promise.all(
    conversations.map(async (conversation) => updateItem({
      dbConnection,
      table: getTableName('Conversations'),
      id: conversation.id,
      expression: 'SET groupDetails = :groupDetails',
      values: { ':groupDetails': null },
      condition: 'attribute_not_exists(groupDetails)',
      returnUpdated: true,
    })),
  );

  console.log(updatedConversations);
};

handler();