fireball-db/lib/param_mapper.js

a lightweight model wrapper for DynamoDB

var curried_prefix, curryRight, ensure_prefix, expression_names, expression_values, isFunction, map_parameters, mapping, ref;

ref = require('lodash'), curryRight = ref.curryRight, isFunction = ref.isFunction;

ensure_prefix = function(params, prefix) {
  var key, results, value;
  results = {};
  for (key in params) {
    value = params[key];
    if (!key.startsWith(prefix)) {
      key = "" + prefix + key;
    }
    results[key] = value;
  }
  return results;
};

curried_prefix = curryRight(ensure_prefix);

expression_names = curried_prefix('#');

expression_values = curried_prefix(':');

mapping = {
  names: function(key, value) {
    return {
      key: 'ExpressionAttributeNames',
      value: expression_names(value)
    };
  },
  values: function(key, value) {
    return {
      key: 'ExpressionAttributeValues',
      value: expression_values(value)
    };
  },
  condition: 'ConditionExpression',
  update: 'UpdateExpression',
  projection: 'ProjectionExpression',
  filter: 'FilterExpression',
  key_condition: 'KeyConditionExpression',
  index: 'IndexName',
  limit: 'Limit',
  forward: 'ScanIndexForward'
};

map_parameters = function(params) {
  var key, mapped, mapper, result, value;
  result = {};
  for (key in params) {
    value = params[key];
    mapper = mapping[key];
    if (mapper != null) {
      mapped = {
        key: mapper,
        value: value
      };
      if (isFunction(mapper)) {
        mapped = mapper(key, value);
      }
      result[mapped.key] = mapped.value;
    } else {
      result[key] = value;
    }
  }
  return result;
};

module.exports = {
  ensure_prefix: ensure_prefix,
  expression_names: expression_names,
  expression_values: expression_values,
  map_parameters: map_parameters
};