cw_mode_string.sqlx

config { hasOutput: true }
/*
 * Copyright 2024 Google LLC
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

CREATE OR REPLACE AGGREGATE FUNCTION ${self()}(s STRING)
RETURNS STRING
LANGUAGE js 
OPTIONS (
  description="Returns the most frequently occurring argument"
)
AS """
  export function initialState() {
    return {frequencyMap: new Map()};
  }
  export function aggregate(state, value) {
    var frequencyMap  = state.frequencyMap;
    if (frequencyMap.has(value)) {
      frequencyMap.set(value, frequencyMap.get(value) + 1);
    } else {
      frequencyMap.set(value, 1);
    }
  }
  export function merge(state, partial_state) {
    var frequencyMap  = state.frequencyMap;
    for (let [key, count] of partial_state.frequencyMap) {
      if (frequencyMap.has(key)) {
        frequencyMap.set(key, frequencyMap.get(key) + count);
      } else {
        frequencyMap.set(key, count);
      }
    }
  }
  export function finalize(state) {
    var maxCount = 0;
    var maxKey = null;
    for (let [key, count] of state.frequencyMap) {
      if (count > maxCount) {
        maxKey = key;
        maxCount = count;
      }
    }
    return maxKey;
  }
""";