/*
 * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
 * or more contributor license agreements. Licensed under the Elastic License;
 * you may not use this file except in compliance with the Elastic License.
 */

import moment from 'moment-timezone';
import { i18n } from '@kbn/i18n';
import { ExpressionFunctionDefinition, Datatable } from 'src/plugins/expressions/public';
import { DataPublicPluginStart } from 'src/plugins/data/public';
import { search } from '../../../../../src/plugins/data/public';
import { buildResultColumns } from '../../../../../src/plugins/expressions/common';

export type TimeScaleUnit = 's' | 'm' | 'h' | 'd';

export interface TimeScaleArgs {
  dateColumnId: string;
  inputColumnId: string;
  outputColumnId: string;
  targetUnit: TimeScaleUnit;
  outputColumnName?: string;
}

const unitInMs: Record<TimeScaleUnit, number> = {
  s: 1000,
  m: 1000 * 60,
  h: 1000 * 60 * 60,
  d: 1000 * 60 * 60 * 24,
};

export function getTimeScaleFunction(data: DataPublicPluginStart) {
  const timeScale: ExpressionFunctionDefinition<
    'lens_time_scale',
    Datatable,
    TimeScaleArgs,
    Promise<Datatable>
  > = {
    name: 'lens_time_scale',
    type: 'datatable',
    help: '',
    args: {
      dateColumnId: {
        types: ['string'],
        help: '',
        required: true,
      },
      inputColumnId: {
        types: ['string'],
        help: '',
        required: true,
      },
      outputColumnId: {
        types: ['string'],
        help: '',
        required: true,
      },
      outputColumnName: {
        types: ['string'],
        help: '',
      },
      targetUnit: {
        types: ['string'],
        options: ['s', 'm', 'h', 'd'],
        help: '',
        required: true,
      },
    },
    inputTypes: ['datatable'],
    async fn(
      input,
      { dateColumnId, inputColumnId, outputColumnId, outputColumnName, targetUnit }: TimeScaleArgs
    ) {
      const dateColumnDefinition = input.columns.find((column) => column.id === dateColumnId);

      if (!dateColumnDefinition) {
        throw new Error(
          i18n.translate('xpack.lens.functions.timeScale.dateColumnMissingMessage', {
            defaultMessage: 'Specified dateColumnId {columnId} does not exist.',
            values: {
              columnId: dateColumnId,
            },
          })
        );
      }

      const resultColumns = buildResultColumns(
        input,
        outputColumnId,
        inputColumnId,
        outputColumnName,
        { allowColumnOverwrite: true }
      );

      if (!resultColumns) {
        return input;
      }

      const targetUnitInMs = unitInMs[targetUnit];
      const timeInfo = await data.search.aggs.getDateMetaByDatatableColumn(dateColumnDefinition);
      const intervalDuration = timeInfo && search.aggs.parseInterval(timeInfo.interval);

      if (!timeInfo || !intervalDuration) {
        throw new Error(
          i18n.translate('xpack.lens.functions.timeScale.timeInfoMissingMessage', {
            defaultMessage: 'Could not fetch date histogram information',
          })
        );
      }
      // the datemath plugin always parses dates by using the current default moment time zone.
      // to use the configured time zone, we are switching just for the bounds calculation.
      const defaultTimezone = moment().zoneName();
      moment.tz.setDefault(timeInfo.timeZone);

      const timeBounds =
        timeInfo.timeRange && data.query.timefilter.timefilter.calculateBounds(timeInfo.timeRange);

      const result = {
        ...input,
        columns: resultColumns,
        rows: input.rows.map((row) => {
          const newRow = { ...row };

          let startOfBucket = moment(row[dateColumnId]);
          let endOfBucket = startOfBucket.clone().add(intervalDuration);
          if (timeBounds && timeBounds.min) {
            startOfBucket = moment.max(startOfBucket, timeBounds.min);
          }
          if (timeBounds && timeBounds.max) {
            endOfBucket = moment.min(endOfBucket, timeBounds.max);
          }
          const bucketSize = endOfBucket.diff(startOfBucket);
          const factor = bucketSize / targetUnitInMs;

          const currentValue = newRow[inputColumnId];
          if (currentValue != null) {
            newRow[outputColumnId] = Number(currentValue) / factor;
          }

          return newRow;
        }),
      };
      // reset default moment timezone
      moment.tz.setDefault(defaultTimezone);

      return result;
    },
  };
  return timeScale;
}