/*
 * Copyright (C) 2019 StApps
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
import {
  SCBackendConfigurationSearchBoosting,
  SCConfigFile,
  SCSearchBooleanFilter,
  SCSearchFilter,
  SCSearchQuery,
  SCSearchSort,
  SCSportCoursePriceGroup,
  SCThingsField,
  SCThingTypes,
} from '@openstapps/core';
import { ElasticsearchConfig, ScriptSort } from './common';
import {
  ESBooleanFilter,
  ESBooleanFilterArguments,
  ESDucetSort,
  ESFunctionScoreQuery,
  ESFunctionScoreQueryFunction,
  ESGeoDistanceFilter,
  ESGeoDistanceFilterArguments,
  ESGeoDistanceSort,
  ESGeoDistanceSortArguments,
  ESTermFilter,
  ESTypeFilter,
} from './common';

/**
 * Builds a boolean filter. Returns an elasticsearch boolean filter
 */
export function buildBooleanFilter(booleanFilter: SCSearchBooleanFilter): ESBooleanFilterArguments<any> {

  const result: ESBooleanFilterArguments<any> = {
    minimum_should_match: 0,
    must: [],
    must_not: [],
    should: [],
  };

  if (booleanFilter.arguments.operation === 'and') {
    result.must = booleanFilter.arguments.filters.map((filter) => buildFilter(filter));
  }

  if (booleanFilter.arguments.operation === 'or') {
    result.should = booleanFilter.arguments.filters.map((filter) => buildFilter(filter));
    result.minimum_should_match = 1;
  }

  if (booleanFilter.arguments.operation === 'not') {
    result.must_not = booleanFilter.arguments.filters.map((filter) => buildFilter(filter));
  }

  return result;
}

/**
 * Converts Array of Filters to elasticsearch query-syntax
 * @param filter
 */
export function buildFilter(filter: SCSearchFilter): ESTermFilter | ESGeoDistanceFilter | ESBooleanFilter<any> {

  switch (filter.type) {
    case 'value':
      const filterObj: { [field: string]: string } = {};
      filterObj[filter.arguments.field + '.raw'] = filter.arguments.value;
      return {
        term: filterObj,
      };
    case 'availability':
      const startRangeFilter: { [field: string]: { lte: string } } = {};
      startRangeFilter[filter.arguments.fromField] = {
        lte: 'now',
      };

      const endRangeFilter: { [field: string]: { gte: string } } = {};
      endRangeFilter[filter.arguments.toField] = {
        gte: 'now',
      };

      return {
        bool: {
          should: [
            {
              bool: {
                must: [
                  {
                    range: startRangeFilter,
                  },
                  {
                    range: endRangeFilter,
                  },
                ],
              },
            },
            {
              bool: {
                must_not: [
                  {
                    exists: {
                      field: filter.arguments.fromField,
                    },
                  },
                  {
                    exists: {
                      field: filter.arguments.toField,
                    },
                  },
                ],
              },
            },
          ],
        },
      };
    case 'distance':
      const geoObject: ESGeoDistanceFilterArguments = {
        distance: filter.arguments.distanceInM + 'm',
      };
      geoObject[filter.arguments.field] = {
        lat: filter.arguments.lat,
        lon: filter.arguments.lon,
      };
      return {
        geo_distance: geoObject,
      };
    case 'boolean':
      return {
        bool: buildBooleanFilter(filter),
      };
    default:
      throw new Error('Unknown Filter type');
  }
}

/**
 * Builds scorings functions from boosting config
 * @param boosting
 * @returns
 */
export function buildFunctions(boosting: SCBackendConfigurationSearchBoosting[]): ESFunctionScoreQueryFunction[] {

  const functions: ESFunctionScoreQueryFunction[] = [];

  // add a good scoring subset from config file
  boosting.forEach((boostingForOneSCType) => {
    const typeFilter: ESTypeFilter = {
      type: {
        value: boostingForOneSCType.type,
      },
    };

    functions.push({
      filter: typeFilter,
      weight: boostingForOneSCType.factor,
    });

    if (typeof boostingForOneSCType.fields !== 'undefined') {

      const fields = boostingForOneSCType.fields;

      Object.keys(boostingForOneSCType.fields).forEach((fieldName) => {

        const boostingForOneField = fields[fieldName];

        Object.keys(boostingForOneField).forEach((value) => {
          const factor = boostingForOneField[value];

          // build term filter
          const termFilter: ESTermFilter = {
            term: {},
          };
          termFilter.term[fieldName + '.raw'] = value;

          functions.push({
            filter: {
              bool: {
                must: [
                  typeFilter,
                  termFilter,
                ],
                should: [],
              },
            },
            weight: factor,
          });
        });
      });
    }
  });

  return functions;
}
/**
 * Builds body for Elasticsearch requests
 * @param params
 * @param defaultConfig
 * @returns ElasticsearchQuery (body of a search-request)
 */
export function buildQuery(
  params: SCSearchQuery,
  defaultConfig: SCConfigFile,
  elasticsearchConfig: ElasticsearchConfig,
): ESFunctionScoreQuery {

  // if a sort is used it, we may have to narrow down the types so the sort is executable
  let typeFiltersToAppend: ESTypeFilter[] = [];

  if (typeof params.sort !== 'undefined') {
    params.sort.forEach((sort) => {
      // types that the sort is supported on
      const types: SCThingTypes[] = [];

      defaultConfig.backend.sortableFields
        .filter((sortableField) => {
          return sortableField.fieldName === sort.arguments.field && sortableField.sortTypes.indexOf(sort.type) > -1;
        })
        .forEach((sortableField) => {
          if (typeof sortableField.onlyOnTypes !== 'undefined') {
            sortableField.onlyOnTypes.forEach((scType) => {
              if (types.indexOf(scType) === -1) {
                types.push(scType);
              }
            });
          }
        });

      if (types.length > 0) {
        typeFiltersToAppend = types.map((type) => {
          return {
            type: {
              value: type,
            },
          };
        });
      }
    });
  }

  // if config provides an minMatch parameter we use query_string instead of match query
  let query;
  if (typeof elasticsearchConfig.query === 'undefined') {
    query = {
      query_string: {
        analyzer: 'search_german',
        default_field: 'name',
        minimum_should_match: '90%',
        query: (typeof params.query !== 'string') ? '*' : params.query,
      },
    };
  } else if (elasticsearchConfig.query.queryType === 'query_string') {
    query = {
      query_string: {
        analyzer: 'search_german',
        default_field: 'name',
        minimum_should_match: elasticsearchConfig.query.minMatch,
        query: (typeof params.query !== 'string') ? '*' : params.query,
      },
    };
  } else if (elasticsearchConfig.query.queryType === 'dis_max') {
    if (params.query !== '*') {
      query = {
        dis_max: {
          boost: 1.2,
          queries: [
            {
              match: {
                name: {
                  boost: elasticsearchConfig.query.matchBoosting,
                  cutoff_frequency: elasticsearchConfig.query.cutoffFrequency,
                  fuzziness: elasticsearchConfig.query.fuzziness,
                  query: (typeof params.query !== 'string') ? '*' : params.query,
                },
              },
            },
            {
              query_string: {
                analyzer: 'search_german',
                default_field: 'name',
                minimum_should_match: elasticsearchConfig.query.fuzziness,
                query: (typeof params.query !== 'string') ? '*' : params.query,
              },
            },
          ],
          tie_breaker: elasticsearchConfig.query.tieBreaker,
        },

      };
    } else {
      throw new Error('Query Type is not supported. Check your config file and reconfigure your elasticsearch query');
    }
  }

  const functionScoreQuery: ESFunctionScoreQuery = {
    function_score: {
      functions: buildFunctions(defaultConfig.internal.boostings),
      query: {
        bool: {
          minimum_should_match: 0, // if we have no should, nothing can match
          must: [],
          should: [],
        },
      },
      score_mode: 'multiply',
    },
  };

  const mustMatch = functionScoreQuery.function_score.query.bool.must;

  if (Array.isArray(mustMatch)) {
    if (typeof query !== 'undefined') {
      mustMatch.push(query);
    }

    if (typeof params.filter !== 'undefined') {
      mustMatch.push(buildFilter(params.filter));
    }

    // add type filters for sorts
    mustMatch.push.apply(mustMatch, typeFiltersToAppend);
  }
  return functionScoreQuery;
}

/**
 * converts query to
 * @param params
 * @param sortableFields
 * @returns an array of sort queries
 */
export function buildSort(
  sorts: SCSearchSort[],
): Array<ESDucetSort | ESGeoDistanceSort | ScriptSort> {
  return sorts.map((sort) => {
    switch (sort.type) {
      case 'ducet':
        const ducetSort: ESDucetSort = {};
        ducetSort[sort.arguments.field + '.sort'] = sort.order;
        return ducetSort;
      case 'distance':
        const args: ESGeoDistanceSortArguments = {
          mode: 'avg',
          order: sort.order,
          unit: 'm',
        };

        args[sort.arguments.field] = {
          lat: sort.arguments.lat,
          lon: sort.arguments.lon,
        };

        return {
          _geo_distance: args,
        };
      case 'price':
        return {
          _script: {
            order: sort.order,
            script: buildPriceSortScript(sort.arguments.universityRole, sort.arguments.field),
            type: 'number' as 'number',
          },
        };
    }
  });
}

export function buildPriceSortScript(universityRole: keyof SCSportCoursePriceGroup, field: SCThingsField): string {
  return `
  // initialize the sort value with the maximum
  double price = Double.MAX_VALUE;

  // if we have any offers
  if (params._source.containsKey('${field}')) {
    // iterate through all offers
    for (offer in params._source.${field}) {
      // if this offer contains a role specific price
      if (offer.containsKey('prices') && offer.prices.containsKey('${universityRole}')) {
        // if the role specific price is smaller than the cheapest we found
        if (offer.prices.${universityRole} < price) {
          // set the role specific price as cheapest for now
          price = offer.prices.${universityRole};
        }
      } else { // we have no role specific price for our role in this offer
        // if the default price of this offer is lower than the cheapest we found
        if (offer.price < price) {
          // set this price as the cheapest
          price = offer.price;
        }
      }
    }
  }

  // return cheapest price for our role
  return price;
  `;
}