import { QueryController } from '../../Core';
import { IIndexFieldValue } from '../../rest/FieldValue';
import { IListFieldValuesRequest } from '../../rest/ListFieldValuesRequest';
import { IFieldOption } from '../Base/IComponentOptions';
import { IQuerySuggestionKeyword } from './FacetValueSuggestions';

/**
 * Used to define a row returned by an [`IFacetValueSuggestionsProvider`]{@link IFacetValueSuggestionsProvider}.
 */
export interface IFacetValueSuggestionRow {
  /**
   * The score computed by the suggestions provider.
   *
   * A higher score means the results is more relevant.
   */
  score: IFacetValueSuggestionScore;

  /**
   * The field value returned by the suggestion that should be used to filter the results.
   */
  value: string;
  /**
   * The number of results matching the value for the given keyword.
   */
  numberOfResults: number;
  /**
   * The keyword that was used in the query to retrieve results.
   */
  keyword: IQuerySuggestionKeyword;
  /**
   * The field that was used for the suggestions.
   */
  field: IFieldOption;
}

export interface IFacetValueSuggestionScore {
  distanceFromTotalForField: number;
}

interface IFacetValueSuggestionsResponse {
  responses: IFacetValueBatchResponse[];
  reference: IFacetValueReference;
}

interface IFacetValueBatchResponse {
  values: IIndexFieldValue[];
  keyword: IQuerySuggestionKeyword;
}

type IFacetValueReference = {
  fieldsTotal: { [value: string]: number };
  smallestTotal: number;
};

/**
 * Defines options for the [`FacetValueSuggestions`]{@link FacetValueSuggestions} component.
 */
export interface IFacetValueSuggestionsProviderOptions {
  field: string;
  expression?: string;
}

/**
 * Provides suggestions for the [`FacetValueSuggestions`]{@link FacetValueSuggestions} component.
 */
export interface IFacetValueSuggestionsProvider {
  getSuggestions(valuesToSearch: IQuerySuggestionKeyword[]): Promise<IFacetValueSuggestionRow[]>;
}

export class FacetValueSuggestionsProvider implements IFacetValueSuggestionsProvider {
  constructor(private queryController: QueryController, private options: IFacetValueSuggestionsProviderOptions) {}

  public async getSuggestions(valuesToSearch: IQuerySuggestionKeyword[]): Promise<IFacetValueSuggestionRow[]> {
    const fieldsToQuery = await this.getFieldValuesToQuery(valuesToSearch);
    return this.getAllSuggestionsRows(fieldsToQuery.responses, fieldsToQuery.reference);
  }

  private getAllSuggestionsRows(
    fieldResponses: IFacetValueBatchResponse[],
    fieldTotalReference: IFacetValueReference
  ): IFacetValueSuggestionRow[] {
    return fieldResponses.reduce((allValues, fieldResponse) => {
      const suggestionRows = fieldResponse.values.map(indexFieldValue => {
        return <IFacetValueSuggestionRow>{
          numberOfResults: indexFieldValue.numberOfResults,
          keyword: fieldResponse.keyword,
          value: indexFieldValue.value,
          score: this.computeScoreForSuggestionRow(indexFieldValue, fieldTotalReference),
          field: this.options.field
        };
      });
      return allValues.concat(suggestionRows);
    }, []);
  }

  private async getFieldValuesToQuery(valuesToSearch: IQuerySuggestionKeyword[]): Promise<IFacetValueSuggestionsResponse> {
    // The reference request will be used to get the maximum number of values for a given facet value.
    const referenceValuesRequest = this.buildReferenceFieldValueRequest();
    const queryParts = this.getQueryToExecuteParts();

    if (this.options.expression) {
      queryParts.push(this.options.expression);
    }

    const suggestionValuesRequests = valuesToSearch.map(keyword => {
      const queryToExecute = [...queryParts, keyword.text].join(' ');
      return this.buildListFieldValueRequest(queryToExecute);
    });

    const requests = [...suggestionValuesRequests, referenceValuesRequest];
    const values = await this.queryController.getEndpoint().listFieldValuesBatch({
      batch: requests
    });

    const reference = this.computeReferenceFromBatch(values.pop());
    const responses: IFacetValueBatchResponse[] = values.map((value, i) => {
      return <IFacetValueBatchResponse>{
        keyword: valuesToSearch[i],
        values: value
      };
    });

    return <IFacetValueSuggestionsResponse>{
      responses,
      reference
    };
  }

  private computeScoreForSuggestionRow(fieldValue: IIndexFieldValue, reference: IFacetValueReference): IFacetValueSuggestionScore {
    const totalNumberForFieldValue = reference.fieldsTotal[fieldValue.value] || reference.smallestTotal;
    const distanceFromTotalForField: number = (totalNumberForFieldValue - fieldValue.numberOfResults) / totalNumberForFieldValue * 100;
    return {
      distanceFromTotalForField
    };
  }

  private computeReferenceFromBatch(batch: IIndexFieldValue[]): IFacetValueReference {
    const fieldsTotal = {};
    batch.forEach(value => (fieldsTotal[value.value] = value.numberOfResults));
    return {
      fieldsTotal: fieldsTotal,
      smallestTotal: batch[batch.length - 1].numberOfResults
    };
  }

  private buildListFieldValueRequest(queryToExecute: string): IListFieldValuesRequest {
    return {
      field: <string>this.options.field,
      ignoreAccents: true,
      maximumNumberOfValues: 3,
      queryOverride: queryToExecute
    };
  }

  private buildReferenceFieldValueRequest(): IListFieldValuesRequest {
    return {
      field: <string>this.options.field
    };
  }

  private getQueryToExecuteParts(): string[] {
    const lastQuery = this.queryController.getLastQuery();
    const aqWithoutCurrentField =
      lastQuery && lastQuery.aq ? this.removeFieldExpressionFromExpression(this.options.field.toString(), lastQuery.aq) : '';

    return [aqWithoutCurrentField, lastQuery.cq].filter(part => !!part);
  }

  private removeFieldExpressionFromExpression(field: string, expression: string): string {
    const expressionWithParenthesis = '([^)]*)';
    const expressionAsSingleValue = '[^ ]*';
    return expression
      .replace(new RegExp(`${field}==${expressionWithParenthesis}`, 'gi'), '')
      .replace(new RegExp(`${field}==${expressionAsSingleValue}`, 'gi'), '');
  }
}