'use strict';

/**
 * Aggregator.js service
 *
 * @description: A set of functions similar to controller's actions to avoid code duplication.
 */

const _ = require('lodash');
const pluralize = require('pluralize');
const { Builder, Query } = require('strapi-utils');

const Schema = require('./Schema.js');
const GraphQLQuery = require('./Query.js');
/* eslint-disable no-unused-vars */

module.exports = {
  /**
   * Returns all fields of type primitive
   *
   * @returns {Boolean}
   */
  isPrimitiveType: _type => {
    const type = _type.replace('!', '');
    return (
      type === 'Int' ||
      type === 'Float' ||
      type === 'String' ||
      type === 'Boolean' ||
      type === 'DateTime' ||
      type === 'JSON'
    );
  },

  /**
   * Checks if the field is of type enum
   *
   * @returns {Boolean}
   */
  isEnumType: type => {
    return type === 'enumeration';
  },

  /**
   * Returns all fields that are not of type array
   *
   * @returns {Boolean}
   *
   * @example
   *
   * isNotOfTypeArray([String])
   * // => false
   * isNotOfTypeArray(String!)
   * // => true
   */
  isNotOfTypeArray: type => {
    return !/(\[\w+!?\])/.test(type);
  },

  /**
   * Returns all fields of type Integer or float
   */
  isNumberType: type => {
    return type === 'Int' || type === 'Float';
  },

  /**
   * Returns a list of fields that have type included in fieldTypes.
   */
  getFieldsByTypes: (fields, typeCheck, returnType) => {
    return _.reduce(
      fields,
      (acc, fieldType, fieldName) => {
        if (typeCheck(fieldType)) {
          acc[fieldName] = returnType(fieldType, fieldName);
        }
        return acc;
      },
      {},
    );
  },

  /**
   * Use the field resolver otherwise fall through the field value
   *
   * @returns {function}
   */
  fieldResolver: (field, key) => {
    return object => {
      const resolver =
        field.resolve ||
        function resolver(obj, options, context) {
          // eslint-disable-line no-unused-vars
          return obj[key];
        };
      return resolver(object);
    };
  },

  /**
   * Create fields resolvers
   *
   * @return {Object}
   */
  createFieldsResolver: function(fields, resolver, typeCheck) {
    return Object.keys(fields).reduce((acc, fieldKey) => {
      const field = fields[fieldKey];
      // Check if the field is of the correct type
      if (typeCheck(field)) {
        return _.set(acc, fieldKey, (obj, options, context) => {
          return resolver(
            obj,
            options,
            context,
            this.fieldResolver(field, fieldKey),
            fieldKey,
            obj,
            field,
          );
        });
      }
      return acc;
    }, {});
  },

  /**
   * Convert non-primitive type to string (non-primitive types corresponds to a reference to an other model)
   *
   * @returns {String}
   *
   * @example
   *
   * extractType(String!)
   * // => String
   *
   * extractType(user)
   * // => ID
   *
   * extractType(ENUM_TEST_FIELD, enumeration)
   * // => String
   *
   */
  extractType: function(_type, attributeType) {
    return this.isPrimitiveType(_type)
      ? _type.replace('!', '')
      : this.isEnumType(attributeType)
        ? 'String'
        : 'ID';
  },

  /**
   * Build the mongoose aggregator by applying the filters
   */
  getModelAggregator: function(model, filters = {}) {
    return new Query(model)
      .find(filters)
      .execute();
  },

  /**
   * Create the resolvers for each aggregation field
   *
   * @return {Object}
   *
   * @example
   *
   * const model = // Strapi model
   *
   * const fields = {
   *   username: String,
   *   age: Int,
   * }
   *
   * const typeCheck = (type) => type === 'Int' || type === 'Float',
   *
   * const fieldsResoler = createAggregationFieldsResolver(model, fields, 'sum', typeCheck);
   *
   * // => {
   *   age: function ageResolver() { .... }
   * }
   */
  createAggregationFieldsResolver: function(
    model,
    fields,
    operation,
    typeCheck,
  ) {
    return this.createFieldsResolver(
      fields,
      async (obj, options, context, fieldResolver, fieldKey) => {
        // eslint-disable-line no-unused-vars
        const result = await this.getModelAggregator(model, obj).group({
          _id: null,
          [fieldKey]: { [`$${operation}`]: `$${fieldKey}` },
        });
        return _.get(result, `0.${fieldKey}`);
      },
      typeCheck,
    );
  },

  /**
   * Correctly format the data returned by the group by
   */
  preProcessGroupByData: function({ result, fieldKey, filters, model }) {
    const _result = _.toArray(result);
    return _.map(_result, value => {
      const params = {
        ...GraphQLQuery.convertToParams(_.omit(filters, 'where')),
        ...GraphQLQuery.convertToQuery(filters.where),
        [fieldKey]: value._id,
      };

      return {
        key: value._id,
        connection: new Builder(model, params).convert(),
      };
    });
  },

  /**
   * Create the resolvers for each group by field
   *
   * @return {Object}
   *
   * @example
   *
   * const model = // Strapi model
   * const fields = {
   *   username: [UserConnectionUsername],
   *   email: [UserConnectionEmail],
   * }
   * const fieldsResoler = createGroupByFieldsResolver(model, fields);
   *
   * // => {
   *   username: function usernameResolver() { .... }
   *   email: function emailResolver() { .... }
   * }
   */
  createGroupByFieldsResolver: function(model, fields, name) {
    return this.createFieldsResolver(
      fields,
      async (obj, options, context, fieldResolver, fieldKey) => {
        const result = await this.getModelAggregator(model, obj).group({
          _id: `$${fieldKey}`,
        });

        return this.preProcessGroupByData({
          result,
          fieldKey,
          filters: obj,
          model,
        });
      },
      () => true,
    );
  },

  /**
   * This method is the entry point to the GraphQL's Aggregation.
   * It takes as param the model and its fields and it'll create the aggregation types and resolver to it
   * Example:
   *  type User {
   *     username: String,
   *     age: Int,
   *  }
   *
   * It'll create
   *  type UserConnection {
   *    values: [User],
   *    groupBy: UserGroupBy,
   *    aggreate: UserAggregate
   *  }
   *
   *  type UserAggregate {
   *     count: Int
   *     sum: UserAggregateSum
   *     avg: UserAggregateAvg
   *  }
   *
   *  type UserAggregateSum {
   *     age: Float
   *  }
   *
   *  type UserAggregateAvg {
   *    age: Float
   *  }
   *
   *  type UserGroupBy {
   *     username: [UserConnectionUsername]
   *     age: [UserConnectionAge]
   *  }
   *
   *  type UserConnectionUsername {
   *    key: String
   *    connection: UserConnection
   *  }
   *
   *  type UserConnectionAge {
   *    key: Int
   *    connection: UserConnection
   *  }
   *
   */
  formatModelConnectionsGQL: function(fields, model, name, modelResolver) {
    const { globalId } = model;

    const connectionGlobalId = `${globalId}Connection`;
    const aggregatorFormat = this.formatConnectionAggregator(
      fields,
      model,
      name,
    );
    const groupByFormat = this.formatConnectionGroupBy(fields, model, name);
    const connectionFields = {
      values: `[${globalId}]`,
      groupBy: `${globalId}GroupBy`,
      aggregate: `${globalId}Aggregator`,
    };

    let modelConnectionTypes = `type ${connectionGlobalId} {${Schema.formatGQL(
      connectionFields,
    )}}\n\n`;
    if (aggregatorFormat) {
      modelConnectionTypes += aggregatorFormat.type;
    }
    modelConnectionTypes += groupByFormat.type;

    return {
      globalId: connectionGlobalId,
      type: modelConnectionTypes,
      query: {
        [`${pluralize.plural(
          name,
        )}Connection(sort: String, limit: Int, start: Int, where: JSON)`]: connectionGlobalId,
      },
      resolver: {
        Query: {
          [`${pluralize.plural(name)}Connection`]: (obj, options, context) => {
            return options;
          },
        },
        [connectionGlobalId]: {
          values: (obj, options, context) => {
            // Object here contains the key/value of the field that has been grouped-by
            // for instance obj = { where: { country: 'USA' } } so the values here needs to be filtered according to the parent value
            return modelResolver(obj, obj, context);
          },
          groupBy: (obj, options, context) => {
            // eslint-disable-line no-unused-vars
            // There is noting to resolve here, it's the aggregation resolver that will take care of it
            return obj;
          },
          aggregate: (obj, options, context) => {
            // eslint-disable-line no-unused-vars
            const params = {
              ...GraphQLQuery.convertToParams(_.omit(obj, 'where')),
              ...GraphQLQuery.convertToQuery(obj.where),
            };
            // eslint-disable-line no-unused-vars
            // There is noting to resolve here, it's the aggregation resolver that will take care of it
            return new Builder(model, params).convert();
          },
        },
        ...aggregatorFormat.resolver,
        ...groupByFormat.resolver,
      },
    };
  },

  /**
   * Generate the connection type of each non-array field of the model
   *
   * @return {String}
   */
  generateConnectionFieldsTypes: function(fields, model) {
    const { globalId, attributes } = model;
    const primitiveFields = this.getFieldsByTypes(
      fields,
      this.isNotOfTypeArray,
      (type, name) => this.extractType(type, (attributes[name] || {}).type),
    );

    const connectionFields = _.mapValues(primitiveFields, fieldType => ({
      key: fieldType,
      connection: `${globalId}Connection`,
    }));

    return Object.keys(primitiveFields)
      .map(
        fieldKey =>
          `type ${globalId}Connection${_.upperFirst(
            fieldKey,
          )} {${Schema.formatGQL(connectionFields[fieldKey])}}`,
      )
      .join('\n\n');
  },

  formatConnectionGroupBy: function(fields, model, name) {
    const { globalId } = model;
    const groupByGlobalId = `${globalId}GroupBy`;

    // Extract all primitive fields and change their types
    const groupByFields = this.getFieldsByTypes(
      fields,
      this.isNotOfTypeArray,
      (fieldType, fieldName) =>
        `[${globalId}Connection${_.upperFirst(fieldName)}]`,
    );

    // Get the generated field types
    let groupByTypes = `type ${groupByGlobalId} {${Schema.formatGQL(
      groupByFields,
    )}}\n\n`;
    groupByTypes += this.generateConnectionFieldsTypes(fields, model);

    return {
      globalId: groupByGlobalId,
      type: groupByTypes,
      resolver: {
        [groupByGlobalId]: this.createGroupByFieldsResolver(
          model,
          groupByFields,
          name,
        ),
      },
    };
  },

  formatConnectionAggregator: function(fields, model) {
    const { globalId } = model;

    // Extract all fields of type Integer and Float and change their type to Float
    const numericFields = this.getFieldsByTypes(
      fields,
      this.isNumberType,
      () => 'Float',
    );

    // Don't create an aggregator field if the model has not number fields
    const aggregatorGlobalId = `${globalId}Aggregator`;
    const initialFields = {
      count: 'Int',
      totalCount: 'Int',
    };

    // Only add the aggregator's operations if there are some numeric fields
    if (!_.isEmpty(numericFields)) {
      ['sum', 'avg', 'min', 'max'].forEach(agg => {
        initialFields[agg] = `${aggregatorGlobalId}${_.startCase(agg)}`;
      });
    }

    const gqlNumberFormat = Schema.formatGQL(numericFields);
    let aggregatorTypes = `type ${aggregatorGlobalId} {${Schema.formatGQL(
      initialFields,
    )}}\n\n`;

    let resolvers = {
      [aggregatorGlobalId]: {
        count: async (obj, options, context) => {
          // eslint-disable-line no-unused-vars
          // Object here corresponds to the filter that needs to be applied to the aggregation
          return new Query(model)
            .thru((query) => {
              if (_.has(obj, 'limit')) query.limit(obj.limit);
              return query;
            })
            .count(obj)
            .execute();
        },
        totalCount: async (obj, options, context) => {
          // eslint-disable-line no-unused-vars
          // Object here corresponds to the filter that needs to be applied to the aggregation
          return new Query(model)
            .count(obj)
            .execute();
        },
      },
    };

    // Only add the aggregator's operations types and resolver if there are some numeric fields
    if (!_.isEmpty(numericFields)) {
      // Returns the actual object and handle aggregation in the query resolvers
      const defaultAggregatorFunc = (obj, options, context) => {
        // eslint-disable-line no-unused-vars
        return obj;
      };

      aggregatorTypes += `type ${aggregatorGlobalId}Sum {${gqlNumberFormat}}\n\n`;
      aggregatorTypes += `type ${aggregatorGlobalId}Avg {${gqlNumberFormat}}\n\n`;
      aggregatorTypes += `type ${aggregatorGlobalId}Min {${gqlNumberFormat}}\n\n`;
      aggregatorTypes += `type ${aggregatorGlobalId}Max {${gqlNumberFormat}}\n\n`;

      _.merge(resolvers[aggregatorGlobalId], {
        sum: defaultAggregatorFunc,
        avg: defaultAggregatorFunc,
        min: defaultAggregatorFunc,
        max: defaultAggregatorFunc,
      });

      resolvers = {
        ...resolvers,
        [`${aggregatorGlobalId}Sum`]: this.createAggregationFieldsResolver(
          model,
          fields,
          'sum',
          this.isNumberType,
        ),
        [`${aggregatorGlobalId}Avg`]: this.createAggregationFieldsResolver(
          model,
          fields,
          'avg',
          this.isNumberType,
        ),
        [`${aggregatorGlobalId}Min`]: this.createAggregationFieldsResolver(
          model,
          fields,
          'min',
          this.isNumberType,
        ),
        [`${aggregatorGlobalId}Max`]: this.createAggregationFieldsResolver(
          model,
          fields,
          'max',
          this.isNumberType,
        ),
      };
    }

    return {
      globalId: aggregatorGlobalId,
      type: aggregatorTypes,
      resolver: resolvers,
    };
  },
};