import { Injectable } from '@nestjs/common';
import { QueryResult } from 'src/modules/data_sources/query_result.type';
import { QueryService } from 'src/modules/data_sources/query_service.interface';
import { Knex, knex } from 'knex';
import { ConnectionTestResult } from 'src/modules/data_sources/connection_test_result.type';
import { cacheConnection, getCachedConnection } from 'src/helpers/utils.helper';

@Injectable()
export default class MysqlQueryService implements QueryService {

  async run(sourceOptions: any, queryOptions: any, dataSourceId: string, dataSourceUpdatedAt: string): Promise<QueryResult> {

    let result = {
      rows: []
    };
    let query = '';

    if(queryOptions.mode === 'gui') {
      if(queryOptions.operation === 'bulk_update_pkey') {
        query = await this.buildBulkUpdateQuery(queryOptions);
      }
    } else {
      query = queryOptions.query;
    }

    const knexInstance = await this.getConnection(sourceOptions, {}, true, dataSourceId, dataSourceUpdatedAt);

    try {
      result = await knexInstance.raw(query);
    } catch (err) {
      console.log(err);
    }

    return {
      status: 'ok',
      data: result[0]
    }
  }

  async testConnection(sourceOptions: object): Promise<ConnectionTestResult> {
    const knexInstance = await this.getConnection(sourceOptions, {}, false);
    const result = await knexInstance.raw('select @@version;');

    return {
      status: 'ok'
    }
  }

  async buildConnection(sourceOptions: any) {
    const config: Knex.Config = {
      client: 'mysql',
      connection: {
        host : sourceOptions.host,
        user : sourceOptions.username,
        password : sourceOptions.password,
        database : sourceOptions.database,
        port: sourceOptions.port,
        multipleStatements: true,
        ssl: sourceOptions.ssl_enabled ?? false // Disabling by default for backward compatibility
      }
    };

    return knex(config);
  }

  async getConnection(sourceOptions: any, options:any, checkCache: boolean, dataSourceId?: string, dataSourceUpdatedAt?: string): Promise<any> {
    if(checkCache) {
      let connection = await getCachedConnection(dataSourceId, dataSourceUpdatedAt);

      if(connection) {
        return connection;
      } else {
        connection = await this.buildConnection(sourceOptions);
        await cacheConnection(dataSourceId, connection);
        return connection;
      }
    } else {
      return await this.buildConnection(sourceOptions);
    }

  }

  async buildBulkUpdateQuery(queryOptions: any): Promise<string> {
    let queryText = '';

    const tableName = queryOptions['table'];
    const primaryKey = queryOptions['primary_key_column'];
    const records = queryOptions['records'];

    for(const record of records ) {
      queryText = `${queryText} UPDATE ${tableName} SET`;

      for(const key of Object.keys(record)) {
        if(key !== primaryKey) {
          queryText = ` ${queryText} ${key} = '${record[key]}',`;
        }
      }

      queryText = queryText.slice(0, -1);
      queryText = `${queryText} WHERE ${primaryKey} = ${record[primaryKey]};`;
    }

    return queryText.trim();
  }
}