import { escape } from 'sqlstring';
import ClientInterface from '../ClientInterface';
import BaseStatement from './BaseStatement';
const template = require('es6-template-strings');

/**
 * INSERT INTO rtindex VALUES (val1, val2, ...), (val1, val2, ...);
 */

export default class InsertStatement extends BaseStatement {
  protected index: string;
  protected values: any;
  protected type: string;

  constructor(connection: ClientInterface, index: string, values: any, insertType: string = 'INSERT') {
    super(connection);
    if (!index.length) {
      throw Error('real-time index must be valid but empty name provided');
    }
    if (!(values instanceof Array) && (typeof values !== 'object')) {
      throw Error(`Provide an array or an object (key-value pair) values`);
    }
    if ((values instanceof Array) && !values.length) {
      throw Error(`No document to insert`);
    }
    this.connection = connection;
    this.index = index;
    this.values = values;
    this.type = insertType
  }

  /**
   * Formats the VALUES of the document between parenthesis and escapes them.
   * values attribute can be of this types:
   *
   * [{id: 1, title: 'title...'}, {id: 2, title: 'other title'}]
   * OR
   * {id: 1, title: 'title...'}
   */
  protected renderValues(values: object, columns: string[]): string {
    let tmpl: string = columns.map(column => '${'+ column +'}').join(', ');
    for (let i = 0; i < columns.length; i++) {
      if (typeof values[columns[i]] === 'string') {
        values[columns[i]] = escape(values[columns[i]]);
      }
    }
    const compiledTemplate = template(tmpl, values);

    return `(${compiledTemplate})`;
  }

  public generate() : string {
    let valuesFields: string[] = [];
    // array of documents
    if (this.values instanceof Array) {
      const columns: string[] = Object.keys(this.values[0]);
      let expression: string = `${this.type} INTO ${this.index} `;
      expression += `${this.renderColumnList(columns)} VALUES `;

      valuesFields = this.values.map((values) => {
        return this.renderValues(values, columns);
      });

      return `${expression}${valuesFields.join(', ')}`;
    }

    // case of key-value object
    const columns: string[] = Object.keys(this.values);

    return `${this.type} INTO ${this.index} ${this.renderColumnList(columns)} ` +
      `VALUES ${this.renderValues(this.values, columns)}`;
  }

  /**
   * Compiles the list of columns to insert in the correct order
   * the document/s. It goes before VALUES keyword.
   *
   * Example output: (id, title, content)
   */
  protected renderColumnList(columns: string[]) : string {
    return `(${ columns.join(', ') })`;
  }
}