import { Request, Response, Router } from 'express';
import { http } from '@scode/consts';
import { KnexCrudOptions } from './KnexCrudOptions';
import { CrudHandler } from './CrudHandler';
import { Knex } from './KnexInterface';
import { HttpHandler } from './HttpHandler';

export class KnexCrudHandler extends HttpHandler implements CrudHandler {
  protected table: string;
  protected columns: Array<string>;
  protected options: KnexCrudOptions;
  protected knex: Knex;

  public constructor (
    table: string,
    columns: Array<string>,
    options: KnexCrudOptions = {}
  ) {
    super ();
    this.table = table;
    this.columns = columns;
    this.options = options;
    if (this.columns.filter ((val) => val.toLowerCase () === 'id').length > 0) {
      throw new Error (
        'the column id cannot be made available to modification'
      );
    }
  }

  protected validate_body (
    req: Request,
    res: Response
  ): Promise<object> | object {
    if (typeof req.body === 'undefined') {
      res.status (http.status_bad_request);
      res.end ('body was undefined');
      return null;
    }
    try {
      return JSON.parse (req.body);
    }
    catch (e) {
      res.status (http.status_bad_request);
      res.end ('invalid json input');
    }
    return null;
  }

  protected ensure_data (
    data: object,
    res: Response,
    fail_on_undef = true
  ): Promise<object>|object {
    const obj = {};
    const keys = Object.keys (data);
    for (const col of this.columns) {
      if (!keys.includes (col) && fail_on_undef) {
        res.status (http.status_bad_request)
          .end (`missing field: ${col}`);
        return null;
      }
      obj[col] = data[col];
    }
    for (const col of this.options.optional_columns)
      obj[col] = data[col];

    return obj;
  }

  public async create (req: Request, res: Response): Promise<void> {
    if (!await this.options.create_authorization (req, res))
      return;

    const body_data = await this.validate_body (req, res);
    if (body_data === null)
      return;

    const db_data = await this.ensure_data (body_data, res);
    if (db_data === null)
      return;

    const inserted = await this.knex (this.table)
      .returning ('id')
      .insert (db_data);

    res.status (http.status_created)
      .end (inserted[0]);
  }

  public async read (req: Request, res: Response): Promise<void> {
    if (!await this.options.read_authorization (req, res))
      return;

    if (typeof req.headers.id === 'undefined') {
      res.status (http.status_bad_request)
        .end ('id undefined');
      return;
    }

    const json = await this.knex (this.table)
      .select ([
        'id',
        ...this.columns
      ])
      .where ({ id: req.headers.id });

    res.status (json.length > 0 ? http.status_ok : http.status_not_found)
      .json (json[0]);
  }

  public async update (req: Request, res: Response): Promise<void> {
    if (!await this.options.update_authorization (req, res))
      return;

    const body_data = await this.validate_body (req, res);
    if (body_data === null)
      return;

    const db_data = await this.ensure_data (body_data, res, false);
    if (db_data === null)
      return;

    if (typeof req.headers.id === 'undefined') {
      res.status (http.status_bad_request)
        .end ('id undefined');
      return;
    }

    await this.knex (this.table)
      .where ({ id: req.headers.id })
      .update (db_data);

    res.status (http.status_ok)
      .end (inserted[0]);
  }

  public async delete (req: Request, res: Response): Promise<void> {
    if (!await this.options.delete_authorization (req, res))
      return;

    if (typeof req.headers.id === 'undefined') {
      res.status (http.status_bad_request)
        .end ('id undefined');
      return;
    }

    await this.knex (this.table)
      .where ({ id: req.headers.id })
      .delete ();

    res.status (http.status_ok)
      .end ();
  }

  protected async create_or_update (
    req: Request,
    res: Response
  ): Promise<void> {
    if (typeof req.headers.id === 'undefined')
      await this.create (req, res);
    else
      await this.update (req, res);
  }

  public register_handlers (router: Router): void {
    router.post ('/', this.create_or_update);
    router.get ('/', this.read);
    router.delete ('/', this.delete);
  }
}