rljson/example/src/rljson-example.ts

Define and manage relational data structures in JSON

#!/usr/bin/env node

// @license
// Copyright (c) 2019 - 2024 Dr. Gabriel Gatzsche. All Rights Reserved.
//
// Use of this source code is governed by terms that can be
// found in the LICENSE file in the root of this package.

import { JsonHash } from 'gg-json-hash';
import { Rljson } from 'rljson';


const jh = JsonHash.default;

// .............................................................
console.log('Create tables');

let db = Rljson.fromJson({
  tableA: {
    _data: [{ a: 'a0' }, { a: 'a1' }],
  },
  tableB: {
    _data: [{ b: 'b0' }, { b: 'b1' }],
  },
});

// .............................................................
console.log('Each item in the table gets an content based hash code');

const hashA0 = db.hash({ table: 'tableA', index: 0 });
const hashA1 = db.hash({ table: 'tableA', index: 1 });
const hashB0 = db.hash({ table: 'tableB', index: 0 });
const hashB1 = db.hash({ table: 'tableB', index: 1 });

// .............................................................
console.log('The hashcode can be used to access data');
const a0 = db.value({table: 'tableA', itemHash: hashA0, followLink: ['a']});
console.log(a0); // a0

const a1 = db.value({table: 'tableA', itemHash: hashA1, followLink: ['a']});
console.log(a1); // a1

const b0 = db.value({table: 'tableB', itemHash: hashB0, followLink: ['b']});
console.log(b0); // b0

const b1 = db.value({table: 'tableB', itemHash: hashB1, followLink: ['b']});
console.log(b1); // b1

// .............................................................
console.log('Add and merge additional data. The original table is not changed');

db = db.addData({
  tableA: {
    _data: [{ a: 'a2' }],
  },
  tableB: {
    _data: [{ b: 'b2' }],
  },
  tableC: {
    _data: [{ c: 'c0' }],
  },
});

// .............................................................
console.log('Print a list of all values in the database');
const allPaths = db.ls();
console.log(allPaths.map((path) => `- ${path}`).join('\n'));

// .............................................................
console.log('Create interconnected tables');

db = Rljson.fromJson({
  a: {
    _data: [
      {
        value: 'a',
      },
    ],
  },
});

const tableAValueHash = db.hash({ table: 'a', index: 0 });

db = db.addData({
  b: {
    _data: [
      {
        aRef: tableAValueHash,
      },
    ],
  },
});

const tableBValueHash = db.hash({ table: 'b', index: 0 });

// .............................................................
console.log('Join tables when reading values');

const a = db.value({table: 'b', itemHash: tableBValueHash, followLink: ['aRef', 'value']});

console.log(a); // a

// .............................................................
console.log('To hash data in advance use gg_json_hash');
const hashedData = jh.apply({
  tableA: {
    _data: [{ a: 'a0' }, { a: 'a1' }],
  },
});

console.log('Validate hashes when adding data');
db = Rljson.fromJson(hashedData, { validateHashes: true });