lokijs-collections

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lokijs-collections

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TypeScript enhanced collections for LokiJS with data models, constraints (like primary keys and non-null fields), and collection change tracking

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// repository documentation

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LokiJS Collections
==============

TypeScript port of [lokiJS](https://github.com/techfort/LokiJS).
As of version `0.22.0` of this project, lokiJS is no longer a dependency and a `lokijs@1.3.0` is integrates directly into this project.

## Usage
This project is designed to be imported using commonJs `require(...)` calls.
To use this in a web app, it's currently setup to be required and then included in a bundle at build time.

## Setup
Creating a database instance is the most involved task, once the database instance is created the rest is fairly straightfoward. 
You'll need a few things to create a lokijs-collection database:
* A database name
* Data models - one for each collection with schema information about the type of data being stored in each
* (optional) A database persister.  You can use the DummyDataPersister in the 'test/' directory if you don't need to persist your data yet or aren't sure how a data persister works.
You can use defaults for the rest of the settings, most of them work fine

--------
### 1. Example - Creating an in-memory database instance:
```ts
var InMemDbImpl = require("lokijs-collections/db-collections/InMemDbImpl");
var ModelDefinitionsSet = require("lokijs-collections/data-models/ModelDefinitionsSet");
var DtoPropertyConverter = require("@twg2/ts-twg2-ast-codegen/code-types/DtoPropertyConverter");

var databaseName = "...";

// two collection schemas or models, enables a lot of cool TypeScript type checking, fewer bugs, and easy constraint setup (i.e. not-null, unique, auto-generated)
var dataModels = {
    collection_1_name: {
        properties: DtoPropertyConverter.parseAndConvertTemplateMap({
            "id": { primaryKey: true, autoGenerate: true, type: "number" },
            "name": { type: "string" },
            "props": { type: "string[]" },
        })
    },
    collection_2_name: {
        properties: DtoPropertyConverter.parseAndConvertTemplateMap({
            "userId": { type: "string" },
            "note": { type: "string" },
            "timestamp": { autoGenerate: true, type: "Date" },
        })
    }
};

// create the DB instance, there are a lot of configurable settings, this one is using a dummy data persister, everything is in-memory
var dbInst = new InMemDbImpl(databaseName,
    { readAllow: true, writeAllow: true, compressLocalStores: false },
    "for-in-if",
    "collection_meta_data", false,
    ModelDefinitionsSet.fromCollectionModels(dataModels, null/*defaultDataTypes*/),
    (collectionName) => { return { ... }; },
    (obj, collection, dataModel) => {
        return Object.keys(obj);
        // or
        return dataModel.fieldNames;
    }
);
```

--------
### 2. Example - Creating a WebSQL database persister:
__Note:__ the `WebSqlPersister` constructor has several parameters which are highly customizable, please read the class and constructor documentation for details.
```ts
var DbUtil = require("lokijs-collections/persisters/DbUtil");
var WebSqlSpi = require("lokijs-collections/persisters/WebSqlSpi");
var WebSqlPersister = require("lokijs-collections/persisters/WebSqlPersister");

// log to console or other error logger
var trace: WebSqlSpi.Trace = {
    log: (...args: any[]) => ...,
    error: (...args: any[]) => ...,
    text: (...args: any[]) => ...,
};

var sqlInst = WebSqlSpi.newWebSqlDb("persistent-websql-database", null, null, null,
    { trace: trace, logVerbosity: DbUtil.logLevels.ERROR });

var persister = new WebSqlPersister(sqlInst,
    trace,
    () => dbInst.listCollections(),
    (collName, data) => {
        var coll = dbInst.getCollection(collName, true);
        coll.insert(data);
        return coll;
    },
    (itm) => InMemDbImpl.cloneCloneDelete(itm, true),
    null,
    null,
    (err) => trace.error("storage error", err),
    [],
    []
);
```

You now have a working in-memory database using TypeScript. You can skip Example #2 if you do not wish to persist the in-memory database between page/application reloads.
Checkout the 'test/' directory for usage examples.

--------
## Project Structure

### db-collections/
Contains 'DataCollection', a wrapper for a loki.js collection, add/remove/update functions modify the underlying loki.js collection. 
Also contains 'InMemDbImpl' which bridges the gap between an untyped loki.js instance and 'DataCollection'.

### data-models/
ModelDefinitionsSet for creating and managing a group of DataCollectionModels using DtoModels or DataCollectionModels as a starting point.

### change-trackers/
Collections and handlers for tracking lokijs collection changes (i.e. updates, additions, deletions).

### key-constraints/
Collection meta-data and unique/primary key constraint handlers for 'DataCollection'. 
Includes:
- `PrimaryKeyMaintainer` for checking uniqueness of primary keys and/or generating numerical keys (i.e. 1, 2, 3, ...), 
- `NonNullKeyMaintainer` for checking that fields have values

### persisters/
'DataPersister' implementations and helper classes for persisting and restoring in-memory databases.
Currently provides a WebSQL persister with an alpha level IndexedDB persister.

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