@steedos/odata-v4-mongodb/README.md

Service OData requests from a MongoDB data store

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 * @Author: baozhoutao@steedos.com
 * @Date: 2022-07-10 15:44:34
 * @LastEditors: baozhoutao@steedos.com
 * @LastEditTime: 2022-07-10 15:57:25
 * @Description: 
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# OData V4 Service modules - MongoDB Connector

Service OData v4 requests from a MongoDB data store.

## Synopsis
The OData V4 MongoDB Connector provides functionality to convert the various types of OData segments
into MongoDB query objects, that you can execute over a MongoDB database.

## Potential usage scenarios

- Create high speed, standard compliant data sharing APIs

## Usage as server - TypeScript
```javascript
import { createFilter } from '@steedos/odata-v4-mongodb'

//example request:  GET /api/products?$filter=category/id eq 5 or color eq 'Red'
app.get("/api/products", (req: Request, res: Response) => {
    const filter = createFilter(req.query.$filter);
    // collection instance from MongoDB Node.JS Driver
    collection.find(filter, function(err, data){
        res.json({
        	'@odata.context': req.protocol + '://' + req.get('host') + '/api/$metadata#products',
        	value: data
        });
    });
});
```

## Usage ES5
```javascript
var createFilter = require('@steedos/odata-v4-mongodb').createFilter;

app.get("/api/products", function(req, res) {
    var filter = createFilter(req.query.$filter);
    // collection instance from MongoDB Node.JS Driver
    collection.find(filter, function(err, data){
        res.json({
        	'@odata.context': req.protocol + '://' + req.get('host') + '/api/$metadata#products',
        	value: data
        });
    });
})
```

## Supported OData segments

For now **$filter**, **$select**, **$skip** and **$top**

Support for **$expand** is next.

### Supported $filter expressions

The [OData v4 Parser](https://www.npmjs.com/package/odata-v4-parser) layer supports 100% of the specification.
The Connector is supporting basic MongoDB queries.

*We are into creating a comprehensive feature availability chart for V1 release*

    √ expression 5.1.1.6.1: NullValue eq null
    √ expression 5.1.1.6.1: TrueValue eq true
    √ expression 5.1.1.6.1: FalseValue eq false
    √ expression 5.1.1.6.1: IntegerValue lt -128
    √ expression 5.1.1.6.1: DecimalValue eq 34.95
    √ expression 5.1.1.6.1: StringValue eq 'Say Hello,then go'
    √ expression 5.1.1.6.1: DurationValue eq duration'P12DT23H59M59.999999999999S'
    √ expression 5.1.1.6.1: DateValue eq 2012-12-03
    √ expression 5.1.1.6.1: DateTimeOffsetValue eq 2012-12-03T07:16:23Z
    √ expression 5.1.1.6.1: GuidValue eq 01234567-89ab-cdef-0123-456789abcdef
    √ expression 5.1.1.6.1: Int64Value eq 0
    √ expression 5.1.1.6.1: A eq INF
    √ expression 5.1.1.6.1: A eq 0.31415926535897931e1
    √ expression 5.1.1.1.2: A ne 1
    √ expression 5.1.1.1.3: A gt 2
    √ expression 5.1.1.1.4: A ge 3
    √ expression 5.1.1.1.5: A lt 2
    √ expression 5.1.1.1.6: A le 2
    √ expression: A/b eq 1
    √ expression 5.1.1.3: (A/b eq 2) or (B/c lt 4) and ((E gt 5) or (E lt -1))