# assemblyscript-json

![npm version](https://img.shields.io/npm/v/assemblyscript-json) ![npm downloads per month](https://img.shields.io/npm/dm/assemblyscript-json)

JSON encoder / decoder for AssemblyScript.

Special thanks to https://github.com/MaxGraey/bignum.wasm for basic unit testing infra for AssemblyScript.

## Installation

`assemblyscript-json` is available as a [npm package](https://www.npmjs.com/package/assemblyscript-json). You can install `assemblyscript-json` in your AssemblyScript project by running:

`npm install --save assemblyscript-json`

## Usage

### Parsing JSON

```typescript
import { JSON } from "assemblyscript-json"; 

// Parse an object using the JSON object
let jsonObj: JSON.Obj = <JSON.Obj>(JSON.parse('{"hello": "world", "value": 24}'));

// We can then use the .getX functions to read from the object if you know it's type
// This will return the appropriate JSON.X value if the key exists, or null if the key does not exist
let worldOrNull: JSON.Str | null = jsonObj.getString("hello"); // This will return a JSON.Str or null
if (worldOrNull != null) {
  // use .valueOf() to turn the high level JSON.Str type into a string
  let world: string = worldOrNull.valueOf();
}

let numOrNull: JSON.Num | null = jsonObj.getNum("value");
if (numOrNull != null) {
  // use .valueOf() to turn the high level JSON.Num type into a f64
  let value: f64 = numOrNull.valueOf();
}

// If you don't know the value type, get the parent JSON.Value
let valueOrNull: JSON.Value | null = jsonObj.getValue("hello");
  if (valueOrNull != null) {
  let value = <JSON.Value>valueOrNull;

  // Next we could figure out what type we are
  if(value.isString) { 
    // value.isString would be true, so we can cast to a string
    let innerString = (<JSON.Str>value).valueOf();
    let jsonString = (<JSON.Str>value).stringify();

    // Do something with string value
  }
}
```

### Encoding JSON


```typescript
import { JSONEncoder } from "assemblyscript-json";

// Create encoder
let encoder = new JSONEncoder();

// Construct necessary object
encoder.pushObject("obj");
encoder.setInteger("int", 10);
encoder.setString("str", "");
encoder.popObject();

// Get serialized data
let json: Uint8Array = encoder.serialize();

// Or get serialized data as string
let jsonString: string = encoder.stringify();

assert(jsonString, '"obj": {"int": 10, "str": ""}'); // True!
```

### Custom JSON Deserializers

```typescript
import { JSONDecoder, JSONHandler } from "assemblyscript-json";

// Events need to be received by custom object extending JSONHandler.
// NOTE: All methods are optional to implement.
class MyJSONEventsHandler extends JSONHandler {
  setString(name: string, value: string): void {
    // Handle field
  }

  setBoolean(name: string, value: bool): void {
    // Handle field
  }

  setNull(name: string): void {
    // Handle field
  }

  setInteger(name: string, value: i64): void {
    // Handle field
  }

  setFloat(name: string, value: f64): void {
    // Handle field
  }

  pushArray(name: string): bool {
    // Handle array start
    // true means that nested object needs to be traversed, false otherwise
    // Note that returning false means JSONDecoder.startIndex need to be updated by handler
    return true;
  }

  popArray(): void {
    // Handle array end
  }

  pushObject(name: string): bool {
    // Handle object start
    // true means that nested object needs to be traversed, false otherwise
    // Note that returning false means JSONDecoder.startIndex need to be updated by handler
    return true;
  }

  popObject(): void {
    // Handle object end
  }
}

// Create decoder
let decoder = new JSONDecoder<MyJSONEventsHandler>(new MyJSONEventsHandler());

// Create a byte buffer of our JSON. NOTE: Deserializers work on UTF8 string buffers.
let jsonString = '{"hello": "world"}';
let jsonBuffer = Uint8Array.wrap(String.UTF8.encode(jsonString));

// Parse JSON
decoder.deserialize(jsonBuffer); // This will send events to MyJSONEventsHandler
```

Feel free to look through the [tests](https://github.com/nearprotocol/assemblyscript-json/tree/master/assembly/__tests__) for more usage examples.

## Reference Documentation

Reference API Documentation can be found in the [docs directory](./docs).

## License

[MIT](./LICENSE)