SplitStreamOnNewJSON.ts

import events = require('events');

class SplitStreamOnNewJSON extends events.EventEmitter {
    private buffers: Array<any> = new Array<any>();
    private openBracesCount = 0;
    private closeBracesCount = 0;

    public lookForJSON(chunk: Buffer) {
        let start = 0;
        for (let i = 0; i < chunk.length; i++) {
            if (chunk[i] === 123) { // {
                this.openBracesCount++;
            } else if (chunk[i] === 125) { // }
                this.closeBracesCount++;
                if (this.openBracesCount > 0 && (this.openBracesCount == this.closeBracesCount)) {
                    //Found a full JSON
                    //Reset braces counts
                    this.openBracesCount = 0;
                    this.closeBracesCount = 0;
                    //add what we've searched until to buffers, less anything at the start
                    this.buffers.push(chunk.slice(start, i + 1));
                    //Push buffers to consumers
                    this.emit('data', Buffer.concat(this.buffers));
                    //Reset buffers
                    this.buffers = [];
                    //Look for JSONs in the remainder of the chunk
                    this.lookForJSON(chunk.slice(i + 1));
                }
            } else if (this.openBracesCount == 0) {
                //if we find data outside of braces we tell the algorithm to copy only after it
                start = i + 1;
            }
        }
        //If we didn't find anything whole push to buffers, removing anything thats data outside of braces
        this.buffers.push(chunk.slice(start));
    }
}

export = SplitStreamOnNewJSON;