Postitive - Negative Counter CvRDT

PNCounter.ts

function uuid(): string {
    return 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, c => {
        var r = Math.random() * 16 | 0, v = c == 'x' ? r : (r & 0x3 | 0x8)
        return v.toString(16)
    })
}

type NumberMap = { [id: string]: number }

class PNCounter {

    id: string
    ps: NumberMap
    ns: NumberMap

    constructor() {
        let id = uuid()
        this.id = id
        this.ps[id] = 0
        this.ns[id] = 0
    }

    incr(n: number) {
        this.ps[this.id] += n
    }

    decr(n: number) {
        this.ns[this.id] -= n
    }

    query() {
        let value = 0
        for (let id in this.ps) { value += this.ps[id] }
        for (let id in this.ns) { value += this.ns[id]  }
        return value
    }

    merge(c: PNCounter) {
        this.ps = this._merge(this.ps, c.ps, Math.max)
        this.ns = this._merge(this.ns, c.ns, Math.min)
    } 

    private _merge(xs: NumberMap, ys: NumberMap, fn: (x: number, y: number) => number): NumberMap {
        let merged = {}
        for (let id in xs) { merged[id] = 1 }
        for (let id in ys) { merged[id] = 1 }
        for (let id in merged) { merged[id] = fn(xs[id] || 0, ys[id || 0]) }
        return merged
    }
}