NativeScript/nativescript-core/ui/styling/converters.ts

import { AnimationCurve } from "../enums";

const STYLE_CURVE_MAP = Object.freeze({
    "ease": AnimationCurve.ease,
    "linear": AnimationCurve.linear,
    "ease-in": AnimationCurve.easeIn,
    "ease-out": AnimationCurve.easeOut,
    "ease-in-out": AnimationCurve.easeInOut,
    "spring": AnimationCurve.spring,
});

export function timeConverter(value: string): number {
    let result = parseFloat(value);
    if (value.indexOf("ms") === -1) {
        result = result * 1000;
    }

    return Math.max(0.0, result);
}

export function animationTimingFunctionConverter(value: string): any {
    return value ?
        STYLE_CURVE_MAP[value] || parseCubicBezierCurve(value) :
        AnimationCurve.ease;
}

function parseCubicBezierCurve(value: string) {
    const coordsString = /\((.*?)\)/.exec(value);
    const coords = coordsString && coordsString[1]
        .split(",")
        .map(stringToBezieCoords);

    if (value.startsWith("cubic-bezier") &&
        coordsString &&
        coords.length === 4) {

        const [x1, x2, y1, y2] = [...coords];

        return AnimationCurve.cubicBezier(x1, x2, y1, y2);
    } else {
        throw new Error(`Invalid value for animation: ${value}`);
    }
}

function stringToBezieCoords(value: string): number {
    let result = parseFloat(value);
    if (result < 0) {
        return 0;
    } else if (result > 1) {
        return 1;
    }

    return result;
}