'use strict';

Object.defineProperty(exports, '__esModule', { value: true });

const defaultTimestep = (1 / 60) * 1000;
const getCurrentTime = typeof performance !== "undefined"
    ? () => performance.now()
    : () => Date.now();
const onNextFrame = typeof window !== "undefined"
    ? (callback) => window.requestAnimationFrame(callback)
    : (callback) => setTimeout(() => callback(getCurrentTime()), defaultTimestep);

function createRenderStep(runNextFrame) {
    let toRun = [];
    let toRunNextFrame = [];
    let numToRun = 0;
    let isProcessing = false;
    let flushNextFrame = false;
    const toKeepAlive = new WeakSet();
    const step = {
        schedule: (callback, keepAlive = false, immediate = false) => {
            const addToCurrentFrame = immediate && isProcessing;
            const buffer = addToCurrentFrame ? toRun : toRunNextFrame;
            if (keepAlive)
                toKeepAlive.add(callback);
            if (buffer.indexOf(callback) === -1) {
                buffer.push(callback);
                if (addToCurrentFrame && isProcessing)
                    numToRun = toRun.length;
            }
            return callback;
        },
        cancel: (callback) => {
            const index = toRunNextFrame.indexOf(callback);
            if (index !== -1)
                toRunNextFrame.splice(index, 1);
            toKeepAlive.delete(callback);
        },
        process: (frameData) => {
            if (isProcessing) {
                flushNextFrame = true;
                return;
            }
            isProcessing = true;
            [toRun, toRunNextFrame] = [toRunNextFrame, toRun];
            toRunNextFrame.length = 0;
            numToRun = toRun.length;
            if (numToRun) {
                for (let i = 0; i < numToRun; i++) {
                    const callback = toRun[i];
                    callback(frameData);
                    if (toKeepAlive.has(callback)) {
                        step.schedule(callback);
                        runNextFrame();
                    }
                }
            }
            isProcessing = false;
            if (flushNextFrame) {
                flushNextFrame = false;
                step.process(frameData);
            }
        },
    };
    return step;
}

const maxElapsed = 40;
let useDefaultElapsed = true;
let runNextFrame = false;
let isProcessing = false;
const frame = {
    delta: 0,
    timestamp: 0,
};
const stepsOrder = [
    "read",
    "update",
    "preRender",
    "render",
    "postRender",
];
const steps = stepsOrder.reduce((acc, key) => {
    acc[key] = createRenderStep(() => (runNextFrame = true));
    return acc;
}, {});
const sync = stepsOrder.reduce((acc, key) => {
    const step = steps[key];
    acc[key] = (process, keepAlive = false, immediate = false) => {
        if (!runNextFrame)
            startLoop();
        return step.schedule(process, keepAlive, immediate);
    };
    return acc;
}, {});
const cancelSync = stepsOrder.reduce((acc, key) => {
    acc[key] = steps[key].cancel;
    return acc;
}, {});
const flushSync = stepsOrder.reduce((acc, key) => {
    acc[key] = () => steps[key].process(frame);
    return acc;
}, {});
const processStep = (stepId) => steps[stepId].process(frame);
const processFrame = (timestamp) => {
    runNextFrame = false;
    frame.delta = useDefaultElapsed
        ? defaultTimestep
        : Math.max(Math.min(timestamp - frame.timestamp, maxElapsed), 1);
    frame.timestamp = timestamp;
    isProcessing = true;
    stepsOrder.forEach(processStep);
    isProcessing = false;
    if (runNextFrame) {
        useDefaultElapsed = false;
        onNextFrame(processFrame);
    }
};
const startLoop = () => {
    runNextFrame = true;
    useDefaultElapsed = true;
    if (!isProcessing)
        onNextFrame(processFrame);
};
const getFrameData = () => frame;

exports.cancelSync = cancelSync;
exports.default = sync;
exports.flushSync = flushSync;
exports.getFrameData = getFrameData;