opencv-loader.ts

// Copyright (C) 2022-2025 Intel Corporation
// LIMITED EDGE SOFTWARE DISTRIBUTION LICENSE

import type { OpenCVTypes } from '../opencv/interfaces';

const READY_CHECK_INTERVAL_MS = 100;
const OPENCV_LOAD_TIMEOUT_MS = 30_000;

let opencv: OpenCVTypes | null = null;
let loadingPromise: Promise<OpenCVTypes> | null = null;

function delay(ms: number): Promise<void> {
    return new Promise((resolve) => setTimeout(resolve, ms));
}

/**
 * Wait for cv.ready to be available with polling
 * Some OpenCV builds delay initialization of cv.ready
 */
const waitForOpenCVReady = async (cv: OpenCVTypes): Promise<void> => {
    const startTime = Date.now();

    while (Date.now() - startTime < OPENCV_LOAD_TIMEOUT_MS) {
        // Check if cv.ready exists and is a Promise-like object
        if (cv && typeof cv.ready === 'object' && 'then' in cv.ready) {
            try {
                await cv.ready;
                return; // Success
            } catch (error) {
                console.error('Error waiting for cv.ready:', error);
                throw error;
            }
        }

        // Check if cv.ready is already resolved (some builds may have it pre-resolved)
        if (cv && cv.onload && typeof cv.onload === 'function') {
            return;
        }

        // cv.ready not available yet, wait and retry
        await delay(READY_CHECK_INTERVAL_MS);
    }

    throw new Error(
        `Timeout waiting for cv.ready (${OPENCV_LOAD_TIMEOUT_MS}ms). ` +
            'OpenCV may not be properly built or the file is corrupted.'
    );
};

export const OpenCVLoader = async (): Promise<OpenCVTypes> => {
    if (opencv) return opencv;
    if (loadingPromise) return loadingPromise;

    loadingPromise = Promise.race([
        (async () => {
            try {
                const cv: OpenCVTypes = await import('../opencv/4.9.0/opencv.js');

                // Wait for cv.ready with polling and timeout
                await waitForOpenCVReady(cv);

                if (!cv.Mat) {
                    throw new Error('OpenCV missing essential methods');
                }
                opencv = cv;
                return opencv;
            } catch (error) {
                loadingPromise = null;
                throw error;
            }
        })(),
        new Promise<never>((_, reject) =>
            setTimeout(
                () => reject(new Error(`OpenCV loading timeout (${OPENCV_LOAD_TIMEOUT_MS}ms)`)),
                OPENCV_LOAD_TIMEOUT_MS
            )
        ),
    ]);

    return loadingPromise;
};