resolver.ts

import { parse, join } from "path";
import { statSync } from "fs";

export function getResolver(platforms: string[], explicitResolve: string[] = []) {
    const platformSpecificExt = [".ts", ".js", ".scss", ".less", ".css", ".html", ".xml", ".vue", ".json"];
    const nsPackageFilters = [
        'nativescript',
        'tns',
        'ns'
    ];

    return function (path: string) {
        const nmIndex = path.lastIndexOf('node_modules');

        if (nmIndex !== -1) {
            const subPath = path.substr(nmIndex + 'node_modules'.length).replace(/\\/g, '/');
            const shouldResolve = explicitResolve.length && explicitResolve.some(packageName => subPath.indexOf(packageName) !== -1);
            const pathParts = subPath.split(/[/\-_]/);
    
            if (!shouldResolve && pathParts.every(p => nsPackageFilters.every(f => f !== p))) {
                return path;
            }
        }

        const { dir, name, ext } = parse(path);

        if (platformSpecificExt.indexOf(ext) === -1) {
            return path;
        }

        for (const platform of platforms) {
            const platformFileName = `${name}.${platform}${ext}`;
            const platformPath = toSystemPath(join(dir, platformFileName));

            try {
                if (statSync(platformPath)) {
                    return platformPath;
                }
            } catch (_e) {
                // continue checking the other platforms
            }
        }

        return path;
    }
}

// Convert paths from \c\some\path to c:\some\path
function toSystemPath(path: string) {
    if (!process.platform.startsWith("win32")) {
        return path;
    }

    const drive = path.match(/^\\(\w)\\(.*)$/);
    return drive ?
        `${drive[1]}:\\${drive[2]}` :
        path;
}