Migrate .NET Framework Web.config file to .NET Core appsettings.json

migrate-configs.js

const fs = require('fs');
const path = require('path');

migrateConfigs(fs.readdirSync(`C:/Solution1/Project1/Config`), `C:/Solution1/Project1/Config`);

function migrateConfigs(files, folder) {
    files = files.filter(f => f.endsWith('.config') && f.startsWith('App.'));
    for(const fileName of files) {
        console.log(fileName)
        const appConfig = {
            ConnectionStrings: {}
        };
        let fileContent = fs.readFileSync(path.join(folder, fileName)).toString();

        const appSettingsContent = fileContent.match(/<appSettings>([\s\w\W]*)<\/appSettings>/gm);
        if(appSettingsContent) {
            const asMatch = appSettingsContent[0].matchAll(/<add .*key="(.*)".*value="(.*?)".*\/>.*$/gm);
            for(const m of asMatch) {
                const [_, key, value] = m;
                appConfig[key] = value;
            }
        }

        const connStringsContent = fileContent.match(/<connectionStrings>([\s\w\W]*)<\/connectionStrings>/gm);
        if(connStringsContent) {
            const csMatch = connStringsContent[0].matchAll(/<add [\w\W\s]*name="(.*)"[\w\W\s]*connectionString="(.*)"[\w\W\s]*?\/>/gm);
            for(const m of csMatch) {
                const [_, key, value] = m;
                appConfig.ConnectionStrings[key] = value;
            }
        }

        // Web.Configuration1.config -> appsettings.Configuration1.json
        
        if(fileName !== 'App.config') {
            const [_, name] = fileName.match(/App\.(.*)\.config/);
            fs.writeFileSync(path.join(folder, `appsettings.${name}.json`), JSON.stringify(appConfig, null, '  '));
        } else {
            fs.writeFileSync(path.join(folder, `appsettings.json`), JSON.stringify(appConfig, null, '  '));
        }
    }
}