how to use shell script if else condition block in Jenkins declarative pipeline

how to use shell script if else condition block in Jenkins declarative pipeline

below are the shell script commands I wanted to run in a Jenkins pipeline stage, the way we run them using shell script/command line

#!/bin/sh
var=$(git status -s)
echo ${#var}
if [ ${#var} -eq 0 ]
then
  echo "tree is clean"
else
  echo "tree is dirty, please commit changes before running this"
  git add -A
  git commit -m "updated terraform files"
  git push
fi

echo "End of script"

These steps are working fine inside Linux and Jenkins shell/command prompt. How do I replicate same inside jenkins pipeline?

This is what I have tried but it's failing

# jenkins pipeline

pipeline {
    agent  any
    stages {
        stage('Test') {
            steps {
                sh 'node --version'
                sh 'pwd'
                sh 'sleep 15'
                script {
                    sh 'pwd'
                    sh 'var=$(git status -s)'
                    sh 'echo ${#var}' # till here it's working, but if block it's failing. I guess perhaps because if block is actually written in groovy syntax not linux/shell script 'if else' block
                     if ( ${#var} -eq 0 ) {
                         sh 'echo tree is clean'
                     }else {
                         sh 'echo tree is dirty please commit your code changes'
                     }
                }
                sh 'sleep 5'
            }
        }
    }
}

Quick response will be appreciated.