APIG custom authorizer for header validation

apig_customer_authorizer.js

exports.handler =  (event, context, callback) => {
    console.log(event)
    var token = event.authorizationToken.toLowerCase();
    switch (token) {
        case 'dalvik':
            callback(null, generatePolicy('user', 'Allow', event.methodArn, token));
            break;
        // case 'deny':
        //     callback(null, generatePolicy('user', 'Deny', event.methodArn));
        //     break;
        // case 'unauthorized':
        //     callback("Unauthorized");   // Return a 401 Unauthorized response
        //     break;
        // default:
        //     callback("Error: Invalid User-Agent"); // Return a 500 Invalid token response
        default:
            callback(null, generatePolicy('user', 'Deny', event.methodArn));
            break;
            //callback("Unauthorized"); 
    };
};

// Help function to generate an IAM policy
var generatePolicy = (principalId, effect, resource, token) => {
    var authResponse = {};
    
    authResponse.principalId = principalId;
    if (effect && resource) {
        var policyDocument = {};
        policyDocument.Version = '2012-10-17'; 
        policyDocument.Statement = [];
        var statementOne = {};
        statementOne.Action = 'execute-api:Invoke'; 
        statementOne.Effect = effect;
        statementOne.Resource = resource;
        policyDocument.Statement[0] = statementOne;
        authResponse.policyDocument = policyDocument;
    }
    
    // Optional output with custom properties of the String, Number or Boolean type.
    authResponse.context = {
        "UserAgent": token
        // "stringKey": "stringval",
        // "numberKey": 123,
        // "booleanKey": true
    };
    return authResponse;
}