Replace transformer example

example.ts

function foo() {}
var a = foo();
var b = foo();
function bar() {
    const foo = 1;
    return foo + 2;
}

transformer.ts

import * as ts from 'typescript';
const replace = {
    from: 'foo',
    to: 'xxx',
};
export default function(program: ts.Program) {
    const checker = program.getTypeChecker();
    return (ctx: ts.TransformationContext) => sourceFile => {
        const fromSymbol = checker
            .getSymbolsInScope(sourceFile, ts.SymbolFlags.Function)
            .find(symbol => symbol.escapedName === replace.from);
        if (!fromSymbol) return sourceFile;

        function visitor(node: ts.Node): ts.Node {
            if (ts.isFunctionDeclaration(node)) {
                const symbol = checker.getSymbolAtLocation(node.name);
                if (symbol === fromSymbol) {
                    node = ts.updateFunctionDeclaration(
                        node,
                        node.decorators,
                        node.modifiers,
                        node.asteriskToken,
                        ts.createIdentifier(replace.to),
                        node.typeParameters,
                        node.parameters,
                        node.type,
                        node.body
                    );
                }
            }
            if (ts.isCallExpression(node)) {
                const symbol = checker.getSymbolAtLocation(node.expression);
                if (symbol === fromSymbol) {
                    node = ts.updateCall(node, ts.createIdentifier(replace.to), node.typeArguments, node.arguments);
                }
            }
            return ts.visitEachChild(node, visitor, ctx);
        }
        return ts.visitEachChild(sourceFile, visitor, ctx);
    };
}