import ts from 'typescript';

interface ClassResult {
  symbol: ts.Symbol | undefined;
  expressionWithType: ts.ExpressionWithTypeArguments;
  node: ts.Node;
}

/**
 * Helping utility to find all classes in a file that extend from something
 */
export const findInheritedClasses =
  (checker: ts.TypeChecker) =>
  (sourceFile: ts.SourceFile): ClassResult[] => {
    const result: ClassResult[] = [];
    ts.forEachChild(sourceFile, visit);

    return result;

    function visit(node: ts.Node) {
      if (ts.isClassDeclaration(node) && node.name && node.heritageClauses) {
        /**
         * Find the Heritage Clause that matches `ExtendsKeyword` as we can potentially encounter
         * other clauses like `implements` etc.
         */
        const extendedClause = node.heritageClauses.find(
          (item) => item.token === ts.SyntaxKind.ExtendsKeyword
        );

        if (!extendedClause) {
          return;
        }

        const abstractBaseClass = extendedClause.types[0];

        // that's the actual class
        const classSymbol = checker.getSymbolAtLocation(node.name);

        result.push({
          symbol: classSymbol,
          expressionWithType: abstractBaseClass,
          node
        });
      }
    }
  };