/**
   * @fileoverview Rule to disallow async functions which have no `await` expression.
   * @author Toru Nagashima
   */
  
  "use strict";
  
  //------------------------------------------------------------------------------
  // Requirements
  //------------------------------------------------------------------------------
  
  const astUtils = require("../ast-utils");
  
  //------------------------------------------------------------------------------
  // Helpers
  //------------------------------------------------------------------------------
  
  /**
   * Capitalize the 1st letter of the given text.
   *
   * @param {string} text - The text to capitalize.
   * @returns {string} The text that the 1st letter was capitalized.
   */
  function capitalizeFirstLetter(text) {
      return text[0].toUpperCase() + text.slice(1);
  }
  
  //------------------------------------------------------------------------------
  // Rule Definition
  //------------------------------------------------------------------------------
  
  module.exports = {
      meta: {
          docs: {
              description: "disallow async functions which have no `await` expression",
              category: "Best Practices",
              recommended: false
          },
          schema: []
      },
  
      create(context) {
          const sourceCode = context.getSourceCode();
          let scopeInfo = null;
  
          /**
           * Push the scope info object to the stack.
           *
           * @returns {void}
           */
          function enterFunction() {
              scopeInfo = {
                  upper: scopeInfo,
                  hasAwait: false
              };
          }
  
          /**
           * Pop the top scope info object from the stack.
           * Also, it reports the function if needed.
           *
           * @param {ASTNode} node - The node to report.
           * @returns {void}
           */
          function exitFunction(node) {
              if (node.async && !scopeInfo.hasAwait && !astUtils.isEmptyFunction(node)) {
                  context.report({
                      node,
                      loc: astUtils.getFunctionHeadLoc(node, sourceCode),
                      message: "{{name}} has no 'await' expression.",
                      data: {
                          name: capitalizeFirstLetter(
                              astUtils.getFunctionNameWithKind(node)
                          )
                      }
                  });
              }
  
              scopeInfo = scopeInfo.upper;
          }
  
          return {
              FunctionDeclaration: enterFunction,
              FunctionExpression: enterFunction,
              ArrowFunctionExpression: enterFunction,
              "FunctionDeclaration:exit": exitFunction,
              "FunctionExpression:exit": exitFunction,
              "ArrowFunctionExpression:exit": exitFunction,
  
              AwaitExpression() {
                  scopeInfo.hasAwait = true;
              }
          };
      }
  };