/**
   * @fileoverview Rule to enforce declarations in program or function body root.
   * @author Brandon Mills
   */
  
  "use strict";
  
  //------------------------------------------------------------------------------
  // Rule Definition
  //------------------------------------------------------------------------------
  
  module.exports = {
      meta: {
          docs: {
              description: "disallow variable or `function` declarations in nested blocks",
              category: "Possible Errors",
              recommended: true
          },
  
          schema: [
              {
                  enum: ["functions", "both"]
              }
          ]
      },
  
      create(context) {
  
          /**
           * Find the nearest Program or Function ancestor node.
           * @returns {Object} Ancestor's type and distance from node.
           */
          function nearestBody() {
              const ancestors = context.getAncestors();
              let ancestor = ancestors.pop(),
                  generation = 1;
  
              while (ancestor && ["Program", "FunctionDeclaration",
                  "FunctionExpression", "ArrowFunctionExpression"
              ].indexOf(ancestor.type) < 0) {
                  generation += 1;
                  ancestor = ancestors.pop();
              }
  
              return {
  
                  // Type of containing ancestor
                  type: ancestor.type,
  
                  // Separation between ancestor and node
                  distance: generation
              };
          }
  
          /**
           * Ensure that a given node is at a program or function body's root.
           * @param {ASTNode} node Declaration node to check.
           * @returns {void}
           */
          function check(node) {
              const body = nearestBody(node),
                  valid = ((body.type === "Program" && body.distance === 1) ||
                      body.distance === 2);
  
              if (!valid) {
                  context.report({ node, message: "Move {{type}} declaration to {{body}} root.", data: {
                      type: (node.type === "FunctionDeclaration"
                              ? "function" : "variable"),
                      body: (body.type === "Program"
                              ? "program" : "function body")
                  } });
              }
          }
  
          return {
  
              FunctionDeclaration: check,
              VariableDeclaration(node) {
                  if (context.options[0] === "both" && node.kind === "var") {
                      check(node);
                  }
              }
  
          };
  
      }
  };