/**
 * @fileoverview Rule to flag when initializing to undefined
 * @author Ilya Volodin
 */

'use strict';

const astUtils = require('./utils/ast-utils');

//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------

/** @type {import('../types').Rule.RuleModule} */
module.exports = {
  meta: {
    type: 'suggestion',

    docs: {
      description: 'Disallow initializing variables to `undefined`',
      recommended: false,
      frozen: true,
      url: 'https://eslint.org/docs/latest/rules/no-undef-init',
    },

    schema: [],
    fixable: 'code',

    messages: {
      unnecessaryUndefinedInit:
        "It's not necessary to initialize '{{name}}' to undefined.",
    },
  },

  create(context) {
    const sourceCode = context.sourceCode;

    return {
      VariableDeclarator(node) {
        const name = sourceCode.getText(node.id),
          init = node.init && node.init.name,
          scope = sourceCode.getScope(node),
          undefinedVar = astUtils.getVariableByName(scope, 'undefined'),
          shadowed = undefinedVar && undefinedVar.defs.length > 0,
          lastToken = sourceCode.getLastToken(node);

        if (init === 'undefined' && node.parent.kind !== 'const' && !shadowed) {
          context.report({
            node,
            messageId: 'unnecessaryUndefinedInit',
            data: { name },
            fix(fixer) {
              if (node.parent.kind === 'var') {
                return null;
              }

              if (
                node.id.type === 'ArrayPattern' ||
                node.id.type === 'ObjectPattern'
              ) {
                // Don't fix destructuring assignment to `undefined`.
                return null;
              }

              if (sourceCode.commentsExistBetween(node.id, lastToken)) {
                return null;
              }

              return fixer.removeRange([node.id.range[1], node.range[1]]);
            },
          });
        }
      },
    };
  },
};