'use strict';
const {
	isIdentifierName,
	isStrictReservedWord,
	isKeyword,
} = require('@babel/helper-validator-identifier');
const resolveVariableName = require('./resolve-variable-name.js');
const getReferences = require('./get-references.js');

// https://github.com/microsoft/TypeScript/issues/2536#issuecomment-87194347
const typescriptReservedWords = new Set([
	'break',
	'case',
	'catch',
	'class',
	'const',
	'continue',
	'debugger',
	'default',
	'delete',
	'do',
	'else',
	'enum',
	'export',
	'extends',
	'false',
	'finally',
	'for',
	'function',
	'if',
	'import',
	'in',
	'instanceof',
	'new',
	'null',
	'return',
	'super',
	'switch',
	'this',
	'throw',
	'true',
	'try',
	'typeof',
	'var',
	'void',
	'while',
	'with',
	'as',
	'implements',
	'interface',
	'let',
	'package',
	'private',
	'protected',
	'public',
	'static',
	'yield',
	'any',
	'boolean',
	'constructor',
	'declare',
	'get',
	'module',
	'require',
	'number',
	'set',
	'string',
	'symbol',
	'type',
	'from',
	'of',
]);

// Copied from https://github.com/babel/babel/blob/fce35af69101c6b316557e28abf60bdbf77d6a36/packages/babel-types/src/validators/isValidIdentifier.ts#L7
// Use this function instead of `require('@babel/types').isIdentifier`, since `@babel/helper-validator-identifier` package is much smaller
const isValidIdentifier = name =>
	typeof name === 'string'
	&& !isKeyword(name)
	&& !isStrictReservedWord(name, true)
	&& isIdentifierName(name)
	&& name !== 'arguments'
	&& !typescriptReservedWords.has(name);

/*
Unresolved reference is probably from the global scope. We should avoid using that name.

For example, like `foo` and `bar` below.

```
function unicorn() {
	return foo;
}

function unicorn() {
	return function() {
		return bar;
	};
}
```
*/
const isUnresolvedName = (name, scope) =>
	getReferences(scope).some(({identifier, resolved}) => identifier && identifier.name === name && !resolved);

const isSafeName = (name, scopes) =>
	!scopes.some(scope => resolveVariableName(name, scope) || isUnresolvedName(name, scope));

const alwaysTrue = () => true;

/**
Rule-specific name check function.

@callback isSafe
@param {string} name - The generated candidate name.
@param {Scope[]} scopes - The same list of scopes you pass to `avoidCapture`.
@returns {boolean} - `true` if the `name` is ok.
*/

/**
Generates a unique name prefixed with `name` such that:
- it is not defined in any of the `scopes`,
- it is not a reserved word,
- it is not `arguments` in strict scopes (where `arguments` is not allowed),
- it does not collide with the actual `arguments` (which is always defined in function scopes).

Useful when you want to rename a variable (or create a new variable) while being sure not to shadow any other variables in the code.

@param {string} name - The desired name for a new variable.
@param {Scope[]} scopes - The list of scopes the new variable will be referenced in.
@param {isSafe} [isSafe] - Rule-specific name check function.
@returns {string} - Either `name` as is, or a string like `${name}_` suffixed with underscores to make the name unique.
*/
module.exports = (name, scopes, isSafe = alwaysTrue) => {
	if (!isValidIdentifier(name)) {
		name += '_';

		if (!isValidIdentifier(name)) {
			return;
		}
	}

	while (!isSafeName(name, scopes) || !isSafe(name, scopes)) {
		name += '_';
	}

	return name;
};