<?php declare(strict_types = 1);

namespace SlevomatCodingStandard\Sniffs\ControlStructures;

use PHP_CodeSniffer\Files\File;
use PHP_CodeSniffer\Sniffs\Sniff;
use PHP_CodeSniffer\Util\Tokens;
use SlevomatCodingStandard\Helpers\ConditionHelper;
use SlevomatCodingStandard\Helpers\FixerHelper;
use SlevomatCodingStandard\Helpers\TokenHelper;
use function array_key_exists;
use function in_array;
use function sprintf;
use function strtolower;
use const T_ELSE;
use const T_FALSE;
use const T_IF;
use const T_RETURN;
use const T_SEMICOLON;
use const T_TRUE;

class UselessIfConditionWithReturnSniff implements Sniff
{

	public const CODE_USELESS_IF_CONDITION = 'UselessIfCondition';

	public bool $assumeAllConditionExpressionsAreAlreadyBoolean = false;

	/**
	 * @return array<int, (int|string)>
	 */
	public function register(): array
	{
		return [
			T_IF,
		];
	}

	public function process(File $phpcsFile, int $ifPointer): void
	{
		$tokens = $phpcsFile->getTokens();

		if (!array_key_exists('scope_closer', $tokens[$ifPointer])) {
			// If without curly braces is not supported.
			return;
		}

		$ifBooleanPointer = $this->findBooleanAfterReturnInScope($phpcsFile, $tokens[$ifPointer]['scope_opener']);
		if ($ifBooleanPointer === null) {
			return;
		}

		$newCondition = static fn (): string => strtolower($tokens[$ifBooleanPointer]['content']) === 'true'
			? TokenHelper::getContent(
				$phpcsFile,
				$tokens[$ifPointer]['parenthesis_opener'] + 1,
				$tokens[$ifPointer]['parenthesis_closer'] - 1,
			)
			: ConditionHelper::getNegativeCondition(
				$phpcsFile,
				$tokens[$ifPointer]['parenthesis_opener'] + 1,
				$tokens[$ifPointer]['parenthesis_closer'] - 1,
			);

		$elsePointer = TokenHelper::findNextEffective($phpcsFile, $tokens[$ifPointer]['scope_closer'] + 1);

		$errorParameters = [
			'Useless condition.',
			$ifPointer,
			self::CODE_USELESS_IF_CONDITION,
		];

		if (
			$elsePointer !== null
			&& $tokens[$elsePointer]['code'] === T_ELSE
		) {
			if (!array_key_exists('scope_closer', $tokens[$elsePointer])) {
				// Else without curly braces is not supported.
				return;
			}

			$elseBooleanPointer = $this->findBooleanAfterReturnInScope($phpcsFile, $tokens[$elsePointer]['scope_opener']);
			if ($elseBooleanPointer === null) {
				return;
			}

			if (!$this->isFixable($phpcsFile, $ifPointer, $tokens[$elsePointer]['scope_closer'])) {
				$phpcsFile->addError(...$errorParameters);
				return;
			}

			$fix = $phpcsFile->addFixableError(...$errorParameters);

			if (!$fix) {
				return;
			}

			$phpcsFile->fixer->beginChangeset();

			FixerHelper::change($phpcsFile, $ifPointer, $tokens[$elsePointer]['scope_closer'], sprintf('return %s;', $newCondition()));

			$phpcsFile->fixer->endChangeset();
		} else {
			$returnPointer = TokenHelper::findNextEffective($phpcsFile, $tokens[$ifPointer]['scope_closer'] + 1);

			if ($returnPointer === null) {
				return;
			}

			if ($tokens[$returnPointer]['code'] !== T_RETURN) {
				return;
			}

			$semicolonPointer = $this->findSemicolonAfterReturnWithBoolean($phpcsFile, $returnPointer);
			if ($semicolonPointer === null) {
				return;
			}

			if (!$this->isFixable($phpcsFile, $ifPointer, $semicolonPointer)) {
				$phpcsFile->addError(...$errorParameters);
				return;
			}

			$fix = $phpcsFile->addFixableError(...$errorParameters);

			if (!$fix) {
				return;
			}

			$phpcsFile->fixer->beginChangeset();

			FixerHelper::change($phpcsFile, $ifPointer, $semicolonPointer, sprintf('return %s;', $newCondition()));

			$phpcsFile->fixer->endChangeset();
		}
	}

	private function isFixable(File $phpcsFile, int $ifPointer, int $endPointer): bool
	{
		$tokens = $phpcsFile->getTokens();

		if (TokenHelper::findNext($phpcsFile, Tokens::COMMENT_TOKENS, $ifPointer + 1, $endPointer) !== null) {
			return false;
		}

		if ($this->assumeAllConditionExpressionsAreAlreadyBoolean) {
			return true;
		}

		return ConditionHelper::conditionReturnsBoolean(
			$phpcsFile,
			$tokens[$ifPointer]['parenthesis_opener'] + 1,
			$tokens[$ifPointer]['parenthesis_closer'] - 1,
		);
	}

	private function findBooleanAfterReturnInScope(File $phpcsFile, int $scopeOpenerPointer): ?int
	{
		$tokens = $phpcsFile->getTokens();

		/** @var int $returnPointer */
		$returnPointer = TokenHelper::findNextEffective($phpcsFile, $scopeOpenerPointer + 1);
		if ($tokens[$returnPointer]['code'] !== T_RETURN) {
			return null;
		}

		$booleanPointer = $this->findBooleanAfterReturn($phpcsFile, $returnPointer);
		if ($booleanPointer === null) {
			return null;
		}

		$semicolonPointer = TokenHelper::findNextEffective($phpcsFile, $booleanPointer + 1);
		if ($tokens[$semicolonPointer]['code'] !== T_SEMICOLON) {
			return null;
		}

		return $booleanPointer;
	}

	private function findBooleanAfterReturn(File $phpcsFile, int $returnPointer): ?int
	{
		$tokens = $phpcsFile->getTokens();

		$booleanPointer = TokenHelper::findNextEffective($phpcsFile, $returnPointer + 1);
		if (in_array($tokens[$booleanPointer]['code'], [T_TRUE, T_FALSE], true)) {
			return $booleanPointer;
		}

		return null;
	}

	private function findSemicolonAfterReturnWithBoolean(File $phpcsFile, int $returnPointer): ?int
	{
		$tokens = $phpcsFile->getTokens();

		$booleanPointer = $this->findBooleanAfterReturn($phpcsFile, $returnPointer);
		if ($booleanPointer === null) {
			return null;
		}

		$semicolonPointer = TokenHelper::findNextEffective($phpcsFile, $booleanPointer + 1);
		if ($tokens[$semicolonPointer]['code'] !== T_SEMICOLON) {
			return null;
		}

		return $semicolonPointer;
	}

}
