<?php declare(strict_types = 1);

namespace SlevomatCodingStandard\Sniffs\ControlStructures;

use Exception;
use PHP_CodeSniffer\Files\File;
use PHP_CodeSniffer\Sniffs\Sniff;
use SlevomatCodingStandard\Helpers\ConditionHelper;
use SlevomatCodingStandard\Helpers\FixerHelper;
use SlevomatCodingStandard\Helpers\IndentationHelper;
use SlevomatCodingStandard\Helpers\ScopeHelper;
use SlevomatCodingStandard\Helpers\TokenHelper;
use Throwable;
use function array_key_exists;
use function count;
use function in_array;
use function range;
use function sort;
use function sprintf;
use const T_CLOSE_CURLY_BRACKET;
use const T_CLOSURE;
use const T_COLON;
use const T_DO;
use const T_ELSE;
use const T_ELSEIF;
use const T_FOR;
use const T_FOREACH;
use const T_FUNCTION;
use const T_IF;
use const T_OPEN_CURLY_BRACKET;
use const T_SEMICOLON;
use const T_WHILE;

class EarlyExitSniff implements Sniff
{

	public const CODE_EARLY_EXIT_NOT_USED = 'EarlyExitNotUsed';
	public const CODE_USELESS_ELSEIF = 'UselessElseIf';
	public const CODE_USELESS_ELSE = 'UselessElse';

	public bool $ignoreStandaloneIfInScope = false;

	public bool $ignoreOneLineTrailingIf = false;

	public bool $ignoreTrailingIfWithOneInstruction = false;

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

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

		if ($tokens[$pointer]['code'] === T_IF) {
			$this->processIf($phpcsFile, $pointer);
		} elseif ($tokens[$pointer]['code'] === T_ELSEIF) {
			$this->processElseIf($phpcsFile, $pointer);
		} else {
			$this->processElse($phpcsFile, $pointer);
		}
	}

	private function processElse(File $phpcsFile, int $elsePointer): void
	{
		$tokens = $phpcsFile->getTokens();

		if (!array_key_exists('scope_opener', $tokens[$elsePointer])) {
			// Else without curly braces is not supported.
			return;
		}

		try {
			$allConditionsPointers = $this->getAllConditionsPointers($phpcsFile, $elsePointer);
		} catch (Throwable $e) {
			// Else without curly braces is not supported.
			return;
		}

		if (TokenHelper::findNext(
			$phpcsFile,
			T_FUNCTION,
			$tokens[$elsePointer]['scope_opener'] + 1,
			$tokens[$elsePointer]['scope_closer'],
		) !== null) {
			return;
		}

		$ifPointer = $allConditionsPointers[0];
		$ifEarlyExitPointer = null;
		$elseEarlyExitPointer = null;
		$previousConditionPointer = null;
		$previousConditionEarlyExitPointer = null;

		foreach ($allConditionsPointers as $conditionPointer) {
			$conditionEarlyExitPointer = $this->findEarlyExitInScope(
				$phpcsFile,
				$tokens[$conditionPointer]['scope_opener'],
				$tokens[$conditionPointer]['scope_closer'],
			);

			if ($conditionPointer === $elsePointer) {
				$elseEarlyExitPointer = $conditionEarlyExitPointer;
				continue;
			}

			if (count($allConditionsPointers) > 2 && $conditionEarlyExitPointer === null) {
				return;
			}

			$previousConditionPointer = $conditionPointer;
			$previousConditionEarlyExitPointer = $conditionEarlyExitPointer;

			if ($conditionPointer === $ifPointer) {
				$ifEarlyExitPointer = $conditionEarlyExitPointer;
				continue;
			}
		}

		if ($ifEarlyExitPointer === null && $elseEarlyExitPointer === null) {
			return;
		}

		if ($elseEarlyExitPointer !== null && $previousConditionEarlyExitPointer === null) {
			$fix = $phpcsFile->addFixableError('Use early exit instead of "else".', $elsePointer, self::CODE_EARLY_EXIT_NOT_USED);

			if (!$fix) {
				return;
			}

			$ifCodePointers = $this->getScopeCodePointers($phpcsFile, $ifPointer);
			$elseCode = $this->getScopeCode($phpcsFile, $elsePointer);
			$negativeIfCondition = ConditionHelper::getNegativeCondition(
				$phpcsFile,
				$tokens[$ifPointer]['parenthesis_opener'],
				$tokens[$ifPointer]['parenthesis_closer'],
			);
			$afterIfCode = IndentationHelper::removeIndentation(
				$phpcsFile,
				$ifCodePointers,
				IndentationHelper::getIndentation($phpcsFile, $ifPointer),
			);

			$ifContent = sprintf('if %s {%s}%s%s', $negativeIfCondition, $elseCode, $phpcsFile->eolChar, $afterIfCode);

			$phpcsFile->fixer->beginChangeset();

			FixerHelper::change($phpcsFile, $ifPointer, $tokens[$elsePointer]['scope_closer'], $ifContent);

			$phpcsFile->fixer->endChangeset();

			return;
		}

		$fix = $phpcsFile->addFixableError('Remove useless "else" to reduce code nesting.', $elsePointer, self::CODE_USELESS_ELSE);

		if (!$fix) {
			return;
		}

		$elseCodePointers = $this->getScopeCodePointers($phpcsFile, $elsePointer);
		$afterIfCode = IndentationHelper::removeIndentation(
			$phpcsFile,
			$elseCodePointers,
			IndentationHelper::getIndentation($phpcsFile, $ifPointer),
		);

		$phpcsFile->fixer->beginChangeset();

		$previousConditionContent = sprintf('%s%s', $phpcsFile->eolChar, $afterIfCode);

		FixerHelper::change(
			$phpcsFile,
			$tokens[$previousConditionPointer]['scope_closer'] + 1,
			$tokens[$elsePointer]['scope_closer'],
			$previousConditionContent,
		);

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

	private function processElseIf(File $phpcsFile, int $elseIfPointer): void
	{
		$tokens = $phpcsFile->getTokens();

		try {
			$allConditionsPointers = $this->getAllConditionsPointers($phpcsFile, $elseIfPointer);
		} catch (Throwable $e) {
			// Elseif without curly braces is not supported.
			return;
		}

		if (TokenHelper::findNext(
			$phpcsFile,
			T_FUNCTION,
			$tokens[$elseIfPointer]['scope_opener'] + 1,
			$tokens[$elseIfPointer]['scope_closer'],
		) !== null) {
			return;
		}

		foreach ($allConditionsPointers as $conditionPointer) {
			$conditionEarlyExitPointer = $this->findEarlyExitInScope(
				$phpcsFile,
				$tokens[$conditionPointer]['scope_opener'],
				$tokens[$conditionPointer]['scope_closer'],
			);

			if ($conditionPointer === $elseIfPointer) {
				break;
			}

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

		$fix = $phpcsFile->addFixableError('Use "if" instead of "elseif".', $elseIfPointer, self::CODE_USELESS_ELSEIF);

		if (!$fix) {
			return;
		}

		/** @var int $pointerBeforeElseIfPointer */
		$pointerBeforeElseIfPointer = TokenHelper::findPreviousNonWhitespace($phpcsFile, $elseIfPointer - 1);

		$phpcsFile->fixer->beginChangeset();

		FixerHelper::removeBetween($phpcsFile, $pointerBeforeElseIfPointer, $elseIfPointer);

		$phpcsFile->fixer->addNewline($pointerBeforeElseIfPointer);
		$phpcsFile->fixer->addNewline($pointerBeforeElseIfPointer);

		FixerHelper::replace(
			$phpcsFile,
			$elseIfPointer,
			sprintf('%sif', IndentationHelper::getIndentation($phpcsFile, $allConditionsPointers[0])),
		);

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

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

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

		$nextPointer = TokenHelper::findNextNonWhitespace($phpcsFile, $tokens[$ifPointer]['scope_closer'] + 1);
		if ($nextPointer === null || $tokens[$nextPointer]['code'] !== T_CLOSE_CURLY_BRACKET) {
			return;
		}

		$previousPointer = TokenHelper::findPreviousEffective($phpcsFile, $ifPointer - 1);
		if (
			$this->ignoreStandaloneIfInScope
			&& in_array($tokens[$previousPointer]['code'], [T_OPEN_CURLY_BRACKET, T_COLON], true)
		) {
			return;
		}

		if (
			$this->ignoreOneLineTrailingIf
			&& $tokens[$tokens[$ifPointer]['scope_opener']]['line'] + 2 === $tokens[$tokens[$ifPointer]['scope_closer']]['line']
		) {
			return;
		}

		if ($this->ignoreTrailingIfWithOneInstruction) {
			$pointerBeforeScopeCloser = TokenHelper::findPreviousEffective($phpcsFile, $tokens[$ifPointer]['scope_closer'] - 1);
			if ($tokens[$pointerBeforeScopeCloser]['code'] === T_SEMICOLON) {
				$ignore = true;

				$searchStartPointer = $tokens[$ifPointer]['scope_opener'] + 1;

				while (true) {
					$anotherSemicolonPointer = TokenHelper::findNext(
						$phpcsFile,
						T_SEMICOLON,
						$searchStartPointer,
						$pointerBeforeScopeCloser,
					);
					if ($anotherSemicolonPointer === null) {
						break;
					}

					if (ScopeHelper::isInSameScope($phpcsFile, $anotherSemicolonPointer, $pointerBeforeScopeCloser)) {
						$ignore = false;
						break;
					}

					$searchStartPointer = $anotherSemicolonPointer + 1;
				}

				if ($ignore) {
					return;
				}
			}
		}

		$scopePointer = $tokens[$nextPointer]['scope_condition'];

		if (!in_array($tokens[$scopePointer]['code'], [T_FUNCTION, T_CLOSURE, T_WHILE, T_DO, T_FOREACH, T_FOR], true)) {
			return;
		}

		if ($this->isEarlyExitInScope($phpcsFile, $tokens[$ifPointer]['scope_opener'], $tokens[$ifPointer]['scope_closer'])) {
			return;
		}

		$fix = $phpcsFile->addFixableError('Use early exit to reduce code nesting.', $ifPointer, self::CODE_EARLY_EXIT_NOT_USED);
		if (!$fix) {
			return;
		}

		$ifCodePointers = $this->getScopeCodePointers($phpcsFile, $ifPointer);
		$ifIndentation = IndentationHelper::getIndentation($phpcsFile, $ifPointer);
		$earlyExitCode = $this->getEarlyExitCode($tokens[$scopePointer]['code']);
		$earlyExitCodeIndentation = IndentationHelper::addIndentation($phpcsFile, $ifIndentation);

		$negativeIfCondition = ConditionHelper::getNegativeCondition(
			$phpcsFile,
			$tokens[$ifPointer]['parenthesis_opener'],
			$tokens[$ifPointer]['parenthesis_closer'],
		);
		$afterIfCode = IndentationHelper::removeIndentation($phpcsFile, $ifCodePointers, $ifIndentation);

		$ifContent = sprintf(
			'if %s {%s%s%s;%s%s}%s%s',
			$negativeIfCondition,
			$phpcsFile->eolChar,
			$earlyExitCodeIndentation,
			$earlyExitCode,
			$phpcsFile->eolChar,
			$ifIndentation,
			$phpcsFile->eolChar,
			$afterIfCode,
		);

		$phpcsFile->fixer->beginChangeset();

		FixerHelper::change($phpcsFile, $ifPointer, $tokens[$ifPointer]['scope_closer'], $ifContent);

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

	private function getScopeCode(File $phpcsFile, int $scopePointer): string
	{
		$tokens = $phpcsFile->getTokens();
		return TokenHelper::getContent($phpcsFile, $tokens[$scopePointer]['scope_opener'] + 1, $tokens[$scopePointer]['scope_closer'] - 1);
	}

	/**
	 * @return list<int>
	 */
	private function getScopeCodePointers(File $phpcsFile, int $scopePointer): array
	{
		$tokens = $phpcsFile->getTokens();
		return range($tokens[$scopePointer]['scope_opener'] + 1, $tokens[$scopePointer]['scope_closer'] - 1);
	}

	/**
	 * @param string|int $code
	 */
	private function getEarlyExitCode($code): string
	{
		if (in_array($code, [T_WHILE, T_DO, T_FOREACH, T_FOR], true)) {
			return 'continue';
		}

		return 'return';
	}

	private function findEarlyExitInScope(File $phpcsFile, int $startPointer, int $endPointer): ?int
	{
		$tokens = $phpcsFile->getTokens();

		$ifPointers = TokenHelper::findNextAll($phpcsFile, T_IF, $startPointer + 1, $endPointer);
		foreach ($ifPointers as $ifPointer) {
			if ($tokens[$ifPointer]['level'] - 1 !== $tokens[$startPointer]['level']) {
				continue;
			}

			$conditionPointers = $this->getAllConditionsPointers($phpcsFile, $ifPointer);
			foreach ($conditionPointers as $conditionPointer) {
				if ($this->findEarlyExitInScope(
					$phpcsFile,
					$tokens[$conditionPointer]['scope_opener'],
					$tokens[$conditionPointer]['scope_closer'],
				) === null) {
					return null;
				}
			}
		}

		$lastSemicolonInScopePointer = TokenHelper::findPreviousEffective($phpcsFile, $endPointer - 1, $startPointer);
		return $tokens[$lastSemicolonInScopePointer]['code'] === T_SEMICOLON
			? TokenHelper::findPreviousLocal(
				$phpcsFile,
				TokenHelper::EARLY_EXIT_TOKEN_CODES,
				$lastSemicolonInScopePointer - 1,
				$startPointer,
			)
			: null;
	}

	private function isEarlyExitInScope(File $phpcsFile, int $startPointer, int $endPointer): bool
	{
		return $this->findEarlyExitInScope($phpcsFile, $startPointer, $endPointer) !== null;
	}

	/**
	 * @return list<int>
	 */
	private function getAllConditionsPointers(File $phpcsFile, int $conditionPointer): array
	{
		$tokens = $phpcsFile->getTokens();

		$conditionsPointers = [$conditionPointer];

		if (
			isset($tokens[$conditionPointer]['scope_opener'])
			&& $tokens[$tokens[$conditionPointer]['scope_opener']]['code'] === T_COLON
		) {
			// Alternative control structure syntax.
			throw new Exception(sprintf('"%s" without curly braces is not supported.', $tokens[$conditionPointer]['content']));
		}

		if ($tokens[$conditionPointer]['code'] !== T_IF) {
			$currentConditionPointer = $conditionPointer;
			do {
				$previousConditionCloseParenthesisPointer = TokenHelper::findPreviousEffective($phpcsFile, $currentConditionPointer - 1);
				$currentConditionPointer = $tokens[$previousConditionCloseParenthesisPointer]['scope_condition'];

				$conditionsPointers[] = $currentConditionPointer;
			} while ($tokens[$currentConditionPointer]['code'] !== T_IF);
		}

		if ($tokens[$conditionPointer]['code'] !== T_ELSE) {
			if (!array_key_exists('scope_closer', $tokens[$conditionPointer])) {
				throw new Exception(sprintf('"%s" without curly braces is not supported.', $tokens[$conditionPointer]['content']));
			}

			$currentConditionPointer = TokenHelper::findNextEffective($phpcsFile, $tokens[$conditionPointer]['scope_closer'] + 1);
			if ($currentConditionPointer !== null) {
				while (in_array($tokens[$currentConditionPointer]['code'], [T_ELSEIF, T_ELSE], true)) {
					$conditionsPointers[] = $currentConditionPointer;

					if (!array_key_exists('scope_closer', $tokens[$currentConditionPointer])) {
						throw new Exception(
							sprintf('"%s" without curly braces is not supported.', $tokens[$currentConditionPointer]['content']),
						);
					}

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

		sort($conditionsPointers);

		return $conditionsPointers;
	}

}
