<?php

/*
 * This file is part of Psy Shell.
 *
 * (c) 2012-2020 Justin Hileman
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */

namespace Psy;

use PhpParser\NodeTraverser;
use PhpParser\Parser;
use PhpParser\PrettyPrinter\Standard as Printer;
use Psy\CodeCleaner\AbstractClassPass;
use Psy\CodeCleaner\AssignThisVariablePass;
use Psy\CodeCleaner\CalledClassPass;
use Psy\CodeCleaner\CallTimePassByReferencePass;
use Psy\CodeCleaner\EmptyArrayDimFetchPass;
use Psy\CodeCleaner\ExitPass;
use Psy\CodeCleaner\FinalClassPass;
use Psy\CodeCleaner\FunctionContextPass;
use Psy\CodeCleaner\FunctionReturnInWriteContextPass;
use Psy\CodeCleaner\ImplicitReturnPass;
use Psy\CodeCleaner\InstanceOfPass;
use Psy\CodeCleaner\LabelContextPass;
use Psy\CodeCleaner\LeavePsyshAlonePass;
use Psy\CodeCleaner\ListPass;
use Psy\CodeCleaner\LoopContextPass;
use Psy\CodeCleaner\MagicConstantsPass;
use Psy\CodeCleaner\NamespacePass;
use Psy\CodeCleaner\PassableByReferencePass;
use Psy\CodeCleaner\RequirePass;
use Psy\CodeCleaner\StrictTypesPass;
use Psy\CodeCleaner\UseStatementPass;
use Psy\CodeCleaner\ValidClassNamePass;
use Psy\CodeCleaner\ValidConstantPass;
use Psy\CodeCleaner\ValidConstructorPass;
use Psy\CodeCleaner\ValidFunctionNamePass;
use Psy\Exception\ParseErrorException;

/**
 * A service to clean up user input, detect parse errors before they happen,
 * and generally work around issues with the PHP code evaluation experience.
 */
class CodeCleaner
{
    private $parser;
    private $printer;
    private $traverser;
    private $namespace;

    /**
     * CodeCleaner constructor.
     *
     * @param Parser|null        $parser    A PhpParser Parser instance. One will be created if not explicitly supplied
     * @param Printer|null       $printer   A PhpParser Printer instance. One will be created if not explicitly supplied
     * @param NodeTraverser|null $traverser A PhpParser NodeTraverser instance. One will be created if not explicitly supplied
     */
    public function __construct(Parser $parser = null, Printer $printer = null, NodeTraverser $traverser = null)
    {
        if ($parser === null) {
            $parserFactory = new ParserFactory();
            $parser        = $parserFactory->createParser();
        }

        $this->parser    = $parser;
        $this->printer   = $printer ?: new Printer();
        $this->traverser = $traverser ?: new NodeTraverser();

        foreach ($this->getDefaultPasses() as $pass) {
            $this->traverser->addVisitor($pass);
        }
    }

    /**
     * Get default CodeCleaner passes.
     *
     * @return array
     */
    private function getDefaultPasses()
    {
        $useStatementPass = new UseStatementPass();
        $namespacePass    = new NamespacePass($this);

        // Try to add implicit `use` statements and an implicit namespace,
        // based on the file in which the `debug` call was made.
        $this->addImplicitDebugContext([$useStatementPass, $namespacePass]);

        return [
            // Validation passes
            new AbstractClassPass(),
            new AssignThisVariablePass(),
            new CalledClassPass(),
            new CallTimePassByReferencePass(),
            new FinalClassPass(),
            new FunctionContextPass(),
            new FunctionReturnInWriteContextPass(),
            new InstanceOfPass(),
            new LabelContextPass(),
            new LeavePsyshAlonePass(),
            new ListPass(),
            new LoopContextPass(),
            new PassableByReferencePass(),
            new EmptyArrayDimFetchPass(),
            new ValidConstructorPass(),

            // Rewriting shenanigans
            $useStatementPass,        // must run before the namespace pass
            new ExitPass(),
            new ImplicitReturnPass(),
            new MagicConstantsPass(),
            $namespacePass,           // must run after the implicit return pass
            new RequirePass(),
            new StrictTypesPass(),

            // Namespace-aware validation (which depends on aforementioned shenanigans)
            new ValidClassNamePass(),
            new ValidConstantPass(),
            new ValidFunctionNamePass(),
        ];
    }

    /**
     * "Warm up" code cleaner passes when we're coming from a debug call.
     *
     * This is useful, for example, for `UseStatementPass` and `NamespacePass`
     * which keep track of state between calls, to maintain the current
     * namespace and a map of use statements.
     *
     * @param array $passes
     */
    private function addImplicitDebugContext(array $passes)
    {
        $file = $this->getDebugFile();
        if ($file === null) {
            return;
        }

        try {
            $code = @\file_get_contents($file);
            if (!$code) {
                return;
            }

            $stmts = $this->parse($code, true);
            if ($stmts === false) {
                return;
            }

            // Set up a clean traverser for just these code cleaner passes
            $traverser = new NodeTraverser();
            foreach ($passes as $pass) {
                $traverser->addVisitor($pass);
            }

            $traverser->traverse($stmts);
        } catch (\Throwable $e) {
            // Don't care.
        } catch (\Exception $e) {
            // Still don't care.
        }
    }

    /**
     * Search the stack trace for a file in which the user called Psy\debug.
     *
     * @return string|null
     */
    private static function getDebugFile()
    {
        $trace = \debug_backtrace(DEBUG_BACKTRACE_IGNORE_ARGS);

        foreach (\array_reverse($trace) as $stackFrame) {
            if (!self::isDebugCall($stackFrame)) {
                continue;
            }

            if (\preg_match('/eval\(/', $stackFrame['file'])) {
                \preg_match_all('/([^\(]+)\((\d+)/', $stackFrame['file'], $matches);

                return $matches[1][0];
            }

            return $stackFrame['file'];
        }
    }

    /**
     * Check whether a given backtrace frame is a call to Psy\debug.
     *
     * @param array $stackFrame
     *
     * @return bool
     */
    private static function isDebugCall(array $stackFrame)
    {
        $class    = isset($stackFrame['class']) ? $stackFrame['class'] : null;
        $function = isset($stackFrame['function']) ? $stackFrame['function'] : null;

        return ($class === null && $function === 'Psy\\debug') ||
            ($class === Shell::class && $function === 'debug');
    }

    /**
     * Clean the given array of code.
     *
     * @throws ParseErrorException if the code is invalid PHP, and cannot be coerced into valid PHP
     *
     * @param array $codeLines
     * @param bool  $requireSemicolons
     *
     * @return string|false Cleaned PHP code, False if the input is incomplete
     */
    public function clean(array $codeLines, $requireSemicolons = false)
    {
        $stmts = $this->parse('<?php ' . \implode(PHP_EOL, $codeLines) . PHP_EOL, $requireSemicolons);
        if ($stmts === false) {
            return false;
        }

        // Catch fatal errors before they happen
        $stmts = $this->traverser->traverse($stmts);

        // Work around https://github.com/nikic/PHP-Parser/issues/399
        $oldLocale = \setlocale(LC_NUMERIC, 0);
        \setlocale(LC_NUMERIC, 'C');

        $code = $this->printer->prettyPrint($stmts);

        // Now put the locale back
        \setlocale(LC_NUMERIC, $oldLocale);

        return $code;
    }

    /**
     * Set the current local namespace.
     *
     * @param array|null $namespace (default: null)
     *
     * @return array|null
     */
    public function setNamespace(array $namespace = null)
    {
        $this->namespace = $namespace;
    }

    /**
     * Get the current local namespace.
     *
     * @return array|null
     */
    public function getNamespace()
    {
        return $this->namespace;
    }

    /**
     * Lex and parse a block of code.
     *
     * @see Parser::parse
     *
     * @throws ParseErrorException for parse errors that can't be resolved by
     *                             waiting a line to see what comes next
     *
     * @param string $code
     * @param bool   $requireSemicolons
     *
     * @return array|false A set of statements, or false if incomplete
     */
    protected function parse($code, $requireSemicolons = false)
    {
        try {
            return $this->parser->parse($code);
        } catch (\PhpParser\Error $e) {
            if ($this->parseErrorIsUnclosedString($e, $code)) {
                return false;
            }

            if ($this->parseErrorIsUnterminatedComment($e, $code)) {
                return false;
            }

            if ($this->parseErrorIsTrailingComma($e, $code)) {
                return false;
            }

            if (!$this->parseErrorIsEOF($e)) {
                throw ParseErrorException::fromParseError($e);
            }

            if ($requireSemicolons) {
                return false;
            }

            try {
                // Unexpected EOF, try again with an implicit semicolon
                return $this->parser->parse($code . ';');
            } catch (\PhpParser\Error $e) {
                return false;
            }
        }
    }

    private function parseErrorIsEOF(\PhpParser\Error $e)
    {
        $msg = $e->getRawMessage();

        return ($msg === 'Unexpected token EOF') || (\strpos($msg, 'Syntax error, unexpected EOF') !== false);
    }

    /**
     * A special test for unclosed single-quoted strings.
     *
     * Unlike (all?) other unclosed statements, single quoted strings have
     * their own special beautiful snowflake syntax error just for
     * themselves.
     *
     * @param \PhpParser\Error $e
     * @param string           $code
     *
     * @return bool
     */
    private function parseErrorIsUnclosedString(\PhpParser\Error $e, $code)
    {
        if ($e->getRawMessage() !== 'Syntax error, unexpected T_ENCAPSED_AND_WHITESPACE') {
            return false;
        }

        try {
            $this->parser->parse($code . "';");
        } catch (\Exception $e) {
            return false;
        }

        return true;
    }

    private function parseErrorIsUnterminatedComment(\PhpParser\Error $e, $code)
    {
        return $e->getRawMessage() === 'Unterminated comment';
    }

    private function parseErrorIsTrailingComma(\PhpParser\Error $e, $code)
    {
        return ($e->getRawMessage() === 'A trailing comma is not allowed here') && (\substr(\rtrim($code), -1) === ',');
    }
}
