<?php
/**
 * This source file is part of the open source project
 * ExpressionEngine (https://expressionengine.com)
 *
 * @link      https://expressionengine.com/
 * @copyright Copyright (c) 2003-2022, Packet Tide, LLC (https://www.packettide.com)
 * @license   https://expressionengine.com/license Licensed under Apache License, Version 2.0
 */

namespace ExpressionEngine\Library\Parser\Conditional;

use ExpressionEngine\Library\Parser\AbstractLexer;
use ExpressionEngine\Library\Parser\Conditional\Exception\LexerException;

use ExpressionEngine\Library\Parser\Conditional\Token\Token;
use ExpressionEngine\Library\Parser\Conditional\Token\Boolean;
use ExpressionEngine\Library\Parser\Conditional\Token\Comment;
use ExpressionEngine\Library\Parser\Conditional\Token\Number;
use ExpressionEngine\Library\Parser\Conditional\Token\Operator;
use ExpressionEngine\Library\Parser\Conditional\Token\Other;
use ExpressionEngine\Library\Parser\Conditional\Token\StringLiteral;
use ExpressionEngine\Library\Parser\Conditional\Token\Tag;
use ExpressionEngine\Library\Parser\Conditional\Token\Variable;

use ExpressionEngine\Library\Template\Annotation\Runtime as RuntimeAnnotations;

/**
 * Conditional Lexer
 */
class Lexer extends AbstractLexer
{
    /**
     * Available tokens:
     *
     * private $token_types = array(
     * 	'TEMPLATE_STRING',	// generic
     *  'LD'				// {
     *  'RD'				// }
     * 	'IF',				// if
     * 	'ELSE',				// if:else
     * 	'ELSEIF',			// if:elseif
     * 	'ENDIF',			// /if
     * 	'STRING',			// literal string "foo", or 'foo'. The value does not include quotes
     * 	'NUMBER',			// literal number
     * 	'VARIABLE',
     * 	'OPERATOR',			// an operator from the $operators array
     * 	'MISC',				// other stuff, usually illegal when safety on
     * 	'LP',				// (
     * 	'RP',				// )
     * 	'WHITESPACE',		// \s\r\n\t
     * 	'BOOL',				// TRUE or FALSE (case insensitive)
     * 	'TAG',				// {exp:foo:bar}
     * 	'EOS'				// end of string
     * );
     */

    /**
     * Tag contents
     */
    private $tag_buffer = '';

    /**
     * Tag depth
     */
    private $tag_depth = 0;

    const COMMENT_PATTERN = "
		\{!--		# open tag
		(.*?)		# anything inbetween
		--\}		# closing tag
	";

    /**
     * Regex for boolean values
     */
    const BOOL_PATTERN = "
		\b					# must be its own word
		(true|false)		# The pattern is case insensitive
		(?!(-+)?\w)			# simulate \b with -
	";

    /**
     * Regex for variables
     */
    const VARIABLE_PATTERN = "
		\w*(								# word characters on both ends are ok
			[a-zA-Z]([\w:-]+\w)?			# we need at least one alpha in there
			|								# to avoid things like 5-5, and it can't
			(\w[\w:-]+)?[a-zA-Z]			# begin or end in : or -
		)\w*
	";

    /**
     * Regex for numbers
     */
    const NUMBER_PATTERN = "
		(
			[0-9]*\.[0-9]+					# You must have a number either
			|								# before or after the dot. The other
			[0-9]+\.[0-9]*					# side is then optional: .5, 5., 1.2
			|
			[0-9]+							# Integers are cool, too
		)
	";

    /**
     * Pattern used for all of the above patterns. Run as one
     * to improve performance.
     */
    private $compiled_pattern;

    /**
     * Pattern used to match operators. Automatically generated
     * from the operators array below.
     */
    private $operator_pattern;

    /**
     * Valid operators.
     *
     * If you add one here, you must also add its logic to the boolean
     * expression class. If an operator is the same as the beginning of
     * another, the longer must be first. (e.g. ^= before ^).
     */
    private $operators = array(
        '^=', '*=', '$=', '~',
        '==', '!=', '<=', '>=', '<>', '<', '>',
        '**', '%', '+', '-', '*', '/',
        '.', '!', '^',
        '||', '&&',
        'AND', 'OR', 'XOR'
    );

    protected $lineno_stack = array();
    protected $context_stack = array();

    protected $lineno;
    protected $context;
    protected $annotations;

    public function __construct()
    {
        $this->lineno = 1;
        $this->context = '';

        $this->operator_pattern = $this->compileOperatorPattern();
        $this->compiled_pattern = $this->compilePattern();

        $this->annotations = new RuntimeAnnotations();
        $this->annotations->useSharedStore();
    }

    /**
     * Finds conditionals an returns a token stream for the entire template, with
     * conditional specific tokens.
     *
     * @param $str The template chunk to look through
     * @return array [new chunk, new variables]
     */
    public function tokenize($str)
    {
        $this->str = $str;
        $this->tokens = array();

        while (! $this->eof()) {
            // go to the next LD
            $buffer = $this->seekTo('{');

            // anything we hit in the meantime is template string
            $this->addToken('TEMPLATE_STRING', $buffer);

            // check for template tags
            $this->templateTags();
        }

        if ($this->tag_depth !== 0) {
            throw new LexerException('Unclosed tag.');
        }

        $this->addToken('TEMPLATE_STRING', $this->rest());
        $this->addToken('EOS', true);

        unset($this->str);

        return $this->tokens;
    }

    /**
     * We saw a {, check if it's an ee tag that we can use.
     */
    private function templateTags()
    {
        if ($this->peek(5) == '{/if}') {
            $this->addToken('LD', '{');
            $this->addToken('ENDIF', '/if');
            $this->move(4);
        } elseif ($this->peek(9) == '{if:else}') {
            $this->addToken('LD', '{');
            $this->addToken('ELSE', 'if:else');
            $this->move(8);
        } elseif ($if = $this->peekRegex('\{(if(:elseif)?\s)')) {
            $last = end($this->tokens);

            if (! $last || $last->type != 'COMMENT' || ! $last->conditional_annotation) {
                $annotation_token = new Comment(
                    $this->annotations->create(array(
                        'context' => $this->context,
                        'lineno' => $this->lineno,
                        'conditional' => true
                    ))
                );

                // mark for the parser to remove when the conditional
                // is resolved
                $annotation_token->conditional_annotation = true;

                $this->tokens[] = $annotation_token;
            }

            $this->addToken('LD', '{');

            if (strlen($if) == 4) {
                $this->move(3);
                $this->addToken('IF', 'if');
            } else {
                $this->move(10);
                $this->addToken('ELSEIF', 'if:elseif');
            }

            $this->whitespace();
            $this->expression();
        } elseif ($comment = $this->peekRegex(self::COMMENT_PATTERN, 'usx')) {
            $this->addToken('COMMENT', $this->move(strlen($comment)));

            return;
        } else {
            $this->addToken('TEMPLATE_STRING', $this->next());

            // future: $this->tag();

            if ($this->peek(3) == 'if:') {
                throw new LexerException('if: is a reserved prefix.');
            }

            return;
        }

        $this->whitespace();

        if ($this->peek() == '}') {
            $this->next();
            $this->addToken('RD', '}');
        }
    }

    /**
     * Finds tokens specific to conditional boolean statements.
     */
    private function expression()
    {
        while (! $this->eof()) {
            $this->whitespace();

            $char = $this->peek();

            if ($char == '}' && $this->tag_depth == 0) {  // Checking for balanced curly braces
                return;
            } elseif ($char == '(' || $char == ')') {
                $this->parenthesis();
            } elseif ($this->operator()) {
                ; // nothing
            } elseif ($this->value()) {
                ; // nothing
            } elseif ($char == '{') {
                $this->next();
                $this->tag();
            } else {
                $this->next();
                $this->addToken('MISC', $char);
            }
        }
    }

    /**
     * We've entered a tag, find the end while respecting proper quoting.
     */
    private function tag()
    {
        $this->tag_depth++;
        $this->tag_buffer .= '{';

        while (($char = $this->peek()) !== false) {
            switch ($char) {
                case '}':
                    $this->next();

                    break 2;
                case '"':
                case "'":
                    $this->string();

                    break;
                case '{':
                    $this->next();
                    $this->tag();

                    break;
                default:
                    $this->tag_buffer .= $this->next();
            }
        }

        $this->tag_buffer .= '}';
        $this->tag_depth--;

        if ($this->tag_depth == 0) {
            $this->addToken('TAG', $this->tag_buffer);
            $this->tag_buffer = '';
        }
    }

    /**
     * Try to create a whitespace token at the current offset
     */
    private function whitespace()
    {
        if ($ws = $this->peekRegex('\s+')) {
            $this->move(strlen($ws));
            $this->addToken('WHITESPACE', $ws);
        }
    }

    /**
     * Variables and Scalars
     */
    private function value()
    {
        if (preg_match($this->compiled_pattern, $this->str, $matches)) {
            foreach (array_reverse($matches) as $type => $value) {
                if (is_string($type)) {
                    $this->addToken($type, $value);
                    $this->move(strlen($value));

                    return true;
                }
            }
        }

        $char = $this->peek();

        if ($char == '"' || $char == "'") {
            $this->string();

            return true;
        }

        return false;
    }

    /**
     * Operators
     */
    private function operator()
    {
        $operator = $this->peekRegex($this->operator_pattern, 'usi');

        if (isset($operator)) {
            $this->move(strlen($operator));
            $this->addToken('OPERATOR', $operator);

            return true;
        }

        return false;
    }

    /**
     * Build and add a string token
     */
    private function string()
    {
        $open_quote = $this->next();

        $str = '';
        $backslash = '\\';
        $escapable = array('\\', "'", '"');

        // Add everything up to the next backslash or closing quote
        // and then check if we're done or just escaping.
        while (true) {
            $add = $this->seekTo($open_quote . $backslash);

            if ($this->eof()) {
                throw new LexerException('Unclosed string.');
            }

            $str .= $add;

            if ($open_quote == $this->next()) {
                break;
            }

            $next = $this->next();

            if (! in_array($next, $escapable)) {
                $str .= $backslash;
            }

            $str .= $next;
        }

        // if we're in a tag we need to keep the quotes
        if ($this->tag_depth > 0) {
            $this->tag_buffer .= $open_quote . $str . $open_quote;
        } else {
            $this->addToken('STRING', $str);
        }
    }

    /**
     * Try to create a parenthesis token at the current offset
     */
    private function parenthesis()
    {
        $char = $this->peek();

        if ($char == '(') {
            $this->addToken('LP', '(');
            $this->next();
        } elseif ($char == ')') {
            $this->addToken('RP', ')');
            $this->next();
        }
    }

    /**
     * Create the pattern that matches operators.
     */
    private function compileOperatorPattern()
    {
        $pattern = '';

        foreach ($this->operators as $operator) {
            $operator = preg_quote($operator, '/');

            // Special negative lookahead addition for concatenation
            // 1.2 is a number, not two concatenated numbers. To be consistent
            // with that, 1.2.3 should turn into number (1.2), number (.3). So
            // any concatenation with a trailing number is not a valid operation
            // unless there's whitespace. This is also how PHP's token_get_all()
            // handles it.
            if ($operator == '\.') {
                $operator = $operator . '(?!\d)';
            } elseif (ctype_alpha($operator[0])) {
                $operator = '\b' . $operator . '(?!(-+)?\w)';
            }

            $pattern .= $operator . '|';
        }

        return $pattern = substr($pattern, 0, -1);
    }

    /**
     * Compile the regular expressions into one big
     * matching pattern.
     */
    private function compilePattern()
    {
        return '/(' .
            '(?P<COMMENT>' . self::COMMENT_PATTERN . ')|' .
            '(?P<BOOL>' . self::BOOL_PATTERN . ')|' .
            '(?P<VARIABLE>' . self::VARIABLE_PATTERN . ')|' .
            '(?P<NUMBER>' . self::NUMBER_PATTERN . ')' .
            ')/Aiusx';
    }

    /**
     * Add token to the token stream
     *
     * @param string $type	 The type of token being added
     * @param string $lexeme The value of the token being added
     */
    private function addToken($type, $lexeme)
    {
        // Always store strings, even empty ones
        if ($lexeme != '' || $type == 'STRING') {
            $this->lineno += substr_count($lexeme, "\n");

            // check comments for annotations
            if ($type == 'COMMENT') {
                if ($annotation = $this->annotations->read($lexeme)) {
                    $this->syncWithAnnotation($annotation);
                }
            }

            // EE PRO: we do not need to do anything here 
            // since the template is modified after lexemes are built

            switch ($type) {
                case 'BOOL': $obj = new Boolean($lexeme);

                    break;
                case 'COMMENT': $obj = new Comment($lexeme);

                    break;
                case 'NUMBER': $obj = new Number($lexeme);

                    break;
                case 'OPERATOR': $obj = new Operator($lexeme);

                    break;
                case 'OTHER': $obj = new Other($lexeme);

                    break;
                case 'STRING': $obj = new StringLiteral($lexeme);

                    break;
                case 'TAG': $obj = new Tag($lexeme);

                    break;
                case 'VARIABLE': $obj = new Variable($lexeme);

                    break;
                default:
                    $obj = new Token($type, $lexeme);
            }

            // (Re-)Mark conditional annotation comments so the parser
            // knows that it can remove them after dealing with the
            // conditional.
            if (isset($annotation) && isset($annotation->conditional)) {
                $obj->conditional_annotation = true;
            }

            $obj->lineno = $this->lineno;
            $obj->context = $this->context;

            $this->tokens[] = $obj;
        }
    }

    /**
     * Sync the lexer line number state and context with
     * a given annotation.
     *
     * @param Object $annotation The annotation to sync with
     */
    private function syncWithAnnotation($annotation)
    {
        if (isset($annotation->context)) {
            if ($annotation->context == $this->context) {
                // just a line number marker
                if (isset($annotation->lineno)) {
                    $this->lineno = $annotation->lineno;
                }
            } elseif ($annotation->context == end($this->context_stack)) {
                // returning to a previous context
                $this->context = array_pop($this->context_stack);
                $this->lineno = array_pop($this->lineno_stack);
            } else {
                // entering a new context
                $this->context_stack[] = $this->context;
                $this->lineno_stack[] = $this->lineno;

                $this->lineno = 1;
                $this->context = $annotation->context;
            }
        }

        // If the annotation did not yet have a linenumber, then this is
        // the best guess we have, so we assign it here.
        if (! isset($annotation->lineno)) {
            $annotation->lineno = $this->lineno;
        }
    }
}

// EOF
