<?php

namespace CorpusParole\Libraries\Sparql;

use CorpusParole\Libraries\Utils;

class SparqlQueryAnalyser {

    const SPARQL_PREFIX_BASE_REGEXP = '(((?:prefix\s+([\p{L}-\d]+)\s*\:)|base)\s*\<((?:(?:https?|ftp)://)(?:\S+(?::\S*)?@)?(?:(?!10(?:\.\d{1,3}){3})(?!127(?:\.\d{1,3}){3})(?!169\.254(?:\.\d{1,3}){2})(?!192\.168(?:\.\d{1,3}){2})(?!172\.(?:1[6-9]|2\d|3[0-1])(?:\.\d{1,3}){2})(?:[1-9]\d?|1\d\d|2[01]\d|22[0-3])(?:\.(?:1?\d{1,2}|2[0-4]\d|25[0-5])){2}(?:\.(?:[1-9]\d?|1\d\d|2[0-4]\d|25[0-4]))|(?:(?:[a-z\x{00a1}-\x{ffff}0-9]+-?)*[a-z\x{00a1}-\x{ffff}0-9]+)(?:\.(?:[a-z\x{00a1}-\x{ffff}0-9]+-?)*[a-z\x{00a1}-\x{ffff}0-9]+)*(?:\.(?:[a-z\x{00a1}-\x{ffff}]{2,})))(?::\d{2,5})?(?:/[^\s]*)?)\>)\s*';

    const SPARQL_SELECT_QUERY_REGEXP = '^(?:\s*(?:'.self::SPARQL_PREFIX_BASE_REGEXP.')*select)';

    const SPARQL_ASK_QUERY_REGEXP = '^(?:\s*(?:'.self::SPARQL_PREFIX_BASE_REGEXP.')*ask)';

    const SPARQL_GRAPH_QUERY_REGEXP = '^(?:\s*(?:'.self::SPARQL_PREFIX_BASE_REGEXP.')*(?:(?:construct)|(?:describe)))';

    const SPARQL_LIMIT_OFFSET_QUERY_REGEXP = '(?:(?:(limit\s+(\d+))|(offset\s+(\d+)))\s*)+\s*$';

    const UNKNOWN_QUERY = 0;

    const SELECT_QUERY = 1;

    const GRAPH_QUERY = 2;

    const ASK_QUERY = 2;

    private $query;

    private $queryType = false;

    private $rawPrefixes = false;

    private $prefixes = false;

    private $limit = false;

    private $offset = false;

    private $rawQuery = false;

    private $countVar = false;

    public function __construct($query) {

        $this->query = $query;

    }

    public function getQueryType() {

        if($this->queryType === false) {

            if(preg_match("%".self::SPARQL_SELECT_QUERY_REGEXP."%iu", $this->query) === 1) {

                $this->queryType = self::SELECT_QUERY;

            } elseif(preg_match("%".self::SPARQL_GRAPH_QUERY_REGEXP."%iu", $this->query) === 1) {

                $this->queryType = self::GRAPH_QUERY;

            } elseif(preg_match("%".self::SPARQL_ASK_QUERY_REGEXP."%iu", $this->query) === 1) {

                $this->queryType = self::ASK_QUERY;

            } else {

                $this->queryType = self::UNKNOWN_QUERY;

            }

        }

        return $this->queryType;

    }

    private function extractPrefix() {

        $prefixes = [];

        $rawPrefixes = [];

        $res = preg_replace_callback("%".self::SPARQL_PREFIX_BASE_REGEXP."%iu", function($m) use (&$prefixes, &$rawPrefixes) {

            $rawPrefixes[] = trim($m[0]);

            $prefixes[$m[3]?$m[3]:""] = $m[4];

            return "";

        }, $this->query);

        return [$rawPrefixes, $prefixes, trim($res)];

    }

    public function getRawPrefixes() {

        if($this->rawPrefixes === false) {

            list($this->rawPrefixes, $this->prefixes, $this->rawQuery) = $this->extractPrefix();

        }

        return $this->rawPrefixes;

    }

    public function getPrefixes() {

        if($this->prefixes === false) {

            list($this->rawPrefixes, $this->prefixes, $this->rawQuery) = $this->extractPrefix();

        }

        return $this->prefixes;

    }

    public function getRawQuery() {

        if($this->rawQuery === false) {

            list($this->rawPrefixes, $this->prefixes, $this->rawQuery) = $this->extractPrefix();

        }

        return $this->rawQuery;

    }

    public function getCountVar() {

        if($this->countVar === false) {

            $this->countVar = "?count_cp_".hash('md5', $this->query);

        }

        return $this->countVar;

    }

    public function getCountQuery() {

        return implode(" ", $this->getRawPrefixes())." select (count(*) as ".$this->getCountVar().") { ".$this->getRawQuery()." }";

    }

    private function setLimitOffset() {

        if(preg_match("%".self::SPARQL_LIMIT_OFFSET_QUERY_REGEXP."%iu", $this->query, $m) === 1) {

            for($i=0;$i<(count($m)-1)/2;$i++) {

                if(Utils::startsWith(strtolower($m[2*$i+1]), "limit")) {

                    $this->limit = intval($m[$i*2+2]);

                } elseif (Utils::startsWith(strtolower($m[2*$i+1]), "offset")) {

                    $this->offset = intval($m[$i*2+2]);

                }

            }

        }

        if($this->limit === false) {

            $this->limit = null;

        }

        if($this->offset === false) {

            $this->offset = null;

        }

    }

    public function getLimit() {

        if($this->limit === false) {

            $this->setLimitOffset();

        }

        return $this->limit;

    }

    public function getOffset() {

        if($this->offset === false) {

            $this->setLimitOffset();

        }

        return $this->offset;

    }

}