<?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;
    }

}