<?php
/**
 * Piwik - Open source web analytics
 *
 * @link http://piwik.org
 * @license http://www.gnu.org/licenses/gpl-3.0.html GPL v3 or later
 *
 */

namespace Piwik;

use Exception;

/**
 *
 */
class SegmentExpression
{
    const AND_DELIMITER = ';';
    const OR_DELIMITER = ',';

    const MATCH_EQUAL = '==';
    const MATCH_NOT_EQUAL = '!=';
    const MATCH_GREATER_OR_EQUAL = '>=';
    const MATCH_LESS_OR_EQUAL = '<=';
    const MATCH_GREATER = '>';
    const MATCH_LESS = '<';
    const MATCH_CONTAINS = '=@';
    const MATCH_DOES_NOT_CONTAIN = '!@';

    // Note: you can't write this in the API, but access this feature
    // via field!=        <- IS NOT NULL
    // or via field==     <- IS NULL / empty
    const MATCH_IS_NOT_NULL_NOR_EMPTY = '::NOT_NULL';
    const MATCH_IS_NULL_OR_EMPTY = '::NULL';

    // Special case, since we look up Page URLs/Page titles in a sub SQL query
    const MATCH_ACTIONS_CONTAINS = 'IN';

    const INDEX_BOOL_OPERATOR = 0;
    const INDEX_OPERAND = 1;

    function __construct($string)
    {
        $this->string = $string;
        $this->tree = $this->parseTree();
    }

    protected $joins = array();
    protected $valuesBind = array();
    protected $parsedTree = array();
    protected $tree = array();
    protected $parsedSubExpressions = array();

    /**
     * Given the array of parsed filters containing, for each filter,
     * the boolean operator (AND/OR) and the operand,
     * Will return the array where the filters are in SQL representation
     *
     * @throws Exception
     * @return array
     */
    public function parseSubExpressions()
    {
        $parsedSubExpressions = array();
        foreach ($this->tree as $id => $leaf) {
            $operand = $leaf[self::INDEX_OPERAND];

            $operand = urldecode($operand);

            $operator = $leaf[self::INDEX_BOOL_OPERATOR];
            $pattern = '/^(.+?)(' . self::MATCH_EQUAL . '|'
                . self::MATCH_NOT_EQUAL . '|'
                . self::MATCH_GREATER_OR_EQUAL . '|'
                . self::MATCH_GREATER . '|'
                . self::MATCH_LESS_OR_EQUAL . '|'
                . self::MATCH_LESS . '|'
                . self::MATCH_CONTAINS . '|'
                . self::MATCH_DOES_NOT_CONTAIN
                . '){1}(.*)/';
            $match = preg_match($pattern, $operand, $matches);
            if ($match == 0) {
                throw new Exception('The segment \'' . $operand . '\' is not valid.');
            }

            $leftMember = $matches[1];
            $operation = $matches[2];
            $valueRightMember = urldecode($matches[3]);

            // is null / is not null
            if ($valueRightMember === '') {
                if ($operation == self::MATCH_NOT_EQUAL) {
                    $operation = self::MATCH_IS_NOT_NULL_NOR_EMPTY;
                } elseif ($operation == self::MATCH_EQUAL) {
                    $operation = self::MATCH_IS_NULL_OR_EMPTY;
                } else {
                    throw new Exception('The segment \'' . $operand . '\' has no value specified. You can leave this value empty ' .
                        'only when you use the operators: ' . self::MATCH_NOT_EQUAL . ' (is not) or ' . self::MATCH_EQUAL . ' (is)');
                }
            }

            $parsedSubExpressions[] = array(
                self::INDEX_BOOL_OPERATOR => $operator,
                self::INDEX_OPERAND       => array(
                    $leftMember,
                    $operation,
                    $valueRightMember,
                ));
        }
        $this->parsedSubExpressions = $parsedSubExpressions;
        return $parsedSubExpressions;
    }

    /**
     * Set the given expression
     * @param $parsedSubExpressions
     */
    public function setSubExpressionsAfterCleanup($parsedSubExpressions)
    {
        $this->parsedSubExpressions = $parsedSubExpressions;
    }

    /**
     * @param array $availableTables
     */
    public function parseSubExpressionsIntoSqlExpressions(&$availableTables = array())
    {
        $sqlSubExpressions = array();
        $this->valuesBind = array();
        $this->joins = array();

        foreach ($this->parsedSubExpressions as $leaf) {
            $operator = $leaf[self::INDEX_BOOL_OPERATOR];
            $operandDefinition = $leaf[self::INDEX_OPERAND];

            $operand = $this->getSqlMatchFromDefinition($operandDefinition, $availableTables);

            if ($operand[1] !== null) {
                $this->valuesBind[] = $operand[1];
            }
            $operand = $operand[0];
            $sqlSubExpressions[] = array(
                self::INDEX_BOOL_OPERATOR => $operator,
                self::INDEX_OPERAND       => $operand,
            );
        }

        $this->tree = $sqlSubExpressions;
    }

    /**
     * Given an array representing one filter operand ( left member , operation , right member)
     * Will return an array containing
     * - the SQL substring,
     * - the values to bind to this substring
     *
     * @param array $def
     * @param array $availableTables
     * @throws Exception
     * @return array
     */
    protected function getSqlMatchFromDefinition($def, &$availableTables)
    {
        $field = $def[0];
        $matchType = $def[1];
        $value = $def[2];

        $alsoMatchNULLValues = false;
        switch ($matchType) {
            case self::MATCH_EQUAL:
                $sqlMatch = '=';
                break;
            case self::MATCH_NOT_EQUAL:
                $sqlMatch = '<>';
                $alsoMatchNULLValues = true;
                break;
            case self::MATCH_GREATER:
                $sqlMatch = '>';
                break;
            case self::MATCH_LESS:
                $sqlMatch = '<';
                break;
            case self::MATCH_GREATER_OR_EQUAL:
                $sqlMatch = '>=';
                break;
            case self::MATCH_LESS_OR_EQUAL:
                $sqlMatch = '<=';
                break;
            case self::MATCH_CONTAINS:
                $sqlMatch = 'LIKE';
                $value = '%' . $this->escapeLikeString($value) . '%';
                break;
            case self::MATCH_DOES_NOT_CONTAIN:
                $sqlMatch = 'NOT LIKE';
                $value = '%' . $this->escapeLikeString($value) . '%';
                $alsoMatchNULLValues = true;
                break;

            case self::MATCH_IS_NOT_NULL_NOR_EMPTY:
                $sqlMatch = 'IS NOT NULL AND (' . $field . ' <> \'\' OR ' . $field . ' = 0)';
                $value = null;
                break;

            case self::MATCH_IS_NULL_OR_EMPTY:
                $sqlMatch = 'IS NULL OR ' . $field . ' = \'\' ';
                $value = null;
                break;

            case self::MATCH_ACTIONS_CONTAINS:
                // this match type is not accessible from the outside
                // (it won't be matched in self::parseSubExpressions())
                // it can be used internally to inject sub-expressions into the query.
                // see Segment::getCleanedExpression()
                $sqlMatch = 'IN (' . $value['SQL'] . ')';
                $value = $this->escapeLikeString($value['bind']);
                break;
            default:
                throw new Exception("Filter contains the match type '" . $matchType . "' which is not supported");
                break;
        }

        // We match NULL values when rows are excluded only when we are not doing a
        $alsoMatchNULLValues = $alsoMatchNULLValues && !empty($value);

        if ($matchType === self::MATCH_ACTIONS_CONTAINS
            || is_null($value)
        ) {
            $sqlExpression = "( $field $sqlMatch )";
        } else {
            if ($alsoMatchNULLValues) {
                $sqlExpression = "( $field IS NULL OR $field $sqlMatch ? )";
            } else {
                $sqlExpression = "$field $sqlMatch ?";
            }
        }

        $this->checkFieldIsAvailable($field, $availableTables);

        return array($sqlExpression, $value);
    }

    /**
     * Check whether the field is available
     * If not, add it to the available tables
     *
     * @param string $field
     * @param array $availableTables
     */
    private function checkFieldIsAvailable($field, &$availableTables)
    {
        $fieldParts = explode('.', $field);

        $table = count($fieldParts) == 2 ? $fieldParts[0] : false;

        // remove sql functions from field name
        // example: `HOUR(log_visit.visit_last_action_time)` gets `HOUR(log_visit` => remove `HOUR(`
        $table = preg_replace('/^[A-Z_]+\(/', '', $table);
        $tableExists = !$table || in_array($table, $availableTables);

        if (!$tableExists) {
            $availableTables[] = $table;
        }
    }

    /**
     * Escape the characters % and _ in the given string
     * @param string $str
     * @return string
     */
    private function escapeLikeString($str)
    {
        $str = str_replace("%", "\%", $str);
        $str = str_replace("_", "\_", $str);
        return $str;
    }

    /**
     * Given a filter string,
     * will parse it into an array where each row contains the boolean operator applied to it,
     * and the operand
     *
     * @return array
     */
    protected function parseTree()
    {
        $string = $this->string;
        if (empty($string)) {
            return array();
        }
        $tree = array();
        $i = 0;
        $length = strlen($string);
        $isBackslash = false;
        $operand = '';
        while ($i <= $length) {
            $char = $string[$i];

            $isAND = ($char == self::AND_DELIMITER);
            $isOR = ($char == self::OR_DELIMITER);
            $isEnd = ($length == $i + 1);

            if ($isEnd) {
                if ($isBackslash && ($isAND || $isOR)) {
                    $operand = substr($operand, 0, -1);
                }
                $operand .= $char;
                $tree[] = array(self::INDEX_BOOL_OPERATOR => '', self::INDEX_OPERAND => $operand);
                break;
            }

            if ($isAND && !$isBackslash) {
                $tree[] = array(self::INDEX_BOOL_OPERATOR => 'AND', self::INDEX_OPERAND => $operand);
                $operand = '';
            } elseif ($isOR && !$isBackslash) {
                $tree[] = array(self::INDEX_BOOL_OPERATOR => 'OR', self::INDEX_OPERAND => $operand);
                $operand = '';
            } else {
                if ($isBackslash && ($isAND || $isOR)) {
                    $operand = substr($operand, 0, -1);
                }
                $operand .= $char;
            }
            $isBackslash = ($char == "\\");
            $i++;
        }
        return $tree;
    }

    /**
     * Given the array of parsed boolean logic, will return
     * an array containing the full SQL string representing the filter,
     * the needed joins and the values to bind to the query
     *
     * @throws Exception
     * @return array SQL Query, Joins and Bind parameters
     */
    public function getSql()
    {
        if (count($this->tree) == 0) {
            throw new Exception("Invalid segment, please specify a valid segment.");
        }
        $bind = array();
        $sql = '';
        $subExpression = false;
        foreach ($this->tree as $expression) {
            $operator = $expression[self::INDEX_BOOL_OPERATOR];
            $operand = $expression[self::INDEX_OPERAND];

            if ($operator == 'OR'
                && !$subExpression
            ) {
                $sql .= ' (';
                $subExpression = true;
            } else {
                $sql .= ' ';
            }

            $sql .= $operand;

            if ($operator == 'AND'
                && $subExpression
            ) {
                $sql .= ')';
                $subExpression = false;
            }

            $sql .= " $operator";
        }
        if ($subExpression) {
            $sql .= ')';
        }
        return array(
            'where' => $sql,
            'bind'  => $this->valuesBind,
            'join'  => implode(' ', $this->joins)
        );
    }
}