<?php

/**
 * Defines the parser of the library.
 *
 * This is one of the most important components, along with the lexer.
 *
 * @package SqlParser
 */
namespace SqlParser;

require_once 'common.php';

use SqlParser\Exceptions\ParserException;
use SqlParser\Statements\SelectStatement;
use SqlParser\Statements\TransactionStatement;

/**
 * Takes multiple tokens (contained in a Lexer instance) as input and builds a
 * parse tree.
 *
 * @category Parser
 * @package  SqlParser
 * @author   Dan Ungureanu <udan1107@gmail.com>
 * @license  http://opensource.org/licenses/GPL-2.0 GNU Public License
 */
class Parser
{

    /**
     * Array of classes that are used in parsing the SQL statements.
     *
     * @var array
     */
    public static $STATEMENT_PARSERS = array(

        // MySQL Utility Statements
        'DESCRIBE'          => 'SqlParser\\Statements\\ExplainStatement',
        'DESC'              => 'SqlParser\\Statements\\ExplainStatement',
        'EXPLAIN'           => 'SqlParser\\Statements\\ExplainStatement',
        'FLUSH'             => '',
        'GRANT'             => '',
        'HELP'              => '',
        'SET PASSWORD'      => '',
        'STATUS'            => '',
        'USE'               => '',

        // Table Maintenance Statements
        // https://dev.mysql.com/doc/refman/5.7/en/table-maintenance-sql.html
        'ANALYZE'           => 'SqlParser\\Statements\\AnalyzeStatement',
        'BACKUP'            => 'SqlParser\\Statements\\BackupStatement',
        'CHECK'             => 'SqlParser\\Statements\\CheckStatement',
        'CHECKSUM'          => 'SqlParser\\Statements\\ChecksumStatement',
        'OPTIMIZE'          => 'SqlParser\\Statements\\OptimizeStatement',
        'REPAIR'            => 'SqlParser\\Statements\\RepairStatement',
        'RESTORE'           => 'SqlParser\\Statements\\RestoreStatement',

        // Database Administration Statements
        // https://dev.mysql.com/doc/refman/5.7/en/sql-syntax-server-administration.html
        'SET'               => 'SqlParser\\Statements\\SetStatement',
        'SHOW'              => 'SqlParser\\Statements\\ShowStatement',

        // Data Definition Statements.
        // https://dev.mysql.com/doc/refman/5.7/en/sql-syntax-data-definition.html
        'ALTER'             => 'SqlParser\\Statements\\AlterStatement',
        'CREATE'            => 'SqlParser\\Statements\\CreateStatement',
        'DROP'              => 'SqlParser\\Statements\\DropStatement',
        'RENAME'            => 'SqlParser\\Statements\\RenameStatement',
        'TRUNCATE'          => 'SqlParser\\Statements\\TruncateStatement',

        // Data Manipulation Statements.
        // https://dev.mysql.com/doc/refman/5.7/en/sql-syntax-data-manipulation.html
        'CALL'              => 'SqlParser\\Statements\\CallStatement',
        'DELETE'            => 'SqlParser\\Statements\\DeleteStatement',
        'DO'                => '',
        'HANDLER'           => '',
        'INSERT'            => 'SqlParser\\Statements\\InsertStatement',
        'LOAD'              => '',
        'REPLACE'           => 'SqlParser\\Statements\\ReplaceStatement',
        'SELECT'            => 'SqlParser\\Statements\\SelectStatement',
        'UPDATE'            => 'SqlParser\\Statements\\UpdateStatement',

        // Prepared Statements.
        // https://dev.mysql.com/doc/refman/5.7/en/sql-syntax-prepared-statements.html
        'DEALLOCATE'        => '',
        'EXECUTE'           => '',
        'PREPARE'           => '',

        // Transactional and Locking Statements
        // https://dev.mysql.com/doc/refman/5.7/en/commit.html
        'BEGIN'             => 'SqlParser\\Statements\\TransactionStatement',
        'COMMIT'            => 'SqlParser\\Statements\\TransactionStatement',
        'ROLLBACK'          => 'SqlParser\\Statements\\TransactionStatement',
        'START TRANSACTION' => 'SqlParser\\Statements\\TransactionStatement',
    );

    /**
     * Array of classes that are used in parsing SQL components.
     *
     * @var array
     */
    public static $KEYWORD_PARSERS = array(

        // This is not a proper keyword and was added here to help the
        // formatter.
        'PARTITION BY'          => array(),
        'SUBPARTITION BY'       => array(),

        // This is not a proper keyword and was added here to help the
        // builder.
        '_OPTIONS'              => array(
            'class'             => 'SqlParser\\Components\\OptionsArray',
            'field'             => 'options',
        ),
        'UNION'                 => array(
            'class'             => 'SqlParser\\Components\\UnionKeyword',
            'field'             => 'union',
        ),
        'UNION ALL'             => array(
            'class'             => 'SqlParser\\Components\\UnionKeyword',
            'field'             => 'union',
        ),

        // Actual clause parsers.
        'ALTER'                 => array(
            'class'             => 'SqlParser\\Components\\Expression',
            'field'             => 'table',
            'options'           => array('parseField' => 'table'),
        ),
        'ANALYZE'               => array(
            'class'             => 'SqlParser\\Components\\ExpressionArray',
            'field'             => 'tables',
            'options'           => array('parseField' => 'table'),
        ),
        'BACKUP'                => array(
            'class'             => 'SqlParser\\Components\\ExpressionArray',
            'field'             => 'tables',
            'options'           => array('parseField' => 'table'),
        ),
        'CALL'                  => array(
            'class'             => 'SqlParser\\Components\\FunctionCall',
            'field'             => 'call',
        ),
        'CHECK'                 => array(
            'class'             => 'SqlParser\\Components\\ExpressionArray',
            'field'             => 'tables',
            'options'           => array('parseField' => 'table'),
        ),
        'CHECKSUM'              => array(
            'class'             => 'SqlParser\\Components\\ExpressionArray',
            'field'             => 'tables',
            'options'           => array('parseField' => 'table'),
        ),
        'DROP'                  => array(
            'class'             => 'SqlParser\\Components\\ExpressionArray',
            'field'             => 'fields',
            'options'           => array('parseField' => 'table'),
        ),
        'FROM'                  => array(
            'class'             => 'SqlParser\\Components\\ExpressionArray',
            'field'             => 'from',
            'options'           => array('parseField' => 'table'),
        ),
        'GROUP BY'              => array(
            'class'             => 'SqlParser\\Components\\OrderKeyword',
            'field'             => 'group',
        ),
        'HAVING'                => array(
            'class'             => 'SqlParser\\Components\\Condition',
            'field'             => 'having',
        ),
        'INTO'                  => array(
            'class'             => 'SqlParser\\Components\\IntoKeyword',
            'field'             => 'into',
        ),
        'JOIN'                  => array(
            'class'             => 'SqlParser\\Components\\JoinKeyword',
            'field'             => 'join',
        ),
        'LEFT JOIN'             => array(
            'class'             => 'SqlParser\\Components\\JoinKeyword',
            'field'             => 'join',
        ),
        'LEFT OUTER JOIN'       => array(
            'class'             => 'SqlParser\\Components\\JoinKeyword',
            'field'             => 'join',
        ),
        'ON'                    => array(
            'class'             => 'SqlParser\\Components\\Expression',
            'field'             => 'table',
            'options'           => array('parseField' => 'table'),
        ),
        'RIGHT JOIN'            => array(
            'class'             => 'SqlParser\\Components\\JoinKeyword',
            'field'             => 'join',
        ),
        'RIGHT OUTER JOIN'      => array(
            'class'             => 'SqlParser\\Components\\JoinKeyword',
            'field'             => 'join',
        ),
        'INNER JOIN'            => array(
            'class'             => 'SqlParser\\Components\\JoinKeyword',
            'field'             => 'join',
        ),
        'FULL JOIN'             => array(
            'class'             => 'SqlParser\\Components\\JoinKeyword',
            'field'             => 'join',
        ),
        'STRAIGHT_JOIN'         => array(
            'class'             => 'SqlParser\\Components\\JoinKeyword',
            'field'             => 'join',
        ),
        'LIMIT'                 => array(
            'class'             => 'SqlParser\\Components\\Limit',
            'field'             => 'limit',
        ),
        'OPTIMIZE'              => array(
            'class'             => 'SqlParser\\Components\\ExpressionArray',
            'field'             => 'tables',
            'options'           => array('parseField' => 'table'),
        ),
        'ORDER BY'              => array(
            'class'             => 'SqlParser\\Components\\OrderKeyword',
            'field'             => 'order',
        ),
        'PARTITION'             => array(
            'class'             => 'SqlParser\\Components\\ArrayObj',
            'field'             => 'partition',
        ),
        'PROCEDURE'             => array(
            'class'             => 'SqlParser\\Components\\FunctionCall',
            'field'             => 'procedure',
        ),
        'RENAME'                => array(
            'class'             => 'SqlParser\\Components\\RenameOperation',
            'field'             => 'renames',
        ),
        'REPAIR'                => array(
            'class'             => 'SqlParser\\Components\\ExpressionArray',
            'field'             => 'tables',
            'options'           => array('parseField' => 'table'),
        ),
        'RESTORE'               => array(
            'class'             => 'SqlParser\\Components\\ExpressionArray',
            'field'             => 'tables',
            'options'           => array('parseField' => 'table'),
        ),
        'SET'                   => array(
            'class'             => 'SqlParser\\Components\\SetOperation',
            'field'             => 'set',
        ),
        'SELECT'                => array(
            'class'             => 'SqlParser\\Components\\ExpressionArray',
            'field'             => 'expr',
        ),
        'TRUNCATE'              => array(
            'class'             => 'SqlParser\\Components\\Expression',
            'field'             => 'table',
            'options'           => array('parseField' => 'table'),
        ),
        'UPDATE'                => array(
            'class'             => 'SqlParser\\Components\\ExpressionArray',
            'field'             => 'tables',
            'options'           => array('parseField' => 'table'),
        ),
        'VALUE'                 => array(
            'class'             => 'SqlParser\\Components\\Array2d',
            'field'             => 'values',
        ),
        'VALUES'                => array(
            'class'             => 'SqlParser\\Components\\Array2d',
            'field'             => 'values',
        ),
        'WHERE'                 => array(
            'class'             => 'SqlParser\\Components\\Condition',
            'field'             => 'where',
        ),

    );

    /**
     * The list of tokens that are parsed.
     *
     * @var TokensList
     */
    public $list;

    /**
     * Whether errors should throw exceptions or just be stored.
     *
     * @var bool
     *
     * @see static::$errors
     */
    public $strict = false;

    /**
     * List of errors that occurred during parsing.
     *
     * Usually, the parsing does not stop once an error occurred because that
     * error might be a false positive or a partial result (even a bad one)
     * might be needed.
     *
     * @var ParserException[]
     *
     * @see Parser::error()
     */
    public $errors = array();

    /**
     * List of statements parsed.
     *
     * @var Statement[]
     */
    public $statements = array();

    /**
     * The number of opened brackets.
     *
     * @var int
     */
    public $brackets = 0;

    /**
     * Constructor.
     *
     * @param string|UtfString|TokensList $list   The list of tokens to be parsed.
     * @param bool                        $strict Whether strict mode should be enabled or not.
     */
    public function __construct($list = null, $strict = false)
    {
        if ((is_string($list)) || ($list instanceof UtfString)) {
            $lexer = new Lexer($list, $strict);
            $this->list = $lexer->list;
        } elseif ($list instanceof TokensList) {
            $this->list = $list;
        }

        $this->strict = $strict;

        if ($list !== null) {
            $this->parse();
        }
    }

    /**
     * Builds the parse trees.
     *
     * @return void
     */
    public function parse()
    {

        /**
         * Last transaction.
         *
         * @var TransactionStatement $lastTransaction
         */
        $lastTransaction = null;

        /**
         * Last parsed statement.
         *
         * @var Statement $lastStatement
         */
        $lastStatement = null;

        /**
         * Union's type or false for no union.
         *
         * @var bool|string $unionType
         */
        $unionType = false;

        /**
         * The index of the last token from the last statement.
         *
         * @var int $prevLastIdx
         */
        $prevLastIdx = -1;

        /**
         * The list of tokens.
         *
         * @var TokensList $list
         */
        $list = &$this->list;

        for (; $list->idx < $list->count; ++$list->idx) {
            /**
             * Token parsed at this moment.
             *
             * @var Token $token
             */
            $token = $list->tokens[$list->idx];

            // `DELIMITER` is not an actual statement and it requires
            // special handling.
            if (($token->type === Token::TYPE_NONE)
                && (strtoupper($token->token) === 'DELIMITER')
            ) {
                // Skipping to the end of this statement.
                $list->getNextOfType(Token::TYPE_DELIMITER);
                $prevLastIdx = $list->idx;
                continue;
            }

            // Counting the brackets around statements.
            if ($token->value === '(') {
                ++$this->brackets;
                continue;
            }

            // Statements can start with keywords only.
            // Comments, whitespaces, etc. are ignored.
            if ($token->type !== Token::TYPE_KEYWORD) {
                if (($token->type !== TOKEN::TYPE_COMMENT)
                    && ($token->type !== Token::TYPE_WHITESPACE)
                    && ($token->type !== Token::TYPE_OPERATOR) // `(` and `)`
                    && ($token->type !== Token::TYPE_DELIMITER)
                ) {
                    $this->error(
                        __('Unexpected beginning of statement.'),
                        $token
                    );
                }
                continue;
            }

            if (($token->value === 'UNION') || ($token->value === 'UNION ALL')) {
                $unionType = $token->value;
                continue;
            }

            // Checking if it is a known statement that can be parsed.
            if (empty(static::$STATEMENT_PARSERS[$token->value])) {
                if (!isset(static::$STATEMENT_PARSERS[$token->value])) {
                    // A statement is considered recognized if the parser
                    // is aware that it is a statement, but it does not have
                    // a parser for it yet.
                    $this->error(
                        __('Unrecognized statement type.'),
                        $token
                    );
                }
                // Skipping to the end of this statement.
                $list->getNextOfType(Token::TYPE_DELIMITER);
                $prevLastIdx = $list->idx;
                continue;
            }

            /**
             * The name of the class that is used for parsing.
             *
             * @var string $class
             */
            $class = static::$STATEMENT_PARSERS[$token->value];

            /**
             * Processed statement.
             *
             * @var Statement $statement
             */
            $statement = new $class($this, $this->list);

            // The first token that is a part of this token is the next token
            // unprocessed by the previous statement.
            // There might be brackets around statements and this shouldn't
            // affect the parser
            $statement->first = $prevLastIdx + 1;

            // Storing the index of the last token parsed and updating the old
            // index.
            $statement->last = $list->idx;
            $prevLastIdx = $list->idx;

            // Handles unions.
            if ((!empty($unionType))
                && ($lastStatement instanceof SelectStatement)
                && ($statement instanceof SelectStatement)
            ) {
                /**
                 * This SELECT statement.
                 *
                 * @var SelectStatement $statement
                 */

                /**
                 * Last SELECT statement.
                 *
                 * @var SelectStatement $lastStatement
                 */
                $lastStatement->union[] = array($unionType, $statement);

                // if there are no no delimiting brackets, the `ORDER` and
                // `LIMIT` keywords actually belong to the first statement.
                $lastStatement->order = $statement->order;
                $lastStatement->limit = $statement->limit;
                $statement->order = array();
                $statement->limit = null;

                // The statement actually ends where the last statement in
                // union ends.
                $lastStatement->last = $statement->last;

                $unionType = false;
                continue;
            }

            // Handles transactions.
            if ($statement instanceof TransactionStatement) {
                /**
                 * @var TransactionStatement $statement
                 */
                if ($statement->type === TransactionStatement::TYPE_BEGIN) {
                    $lastTransaction = $statement;
                    $this->statements[] = $statement;
                } elseif ($statement->type === TransactionStatement::TYPE_END) {
                    if ($lastTransaction === null) {
                        // Even though an error occurred, the query is being
                        // saved.
                        $this->statements[] = $statement;
                        $this->error(
                            __('No transaction was previously started.'),
                            $token
                        );
                    } else {
                        $lastTransaction->end = $statement;
                    }
                    $lastTransaction = null;
                }
                continue;
            }

            // Finally, storing the statement.
            if ($lastTransaction !== null) {
                $lastTransaction->statements[] = $statement;
            } else {
                $this->statements[] = $statement;
            }
            $lastStatement = $statement;

        }
    }

    /**
     * Creates a new error log.
     *
     * @param string $msg   The error message.
     * @param Token  $token The token that produced the error.
     * @param int    $code  The code of the error.
     *
     * @throws ParserException Throws the exception, if strict mode is enabled.
     *
     * @return void
     */
    public function error($msg = '', Token $token = null, $code = 0)
    {
        $error = new ParserException($msg, $token, $code);
        if ($this->strict) {
            throw $error;
        }
        $this->errors[] = $error;
    }
}
