<?php

/**
 * A model to manage database changes
 *
 * @author     Time.ly Network Inc.
 * @since      2.0
 *
 * @package    AI1EC
 * @subpackage AI1EC.Database
 */
class Ai1ec_Database_Applicator extends Ai1ec_Base {

    /**
     * @var Ai1ec_Dbi Instance of wpdb object
     */
    protected $_db = NULL;

    /**
     * @var Ai1ec_Database Instance of Ai1ec_Database object
     */
    protected $_database = NULL;

    /**
     * Constructor
     *
     * Initialize object, by storing instance of `wpdb` in local variable
     *
     * @return void Constructor does not return
     */
    public function __construct( Ai1ec_Registry_Object $registry ) {
        parent::__construct( $registry );
        $this->_db       = $registry->get( 'dbi.dbi' );
        $this->_database = $registry->get( 'database.helper' );
    }

    /**
     * remove_instance_duplicates method
     *
     * Remove duplicate instances, from `event_instances` table
     *
     * @param int $depth Private argument, denoting number of iterations to
     *                   try, before reverting to slow approach
     *
     * @return bool Success
     */
    public function remove_instance_duplicates( $depth = 5 ) {
        $use_field  = 'id';
        if ( $depth < 0 ) {
            $use_field = 'post_id';
        }
        $table      = $this->_table( 'event_instances' );
        if ( false === $this->_database->table_exists( $table ) ) {
            return true;
        }
        $duplicates = $this->find_duplicates(
                $table,
                $use_field,
                array( 'post_id', 'start' )
        );
        $count      = count( $duplicates );
        if ( $count > 0 ) {
            $sql_query  = 'DELETE FROM ' . $table .
            ' WHERE ' . $use_field . ' IN ( ' .
            implode( ', ', $duplicates ) . ' )';
            $this->_db->query( $sql_query );
        }
        if ( 'post_id' === $use_field ) { // slow branch
            $event_instance_model = $this->_registry->get(
                'model.event.instance'
            );
            foreach ( $duplicates as $post_id ) {
                try {
                    $event_instance_model->recreate(
                        $this->_registry->get( 'model.event', $post_id )
                    );
                } catch ( Ai1ec_Exception $excpt ) {
                    // discard any internal errors
                }
            }
        } else if ( $count > 0 ) { // retry
            return $this->remove_instance_duplicates( --$depth );
        }
        return true;
    }

    /**
     * find_duplicates method
     *
     * Find a list of duplicates in table, given search key and groupping fields
     *
     * @param string $table   Name of table, to search duplicates in
     * @param string $primary Column, to return values for
     * @param array  $group   List of fields, to group values on
     *
     * @return array List of primary field values
     */
    public function find_duplicates( $table, $primary, array $group ) {
        $sql_query = '
            SELECT
                MIN( {{primary}} ) AS dup_primary -- pop oldest
            FROM {{table}}
            GROUP BY {{group}}
            HAVING COUNT( {{primary}} ) > 1
        ';
        $sql_query = str_replace(
                array(
                    '{{table}}',
                    '{{primary}}',
                    '{{group}}',
                ),
                array(
                    $this->_table( $table ),
                    $this->_escape_column( $primary ),
                    implode(
                            ', ',
                            array_map( array( $this, '_escape_column' ), $group )
                    ),
                ),
                $sql_query
        );
        $result = $this->_db->get_col( $sql_query );
        return $result;
    }

    /**
     * Check list of tables for consistency.
     *
     * @return array List of inconsistencies.
     */
    public function check_db_consistency_for_date_migration() {
        $db_migration = $this->_registry->get( 'database.datetime-migration' );
        /* @var $db_migration Ai1ecdm_Datetime_Migration */
        $tables       = $db_migration->get_tables();
        if ( ! is_array( $tables ) ) {
            return array();
        }

        // for date migration purposes we can assume
        // that all columns need to be the same type
        $info = array();
        foreach( $tables as $t_name => $t_columns ) {
            if ( count( $t_columns ) < 2 ) {
                continue;
            }
            $tbl_error = $this->_check_single_table(
                $t_name,
                $db_migration->get_columns( $t_name ),
                $t_columns
            );
            if ( null !== $tbl_error ) {
                $info[] = $tbl_error;
            }
        }
        return $info;
    }

    /**
     * Check if single table columns are the same type.
     *
     * @param string $t_name    Table name for details purposes.
     * @param array  $db_cols   Columns from database.
     * @param array  $t_columns Columns to check from DDL.
     *
     * @return string|null Inconsistency description, if any.
     */
    protected function _check_single_table(
        $t_name,
        array $db_cols,
        array $t_columns
    ) {
        $type = null;
        foreach ( $db_cols as $c_field => $c_type ) {
            if ( ! in_array( $c_field, $t_columns ) ) {
                continue;
            }
            if ( null === $type ) {
                $type = strtolower( $c_type );
            }
            if ( strtolower( $c_type ) !== $type ) {
                return sprintf(
                    Ai1ec_I18n::__(
                        'Date columns in table %s have different types.'
                    ),
                    $t_name
                );
            }
        }
        return null;
    }

    /**
     * Get fully qualified table name, to use in queries.
     *
     * @param string $table Name of table, to convert.
     *
     * @return string Qualified table name.
     */
    protected function _table( $table ) {
        $prefix = $this->_db->get_table_name( 'ai1ec_' );
        if ( substr( $table, 0, strlen( $prefix ) ) !== $prefix ) {
            $table = $prefix . $table;
        }
        return $table;
    }

    /**
     * _escape_column method
     *
     * Escape column, enquoting it in MySQL specific characters
     *
     * @param string $name Name of column to quote
     *
     * @return string Escaped column name
     */
    protected function _escape_column( $name ) {
        return '`' . $name . '`';
    }

}