<?php
/**
 * @link http://www.yiiframework.com/
 * @copyright Copyright (c) 2008 Yii Software LLC
 * @license http://www.yiiframework.com/license/
 */

namespace yii\db\oci;

use yii\base\InvalidParamException;

/**
 * QueryBuilder is the query builder for Oracle databases.
 *
 * @author Qiang Xue <qiang.xue@gmail.com>
 * @since 2.0
 */
class QueryBuilder extends \yii\db\QueryBuilder
{

    private $sql;

    public function build($query)
    {
        $params = $query->params;
        $clauses = [
            $this->buildSelect($query->select, $params, $query->distinct, $query->selectOption),
            $this->buildFrom($query->from, $params),
            $this->buildJoin($query->join, $params),
            $this->buildWhere($query->where, $params),
            $this->buildGroupBy($query->groupBy),
            $this->buildHaving($query->having, $params),
            $this->buildOrderBy($query->orderBy),
        ];
        $this->sql = implode($this->separator, array_filter($clauses));

        $this->sql = $this->buildLimit($query->limit, $query->offset);

        $unions = $this->buildUnion($query->union, $params);
        if ($unions !== '') {
            $this->sql .= $this->separator . $unions;
        }

        return [$this->sql, $params];
    }

    public function buildLimit($limit, $offset)
    {
        $filters = [];
        if ($this->hasOffset($offset) > 0) {
            $filters[] = 'rowNumId > ' . $offset;
        }

        if ($this->hasLimit($limit)) {
            $filters[] = 'rownum <= ' . $limit;
        }

        if (!empty($filters)) {
            $filter = implode(' and ', $filters);

            return <<<EOD
WITH USER_SQL AS ({$this->sql}),
    PAGINATION AS (SELECT USER_SQL.*, rownum as rowNumId FROM USER_SQL)
SELECT *
FROM PAGINATION
WHERE $filter
EOD;
        } else {
            return $this->sql;
        }
    }

    /**
     * Builds a SQL statement for renaming a DB table.
     *
     * @param  string $table   the table to be renamed. The name will be properly quoted by the method.
     * @param  string $newName the new table name. The name will be properly quoted by the method.
     * @return string the SQL statement for renaming a DB table.
     */
    public function renameTable($table, $newName)
    {
        return 'ALTER TABLE ' . $this->db->quoteTableName($table) . ' RENAME TO ' . $this->db->quoteTableName($newName);
    }

    /**
     * Builds a SQL statement for changing the definition of a column.
     *
     * @param  string $table  the table whose column is to be changed. The table name will be properly quoted by the method.
     * @param  string $column the name of the column to be changed. The name will be properly quoted by the method.
     * @param  string $type   the new column type. The {@link getColumnType} method will be invoked to convert abstract column type (if any)
     *                        into the physical one. Anything that is not recognized as abstract type will be kept in the generated SQL.
     *                        For example, 'string' will be turned into 'varchar(255)', while 'string not null' will become 'varchar(255) not null'.
     * @return string the SQL statement for changing the definition of a column.
     */
    public function alterColumn($table, $column, $type)
    {
        $type = $this->getColumnType($type);

        return 'ALTER TABLE ' . $this->db->quoteTableName($table) . ' MODIFY ' . $this->db->quoteColumnName($column) . ' ' . $this->getColumnType($type);
    }

    /**
     * Builds a SQL statement for dropping an index.
     *
     * @param  string $name  the name of the index to be dropped. The name will be properly quoted by the method.
     * @param  string $table the table whose index is to be dropped. The name will be properly quoted by the method.
     * @return string the SQL statement for dropping an index.
     */
    public function dropIndex($name, $table)
    {
        return 'DROP INDEX ' . $this->db->quoteTableName($name);
    }

    /**
     * @inheritdoc
     */
    public function resetSequence($table, $value = null)
    {
        $tableSchema = $this->db->getTableSchema($table);
        if ($tableSchema === null) {
            throw new InvalidParamException("Unknown table: $table");
        }
        if ($tableSchema->sequenceName === null) {
            return '';
        }

        if ($value !== null) {
            $value = (int) $value;
        } else {
            $value = (int) $this->db->createCommand("SELECT MAX(\"{$tableSchema->primaryKey}\") FROM \"{$tableSchema->name}\"")->queryScalar();
            $value++;
        }

        return "DROP SEQUENCE \"{$tableSchema->name}_SEQ\";"
            . "CREATE SEQUENCE \"{$tableSchema->name}_SEQ\" START WITH {$value} INCREMENT BY 1 NOMAXVALUE NOCACHE";
    }
}
