<?php

namespace StellarWP\Learndash\StellarWP\DB\QueryBuilder\Concerns;

use StellarWP\Learndash\StellarWP\DB\DB;
use StellarWP\Learndash\StellarWP\DB\QueryBuilder\Clauses\RawSQL;
use StellarWP\Learndash\StellarWP\DB\QueryBuilder\Clauses\Select;

/**
 * @since 1.0.0
 */
trait SelectStatement {
	/**
	 * @var Select[]|RawSQL[]
	 */
	protected $selects = [];

	/**
	 * @var bool
	 */
	protected $distinct = false;

	/**
	 * @var bool
	 */
	private $includeSelectKeyword = true;

	/**
	 * @param  array|string  $columns
	 *
	 * @return $this
	 */
	public function select( ...$columns ) {
		$selects = array_map(function ( $select ) {
			if ( is_array( $select ) ) {
				list( $column, $alias ) = $select;

				return new Select( $column, $alias );
			}

			return new Select( $select );
		}, $columns );

		$this->selects = array_merge( $this->selects, $selects );

		return $this;
	}

	/**
	 * Add raw SQL SELECT statement
	 *
	 * @param  string  $sql
	 * @param ...$args
	 */
	public function selectRaw( $sql, ...$args ) {
		$this->selects[] = new RawSQL( $sql, $args );

		return $this;
	}


	/**
	 * Select distinct
	 *
	 * @return $this
	 */
	public function distinct() {
		$this->distinct = true;

		return $this;
	}

	/**
	 * @return string[]
	 */
	protected function getSelectSQL() {
		// Select all by default
		if ( empty( $this->selects ) ) {
			$this->select( '*' );
		}

		$selects = [];

		foreach ( $this->selects as $i => $select ) {
			if ( $select instanceof RawSQL ) {
				if ( $i === 0 ) {
					// If the first element is an instance of RawSQL
					// then we don't need the starting SELECT keyword because we assume that the dev will include that in RawSQL
					$this->includeSelectKeyword = false;
				}
				$selects[] = $select->sql;
				continue;
			}

			if ( $select->alias ) {
				$selects[] = DB::prepare(
					'%1s AS %2s',
					$select->column,
					$select->alias
				);

				continue;
			}

			$selects[] = DB::prepare( '%1s', $select->column );
		}

		$selectStatements = implode( ', ', $selects );

		if ( $this->includeSelectKeyword ) {
			$keyword = 'SELECT ';

			if ( $this->distinct ) {
				$keyword .= 'DISTINCT ';
			}

			return [ $keyword . $selectStatements ];
		}

		return [ $selectStatements ];
	}
}
