<?php

namespace Ulmus\Query;

class OrderBy extends Fragment {
    public int $order = 85;

    public array $orderBy = [];
    
    const SQL_TOKEN = "ORDER BY";
    const SQL_COLLATE = "COLLATE";

    # const 'NULLS LAST|FIRST' must be handlded

    public function set(array $order) : self
    {
        $this->orderBy = $order;
        
        return $this;
    }

    public function add(string|\Stringable $field, string|\Stringable|null $direction = null) : self
    {
        $this->validateDirectionType($direction);

        $this->orderBy[] = [ $field, $direction ];
        
        return $this;
    }

    public function render() : string
    {
        $list = array_map(function($item) {
            list($field, $direction) = $item;
            
            return implode(' ', array_filter([ $field , $direction ?? null ] ));
        }, $this->orderBy);

        return $this->renderSegments([
            static::SQL_TOKEN, implode(", ", $list)
        ]);
    }

    protected function validateDirectionType(mixed $direction) {
        # Could be coming from user-input, we must whitelist
        if (is_string($direction) && ! in_array(strtoupper($direction), [ 'ASC', 'DESC' ])) {
            throw new \Ulmus\Exception\InvalidFieldType(sprintf("Validation of string `%s` failed from query `%s`", $direction, get_class($this)));
        }
    }
}