<?php
namespace DatabaseHelper;

use DatabaseHelper\enums\Join;
use DatabaseHelper\enums\Order;
use http\Exception\InvalidArgumentException;
use SimplePie\Exception;

class Query
{
    use Conditionable;

    protected Schema $schema;
    protected array $columns = ['*'];
    protected array $joins = [];
    public array $orderBy;

    public function __construct(Schema $table) {
        $this->schema = $table;
    }

    public function select(string ...$cols): Query {
        if (!empty($cols))
            $this->columns = $cols;
        foreach ($cols as $col)
            $this->schema->requireColumn($col);
        return $this;
    }

    public function orderBy(string $col, Order $order): Query {
        $this->schema->requireColumn($col);
        $this->orderBy = [
            'name'  => $col,
            'order' => $order
        ];
        return $this;
    }

    public function join(Schema $other, Join $join): Query {
        $foreignKey = null;
        if($this->schema->existsReference($other))
            $foreignKey = $this->schema->foreignKeys[$other->name];
        if ($other->existsReference($this->schema))
            $foreignKey = $other->foreignKeys[$this->schema->name];

        if (is_null($foreignKey))
            throw new InvalidArgumentException('Joins can only applied to referencing columns.');

        // TODO: Implement include instead of merge
        $this->schema->include($other);
        $this->joins[] = [
            'table' => $other->name,
            'type' => $join
        ];

        return $this;
    }

    protected function isOrdered(): bool {
        return !empty($this->orderBy);
    }

    protected function isJoined(): bool {
        return !empty($this->joins);
    }

    public function toSql(): string {
        // Build the SELECT clause.
        $columns = implode(", ", $this->columns);
        $primaryTable = $this->schema->name;
        $sqlStatement = "SELECT $columns FROM $primaryTable";

        // Append join clauses, if any.
        if ($this->isJoined()) {
            foreach ($this->joins as $join) {
                $sqlStatement .= " " . $join['type']->toString() . " NATURAL JOIN " . $join['table'];
            }
        }

        // Append the WHERE clause if conditions exist.
        if ($this->isConditioned()) {
            $whereClause = $this->combineConditions();
            $sqlStatement .= " WHERE $whereClause";
        }

        // Append the ORDER BY clause if ordering is set.
        if ($this->isOrdered()) {
            $orderClause = $this->orderBy['name'] . ' ' . $this->orderBy['order'];
            $sqlStatement .= " ORDER BY $orderClause";
        }

        return esc_sql($sqlStatement);
    }

    public function query(): array {
        global $wpdb;
        $query = $this->toSql();
        $results = $wpdb->get_results($query, ARRAY_A);
        return $this->castResults($results);
    }

    protected function castResults(array $results): array {
        foreach ($results as &$row)
            foreach ($row as $column => &$value)
                if (isset($this->columnTypes[$column]))
                    $value = $this->columnTypes[$column]->valCast($value);
        return $results;
    }
}