Compiler.php

<?php

namespace Silver\Database;

use Silver\Database\Query;

trait Compiler
{
	// Current queries stack
	private static $qstack = [];

	// Should be abstract, but php says: (E_STRICT)
	// Static function Silver\Database\Compiler::compile() should not be abstract
	protected static function compile(object $q) : array
	{
		throw new \Exception("This should be abstract method. Do not call it directly.");
	}

	public static function current(): ?object
	{
		if (self::$qstack) {
			return self::$qstack[0];
		} else {
			return null;
		}
	}

	private static function parentQuery(): ?object
	{
		if (count(self::$qstack) >= 2) {
			return self::$qstack[1];
		}
		return null;
	}

	public function toSql(): array
	{
		try {
			array_unshift(self::$qstack, $this);
			$class = get_called_class();
			$dialect = ucfirst(Db::driverName());
			$pos = strrpos($class, '\\') ?: 0;

			$new = substr_replace($class, '\\' . $dialect, $pos, 0);

			// Remove current bindings
			// (Query can be reused)
			if ($this instanceof Query) {
				$this->clearBindings();
			}

			$sql = class_exists($new)
				? $new::compile($this)
				: $class::compile($this);

			// Add bindings to parent query
			if ($this instanceof Query) {
				if ($p = self::parentQuery()) {
					if ($b = $this->getBindings()) {
						$p->bind($b);
					}
				}
			}

			return $sql;
		} finally {
			array_shift(self::$qstack);
		}
	}

	public function __toString(): string
	{
		try {
			$sqls = $this->toSql();
			return implode(";\n", $sqls);
		} catch (\Exception $e) {
			echo "ERROR __toString(): " . $e->getMessage() . "\n";
			exit;
		}
	}
}