<?php

namespace alveolata\sql;

// require_once(DIR_ALVEOLATA . '/definitions.php');


/**
 * @param array $expressions {list<string>}
 * @return string
 * @author Christian Fraß <frass@greenscale.de>
 */
function conjunction(
	array $expressions
) : string
{
	return (
		implode(
			' AND ',
			array_map(
				function (string $expression) : string {
					return sprintf('(%s)', $expression);
				},
				$expressions
			)
		)
	);
}


/**
 * @param array $expressions {list<string>}
 * @return string
 * @author Christian Fraß <frass@greenscale.de>
 */
function disjunction(
	array $expressions
) : string
{
	return (
		implode(
			' OR ',
			array_map(
				function (string $expression) : string {
					return sprintf('(%s)', $expression);
				},
				$expressions
			)
		)
	);
}


/**
 * expression to check if two sets (~ 1 column tables) are equal (in their elements, not in their order)
 * warning: won't work for empty sets
 * 
 * @author Christian Fraß <frass@greenscale.de>
 */
function set_equal(
	string $set1,
	string $set2
) : string
{
	// (x \ y) ∪ (y \ x) = {}
	return sprintf(
		'(NOT EXISTS (SELECT value FROM (%s) WHERE NOT (value IN (%s)) UNION SELECT value FROM (%s) WHERE NOT (value IN (%s))))',
		$set1,
		$set2,
		$set2,
		$set1
	);
}


/**
 * @param mixed $value
 * @param \Closure $escape
 * @return string
 * @author Christian Fraß <frass@greenscale.de>
 */
function format(
	$value,
	\Closure $escape = null
) : string
{
	if ($escape === null) {
		$escape = (
			function ($x) {
				$replacements = [
					'\'' => '\'\'',
					';' => '\\;',
				];
				$y = $x;
				foreach ($replacements as $from => $to) {
					$y = str_replace($from, $to, $y);
				}
				return $y;
			}
		);
	}
	if ($value === null) {
		return 'NULL';
	}
	else {
		$type = gettype($value);
		switch ($type) {
			case 'boolean': {
				return ($value ? 'TRUE' : 'FALSE');
				break;
			}
			case 'integer': {
				return sprintf('%d', $value);
				break;
			}
			case 'float': 
			case 'double': {
				return sprintf('%.4f', $value);
				break;
			}
			case 'string': {
				return sprintf('\'%s\'', $escape($value));
				break;
			}
			case 'array': {
				return sprintf(
					'(%s)',
					implode(
						',',
						array_map(
							function ($element) : string {
								return format($element);
							},
							(
								empty($value)
								? ['___DUMMY_VALUE___']
								: $value
							)
						)
					)
				);
			}
			default: {
				throw (new \Exception(sprintf('unhandled type "%s" of value %s', $type, json_encode($value))));
				break;
			}
		}
	}
}