<?php

declare(strict_types=1);

function loadRoomPlanningSettings(PDO $pdo): array
{
    $defaults = [
        'single' => 0,
        'double' => 0,
        'multi' => 0,
    ];
    $statement = $pdo->query(
        "SELECT setting_key, price FROM pricing_settings
         WHERE setting_key IN ('room_count_single', 'room_count_double', 'room_count_multi')"
    );
    foreach ($statement->fetchAll(PDO::FETCH_KEY_PAIR) as $key => $value) {
        $type = str_replace('room_count_', '', (string) $key);
        if (array_key_exists($type, $defaults)) {
            $defaults[$type] = max(0, (int) $value);
        }
    }

    return $defaults;
}

function normalizedRoommateName(string $name): string
{
    return mb_strtolower(preg_replace('/\\s+/u', ' ', trim($name)) ?? '', 'UTF-8');
}

function buildRoomPlan(array $participants, array $roomCounts): array
{
    $rooms = [];
    $warnings = [];
    $unassigned = [];
    $available = [
        'single' => max(0, (int) ($roomCounts['single'] ?? 0)),
        'double' => max(0, (int) ($roomCounts['double'] ?? 0)),
        'multi' => max(0, (int) ($roomCounts['multi'] ?? 0)),
    ];
    $roomNumber = ['single' => 0, 'double' => 0, 'multi' => 0];
    $assigned = [];
    $blocked = [];
    $byName = [];

    foreach ($participants as &$participant) {
        $participant['roommate_key'] = normalizedRoommateName((string) ($participant['roommate_requests'] ?? ''));
        $participant['name_key'] = normalizedRoommateName((string) $participant['name']);
        $byName[$participant['name_key']][] = $participant;
    }
    unset($participant);

    $addRoom = static function (string $type, array $members) use (&$rooms, &$roomNumber, &$available, &$assigned): bool {
        if (($available[$type] ?? 0) < 1) {
            return false;
        }
        $roomNumber[$type]++;
        $capacity = $type === 'single' ? 1 : ($type === 'double' ? 2 : 4);
        $rooms[] = [
            'type' => $type,
            'number' => $roomNumber[$type],
            'capacity' => $capacity,
            'members' => $members,
        ];
        $available[$type]--;
        foreach ($members as $member) {
            $assigned[(string) $member['id']] = true;
        }
        return true;
    };

    // Mutual wishes are handled first, but only when both participants requested the same room type.
    foreach ($participants as $participant) {
        $id = (string) $participant['id'];
        if (isset($assigned[$id]) || $participant['roommate_key'] === '') {
            continue;
        }
        foreach ($byName[$participant['roommate_key']] ?? [] as $requested) {
            $requestedId = (string) $requested['id'];
            if ($requestedId === $id || isset($assigned[$requestedId])) {
                continue;
            }
            $mutual = $requested['roommate_key'] === $participant['name_key'];
            $sameType = $requested['room_type'] === $participant['room_type'];
            if (!$mutual || !$sameType) {
                continue;
            }
            if (!$addRoom((string) $participant['room_type'], [$participant, $requested])) {
                $warnings[] = sprintf(
                    'Der gegenseitige Zimmerwunsch von %s und %s konnte nicht erfüllt werden: kein %s-Zimmer verfügbar.',
                    $participant['name'],
                    $requested['name'],
                    $participant['room_type'] === 'double' ? 'Doppel' : 'Mehrbett'
                );
                $unassigned[$id] = $participant;
                $unassigned[$requestedId] = $requested;
                $blocked[$id] = true;
                $blocked[$requestedId] = true;
            }
            break;
        }
    }

    foreach (['single', 'double', 'multi'] as $type) {
        $waiting = [];
        foreach ($participants as $participant) {
            $id = (string) $participant['id'];
            if (!isset($assigned[$id]) && !isset($blocked[$id]) && $participant['room_type'] === $type) {
                $waiting[] = $participant;
            }
        }
        $capacity = $type === 'single' ? 1 : ($type === 'double' ? 2 : 4);
        while ($waiting !== []) {
            $group = array_splice($waiting, 0, $capacity);
            if (!$addRoom($type, $group)) {
                foreach ($group as $participant) {
                    $unassigned[(string) $participant['id']] = $participant;
                }
                $warnings[] = sprintf(
                    '%d Teilnehmer mit Wunsch %s konnten keinem verfügbaren Zimmer zugeordnet werden.',
                    count($group),
                    $type === 'single' ? 'Einzelzimmer' : ($type === 'double' ? 'Doppelzimmer' : 'Mehrbettzimmer')
                );
            }
        }
    }

    foreach ($unassigned as $participant) {
        $warnings[] = sprintf('Nicht eingeplant: %s (%s).', $participant['name'], $participant['email']);
    }

    return [
        'rooms' => $rooms,
        'warnings' => array_values(array_unique($warnings)),
        'unassigned' => array_values($unassigned),
        'available' => $available,
    ];
}