<?php namespace MapGuesser\Repository;

use Generator;
use SokoWeb\Database\Query\Select;
use MapGuesser\PersistentData\Model\Challenge;
use MapGuesser\PersistentData\Model\Map;
use MapGuesser\PersistentData\Model\Place;

class PlaceRepository
{
    public function getById(int $placeId): ?Place
    {
        return \Container::$persistentDataManager->selectFromDbById($placeId, Place::class);
    }

    public function getAllForMap(Map $map): Generator
    {
        $select = new Select(\Container::$dbConnection);
        $select->where('map_id', '=', $map->getId());

        yield from \Container::$persistentDataManager->selectMultipleFromDb($select, Place::class);
    }

    //TODO: use Map and User instead of id
    public function getRandomNPlaces(int $mapId, int $n, ?int $userId): array
    {
        if (!isset($userId)) { // anonymous single player
            return $this->getRandomNForMapWithValidPano($mapId, $n);
        } else { // authorized user or multiplayer game with selection based on what the host played before
            $unvisitedPlaces = $this->getRandomUnvisitedNForMapWithValidPano($mapId, $n, $userId);
            if (count($unvisitedPlaces) == $n) {
                return $unvisitedPlaces;
            }

            $oldPlaces = $this->getRandomOldNForMapWithValidPano($mapId, $n - count($unvisitedPlaces), $userId);

            return array_merge($unvisitedPlaces, $oldPlaces);
        }
    }

    //TODO: use Map instead of id
    private function getRandomNForMapWithValidPano(int $mapId, int $n): array
    {
        $places = [];

        $select = new Select(\Container::$dbConnection, 'places');
        $select->where('map_id', '=', $mapId);
        $numberOfPlaces = $select->count();

        $exclude = [];
        for ($i = 1; $i <= $n; ++$i) {
            $place = $this->getRandomForMapWithValidPano($numberOfPlaces, $select, $exclude);

            $places[] = $place;
            $exclude[] = $place->getId();
        }

        return $places;
    }

    private function getRandomForMapWithValidPano(int $numberOfPlaces, Select $select, array &$exclude, ?callable $pickRandomInt = null): ?Place
    {
        do {
            $numberOfPlacesLeft = $numberOfPlaces - count($exclude);
            $place = $this->selectRandomFromDbForMap($numberOfPlacesLeft, $select, $exclude, $pickRandomInt);
            if ($place === null) {
                // there is no more never visited place left
                return null;
            }

            $panoId = $place->getFreshPanoId();
            if ($panoId === null) {
                $exclude[] = $place->getId();
            }
        } while ($panoId === null);

        return $place;
    }

    private function selectRandomFromDbForMap(int $numberOfPlacesLeft, Select $select, array $exclude, ?callable $pickRandomInt): ?Place
    {
        if ($numberOfPlacesLeft <= 0)
            return null;

        if (!isset($pickRandomInt)) {
            $randomOffset = random_int(0, $numberOfPlacesLeft - 1);
        } else {
            $randomOffset = $pickRandomInt($numberOfPlacesLeft);
        }

        $select->where('id', 'NOT IN', $exclude);
        $select->limit(1, $randomOffset);

        return \Container::$persistentDataManager->selectFromDb($select, Place::class);
    }

    // Never visited places
    private function getRandomUnvisitedNForMapWithValidPano(int $mapId, int $n, int $userId): array
    {
        $places = [];
        $exclude = [];

        // list of places visited by user
        $selectPlacesByCurrentUser = new Select(\Container::$dbConnection, 'user_played_place');
        $selectPlacesByCurrentUser->columns(['place_id', 'last_time']);
        $selectPlacesByCurrentUser->where('user_id', '=', $userId);
        $selectPlacesByCurrentUser->setDerivedTableAlias('places_by_current_user');

        // count the places never visited
        $selectUnvisited = new Select(\Container::$dbConnection, 'places');
        $selectUnvisited->leftJoin($selectPlacesByCurrentUser, ['places', 'id'], '=', ['places_by_current_user', 'place_id']);
        $selectUnvisited->where('map_id', '=', $mapId);
        $selectUnvisited->where(['places_by_current_user', 'last_time'], '=', null);
        $numberOfUnvisitedPlaces = $selectUnvisited->count();

        // look for as many new places as possible but maximum $n
        do {
            $place = $this->getRandomForMapWithValidPano($numberOfUnvisitedPlaces, $selectUnvisited, $exclude);
            if (isset($place)) {
                $places[] = $place;
                $exclude[] = $place->getId();
            }
        } while (count($places) < $n && isset($place));

        return $places;
    }

    // Places visited in the longest time
    private function getRandomOldNForMapWithValidPano(int $mapId, int $n, int $userId): array
    {
        $places = [];
        $exclude = [];

        // list of places visited by user
        $selectPlacesByCurrentUser = new Select(\Container::$dbConnection, 'user_played_place');
        $selectPlacesByCurrentUser->columns(['place_id', 'last_time']);
        $selectPlacesByCurrentUser->where('user_id', '=', $userId);
        $selectPlacesByCurrentUser->setDerivedTableAlias('places_by_current_user');

        // count places that were visited at least once
        $selectOldPlaces = new Select(\Container::$dbConnection, 'places');
        $selectOldPlaces->innerJoin($selectPlacesByCurrentUser, ['places', 'id'], '=', ['places_by_current_user', 'place_id']);
        $selectOldPlaces->where('map_id', '=', $mapId);
        $numberOfOldPlaces = $selectOldPlaces->count();

        // set order by datetime, oldest first
        $selectOldPlaces->orderBy('last_time');

        // selection algorithm with preference (weighting) for older places using Box-Muller transform
        $pickGaussianRandomInt = function($numberOfPlaces) {
            $stdev = 0.2;
            $avg = 0.0;
            $x = mt_rand() / mt_getrandmax();
            $y = mt_rand() / mt_getrandmax();
            $randomNum = abs(sqrt(-2 * log($x)) * cos(2 * pi() * $y) * $stdev + $avg);
            return (int) min($randomNum * $numberOfPlaces, $numberOfPlaces - 1);
        };

        // look for n - numberOfUnvisitedPlaces places
        while (count($places) < $n)
        {
            $place = $this->getRandomForMapWithValidPano($numberOfOldPlaces, $selectOldPlaces, $exclude, $pickGaussianRandomInt);
            if (isset($place))
            {
                $places[] = $place;
                $exclude[] = $place->getId();
            }
        }

        return $places;
    }

    public function getByRoundInChallenge(Challenge $challenge, int $round): ?Place
    {
        $select = new Select(\Container::$dbConnection);
        $select->innerJoin('place_in_challenge', ['places', 'id'], '=', ['place_in_challenge', 'place_id']);
        $select->where(['place_in_challenge', 'challenge_id'], '=', $challenge->getId());
        $select->orderBy(['place_in_challenge', 'round']);
        $select->limit(1, $round);

        return \Container::$persistentDataManager->selectFromDb($select, Place::class);
    }

    public function getAllInChallenge(Challenge $challenge): Generator
    {
        $select = new Select(\Container::$dbConnection);
        $select->innerJoin('place_in_challenge', ['places', 'id'], '=', ['place_in_challenge', 'place_id']);
        $select->where(['place_in_challenge', 'challenge_id'], '=', $challenge->getId());
        $select->orderBy(['place_in_challenge', 'round']);

        yield from \Container::$persistentDataManager->selectMultipleFromDb($select, Place::class);
    }

}