CSL Draw Calculator

draw-calculator.php

<?php

$schedule = json_decode('{
    "ballmark" : {
        "2016-03-14": "unisay",
        "2016-03-21": "discosaur"
    },
    "discosaur" : {
        "2016-03-14": "phoenix",
        "2016-03-21": "ballmark"
    },
    "disky" : {
        "2016-03-14": "theme",
        "2016-03-21": "honey"
    },
    "honey" : {
        "2016-03-14": "sado",
        "2016-03-21": "disky"
    },
    "phoenix" : {
        "2016-03-14": "discosaur",
        "2016-03-21": "sambal"
    },
    "sado" : {
        "2016-03-14": "honey",
        "2016-03-21": "unisax"
    },
    "sambal" : {
        "2016-03-14": "unisax",
        "2016-03-21": "phoenix"
    },
    "theme" : {
        "2016-03-14": "disky",
        "2016-03-21": "unisay"
    },
    "unisax" : {
        "2016-03-14": "sambal",
        "2016-03-21": "sado"
    },
    "unisay" : {
        "2016-03-14": "ballmark",
        "2016-03-21": "theme"
    }
}', true);
$nights = [
    "2016-03-14",
    "2016-03-21",
    "2016-03-28",
    "2016-04-04",
    "2016-04-11",
    "2016-04-18",
    "2016-04-25",
    "2016-05-02",
    "2016-05-09",
];
$teams = [
    "ballmark",
    "discosaur",
    "disky",
    "honey",
    "phoenix",
    "sado",
    "sambal",
    "theme",
    "unisax",
    "unisay",
];
$currentNightIndex = 2;


if (hasNightlyDuplicates($schedule)) {
    echo "A night exists where a team is scheduled to play at least twice.\n";
    die;
}

if (hasRepeatGames($schedule)) {
    echo "There are repeat games.\n";
    die;
}

// while schedule is incomplete
while (isIncomplete($schedule, $nights)) {
    // determine current night
    $currentNight = $nights[$currentNightIndex];

    // generate a random draw for the night
    shuffle($teams);

    for ($i = 0; $i < 5; $i++) {
        // pair up every i and i + 5 team
        $schedule[$teams[$i]][$currentNight] = $teams[$i + 5];
        $schedule[$teams[$i + 5]][$currentNight] = $teams[$i];
    }

    // if draw is NOT legit
    if (hasNightlyDuplicates($schedule) || hasRepeatGames($schedule)) {
        // delete it
        foreach ($schedule as &$team) {
            unset($team[$currentNight]);
        }
    } else {
        // set currentNightIndex to the next one.
        $currentNightIndex++;
    }
}

echo json_encode($schedule);

function hasNightlyDuplicates($schedule) {
    $nights = [];
    foreach ($schedule as $team => $matches) {
        foreach ($matches as $night => $opponent) {
            $nights[$night][] = $opponent;
        }
    }
    foreach ($nights as $teams) {
        if (count(array_unique($teams)) < count($teams)) {
            return true;
        }
    }
    return false;
}

function hasRepeatGames($schedule) {
    foreach($schedule as $team => $matches) {
        if (count(array_unique(array_values($matches))) < count($matches)) {
            return true;
        }
    }
    return false;
}

function isIncomplete($schedule, $nights) {
    foreach($schedule as $team => $matches) {
        if (count($matches) < count($nights)) {
            return true;
        }
    }
    return false;
}