<?php

// number of winners
$max_winners = 10;

// seed mersenne twister with fixed value
mt_srand(12345);

// read entries
$entries = readlines("entries.txt");

// read votes
$votes = array();
$votefiles = scandir("votes");
foreach($votefiles as $file) {
    if(preg_match("/\.txt$/", $file))
        $votes[basename($file, ".txt")] = readlines("votes/" . $file);
}

echo "Entries:\n";
print_r($entries);
echo "Votes:\n";
print_r($votes);

// calculate winners
$winners = repeated_instant_runoff_vote($entries, $votes, min($max_winners, count($entries)));

// print result
echo "#################### All winners ####################\n";
print_r($winners);

function readlines($file) {
    $lines = explode("\n", file_get_contents($file));
    $ret = array();
    foreach($lines as $line) {
        $l = trim($line);
        if($l != "")
            $ret[] = $l;
    }
    return $ret;
}

function random_real($a, $b) {
    return $a + ($b - $a) * mt_rand() / mt_getrandmax();
}

function repeated_instant_runoff_vote($entries, $votes, $repeats) {

    // make sure all votes are valid
    foreach($votes as $voter => $vote) {
        foreach($vote as $e) {
            if(!in_array($e, $entries)) {
                die("Error: invalid vote for '$e' from '$voter'!\n");
            }
        }
    }

    // one more winner and one less candidate after each iteration
    $candidates = array_fill_keys($entries, 0);
    $winners = array();
    for($rep = 0; $rep < $repeats; ++$rep) {

        echo "#################### Winner " . ($rep + 1) . " ####################\n";

        // start voting
        $candidates_left = $candidates;
        while(count($candidates_left) > 1) {

            // count votes
            $scores = $candidates_left;
            foreach($votes as $vote) {
                foreach($vote as $e) {
                    if(isset($scores[$e])) {
                        ++$scores[$e];
                        break;
                    }
                }
            }

            // random tie-breaker
            foreach($scores as &$s) {
                $s += random_real(0.01, 0.09);
            }
            unset($s);

            // sort and eliminate the candidate with the lowest score
            arsort($scores);
            end($scores);
            $eliminate = key($scores);
            unset($candidates_left[$eliminate]);

            print_r($scores);
            echo "'" . $eliminate . "' eliminated.\n";
        }

        // get the winner
        reset($candidates_left);
        $winner = key($candidates_left);
        unset($candidates[$winner]);
        $winners[] = $winner;

        echo "=> Winner " . ($rep + 1) . " is '" . $winner . "'\n";

    }

    return $winners;

}

?>