<?php

const DEFAULT_SUGGESTION_AMOUNT = 3;

$suggestionAmount = 0;
if (isset($_SERVER['REQUEST_METHOD'])) {
    if (!isset($_GET['input'])) {
        die("Please use the script with a GET parameter 'input' that consist of first letters of a search string. " .
            "Optionally 'suggestions' parameter can be set as a number of suggestions. " .
            "Usage: '/search-suggestions.php?input=Alex&suggestions=3'\n");
    }

    $input = filter_input(INPUT_GET, 'input', FILTER_SANITIZE_STRING);
    if (0 === strlen($input)) {
        die("Please use the script with a GET parameter 'input' that consist of first letters of a search string. " .
            "Optionally 'suggestions' parameter can be set as a number of suggestions. " .
            "Usage: '/search-suggestions.php?input=Alex&suggestions=3'\n");
    }

    $suggestionAmount = (int)filter_input(INPUT_GET, 'suggestions', FILTER_SANITIZE_NUMBER_INT);
} elseif (!isset($argv[1])) {
    die("Please run the script with a first parameter that consist of first letters of a search string." .
        "Optionally the second parameter can be set as a number of suggestions. " .
        "Usage: 'php search-suggestions.php Alex 5'\n");
} else {
    $input = filter_var($argv[1], FILTER_SANITIZE_STRING);
    if (0 === strlen($input)) {
        die("Please run the script with a first parameter that consist of first letters of a search string." .
            "Optionally the second parameter can be set as a number of suggestions. " .
            "Usage: 'php search-suggestions.php Alex 5'\n");
    }

    if (isset($argv[2])) {
        $suggestionAmount = (int)filter_var($argv[2], FILTER_SANITIZE_NUMBER_INT);
    }
}

$suggestionAmount = abs($suggestionAmount ?: DEFAULT_SUGGESTION_AMOUNT);

$input = ucwords($input);

$suggestions = [];
$farSuggestions = [];

$exactMatchesCount = 0;

$dictionary = new SplFileObject('names.csv');
$dictionary->setFlags(SplFileObject::READ_CSV);
$dictionary->next();

foreach ($dictionary as $row) {
    if (!isset($row[1])) {
        continue;
    }

    $firstLetterIsDifferent = !(substr($row[1], 0, 1) === substr($input, 0, 1));
    $nameAlreadyAdded = in_array($row[1], $suggestions) || in_array($row[1], $farSuggestions);
    if ($firstLetterIsDifferent || $nameAlreadyAdded) {
        continue;
    }

    $subString = substr($row[1], 0, strlen($input));
    if ($subString === $input) {
        array_unshift($suggestions, $row[1]);
        if (++$exactMatchesCount === $suggestionAmount) {
            break;
        }
    } elseif (count($suggestions) < $suggestionAmount && 1 === levenshtein($input, $subString)) {
        $suggestions[] = $row[1];
    } elseif (count($farSuggestions) < $suggestionAmount && 2 === levenshtein($input, $subString)) {
        $farSuggestions[] = $row[1];
    }
}

if (count($suggestions) < $suggestionAmount && count($farSuggestions) > 0) {
    $suggestions = array_merge($suggestions, array_slice($farSuggestions, 0, $suggestionAmount - count($suggestions)));
} elseif (count($suggestions) > $suggestionAmount) {
    $suggestions = array_slice($suggestions, 0, $suggestionAmount);
}

echo json_encode($suggestions);