<?php

declare(strict_types = 1);

namespace sid;

$CONFIG = [
    'base-dir'         => __DIR__ . '/downloads/',
    'start-from'       => 1,
    'count'            => 2000,
    'output-extension' => '', // jpg|gif|png|mp3|mp4|webm etc.
    'logs-file'        => 'Logs.txt' // See the log file in %base-dir%. Leave empty to disable file logs
];

// No changes required after this line
$baseDir   = rtrim($CONFIG['base-dir'], '\/') . DIRECTORY_SEPARATOR;
$startFrom = $CONFIG['start-from'];
$count     = $CONFIG['count'];
$stopAfter = $startFrom + $count - 1;
$ext       = !empty($CONFIG['output-extension']) ? '.' . $CONFIG['output-extension'] : '';

global $enableLogs, $logFile;

$enableLogs = !empty($CONFIG['logs-file']);
$logFile    = $baseDir . $CONFIG['logs-file'];

// Check base dir
if (!file_exists($baseDir)) {
    say('Error. The destination directory does not exist.');
    exit(1);
}

// Check the log file
if ($enableLogs) {
    if (!file_exists($logFile)) {
        file_put_contents($logFile, '');

        if (!file_exists($logFile)) {
            say('Error. Failed to create a log file ' . $logFile);
            exit(2);
        }
    }
}

// All ready to start
$fails = new FailuresRecorder($startFrom);

for ($i = $startFrom, $done = 0; $i <= $stopAfter; $i++, $done++) {
    // Notify about the progress
    if ($done % 50 == 0) {
        say("{$done}/{$count} done...");
    }

    $file = "{$baseDir}{$i}{$ext}";

    if (file_exists($file)) {
        $fails->nextSucceed();
    } else {
        $fails->nextFailed();
    }
}

$fails->finish();

say('Finished.');
say("Failed to download the following files: {$fails}.");

exit(0);

function say(string $message)
{
    global $enableLogs, $logFile;

    echo $message, PHP_EOL;

    if ($enableLogs) {
        file_put_contents($logFile, $message . PHP_EOL, FILE_APPEND);
    }
}

/**
 * Record failures like: 2, 4, 10-12, 17-43.
 */
class FailuresRecorder
{
    const STATUS_FAILED     = 0;
    const STATUS_SUCCEED    = 1;
    const STATUS_UNASSIGNED = 2;

    protected $failures = []; // ["2", "4", "10-12", "17-43"]
    protected $failuresCount = 0; // 32

    protected $firstFailId = 0;
    protected $lastFailId  = 0;

    protected $currentId = 1;
    protected $currentStatus = self::STATUS_UNASSIGNED;

    public function __construct(int $startId)
    {
        $this->currentId = $startId;
    }

    public function nextSucceed()
    {
        switch ($this->currentStatus) {
            case self::STATUS_FAILED:
                if ($this->lastFailId == $this->firstFailId) {
                    $this->failures[] = $this->lastFailId;
                } else {
                    $this->failures[] = $this->firstFailId . '-' . $this->lastFailId;
                }
                break;

            case self::STATUS_SUCCEED:
                break;
        }

        $this->currentId++;
        $this->currentStatus = self::STATUS_SUCCEED;
    }

    public function nextFailed()
    {
        $this->lastFailId = $this->currentId;

        switch ($this->currentStatus) {
            case self::STATUS_SUCCEED:
            case self::STATUS_UNASSIGNED:
                $this->firstFailId = $this->currentId;
                break;
        }

        $this->failuresCount++;
        $this->currentId++;
        $this->currentStatus = self::STATUS_FAILED;
    }

    public function finish()
    {
        $this->nextSucceed();
    }

    public function getFailures(): array
    {
        return $this->failures;
    }

    public function getFailuresCount(): int
    {
        return $this->failuresCount;
    }

    public function hasFailures(): bool
    {
        return !empty($this->failures);
    }

    public function __toString(): string
    {
        if ($this->hasFailures()) {
            return implode(', ', $this->failures) . " ({$this->failuresCount} in total)";
        } else {
            return 'none';
        }
    }
} // class FailuresRecorder