<?php

declare(strict_types=1);

namespace App\Framework\Ksuid;

use App\Framework\Random\RandomGenerator;
use DateTimeImmutable;
use InvalidArgumentException;

/**
 * KSUID Generator Service
 *
 * Generates K-Sortable Unique Identifiers with timestamp ordering.
 */
final readonly class KsuidGenerator
{
    public function __construct(
        private RandomGenerator $randomGenerator
    ) {
    }

    /**
     * Generate a new KSUID with current timestamp
     */
    public function generate(): Ksuid
    {
        return $this->generateAt(time());
    }

    /**
     * Generate a KSUID at a specific Unix timestamp
     */
    public function generateAt(int $timestamp): Ksuid
    {
        if ($timestamp < Ksuid::EPOCH) {
            throw new InvalidArgumentException('Timestamp cannot be before KSUID epoch (2014-05-13)');
        }

        // Generate 16 random bytes for payload
        $payload = $this->randomGenerator->bytes(Ksuid::PAYLOAD_BYTES);

        return Ksuid::fromTimestampAndPayload($timestamp, $payload);
    }

    /**
     * Generate a KSUID at a specific DateTime
     */
    public function generateAtDateTime(DateTimeImmutable $dateTime): Ksuid
    {
        return $this->generateAt($dateTime->getTimestamp());
    }

    /**
     * Generate a KSUID for the past (useful for testing)
     */
    public function generateInPast(int $secondsAgo): Ksuid
    {
        $timestamp = time() - $secondsAgo;

        return $this->generateAt($timestamp);
    }

    /**
     * Generate a batch of KSUIDs with the same timestamp
     */
    public function generateBatch(int $count, ?int $timestamp = null): array
    {
        if ($count <= 0) {
            throw new InvalidArgumentException('Count must be positive');
        }

        if ($count > 10000) {
            throw new InvalidArgumentException('Batch size cannot exceed 10000');
        }

        $timestamp ??= time();
        $ksuids = [];
        $used = [];

        while (count($ksuids) < $count) {
            $payload = $this->randomGenerator->bytes(Ksuid::PAYLOAD_BYTES);
            $payloadHex = bin2hex($payload);

            // Ensure uniqueness within batch
            if (! isset($used[$payloadHex])) {
                $ksuids[] = Ksuid::fromTimestampAndPayload($timestamp, $payload);
                $used[$payloadHex] = true;
            }
        }

        return $ksuids;
    }

    /**
     * Generate a sequence of KSUIDs with incrementing timestamps
     */
    public function generateSequence(int $count, int $intervalSeconds = 1): array
    {
        if ($count <= 0) {
            throw new InvalidArgumentException('Count must be positive');
        }

        if ($count > 1000) {
            throw new InvalidArgumentException('Sequence size cannot exceed 1000');
        }

        if ($intervalSeconds < 0) {
            throw new InvalidArgumentException('Interval must be non-negative');
        }

        $ksuids = [];
        $timestamp = time();

        for ($i = 0; $i < $count; $i++) {
            $ksuids[] = $this->generateAt($timestamp + ($i * $intervalSeconds));
        }

        return $ksuids;
    }

    /**
     * Generate a KSUID with specific prefix in payload (for testing/debugging)
     */
    public function generateWithPrefix(string $prefix): Ksuid
    {
        $maxPrefixLength = Ksuid::PAYLOAD_BYTES - 1; // Reserve at least 1 byte for randomness

        if (strlen($prefix) > $maxPrefixLength) {
            throw new InvalidArgumentException("Prefix cannot exceed {$maxPrefixLength} bytes");
        }

        $remainingBytes = Ksuid::PAYLOAD_BYTES - strlen($prefix);
        $randomSuffix = $this->randomGenerator->bytes($remainingBytes);
        $payload = $prefix . $randomSuffix;

        return Ksuid::fromTimestampAndPayload(time(), $payload);
    }

    /**
     * Parse a KSUID string and validate it
     */
    public function parse(string $ksuidString): Ksuid
    {
        return Ksuid::fromString($ksuidString);
    }

    /**
     * Validate if a string is a valid KSUID
     */
    public function isValid(string $value): bool
    {
        if (strlen($value) !== Ksuid::ENCODED_LENGTH) {
            return false;
        }

        try {
            Ksuid::fromString($value);

            return true;
        } catch (InvalidArgumentException) {
            return false;
        }
    }

    /**
     * Get the minimum possible KSUID for a timestamp
     */
    public function getMinForTimestamp(int $timestamp): Ksuid
    {
        $payload = str_repeat("\0", Ksuid::PAYLOAD_BYTES);

        return Ksuid::fromTimestampAndPayload($timestamp, $payload);
    }

    /**
     * Get the maximum possible KSUID for a timestamp
     */
    public function getMaxForTimestamp(int $timestamp): Ksuid
    {
        $payload = str_repeat("\xFF", Ksuid::PAYLOAD_BYTES);

        return Ksuid::fromTimestampAndPayload($timestamp, $payload);
    }

    /**@return array{min: \App\Framework\Ksuid\Ksuid, max: \App\Framework\Ksuid\Ksuid}
     * Generate KSUIDs for a time range (useful for queries)
     */
    public function generateTimeRange(int $startTimestamp, int $endTimestamp): array
    {
        if ($startTimestamp >= $endTimestamp) {
            throw new InvalidArgumentException('Start timestamp must be before end timestamp');
        }

        return [
            'min' => $this->getMinForTimestamp($startTimestamp),
            'max' => $this->getMaxForTimestamp($endTimestamp),
        ];
    }

    /**
     * Create factory method
     */
    public static function create(RandomGenerator $randomGenerator): self
    {
        return new self($randomGenerator);
    }
}