<?php

namespace App\Services;

use Illuminate\Http\Request;
use Illuminate\Support\Str;

class NavigationContextService
{
    private const SESSION_KEY = 'navigation';
    private const MAX_CONTEXTS = 30;
    private const MAX_STACK_SIZE = 20;
    private const TTL_SECONDS = 86400;

    public function getOrCreateToken(Request $request): string
    {
        $this->pruneExpired();

        $token = trim((string) $request->input('nav', ''));
        if ($token !== '' && $this->contextExists($token)) {
            return $token;
        }

        $token = bin2hex(random_bytes(8));
        $this->saveContext($token, [
            'updated_at' => time(),
            'stack' => [],
        ]);

        return $token;
    }

    public function rememberCurrentPage(Request $request, string $token): void
    {
        if (!$this->isGetPage($request)) {
            return;
        }

        $this->appendUrl($token, $request->fullUrl());
    }

    public function backUrl(Request $request, string $token, ?string $fallback = null): ?string
    {
        $context = $this->context($token);
        $stack = $context['stack'] ?? [];

        if (empty($stack)) {
            return $fallback;
        }

        $currentUrl = $this->normalizeUrl($request->fullUrl());
        $lastUrl = end($stack);

        if ($lastUrl === $currentUrl) {
            $previousUrl = prev($stack);
            return $previousUrl !== false ? $previousUrl : $fallback;
        }

        return $lastUrl ?: $fallback;
    }

    public function parentUrl(string $token, ?string $fallback = null): ?string
    {
        $context = $this->context($token);
        $stack = $context['stack'] ?? [];

        if (empty($stack)) {
            return $fallback;
        }

        $lastUrl = array_pop($stack);
        if (empty($stack)) {
            return $fallback ?? $lastUrl;
        }

        return end($stack) ?: $fallback;
    }

    public function routeParams(array $params, string $token): array
    {
        return array_merge($params, ['nav' => $token]);
    }

    public function pruneExpired(): void
    {
        $contexts = session(self::SESSION_KEY, []);
        if (empty($contexts)) {
            return;
        }

        $now = time();
        foreach ($contexts as $token => $context) {
            $updatedAt = (int) ($context['updated_at'] ?? 0);
            if ($updatedAt < ($now - self::TTL_SECONDS)) {
                unset($contexts[$token]);
            }
        }

        if (count($contexts) > self::MAX_CONTEXTS) {
            uasort($contexts, static fn (array $left, array $right) => ($left['updated_at'] ?? 0) <=> ($right['updated_at'] ?? 0));
            $contexts = array_slice($contexts, -self::MAX_CONTEXTS, null, true);
        }

        session([self::SESSION_KEY => $contexts]);
    }

    public function forgetToken(string $token): void
    {
        $contexts = session(self::SESSION_KEY, []);
        unset($contexts[$token]);
        session([self::SESSION_KEY => $contexts]);
    }

    private function appendUrl(string $token, string $url): void
    {
        $normalizedUrl = $this->normalizeUrl($url);
        if ($normalizedUrl === '') {
            return;
        }

        $context = $this->context($token);
        $stack = $context['stack'] ?? [];

        $stack = array_values(array_filter($stack, static fn (string $storedUrl) => $storedUrl !== $normalizedUrl));
        $stack[] = $normalizedUrl;

        if (count($stack) > self::MAX_STACK_SIZE) {
            $stack = array_slice($stack, -self::MAX_STACK_SIZE);
        }

        $context['updated_at'] = time();
        $context['stack'] = $stack;

        $this->saveContext($token, $context);
    }

    private function normalizeUrl(string $url): string
    {
        $parts = parse_url($url);
        if ($parts === false || empty($parts['path'])) {
            return '';
        }

        $query = [];
        if (!empty($parts['query'])) {
            parse_str($parts['query'], $query);
            unset($query['nav']);
        }

        $normalizedUrl = '';
        if (!empty($parts['scheme'])) {
            $normalizedUrl .= $parts['scheme'] . '://';
        }

        if (!empty($parts['user'])) {
            $normalizedUrl .= $parts['user'];
            if (!empty($parts['pass'])) {
                $normalizedUrl .= ':' . $parts['pass'];
            }
            $normalizedUrl .= '@';
        }

        if (!empty($parts['host'])) {
            $normalizedUrl .= $parts['host'];
        }

        if (!empty($parts['port'])) {
            $normalizedUrl .= ':' . $parts['port'];
        }

        $normalizedUrl .= $parts['path'];

        if (!empty($query)) {
            $normalizedUrl .= '?' . http_build_query($query);
        }

        return $normalizedUrl;
    }

    private function isGetPage(Request $request): bool
    {
        return strtoupper($request->method()) === 'GET';
    }

    private function contextExists(string $token): bool
    {
        return array_key_exists($token, session(self::SESSION_KEY, []));
    }

    private function context(string $token): array
    {
        return session(self::SESSION_KEY . '.' . $token, [
            'updated_at' => time(),
            'stack' => [],
        ]);
    }

    private function saveContext(string $token, array $context): void
    {
        session([self::SESSION_KEY . '.' . $token => $context]);
    }
}