<?php

declare(strict_types=1);

namespace KTXF\Cache\Store;

use KTXF\Cache\CacheScope;
use KTXF\Cache\EphemeralCacheInterface;

/**
 * File-based Ephemeral Cache Implementation
 * 
 * Stores cache entries as serialized files with expiration metadata.
 * Directory structure: var/cache/{scope}/{usage}/{key_hash}.cache
 */
class FileEphemeralCache implements EphemeralCacheInterface
{
    private string $basePath;
    private ?string $tenantId = null;
    private ?string $userId = null;

    public function __construct(string $projectDir)
    {
        $this->basePath = rtrim($projectDir, '/') . '/var/cache';
    }

    /**
     * Set the tenant context for scoped operations
     */
    public function setTenantContext(?string $tenantId): void
    {
        $this->tenantId = $tenantId;
    }

    /**
     * Set the user context for scoped operations
     */
    public function setUserContext(?string $userId): void
    {
        $this->userId = $userId;
    }

    /**
     * @inheritDoc
     */
    public function get(string $key, CacheScope $scope, string $usage): mixed
    {
        $path = $this->buildPath($key, $scope, $usage);
        
        if (!file_exists($path)) {
            return null;
        }

        $entry = $this->readEntry($path);
        
        if ($entry === null) {
            return null;
        }

        // Check expiration
        if ($entry['expiresAt'] > 0 && $entry['expiresAt'] < time()) {
            @unlink($path);
            return null;
        }

        return $entry['value'];
    }

    /**
     * @inheritDoc
     */
    public function set(string $key, mixed $value, CacheScope $scope, string $usage, ?int $ttl = null): bool
    {
        $path = $this->buildPath($key, $scope, $usage);
        $dir = dirname($path);

        if (!is_dir($dir)) {
            if (!mkdir($dir, 0755, true) && !is_dir($dir)) {
                return false;
            }
        }

        $ttl = $ttl ?? self::DEFAULT_TTL;
        $entry = [
            'key' => $key,
            'value' => $value,
            'createdAt' => time(),
            'expiresAt' => $ttl > 0 ? time() + $ttl : 0,
        ];

        return $this->writeEntry($path, $entry);
    }

    /**
     * @inheritDoc
     */
    public function has(string $key, CacheScope $scope, string $usage): bool
    {
        return $this->get($key, $scope, $usage) !== null;
    }

    /**
     * @inheritDoc
     */
    public function delete(string $key, CacheScope $scope, string $usage): bool
    {
        $path = $this->buildPath($key, $scope, $usage);
        
        if (file_exists($path)) {
            return @unlink($path);
        }

        return true;
    }

    /**
     * @inheritDoc
     */
    public function clear(CacheScope $scope, string $usage): int
    {
        $dir = $this->buildDir($scope, $usage);
        
        if (!is_dir($dir)) {
            return 0;
        }

        $count = 0;
        $files = glob($dir . '/*.cache');
        
        foreach ($files as $file) {
            if (@unlink($file)) {
                $count++;
            }
        }

        return $count;
    }

    /**
     * @inheritDoc
     */
    public function cleanup(): int
    {
        $count = 0;
        $now = time();
        
        // Scan all scope directories
        $scopeDirs = glob($this->basePath . '/*', GLOB_ONLYDIR);
        
        foreach ($scopeDirs as $scopeDir) {
            $files = $this->findCacheFiles($scopeDir);
            
            foreach ($files as $file) {
                $entry = $this->readEntry($file);
                
                if ($entry !== null && $entry['expiresAt'] > 0 && $entry['expiresAt'] < $now) {
                    if (@unlink($file)) {
                        $count++;
                    }
                }
            }
        }

        return $count;
    }

    /**
     * @inheritDoc
     */
    public function remember(string $key, callable $callback, CacheScope $scope, string $usage, ?int $ttl = null): mixed
    {
        $value = $this->get($key, $scope, $usage);
        
        if ($value !== null) {
            return $value;
        }

        $value = $callback();
        $this->set($key, $value, $scope, $usage, $ttl);
        
        return $value;
    }

    /**
     * @inheritDoc
     */
    public function increment(string $key, CacheScope $scope, string $usage, int $amount = 1): int|false
    {
        $path = $this->buildPath($key, $scope, $usage);
        
        // Use file locking for atomic increment
        $handle = @fopen($path, 'c+');
        if ($handle === false) {
            // File doesn't exist, create with initial value
            $dir = dirname($path);
            if (!is_dir($dir)) {
                if (!mkdir($dir, 0755, true) && !is_dir($dir)) {
                    return false;
                }
            }
            
            $handle = @fopen($path, 'c+');
            if ($handle === false) {
                return false;
            }
        }

        if (!flock($handle, LOCK_EX)) {
            fclose($handle);
            return false;
        }

        try {
            $content = stream_get_contents($handle);
            $entry = $content ? @unserialize($content) : null;
            
            if ($entry === null || ($entry['expiresAt'] > 0 && $entry['expiresAt'] < time())) {
                // Initialize new entry
                $newValue = $amount;
                $entry = [
                    'key' => $key,
                    'value' => $newValue,
                    'createdAt' => time(),
                    'expiresAt' => time() + self::DEFAULT_TTL,
                ];
            } else {
                $newValue = (int)$entry['value'] + $amount;
                $entry['value'] = $newValue;
            }

            ftruncate($handle, 0);
            rewind($handle);
            fwrite($handle, serialize($entry));
            
            return $newValue;
        } finally {
            flock($handle, LOCK_UN);
            fclose($handle);
        }
    }

    /**
     * @inheritDoc
     */
    public function decrement(string $key, CacheScope $scope, string $usage, int $amount = 1): int|false
    {
        return $this->increment($key, $scope, $usage, -$amount);
    }

    /**
     * Build the full path for a cache entry
     */
    private function buildPath(string $key, CacheScope $scope, string $usage): string
    {
        $dir = $this->buildDir($scope, $usage);
        $hash = $this->hashKey($key);
        
        return $dir . '/' . $hash . '.cache';
    }

    /**
     * Build the directory path for a scope/usage combination
     */
    private function buildDir(CacheScope $scope, string $usage): string
    {
        $prefix = $scope->buildPrefix($this->tenantId, $this->userId);
        $usage = preg_replace('/[^a-zA-Z0-9_-]/', '_', $usage);
        
        return $this->basePath . '/' . $prefix . '/' . $usage;
    }

    /**
     * Hash a cache key for filesystem safety
     */
    private function hashKey(string $key): string
    {
        // Use a prefix of the original key for debugging + hash for uniqueness
        $safe = preg_replace('/[^a-zA-Z0-9_-]/', '_', substr($key, 0, 32));
        $hash = substr(hash('sha256', $key), 0, 16);
        
        return $safe . '_' . $hash;
    }

    /**
     * Read and unserialize a cache entry
     */
    private function readEntry(string $path): ?array
    {
        $content = @file_get_contents($path);
        
        if ($content === false) {
            return null;
        }

        $entry = @unserialize($content);
        
        if (!is_array($entry) || !isset($entry['value'])) {
            return null;
        }

        return $entry;
    }

    /**
     * Serialize and write a cache entry atomically
     */
    private function writeEntry(string $path, array $entry): bool
    {
        $content = serialize($entry);
        $tempPath = $path . '.tmp.' . getmypid();
        
        if (file_put_contents($tempPath, $content, LOCK_EX) === false) {
            return false;
        }

        chmod($tempPath, 0600);
        
        if (!rename($tempPath, $path)) {
            @unlink($tempPath);
            return false;
        }

        return true;
    }

    /**
     * Recursively find all cache files in a directory
     */
    private function findCacheFiles(string $dir): array
    {
        $files = [];
        
        $iterator = new \RecursiveIteratorIterator(
            new \RecursiveDirectoryIterator($dir, \RecursiveDirectoryIterator::SKIP_DOTS),
            \RecursiveIteratorIterator::LEAVES_ONLY
        );
        
        foreach ($iterator as $file) {
            if ($file->isFile() && $file->getExtension() === 'cache') {
                $files[] = $file->getPathname();
            }
        }

        return $files;
    }
}