<?php

namespace App\Services;

use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Http;
use Illuminate\Support\Facades\Log;
use Illuminate\Support\Facades\File;
use Carbon\Carbon;

/**
 * NAKS Multi-Module Synchronization Service
 * 
 * Synchronizes NAKS data across multiple project sites for various modules:
 * - NAKS Technology (naks_certificates)
 * - NAKS Welder (naks_welders)
 * - NAKS Consumables (naks_consumables)
 * - NAKS Expert (register_of_experts)
 * - NAKS Equipment (welding_equipment)
 * 
 * Each site runs this service to pull data from other sites.
 */
class NaksSyncService
{
    protected string $basePdfPath = 'documents/003_Welding_Database';
    protected int $timeout = 30;
    protected int $batchSize = 100;
    
    protected ?string $adminEmail = null;
    protected ?string $adminPassword = null;
    protected ?string $currentSiteUrl = null;
    
    /**
     * Module configurations
     * Each module defines its table, unique keys, and PDF folder
     */
    protected array $modules = [
        'technology' => [
            'name' => 'NAKS Technology',
            'table' => 'naks_certificates',
            'unique_keys' => ['short_number', 'certificate_no'],
            'pdf_folder' => '0000_Naks Technology',
            'download_field' => 'download',
        ],
        'welder' => [
            'name' => 'NAKS Welder',
            'table' => 'naks_welders',
            'unique_keys' => ['naks_certificate_no', 'welder_id'],
            'pdf_folder' => '0003_Naks Welder',
            'download_field' => 'download',
        ],
        'consumables' => [
            'name' => 'NAKS Consumables',
            'table' => 'naks_consumables',
            'unique_keys' => ['naks_certificate_no', 'batch_number'],
            'pdf_folder' => '0002_Naks Consumables',
            'download_field' => 'download',
        ],
        'expert' => [
            'name' => 'NAKS Expert',
            'table' => 'register_of_experts',
            'unique_keys' => ['certificate_no'],
            'pdf_folder' => '0004_Naks Expert',
            'download_field' => 'download',
        ],
        'equipment' => [
            'name' => 'NAKS Equipment',
            'table' => 'welding_equipment',
            'unique_keys' => ['attestation'],
            'pdf_folder' => '0001_Naks Equipment',
            'download_field' => 'download',
        ],
    ];
    
    protected array $stats = [
        'total_projects' => 0,
        'successful_projects' => 0,
        'failed_projects' => [],
        'modules' => [],
        'errors' => [],
    ];
    
    public function __construct()
    {
        $this->adminEmail = env('SYNC_ADMIN_EMAIL');
        $this->adminPassword = env('SYNC_ADMIN_PASSWORD');
        $this->currentSiteUrl = rtrim(config('app.url'), '/');
    }
    
    /**
     * Get available modules
     */
    public function getModules(): array
    {
        return $this->modules;
    }
    
    /**
     * Get module configuration by key
     */
    public function getModuleConfig(string $moduleKey): ?array
    {
        return $this->modules[$moduleKey] ?? null;
    }
    
    /**
     * Run the full synchronization process
     * 
     * @param string $moduleFilter Module to sync ('all' or specific module key)
     * @param string|null $specificProject Filter to sync only a specific project
     * @param bool $dryRun If true, don't make any changes
     * @param bool $force If true, sync all records (ignore last_synced_id)
     * @return array Statistics about the sync operation
     */
    public function sync(
        string $moduleFilter = 'all',
        ?string $specificProject = null,
        bool $dryRun = false,
        bool $force = false
    ): array {
        Log::info("🔄 NAKS Multi-Module Sync Started", [
            'module_filter' => $moduleFilter,
            'specific_project' => $specificProject,
            'dry_run' => $dryRun,
            'force' => $force,
        ]);
        
        if (!$this->adminEmail || !$this->adminPassword) {
            $error = 'SYNC_ADMIN_EMAIL or SYNC_ADMIN_PASSWORD not configured in .env';
            Log::error($error);
            $this->stats['errors'][] = $error;
            return $this->stats;
        }
        
        // Determine which modules to sync
        $modulesToSync = $this->getModulesToSync($moduleFilter);
        
        if (empty($modulesToSync)) {
            $error = "Invalid module: {$moduleFilter}. Available: " . implode(', ', array_keys($this->modules));
            Log::error($error);
            $this->stats['errors'][] = $error;
            return $this->stats;
        }
        
        // Initialize module stats
        foreach ($modulesToSync as $moduleKey => $moduleConfig) {
            $this->stats['modules'][$moduleKey] = [
                'name' => $moduleConfig['name'],
                'total_synced' => 0,
                'total_inserted' => 0,
                'total_updated' => 0,
                'total_skipped' => 0,
                'total_pdfs_downloaded' => 0,
            ];
        }
        
        try {
            $projects = $this->getProjectUrls();
            $this->stats['total_projects'] = count($projects);
            
            foreach ($projects as $project) {
                $projectUrl = rtrim($project['url'], '/');
                $projectName = $project['project_name'] ?? $projectUrl;
                
                // Skip if filtering by specific project
                if ($specificProject && !$this->matchesProject($projectUrl, $projectName, $specificProject)) {
                    continue;
                }
                
                // Skip current site (don't sync from ourselves)
                if ($this->isSameSite($projectUrl)) {
                    Log::debug("Skipping current site: {$projectUrl}");
                    continue;
                }
                
                try {
                    $this->syncFromProject($projectUrl, $projectName, $modulesToSync, $dryRun, $force);
                    $this->stats['successful_projects']++;
                } catch (\Exception $e) {
                    Log::error("Failed to sync from project: {$projectName}", [
                        'url' => $projectUrl,
                        'error' => $e->getMessage(),
                    ]);
                    $this->stats['failed_projects'][] = [
                        'name' => $projectName,
                        'url' => $projectUrl,
                        'error' => $e->getMessage(),
                    ];
                }
            }
        } catch (\Exception $e) {
            Log::error("NAKS Sync failed: " . $e->getMessage());
            $this->stats['errors'][] = $e->getMessage();
        }
        
        Log::info("🔄 NAKS Multi-Module Sync Completed", $this->stats);
        
        return $this->stats;
    }
    
    /**
     * Get modules to sync based on filter
     */
    protected function getModulesToSync(string $filter): array
    {
        if ($filter === 'all') {
            return $this->modules;
        }
        
        if (isset($this->modules[$filter])) {
            return [$filter => $this->modules[$filter]];
        }
        
        return [];
    }
    
    /**
     * Get list of project URLs from the API
     */
    public function getProjectUrls(): array
    {
        $response = Http::timeout($this->timeout)
            ->get($this->currentSiteUrl . '/api/project-app-urls');
        
        if (!$response->successful()) {
            throw new \Exception("Failed to fetch project URLs: " . $response->status());
        }
        
        $data = $response->json();
        
        if (!isset($data['data']) || !is_array($data['data'])) {
            throw new \Exception("Invalid project URLs response format");
        }
        
        return $data['data'];
    }
    
    /**
     * Authenticate with a remote site and get bearer token
     */
    public function authenticate(string $baseUrl): ?string
    {
        try {
            $response = Http::timeout($this->timeout)
                ->post(rtrim($baseUrl, '/') . '/api/login', [
                    'email' => $this->adminEmail,
                    'password' => $this->adminPassword,
                ]);
            
            if (!$response->successful()) {
                Log::warning("Authentication failed for {$baseUrl}", [
                    'status' => $response->status(),
                ]);
                return null;
            }
            
            $data = $response->json();
            
            return $data['data']['access_token'] ?? null;
        } catch (\Exception $e) {
            Log::error("Authentication error for {$baseUrl}: " . $e->getMessage());
            return null;
        }
    }
    
    /**
     * Fetch records from a remote site for a specific module
     */
    public function fetchRecords(string $baseUrl, string $token, string $tableName, int $afterId = 0, int $take = 100): array
    {
        $url = rtrim($baseUrl, '/') . '/api/' . $tableName . '/read';
        
        $params = [
            'take' => $take,
            'sort' => json_encode([['selector' => 'id', 'desc' => false]]),
        ];
        
        if ($afterId > 0) {
            $params['filter'] = json_encode(['id', '>', $afterId]);
        }
        
        $response = Http::timeout($this->timeout)
            ->withToken($token)
            ->get($url, $params);
        
        if (!$response->successful()) {
            throw new \Exception("Failed to fetch records from {$tableName}: " . $response->status());
        }
        
        $data = $response->json();
        
        return $data['data'] ?? [];
    }
    
    /**
     * Sync all modules from a specific project
     */
    protected function syncFromProject(
        string $projectUrl,
        string $projectName,
        array $modulesToSync,
        bool $dryRun,
        bool $force
    ): void {
        Log::info("Syncing from project: {$projectName}", ['url' => $projectUrl]);
        
        // Authenticate once for all modules
        $token = $this->authenticate($projectUrl);
        if (!$token) {
            throw new \Exception("Authentication failed");
        }
        
        // Sync each module
        foreach ($modulesToSync as $moduleKey => $moduleConfig) {
            try {
                $this->syncModuleFromProject(
                    $projectUrl,
                    $projectName,
                    $token,
                    $moduleKey,
                    $moduleConfig,
                    $dryRun,
                    $force
                );
            } catch (\Exception $e) {
                Log::error("Failed to sync module {$moduleKey} from {$projectName}: " . $e->getMessage());
                $this->stats['errors'][] = "Module {$moduleKey} from {$projectName}: " . $e->getMessage();
            }
        }
    }
    
    /**
     * Sync a specific module from a project
     */
    protected function syncModuleFromProject(
        string $projectUrl,
        string $projectName,
        string $token,
        string $moduleKey,
        array $moduleConfig,
        bool $dryRun,
        bool $force
    ): void {
        $tableName = $moduleConfig['table'];
        
        Log::info("Syncing module: {$moduleConfig['name']} from {$projectName}");
        
        // Get last synced ID
        $lastSyncedId = $force ? 0 : $this->getLastSyncedId($tableName, $projectUrl);
        Log::debug("Last synced ID for {$tableName} from {$projectName}: {$lastSyncedId}");
        
        $moduleStats = [
            'synced' => 0,
            'inserted' => 0,
            'updated' => 0,
            'skipped' => 0,
            'pdfs' => 0,
        ];
        
        $maxId = $lastSyncedId;
        $hasMore = true;
        
        while ($hasMore) {
            // Fetch batch of records
            $records = $this->fetchRecords($projectUrl, $token, $tableName, $maxId, $this->batchSize);
            
            if (empty($records)) {
                $hasMore = false;
                break;
            }
            
            foreach ($records as $record) {
                $recordId = $record['id'] ?? 0;
                $maxId = max($maxId, $recordId);
                
                try {
                    $result = $this->syncRecord($record, $moduleConfig, $projectUrl, $projectName, $dryRun);
                    
                    $moduleStats['synced']++;
                    
                    switch ($result['action']) {
                        case 'inserted':
                            $moduleStats['inserted']++;
                            break;
                        case 'updated':
                            $moduleStats['updated']++;
                            break;
                        case 'skipped':
                            $moduleStats['skipped']++;
                            break;
                    }
                    
                    // Download PDF if needed
                    $downloadField = $moduleConfig['download_field'] ?? 'download';
                    if ($result['action'] !== 'skipped' && !$dryRun && !empty($record[$downloadField])) {
                        if ($this->downloadPdf($projectUrl, $record[$downloadField], $moduleConfig['pdf_folder'])) {
                            $moduleStats['pdfs']++;
                        }
                    }
                } catch (\Exception $e) {
                    Log::warning("Failed to sync record", [
                        'module' => $moduleKey,
                        'id' => $recordId,
                        'error' => $e->getMessage(),
                    ]);
                }
            }
            
            // If we got less than batch size, we're done
            if (count($records) < $this->batchSize) {
                $hasMore = false;
            }
        }
        
        // Update sync state
        if (!$dryRun && $maxId > $lastSyncedId) {
            $this->updateSyncState($tableName, $projectUrl, $maxId, $moduleStats['synced']);
        }
        
        // Update global stats
        $this->stats['modules'][$moduleKey]['total_synced'] += $moduleStats['synced'];
        $this->stats['modules'][$moduleKey]['total_inserted'] += $moduleStats['inserted'];
        $this->stats['modules'][$moduleKey]['total_updated'] += $moduleStats['updated'];
        $this->stats['modules'][$moduleKey]['total_skipped'] += $moduleStats['skipped'];
        $this->stats['modules'][$moduleKey]['total_pdfs_downloaded'] += $moduleStats['pdfs'];
        
        Log::info("Completed sync of {$moduleConfig['name']} from {$projectName}", $moduleStats);
    }
    
    /**
     * Sync a single record
     * 
     * @param string $projectName The project name where the record is synced from (stored in source_project column)
     * @return array ['action' => 'inserted'|'updated'|'skipped', 'local_id' => int|null]
     */
    public function syncRecord(array $record, array $moduleConfig, string $sourceUrl, string $projectName, bool $dryRun = false): array
    {
        $tableName = $moduleConfig['table'];
        $uniqueKeys = $moduleConfig['unique_keys'];
        
        // Build unique key conditions
        $conditions = [];
        foreach ($uniqueKeys as $key) {
            $value = $record[$key] ?? null;
            if ($value === null || $value === '') {
                return ['action' => 'skipped', 'local_id' => null, 'reason' => "missing_unique_key: {$key}"];
            }
            $conditions[$key] = $value;
        }
        
        // Check if record exists locally
        $query = DB::table($tableName);
        foreach ($conditions as $field => $value) {
            $query->where($field, $value);
        }
        $existing = $query->first();
        
        // Prepare data for insert/update
        $data = $this->prepareRecordData($record, $tableName);
        
        if ($existing) {
            // Compare updated_at to decide if we should update
            $remoteUpdatedAt = isset($record['updated_at']) ? Carbon::parse($record['updated_at']) : null;
            $localUpdatedAt = isset($existing->updated_at) ? Carbon::parse($existing->updated_at) : null;
            
            // Only update if remote is newer
            if ($remoteUpdatedAt && $localUpdatedAt && $remoteUpdatedAt <= $localUpdatedAt) {
                return ['action' => 'skipped', 'local_id' => $existing->id, 'reason' => 'local_is_newer'];
            }
            
            if (!$dryRun) {
                // Add source_project to track where the record came from
                $data['source_project'] = $projectName;
                
                DB::table($tableName)
                    ->where('id', $existing->id)
                    ->update($data);
            }
            
            return ['action' => 'updated', 'local_id' => $existing->id];
        } else {
            if (!$dryRun) {
                // Add source_project to track where the record came from
                $data['source_project'] = $projectName;
                
                $newId = DB::table($tableName)->insertGetId($data);
                return ['action' => 'inserted', 'local_id' => $newId];
            }
            
            return ['action' => 'inserted', 'local_id' => null];
        }
    }
    
    /**
     * Prepare record data for database insert/update
     */
    protected function prepareRecordData(array $record, string $tableName): array
    {
        // Remove fields that should not be copied
        $excludeFields = ['id', 'uid'];
        
        $data = [];
        $columns = \Schema::getColumnListing($tableName);
        
        foreach ($record as $key => $value) {
            if (in_array($key, $excludeFields)) {
                continue;
            }
            
            if (in_array($key, $columns)) {
                $data[$key] = $value;
            }
        }
        
        // Update timestamps
        $data['updated_at'] = now();
        
        // If inserting, set created_at
        if (!isset($data['created_at'])) {
            $data['created_at'] = now();
        }
        
        return $data;
    }
    
    /**
     * Download PDF file from remote site
     */
    public function downloadPdf(string $baseUrl, string $remotePath, string $pdfFolder): bool
    {
        if (empty($remotePath)) {
            return false;
        }
        
        // Extract just the filename
        $filename = basename($remotePath);
        
        // Local path
        $localPath = storage_path($this->basePdfPath . '/' . $pdfFolder . '/' . $filename);
        
        // Skip if file already exists locally
        if (File::exists($localPath)) {
            return false;
        }
        
        try {
            // Construct download URL
            $downloadUrl = rtrim($baseUrl, '/') . '/' . ltrim($remotePath, '/');
            
            $response = Http::timeout(60)->get($downloadUrl);
            
            if (!$response->successful()) {
                Log::warning("Failed to download PDF: {$downloadUrl}", [
                    'status' => $response->status(),
                ]);
                return false;
            }
            
            // Ensure directory exists
            $directory = dirname($localPath);
            if (!File::isDirectory($directory)) {
                File::makeDirectory($directory, 0755, true);
            }
            
            // Save file
            File::put($localPath, $response->body());
            
            Log::debug("Downloaded PDF: {$filename} to {$pdfFolder}");
            return true;
        } catch (\Exception $e) {
            Log::warning("Error downloading PDF: " . $e->getMessage(), [
                'url' => $baseUrl,
                'path' => $remotePath,
            ]);
            return false;
        }
    }
    
    /**
     * Get the last synced ID for a table and source URL
     */
    public function getLastSyncedId(string $tableName, string $sourceUrl): int
    {
        $state = DB::table('sync_states')
            ->where('table_name', $tableName)
            ->where('source_url', $sourceUrl)
            ->first();
        
        return $state ? (int) $state->last_synced_id : 0;
    }
    
    /**
     * Update the sync state for a table and source URL
     */
    public function updateSyncState(string $tableName, string $sourceUrl, int $lastId, int $syncedCount = 0): void
    {
        $existing = DB::table('sync_states')
            ->where('table_name', $tableName)
            ->where('source_url', $sourceUrl)
            ->first();
        
        if ($existing) {
            DB::table('sync_states')
                ->where('id', $existing->id)
                ->update([
                    'last_synced_id' => $lastId,
                    'last_synced_at' => now(),
                    'synced_count' => $existing->synced_count + $syncedCount,
                    'updated_at' => now(),
                ]);
        } else {
            DB::table('sync_states')->insert([
                'table_name' => $tableName,
                'source_url' => $sourceUrl,
                'last_synced_id' => $lastId,
                'last_synced_at' => now(),
                'synced_count' => $syncedCount,
                'created_at' => now(),
                'updated_at' => now(),
            ]);
        }
    }
    
    /**
     * Check if a URL matches the current site
     */
    protected function isSameSite(string $url): bool
    {
        $normalizedUrl = $this->normalizeUrl($url);
        $normalizedCurrent = $this->normalizeUrl($this->currentSiteUrl);
        
        return $normalizedUrl === $normalizedCurrent;
    }
    
    /**
     * Normalize URL for comparison
     */
    protected function normalizeUrl(string $url): string
    {
        $parsed = parse_url($url);
        $host = $parsed['host'] ?? '';
        
        // Remove common prefixes/suffixes
        $host = str_replace(['www.', '/admin'], '', $host);
        
        return strtolower($host);
    }
    
    /**
     * Check if a project matches the filter
     */
    protected function matchesProject(string $url, string $name, string $filter): bool
    {
        $filter = strtolower($filter);
        
        return str_contains(strtolower($url), $filter) ||
               str_contains(strtolower($name), $filter);
    }
    
    /**
     * Get sync statistics
     */
    public function getStats(): array
    {
        return $this->stats;
    }
    
    /**
     * Reset sync state for a specific table/source or all
     */
    public function resetSyncState(?string $tableName = null, ?string $sourceUrl = null): int
    {
        $query = DB::table('sync_states');
        
        if ($tableName) {
            $query->where('table_name', $tableName);
        }
        
        if ($sourceUrl) {
            $query->where('source_url', $sourceUrl);
        }
        
        return $query->delete();
    }
    
    /**
     * Get all sync states, optionally filtered by table
     */
    public function getSyncStates(?string $tableName = null): array
    {
        $query = DB::table('sync_states');
        
        if ($tableName) {
            $query->where('table_name', $tableName);
        }
        
        return $query->orderBy('table_name')->orderBy('source_url')->get()->toArray();
    }
}