<?php

declare(strict_types=1);

namespace OCA\AnalyticsHub\Service;

use OCA\AnalyticsHub\Model\ClientConfig;
use OCP\IConfig;
use OCP\Util\Logger;
use OCP\Util\SimplePDOMapper;

/**
 * Google Analytics Data API v1 Service
 * Handles GA4 API calls with OAuth token refresh
 */
class GoogleAnalyticsService {

    private IConfig $config;
    private ?Logger $logger;
    private ?DatabaseService $dbService;

    // GA4 API endpoints
    private const GA_API_BASE = 'https://analyticsdata.googleapis.com/v1beta';
    private const TOKEN_REFRESH_URL = 'https://oauth2.googleapis.com/token';

    public function __construct(IConfig $config, ?DatabaseService $dbService) {
        $this->config = $config;
        $this->logger = \OC::$server->getLogger();
        $this->dbService = $dbService;
    }

    /**
     * Check if Google Analytics is configured
     */
    public function isConfigured(): bool {
        $clientId = $this->config->getAppValue('google_client_id', AppInfo::APP_NAME);
        $clientSecret = $this->config->getAppValue('google_client_secret', AppInfo::APP_NAME);
        $refreshToken = $this->config->getAppValue('google_refresh_token', AppInfo::APP_NAME);

        return !empty($clientId) && !empty($clientSecret) && !empty($refreshToken);
    }

    /**
     * Check if LLM service is configured
     */
    public function isLLMConfigured(): bool {
        $apiKey = $this->config->getAppValue('anthropic_api_key', AppInfo::APP_NAME);
        return !empty($apiKey);
    }

    /**
     * Get client by slug
     */
    public function getClientBySlug(string $slug): ?ClientConfig {
        $clients = $this->getClients();
        foreach ($clients as $client) {
            if ($client->getSlug() === $slug) {
                return $client;
            }
        }
        return null;
    }

    /**
     * Get all active clients
     */
    public function getActiveClients(): array {
        $clients = $this->getClients();
        return array_filter($clients, fn($c) => $c->isActive());
    }

    /**
     * Get all clients
     */
    private function getClients(): array {
        $json = $this->config->getAppValue('clients_json', AppInfo::APP_NAME);
        if (empty($json)) {
            return [];
        }

        $data = json_decode($json, true);
        if (!is_array($data['clients'] ?? null)) {
            return [];
        }

        return array_map(fn($c) => ClientConfig::fromJson($c), $data['clients']);
    }

    /**
     * Get client count
     */
    public function getClientCount(): int {
        return count($this->getClients());
    }

    /**
     * Fetch GA4 data
     */
    public function fetchGA4Data(ClientConfig $client, string $dateRange = '7d'): array {
        $this->logger->info("Fetching GA4 data for: {$client->getName()}");

        try {
            // Get fresh access token
            $accessToken = $this->getFreshAccessToken();

            // Build API request URL
            $propertyId = $client->getPropertyId();
            $url = self::GA_API_BASE . "/properties/{$propertyId}:runReport";

            // Build request body
            $requestBody = [
                'dateRanges' => [
                    [
                        'startDate' => $this->getDateRange($dateRange, 'start'),
                        'endDate' => $this->getDateRange($dateRange, 'end'),
                    ]
                ],
                'metrics' => [
                    'sessions',
                    'totalUsers',
                    'conversions',
                    'eventCount'
                ],
                'dimensions' => [
                    'date',
                    'sessionDefaultChannelGroup',
                    'pagePath'
                ]
            ];

            // Make HTTP request
            $response = $this->makeGARequest($url, $accessToken, $requestBody);

            if (!$response) {
                throw new \Exception('Failed to fetch GA4 data');
            }

            $responseData = $this->parseGAResponse($response);

            if (!$responseData) {
                throw new \Exception('Invalid GA4 response format');
            }

            $this->logger->info("GA4 data fetched successfully");

            return $responseData;

        } catch (\Exception $e) {
            $this->logger->error("GA4 fetch failed: {$e->getMessage()}");
            throw $e;
        }
    }

    /**
     * Get fresh access token
     */
    private function getFreshAccessToken(): string {
        $refreshToken = $this->config->getAppValue('google_refresh_token', AppInfo::APP_NAME);

        if (empty($refreshToken)) {
            throw new \Exception('Refresh token not configured');
        }

        try {
            $response = $this->refreshAccessToken($refreshToken);

            if (!$response || empty($response['access_token'])) {
                throw new \Exception('Failed to refresh access token');
            }

            $this->logger->info("Access token refreshed");

            return $response['access_token'];

        } catch (\Exception $e) {
            $this->logger->error("Token refresh failed: {$e->getMessage()}");

            // Check if it's an expired token error
            if (str_contains($e->getMessage(), 'invalid_grant')) {
                throw new TokenExpiredException('Refresh token expired - re-run OAuth setup');
            }

            throw $e;
        }
    }

    /**
     * Refresh access token using refresh token
     */
    private function refreshAccessToken(string $refreshToken): ?array {
        $clientId = $this->config->getAppValue('google_client_id', AppInfo::APP_NAME);
        $clientSecret = $this->config->getAppValue('google_client_secret', AppInfo::APP_NAME);

        $url = self::TOKEN_REFRESH_URL;
        $data = [
            'client_id' => $clientId,
            'client_secret' => $clientSecret,
            'refresh_token' => $refreshToken,
            'grant_type' => 'refresh_token'
        ];

        $response = $this->makeHttpPOST($url, $data, []);

        if (!$response) {
            return null;
        }

        return json_decode($response, true);
    }

    /**
     * Make HTTP POST request
     */
    private function makeHttpPOST(string $url, array $data, array $headers = []): ?string {
        $ch = curl_init();

        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_POST, true);
        curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($data));
        curl_setopt($ch, CURLOPT_HTTPHEADER, array_merge([
            'Content-Type: application/json'
        ], $headers));

        $response = curl_exec($ch);
        $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);

        if (curl_errno($ch)) {
            $this->logger->error("Curl error: " . curl_error($ch));
            curl_close($ch);
            return null;
        }

        if ($httpCode !== 200) {
            $this->logger->error("HTTP {$httpCode} from: {$url}");
        }

        curl_close($ch);

        return $httpCode === 200 ? $response : null;
    }

    /**
     * Make GA4 API request with auth
     */
    private function makeGARequest(string $url, string $accessToken, array $body): ?array {
        $ch = curl_init();

        curl_setopt($ch, CURLOPT_URL, $url);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_POST, true);
        curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($body));
        curl_setopt($ch, CURLOPT_HTTPHEADER, [
            'Content-Type: application/json',
            'Authorization: Bearer ' . $accessToken
        ]);
        curl_setopt($ch, CURLOPT_TIMEOUT, 30);

        $response = curl_exec($ch);
        $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);

        if (curl_errno($ch)) {
            $this->logger->error("GA4 API curl error: " . curl_error($ch));
            curl_close($ch);
            return null;
        }

        if ($httpCode !== 200) {
            $this->logger->error("GA4 API HTTP {$httpCode}");
        }

        curl_close($ch);

        return $httpCode === 200 ? json_decode($response, true) : null;
    }

    /**
     * Parse GA4 response
     */
    private function parseGAResponse(string $response): ?array {
        $decoded = json_decode($response, true);

        if (json_last_error() !== JSON_ERROR_NONE) {
            $this->logger->error("JSON decode error");
            return null;
        }

        // Check for runReport response
        if (!isset($decoded['runs'])) {
            $this->logger->error("Invalid GA4 response format - missing runs");
            return null;
        }

        // Process runs
        $runs = $decoded['runs'] ?? [];

        // Extract data from runs (GA4 returns array of run objects)
        $data = [];
        foreach ($runs as $run) {
            if (isset($run['rows'])) {
                foreach ($run['rows'] as $row) {
                    foreach ($row['dimensionValues'] ?? [] as $i => $value) {
                        $data[$i] = $value;
                    }
                    foreach ($row['metricValues'] ?? [] as $i => $value) {
                        $data[$i] = $value;
                    }
                }
            }
        }

        return empty($data) ? null : [
            'dates' => $data,
            'metrics' => $this->extractMetrics($runs)
        ];
    }

    /**
     * Extract metrics from GA4 response
     */
    private function extractMetrics(array $runs): array {
        $metrics = [
            'sessions' => [],
            'totalUsers' => [],
            'conversions' => [],
            'eventCount' => []
        ];

        foreach ($runs as $run) {
            if (isset($run['rows'])) {
                foreach ($run['rows'] as $row) {
                    foreach ($row['metricValues'] ?? [] as $i => $value) {
                        $metric = $row['metricValues'][$i]['name'] ?? null;

                        if ($metric === 'sessions') {
                            $metrics['sessions'][] = $value['value'] ?? 0;
                        } elseif ($metric === 'totalUsers') {
                            $metrics['totalUsers'][] = $value['value'] ?? 0;
                        } elseif ($metric === 'conversions') {
                            $metrics['conversions'][] = $value['value'] ?? 0;
                        } elseif ($metric === 'eventCount') {
                            $metrics['eventCount'][] = $value['value'] ?? 0;
                        }
                    }
                }
            }
        }

        return $metrics;
    }

    /**
     * Get date range (last N days)
     */
    private function getDateRange(string $range, string $type): string {
        $days = (int)str_replace(['d', 'w', 'm'], '', $range);

        $date = new \DateTime();

        if ($type === 'start') {
            $date->modify("-{$days} days");
        } else {
            $date->modify("-{$days} days");
        }

        return $date->format('Y-m-d');
    }

    /**
     * Save report to Nextcloud
     */
    public function saveReport(ClientConfig $client, string $markdown): array {
        $basePath = $client->getWebdavConfig()['base_path'] ?? '/AIGeneratedReports';
        $filename = "Report_" . date('Y-m-d') . ".md";
        $fullPath = $basePath . '/' . $filename;

        $this->logger->info("Saving report to: {$fullPath}");

        // Use Nextcloud file API
        $folder = $this->ensureNextcloudFolder($basePath);
        if (!$folder) {
            throw new \Exception("Failed to create Nextcloud folder: {$basePath}");
        }

        $file = $folder->newFile($filename);
        $file->putContent($markdown);

        $this->logger->info("Report saved: {$fullPath}");

        return [
            'file_path' => $fullPath,
            'file_size' => strlen($markdown)
        ];
    }

    /**
     * Get report by ID
     */
    public function getReportById(int $id): ?array {
        $report = $this->dbService->getReportById($id);

        if (!$report) {
            return null;
        }

        return [
            'id' => $report['id'],
            'client_id' => $report['client_id'],
            'client_name' => $report['client_name'],
            'report_date' => $report['report_date'],
            'file_path' => $report['file_path'],
            'file_size' => $report['file_size'],
            'created_at' => $report['created_at']
        ];
    }

    /**
     * Get all reports
     */
    public function getAllReports(): array {
        $reports = $this->dbService->getAllReports();

        return array_map(function($r) {
            return [
                'id' => $r['id'],
                'client_id' => $r['client_id'],
                'client_name' => $r['client_name'],
                'report_date' => $r['report_date'],
                'file_path' => $r['file_path'],
                'file_size' => $r['file_size'],
                'created_at' => $r['created_at']
            ];
        }, $reports);
    }

    /**
     * Generate reports for all active clients
     */
    public function generateForAllClients(): array {
        $clients = $this->getActiveClients();
        $results = [];

        foreach ($clients as $client) {
            try {
                $this->generateReportForClient($client);
                $results[$client->getSlug()] = 'success';
            } catch (\Exception $e) {
                $results[$client->getSlug()] = "error: {$e->getMessage()}";
            }
        }

        return $results;
    }

    /**
     * Generate report for a single client
     */
    private function generateReportForClient(ClientConfig $client): void {
        $this->logger->info("Generating report for: {$client->getName()}");

        $rawData = $this->fetchGA4Data($client, '7d');

        // Process with DataProcessor
        $processor = new \OCA\AnalyticsHub\Service\DataProcessor($this->config);
        $processed = $processor->process($rawData, $client);

        // Generate with LLM
        $llmService = new \OCA\AnalyticsHub\Service\LLMService($this->config);
        $markdown = $llmService->generate($processed, $client);

        // Save to Nextcloud
        $result = $this->saveReport($client, $markdown);

        $this->logger->info("Report generated and saved");
    }

    /**
     * Get last report time
     */
    public function getLastReportTime(): ?string {
        $report = $this->dbService->getLatestReport();

        return $report ? $report['created_at'] : null;
    }

    /**
     * Ensure Nextcloud folder exists
     */
    private function ensureNextcloudFolder(string $path) ?\OCP\Files\Folder {
        $userFolder = \OC::$server->getUserFolder();

        if (!$userFolder->nodeExists($path)) {
            $this->logger->info("Creating Nextcloud folder: {$path}");
            return $userFolder->newFolder($path);
        }

        return $userFolder->get($path);
    }
}