<?php

declare(strict_types=1);

namespace App\Services;

use Exception;

final class AiExtractionService
{
    private string $apiKey;
    private string $model;

    public function __construct()
    {
        $this->apiKey = $_ENV['GEMINI_API_KEY'] ?? '';
        $this->model = $_ENV['GEMINI_MODEL'] ?? 'gemini-2.0-flash';
    }

    public function extractInvoiceData(string $filePath, string $mimeType): array
    {
        if (empty($this->apiKey)) {
            throw new Exception("Gemini API Key is missing. Please configure it in .env");
        }

        $fileContent = file_get_contents($filePath);
        if ($fileContent === false) {
            throw new Exception("Could not read uploaded invoice file.");
        }

        $base64Data = base64_encode($fileContent);

        $prompt = "Please extract the following information from this invoice and return it strictly as JSON without markdown blocks or backticks:\n"
            . "- invoice_number\n"
            . "- invoice_date (YYYY-MM-DD)\n"
            . "- total_amount\n"
            . "- tax_amount\n"
            . "- vendor_name\n"
            . "- vendor_tax_number";

        $payload = [
            'contents' => [
                [
                    'parts' => [
                        ['text' => $prompt],
                        [
                            'inline_data' => [
                                'mime_type' => $mimeType,
                                'data' => $base64Data
                            ]
                        ]
                    ]
                ]
            ],
            'generationConfig' => [
                'temperature' => 0.1,
                'response_mime_type' => 'application/json'
            ]
        ];

        $url = "https://generativelanguage.googleapis.com/v1beta/models/{$this->model}:generateContent?key={$this->apiKey}";

        $ch = curl_init($url);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_POST, true);
        curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($payload));
        curl_setopt($ch, CURLOPT_HTTPHEADER, [
            'Content-Type: application/json'
        ]);

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

        if ($httpCode !== 200) {
            throw new Exception("AI Extraction failed. HTTP Code: {$httpCode}. Response: {$response}");
        }

        $result = json_decode($response, true);
        $text = $result['candidates'][0]['content']['parts'][0]['text'] ?? '{}';
        
        $data = json_decode($text, true);
        if (!is_array($data)) {
            throw new Exception("Failed to parse AI output as JSON: {$text}");
        }

        return $data;
    }
}