<?php

namespace App\Ocr\Providers;

use App\Ocr\OcrProviderInterface;
use Carbon\CarbonImmutable;
use Illuminate\Support\Facades\Http;
use Illuminate\Support\Facades\Log;
use Throwable;

/**
 * Mistral (FR) Pixtral vision API — extracts structured fields from an
 * image of a certificate and returns them as JSON.
 *
 * @see https://docs.mistral.ai/capabilities/vision/
 */
class MistralProvider implements OcrProviderInterface
{
    private const ENDPOINT = 'https://api.mistral.ai/v1/chat/completions';

    private const MODEL = 'pixtral-12b-2409';

    private const PROMPT = 'You are analyzing an image of a certificate or diploma. '
        .'Return ONLY a JSON object with two keys: "title" (a concise name for the certificate) '
        .'and "expires_at" (the expiry or valid-until date in YYYY-MM-DD format, or null if none is visible).';

    /**
     * @return array{title?: string|null, expires_at?: string|null}
     */
    public function analyze(string $filePath, ?string $apiKey): array
    {
        if (blank($apiKey) || ! is_readable($filePath)) {
            return [];
        }

        $dataUri = $this->toDataUri($filePath);

        if ($dataUri === null) {
            return [];
        }

        try {
            $response = Http::withToken($apiKey)
                ->timeout(45)
                ->post(self::ENDPOINT, [
                    'model' => self::MODEL,
                    'response_format' => ['type' => 'json_object'],
                    'messages' => [[
                        'role' => 'user',
                        'content' => [
                            ['type' => 'text', 'text' => self::PROMPT],
                            ['type' => 'image_url', 'image_url' => $dataUri],
                        ],
                    ]],
                ]);

            if ($response->failed()) {
                Log::warning('Mistral OCR request failed.', ['status' => $response->status()]);

                return [];
            }

            $content = $response->json('choices.0.message.content');

            return $this->parseContent(is_string($content) ? $content : '');
        } catch (Throwable $e) {
            Log::warning('Mistral OCR analysis threw an exception.', ['message' => $e->getMessage()]);

            return [];
        }
    }

    private function toDataUri(string $filePath): ?string
    {
        $mime = mime_content_type($filePath) ?: 'image/jpeg';

        // Pixtral is a vision model and only accepts images, not PDFs.
        if (! str_starts_with($mime, 'image/')) {
            return null;
        }

        return 'data:'.$mime.';base64,'.base64_encode((string) file_get_contents($filePath));
    }

    /**
     * @return array{title?: string|null, expires_at?: string|null}
     */
    private function parseContent(string $content): array
    {
        $decoded = json_decode($content, true);

        if (! is_array($decoded)) {
            return [];
        }

        $title = data_get($decoded, 'title');
        $expiresAt = data_get($decoded, 'expires_at');

        return array_filter([
            'title' => filled($title) && is_string($title) ? trim($title) : null,
            'expires_at' => $this->normalizeDate($expiresAt),
        ], fn ($value) => $value !== null);
    }

    private function normalizeDate(mixed $value): ?string
    {
        if (! filled($value) || ! is_string($value)) {
            return null;
        }

        try {
            return CarbonImmutable::parse($value)->toDateString();
        } catch (Throwable) {
            return null;
        }
    }
}