<?php

namespace App\Services\LlmPrediction;

use App\Enums\PredictionSource;
use App\Enums\TrendDirection;
use App\Models\BrentPrice;
use App\Models\PricePrediction;
use App\Services\ApiLogger;
use Illuminate\Support\Collection;
use Illuminate\Support\Facades\Http;
use Illuminate\Support\Facades\Log;
use Throwable;

class GeminiPredictionProvider implements OilPredictionProvider
{
    private const int LLM_MAX_CONFIDENCE = 85;

    public function __construct(
        private readonly ApiLogger $apiLogger,
    ) {}

    public function predict(Collection $prices): ?PricePrediction
    {
        if (! config('services.gemini.api_key')) {
            return null;
        }

        $priceList = $prices->sortBy('date')
            ->map(fn (BrentPrice $p) => $p->date->toDateString().': $'.$p->price_usd)
            ->implode("\n");

        $model = config('services.gemini.model', 'gemini-2.0-flash');
        $url = "https://generativelanguage.googleapis.com/v1beta/models/{$model}:generateContent";

        try {
            $response = $this->apiLogger->send('gemini', 'POST', $url, fn () => Http::timeout(15)
                ->withQueryParameters(['key' => config('services.gemini.api_key')])
                ->post($url, [
                    'contents' => [[
                        'parts' => [['text' => $this->prompt($priceList)]],
                    ]],
                    'generationConfig' => [
                        'responseMimeType' => 'application/json',
                        'responseSchema' => [
                            'type' => 'OBJECT',
                            'properties' => [
                                'direction' => [
                                    'type' => 'STRING',
                                    'enum' => ['rising', 'falling', 'flat'],
                                ],
                                'confidence' => ['type' => 'INTEGER'],
                                'reasoning' => ['type' => 'STRING'],
                            ],
                            'required' => ['direction', 'confidence', 'reasoning'],
                        ],
                    ],
                ]));

            if (! $response->successful()) {
                Log::error('GeminiPredictionProvider: request failed', ['status' => $response->status()]);

                return null;
            }

            $text = $response->json('candidates.0.content.parts.0.text') ?? '';
            $data = json_decode($text, true);

            if (! isset($data['direction'], $data['confidence'], $data['reasoning'])) {
                Log::error('GeminiPredictionProvider: unexpected response format', ['text' => $text]);

                return null;
            }

            $direction = TrendDirection::tryFrom($data['direction']);

            if ($direction === null) {
                Log::error('GeminiPredictionProvider: invalid direction', ['direction' => $data['direction']]);

                return null;
            }

            return new PricePrediction([
                'predicted_for' => now()->toDateString(),
                'source' => PredictionSource::Llm,
                'direction' => $direction,
                'confidence' => min((int) $data['confidence'], self::LLM_MAX_CONFIDENCE),
                'reasoning' => $data['reasoning'],
                'generated_at' => now(),
            ]);
        } catch (Throwable $e) {
            Log::error('GeminiPredictionProvider: predict failed', ['error' => $e->getMessage()]);

            return null;
        }
    }

    private function prompt(string $priceList): string
    {
        return <<<PROMPT
            You are analyzing Brent crude oil price data for a UK fuel price alert service.
            Predict the short-term direction over the next 3–5 days.

            Recent Brent crude prices (USD/barrel):
            {$priceList}

            Respond with direction (rising, falling, or flat), a confidence score (0–85),
            and a one-sentence reasoning.
            PROMPT;
    }
}
