<?php

namespace App\Services\Agent\OpenAi;

use App\Services\Agent\ProviderEvent;

class OpenAiEventNormalizer
{
    /**
     * Normalizes a single SSE payload into ProviderEvent values.
     *
     * @return array<int, ProviderEvent>
     */
    public function normalize(string $payload): array
    {
        if (trim($payload) === '[DONE]') {
            return [ProviderEvent::done('done')];
        }

        $decoded = json_decode($payload, true);

        if (! is_array($decoded)) {
            return [ProviderEvent::error('INVALID_JSON', 'Agent provider returned invalid JSON', [
                'raw' => $payload,
            ])];
        }

        $events = [];
        $choices = $decoded['choices'] ?? [];
        $firstChoice = is_array($choices) ? ($choices[0] ?? null) : null;
        $delta = is_array($firstChoice) ? ($firstChoice['delta'] ?? null) : null;

        if (is_array($delta)) {
            $content = $delta['content'] ?? null;
            if (is_string($content) && $content !== '') {
                $events[] = ProviderEvent::messageDelta($content);
            }
        }

        if (is_array($firstChoice) && array_key_exists('finish_reason', $firstChoice) && $firstChoice['finish_reason'] !== null) {
            $events[] = ProviderEvent::done((string) $firstChoice['finish_reason']);
        }

        if (isset($decoded['usage']) && is_array($decoded['usage'])) {
            $events[] = ProviderEvent::usage($decoded['usage']);
        }

        return $events;
    }
}