ars-backend/app/Services/Agent/OpenAi/ChatCompletionsRequestBuilder.php

<?php

namespace App\Services\Agent\OpenAi;

use App\Models\Message;
use App\Services\Agent\AgentContext;
use App\Services\Tool\ToolRegistry;

class ChatCompletionsRequestBuilder
{
    public function __construct(
        private readonly ToolRegistry $toolRegistry,
        private ?string $model = null,
        private ?float $temperature = null,
        private ?float $topP = null,
        private ?bool $includeUsage = null,
        private ?string $toolChoice = null,
    ) {
        $this->model = $this->model ?? (string) config('agent.openai.model', 'gpt-4o-mini');
        $this->temperature = $this->temperature ?? (float) config('agent.openai.temperature', 0.7);
        $this->topP = $this->topP ?? (float) config('agent.openai.top_p', 1.0);
        $this->includeUsage = $this->includeUsage ?? (bool) config('agent.openai.include_usage', false);
        $this->toolChoice = $this->toolChoice ?? (string) config('agent.tools.tool_choice', 'auto');
    }

    /**
     * Builds an OpenAI-compatible Chat Completions payload from AgentContext.
     *
     * @param array<string, mixed> $options
     * @return array<string, mixed>
     */
    public function build(AgentContext $context, array $options = []): array
    {
        $payload = [
            'model' => (string) ($options['model'] ?? $this->model),
            'messages' => $this->buildMessages($context),
            'stream' => true,
        ];

        if (array_key_exists('temperature', $options)) {
            $payload['temperature'] = (float) $options['temperature'];
        } else {
            $payload['temperature'] = (float) $this->temperature;
        }

        if (array_key_exists('top_p', $options)) {
            $payload['top_p'] = (float) $options['top_p'];
        } else {
            $payload['top_p'] = (float) $this->topP;
        }

        if (array_key_exists('max_tokens', $options)) {
            $payload['max_tokens'] = (int) $options['max_tokens'];
        }

        if (array_key_exists('stop', $options)) {
            $payload['stop'] = $options['stop'];
        }

        if (array_key_exists('stream_options', $options)) {
            $payload['stream_options'] = $options['stream_options'];
        } elseif ($this->includeUsage) {
            $payload['stream_options'] = ['include_usage' => true];
        }

        if (array_key_exists('response_format', $options)) {
            $payload['response_format'] = $options['response_format'];
        }

        $toolsSpec = $this->toolRegistry->openAiToolsSpec();

        if (! empty($toolsSpec)) {
            $payload['tools'] = $toolsSpec;
            $payload['tool_choice'] = $options['tool_choice'] ?? $this->toolChoice ?? 'auto';
        }

        return $payload;
    }

    /**
     * @return array<int, array<string, mixed>>
     */
    private function buildMessages(AgentContext $context): array
    {
        $messages = [];

        if ($context->systemPrompt !== '') {
            $messages[] = [
                'role' => 'system',
                'content' => $context->systemPrompt,
            ];
        }

        foreach ($context->messages as $message) {
            $role = $this->mapRole((string) ($message['role'] ?? ''));
            $content = $message['content'] ?? null;
            $type = (string) ($message['type'] ?? '');
            $payload = $message['payload'] ?? null;

            if (! $role || ! is_string($content) || $content === '') {
                $content = null;
            }

            if ($type === 'tool.call' && is_array($payload)) {
                $toolCall = $this->normalizeToolCallPayload($payload, $content);
                if ($toolCall) {
                    $messages[] = $toolCall;
                }
                continue;
            }

            if ($type === 'tool.result' && is_array($payload)) {
                $toolResult = $this->normalizeToolResultPayload($payload, $content);
                if ($toolResult) {
                    $messages[] = $toolResult;
                }
                continue;
            }

            if ($content !== null) {
                $messages[] = [
                    'role' => $role,
                    'content' => $content,
                ];
            }
        }

        return $messages;
    }

    private function mapRole(string $role): ?string
    {
        return match ($role) {
            Message::ROLE_USER => 'user',
            Message::ROLE_AGENT => 'assistant',
            Message::ROLE_SYSTEM => 'system',
            default => null,
        };
    }

    /**
     * @param array<string, mixed> $payload
     * @return array<string, mixed>|null
     */
    private function normalizeToolCallPayload(array $payload, ?string $content): ?array
    {
        $toolCallId = $payload['tool_call_id'] ?? null;
        $name = $payload['name'] ?? null;
        $arguments = $payload['arguments'] ?? null;

        if (! is_string($toolCallId) || ! is_string($name) || $toolCallId === '' || $name === '') {
            return null;
        }

        $argumentsString = is_string($arguments) ? $arguments : json_encode($arguments, JSON_UNESCAPED_UNICODE);

        return [
            'role' => 'assistant',
            'content' => $content,
            'tool_calls' => [
                [
                    'id' => $toolCallId,
                    'type' => 'function',
                    'function' => [
                        'name' => $name,
                        'arguments' => $argumentsString ?? '',
                    ],
                ],
            ],
        ];
    }

    /**
     * @param array<string, mixed> $payload
     * @return array<string, mixed>|null
     */
    private function normalizeToolResultPayload(array $payload, ?string $content): ?array
    {
        $toolCallId = $payload['tool_call_id'] ?? null;
        $name = $payload['name'] ?? null;

        if (! is_string($toolCallId) || $toolCallId === '') {
            return null;
        }

        $resultContent = $content ?? ($payload['output'] ?? null);

        if (! is_string($resultContent)) {
            $resultContent = json_encode($payload['output'] ?? $payload, JSON_UNESCAPED_UNICODE);
        }

        return [
            'role' => 'tool',
            'tool_call_id' => $toolCallId,
            'name' => is_string($name) ? $name : null,
            'content' => $resultContent,
        ];
    }
}