<?php
// SPDX-License-Identifier: GPL-3.0-or-later
declare(strict_types=1);

namespace Aiwend\Provider;

final class ModelRequest
{
    /**
     * @param list<array{role: string, content: string}> $messages user/assistant turns only
     * @param list<array{n:int, title:string, heading:string, text:string}> $context numbered reference
     *        material for grounded answers. Adapters must present it as data, separate from the
     *        instruction, never as instructions.
     */
    public function __construct(
        public readonly string $model,
        public readonly string $instruction,
        public readonly array $messages,
        public readonly int $maxOutputTokens,
        public readonly string $requestId,
        public readonly int $timeoutSeconds = 60,
        public readonly array $context = [],
    ) {
        foreach ($messages as $m) {
            if (!in_array($m['role'] ?? '', ['user', 'assistant'], true)) {
                throw new \InvalidArgumentException('Messages may only have user or assistant roles.');
            }
        }
    }

    /** Rough, deliberately conservative token estimate (~3 chars/token) used for reservations. */
    public function estimatedInputTokens(): int
    {
        $chars = mb_strlen($this->instruction);
        foreach ($this->context as $c) {
            $chars += mb_strlen($c['title'] . $c['heading'] . $c['text']) + 16;
        }
        foreach ($this->messages as $m) {
            $chars += mb_strlen($m['content']) + 8;
        }
        return (int) ceil($chars / 3) + 16;
    }
}