<?php
declare(strict_types=1);

require_once __DIR__ . '/FreeTier.php';

/**
 * Tier-aware model routing for tools that expose the existing engine selector.
 *
 * Plus/trial users get the cost-controlled Azure mini path. Pro users get the
 * full Azure path. CaveauAI sessions keep the engine requested by their UI.
 */
final class ToolModels
{
    public const TIMELINE_QUICK_CHAR_LIMIT = 25000;
    public const TIMELINE_STANDARD_CHAR_LIMIT = 55000;
    public const TIMELINE_DEEP_CHAR_LIMIT = 128000;

    public static function engineForUser(int $userId, string $requestedEngine): string
    {
        $valid = ['nova_lite', 'azure_mini', 'azure_full', 'gpu', 'regex'];
        $requestedEngine = in_array($requestedEngine, $valid, true) ? $requestedEngine : 'azure_mini';

        if ($userId <= 0) {
            return $requestedEngine;
        }

        return match (FreeTier::tier($userId)) {
            'pro'   => $requestedEngine,
            'plus'  => $requestedEngine === 'azure_full' ? 'azure_mini' : $requestedEngine,
            default => in_array($requestedEngine, ['nova_lite', 'regex'], true) ? $requestedEngine : 'nova_lite',
        };
    }

    public static function timelineRoute(int $userId, string $requestedEngine, string $text): array
    {
        $valid = ['nova_lite', 'azure_mini', 'azure_full'];
        $requestedEngine = in_array($requestedEngine, $valid, true) ? $requestedEngine : 'azure_mini';
        $tierEngine = self::engineForUser($userId, $requestedEngine);
        $charCount = mb_strlen($text, 'UTF-8');

        if ($charCount > self::TIMELINE_DEEP_CHAR_LIMIT) {
            throw new DbnToolsHttpException(
                'This timeline input is too large after selected documents or My Case context were added. Split the file or use fewer selected documents.',
                413,
                'timeline_input_too_large',
                ['input_char_count' => $charCount, 'max_chars' => self::TIMELINE_DEEP_CHAR_LIMIT]
            );
        }

        $effectiveEngine = $tierEngine;
        if ($charCount > self::TIMELINE_STANDARD_CHAR_LIMIT) {
            $effectiveEngine = 'azure_full';
        } elseif ($charCount > self::TIMELINE_QUICK_CHAR_LIMIT && $effectiveEngine === 'nova_lite') {
            $effectiveEngine = 'azure_mini';
        }

        return [
            'requested_engine' => $requestedEngine,
            'tier_engine' => $tierEngine,
            'effective_engine' => $effectiveEngine,
            'auto_upgraded_engine' => $effectiveEngine !== $tierEngine,
            'input_char_count' => $charCount,
            'engine_limit_chars' => self::timelineEngineLimit($effectiveEngine),
            'credits' => self::timelineCredits($effectiveEngine),
        ];
    }

    public static function timelineCredits(string $engine): int
    {
        return $engine === 'azure_full' ? 2 : 1;
    }

    public static function timelineEngineLimit(string $engine): int
    {
        return match ($engine) {
            'nova_lite' => self::TIMELINE_QUICK_CHAR_LIMIT,
            'azure_mini' => self::TIMELINE_STANDARD_CHAR_LIMIT,
            default => self::TIMELINE_DEEP_CHAR_LIMIT,
        };
    }
}