using FreeSql.DataAnnotations;
using System.Text.Json;

namespace Store.Modules.CloudProduct.Entities;

/// <summary>跨用户复用的图片识别数据，仅存储成功识别结果。</summary>
[Table(Name = "image_analysis_cache")]
public sealed class ImageAnalysisCache
{
    /// <summary>客户端指定的 MD5 缓存键，统一保存为 32 位小写十六进制。</summary>
    [Column(IsPrimary = true, StringLength = 32)]
    public string CacheKey { get; set; } = "";
    /// <summary>模型识别结果的 JSON 字符串数组，空数组表示未识别到文字或品牌。</summary>
    [Column(DbType = "longtext")]
    public string RecognitionResult { get; set; } = "";
    /// <summary>缓存最近更新时间，UTC。</summary>
    public DateTime UpdatedAt { get; set; }

    /// <summary>从 UpdatedAt 起算的缓存有效小时数，命中时不续期。</summary>
    public int ExpiresAt { get; set; }

    /// <summary>每轮成功识别后更新有效期：空结果逐级延长，有内容则重置级别。</summary>
    public void RecordExpiration(bool isEmpty, DateTime utcNow)
    {
        // 新记录和上次有内容的记录，首次为空时均从 24 小时起算。
        ExpiresAt = isEmpty ? ExpiresAt switch
        {
            24 => 48,
            48 => 96,
            96 => 192,
            192 or 384 => 384,
            _ => 24
        } : 720;
        UpdatedAt = utcNow;
    }

    /// <summary>仅复用有效期内的数组，旧对象格式需要重新识别。</summary>
    public string[]? ReadFreshResult(DateTime utcNow)
    {
        if (utcNow >= UpdatedAt.AddHours(ExpiresAt) || !RecognitionResult.TrimStart().StartsWith('['))
            return null;

        return JsonSerializer.Deserialize<string[]>(RecognitionResult);
    }
}