using WenChuanyi.Api.Models;

namespace WenChuanyi.Api.Services;

/// <summary>取件码/管理码生成与查重（冲突自动重生成）</summary>
public class CodeGeneratorService
{
    // 排除易混淆 0/O/1/I/l
    private const string AdminChars = "ABCDEFGHJKMNPQRSTUVWXYZabcdefghjkmnpqrstuvwxyz23456789";

    private readonly IFreeSql _fsql;

    public CodeGeneratorService(IFreeSql fsql) => _fsql = fsql;

    /// <summary>生成 length 位纯数字取件码（全局唯一）</summary>
    public async Task<string> GeneratePickCodeAsync(int length)
    {
        for (var i = 0; i < 30; i++)
        {
            var code = GenerateDigits(length);
            var exists = await _fsql.Select<FileItem>().Where(f => f.PickCode == code).AnyAsync();
            if (!exists)
            {
                return code;
            }
        }
        throw new InvalidOperationException("取件码生成冲突次数过多，请重试");
    }

    /// <summary>生成 8 位字母数字管理码（全局唯一）</summary>
    public async Task<string> GenerateAdminCodeAsync()
    {
        for (var i = 0; i < 30; i++)
        {
            var code = new string(Enumerable.Range(0, 8)
                .Select(_ => AdminChars[Random.Shared.Next(AdminChars.Length)]).ToArray());
            var exists = await _fsql.Select<FileItem>().Where(f => f.AdminCode == code).AnyAsync();
            if (!exists)
            {
                return code;
            }
        }
        throw new InvalidOperationException("管理码生成冲突次数过多，请重试");
    }

    private static string GenerateDigits(int length)
    {
        var first = Random.Shared.Next(1, 10); // 首位非 0
        var sb = new System.Text.StringBuilder();
        sb.Append(first);
        for (var i = 1; i < length; i++)
        {
            sb.Append(Random.Shared.Next(0, 10));
        }
        return sb.ToString();
    }
}