using Microsoft.Extensions.Logging;

namespace MoShiro.Backend.Application;

/// <summary>
/// 审计日志里的一行：谁（<see cref="Actor"/>，用户名或 <c>key:令牌名</c>）、怎么登录的（<see cref="Method"/>）、做了什么（<see cref="Action"/>，
/// 管理接口的 operationId，或 <c>auth.login</c> 这类登录事件）、对谁（<see cref="Target"/>）、结果如何。
/// </summary>
public sealed record AuditRecord(long Id, long AtMs, string? UserId, string Actor, string Method, string Action, string? Target, string? Detail, string? Remote, bool Success);

public sealed record AuditQuery(long? BeforeId, int Limit, string? Actor, string? Action);

/// <summary>审计日志只追加：没有修改和单条删除，只按保留期整体清理。</summary>
public sealed partial class AuditService
{
    /// <summary>保留一年。审计记录的是谁动过信任相关的东西，比监测数据留得久。</summary>
    public const int RetentionDays = 365;

    private readonly IAuditStore _store;
    private readonly TimeProvider _time;
    private readonly ILogger<AuditService> _logger;

    public AuditService(IAuditStore store, TimeProvider time, ILogger<AuditService> logger)
    {
        _store = store;
        _time = time;
        _logger = logger;
    }

    /// <summary>记一条。写不进去只记日志，不能因为审计失败而让已经完成的操作报错。</summary>
    public async ValueTask RecordAsync(Principal principal, string action, string? target, string? detail, string? remote, bool success, CancellationToken ct = default) =>
        await RecordAsync(principal.UserId, principal.Label, MethodOf(principal), action, target, detail, remote, success, ct);

    public async ValueTask RecordAsync(string? userId, string actor, string method, string action, string? target, string? detail, string? remote, bool success, CancellationToken ct = default)
    {
        try
        {
            await _store.AddAsync(new AuditRecord(0, _time.GetUtcNow().ToUnixTimeMilliseconds(), userId, actor, method, action, Clip(target, 200), Clip(detail, 500), remote, success), ct);
        }
        catch (Exception ex) when (ex is not OperationCanceledException)
        {
            LogFailed(ex, action);
        }
    }

    public ValueTask<IReadOnlyList<AuditRecord>> ListAsync(AuditQuery query, CancellationToken ct) => _store.ListAsync(query, ct);

    public ValueTask<int> PruneAsync(long nowMs, CancellationToken ct) => _store.DeleteOlderThanAsync(nowMs - (RetentionDays * 86_400_000L), ct);

    /// <summary>登录方式：密码、passkey，或 API key。</summary>
    public static string MethodOf(Principal principal) =>
        principal.Kind == PrincipalKind.Anonymous ? "anonymous"
        : principal.Kind == PrincipalKind.Token && principal.UserId is null ? "key"
        : principal.AuthMethod.Length > 0 ? principal.AuthMethod : AuthMethods.Password;

    private static string? Clip(string? text, int max) => text is { } t && t.Length > max ? t[..max] : text;

    [LoggerMessage(Level = LogLevel.Warning, Message = "could not write the audit record for {Action}")]
    private partial void LogFailed(Exception exception, string action);
}