using System.Text.Json;
using Fleet.Core;
using MoShiro.Protocol;

namespace MoShiro.Measurement;

/// <summary>Agent 单调时钟（微秒）与 UTC（毫秒）的对应关系：块头里的时钟锚点。</summary>
public readonly record struct ClockAnchor(long ListenerMonoUs, long UtcMs);

/// <summary>
/// 给合并好的流盖章：生成完整的块头（任务/测试、参数快照、端口、时钟锚点、起止时间）。
/// 起止时间由数据本身的时间戳换算得出，而不是取收到列块的时刻，所以不受拨号方交付延迟的影响。
/// </summary>
public static class ChunkFinalizer
{
    public const int MaxDurationMs = 600_000;

    public static RawChunk Finalize(
        KindSpec spec,
        RawChunk fragment,
        IReadOnlyList<RawStream> streams,
        NodeId agent,
        ClockAnchor anchor,
        IReadOnlyDictionary<string, JsonElement> resolvedParams,
        int port,
        ChunkId id)
    {
        RawChunkHeader source = fragment.Header;
        long offsetUs = source.Clock.DialerOffsetUs;
        long min = long.MaxValue;
        long max = long.MinValue;
        foreach (RawStream stream in streams)
        {
            if (stream.Name == "tcp_info")
            {
                continue; // 这个流的时钟取决于 side 列，不参与起止时间的计算
            }

            foreach (RawColumn column in stream.Columns)
            {
                if (column.Role == ColumnRole.None)
                {
                    continue;
                }

                for (int i = 0; i < stream.Count; i++)
                {
                    if (!column.IsValid(i))
                    {
                        continue;
                    }

                    long utc = ToUtcMs(column.Values[i], column.Role, anchor, offsetUs);
                    min = Math.Min(min, utc);
                    max = Math.Max(max, utc);
                }
            }
        }

        long start = min == long.MaxValue ? anchor.UtcMs - source.DurationMs : min;
        int duration = (int)Math.Clamp(Math.Max(source.DurationMs, min == long.MaxValue ? 0 : max - start), 1, MaxDurationMs);

        var header = new RawChunkHeader
        {
            ChunkId = id,
            Kind = spec.Id,
            TaskId = source.TaskId,
            TestId = source.TestId,
            Phase = source.Phase,
            AgentId = agent,
            DialerId = source.DialerId,
            IpVersion = source.IpVersion,
            Target = null,
            Params = new Dictionary<string, JsonElement>(resolvedParams),
            Port = port,
            Direction = source.Direction,
            StartUtcMs = start,
            DurationMs = duration,
            Partial = false,
            Clock = new ChunkClock { ListenerMonoUs = anchor.ListenerMonoUs, UtcMs = anchor.UtcMs, DialerOffsetUs = offsetUs },
        };
        return new RawChunk(header, streams);
    }

    public static long ToUtcMs(long value, ColumnRole role, ClockAnchor anchor, long dialerOffsetUs)
    {
        long listenerUs = role == ColumnRole.TsDialer ? value + dialerOffsetUs : value;
        long delta = listenerUs - anchor.ListenerMonoUs;
        return anchor.UtcMs + (delta >= 0 ? delta / 1000 : -((-delta + 999) / 1000));
    }
}