using System.Diagnostics;
using AcDream.Runtime;

namespace AcDream.App.Streaming;

/// <summary>
/// <c>ACDREAM_PROBE_REVEAL_TIMING=1</c> (see
/// <see cref="StreamingDiagnostics.ProbeRevealTiming"/>): wall-clock
/// attribution of one login/portal hold. Emits <c>[reveal-timing]</c> lines:
///
/// <list type="bullet">
/// <item><c>event=begin</c> — the hold starts, with the required window and
/// its landblock count.</item>
/// <item><c>event=render-ready / composites-ready / collision-ready /
/// gate-ready / materialized</c> — first-true edges with elapsed ms. The
/// readiness barrier OBSERVES the dimensions serially (composites are only
/// evaluated once render is ready, collision once both are), so each edge's
/// delta over the previous one is that dimension's observed TAIL, not its
/// total concurrent cost — the progress lines carry the concurrency
/// shape.</item>
/// <item>1 Hz progress — elapsed, the three flags, and the resident
/// landblock count, so a budget-paced linear drip is visually obvious in the
/// log.</item>
/// <item><c>SUMMARY</c> once at the viewport reveal — the per-edge
/// timeline on one line.</item>
/// </list>
///
/// Diagnostic-only: never constructed unless the probe env is set, changes
/// no behavior, and costs one branch per <c>Evaluate</c> poll otherwise.
/// </summary>
internal sealed class RevealTimingProbe
{
    private readonly Func<int>? _loadedLandblockCount;
    private readonly Stopwatch _clock = new();
    private long _generation;
    private string _kind = "";
    private int _windowLandblocks;
    private bool _render;
    private bool _composites;
    private bool _collision;
    private bool _gateReady;
    private bool _materialized;
    private bool _summarized;
    private long _renderMs = -1;
    private long _compositesMs = -1;
    private long _collisionMs = -1;
    private long _gateReadyMs = -1;
    private long _materializedMs = -1;
    private long _lastProgressMs;

    public RevealTimingProbe(Func<int>? loadedLandblockCount) =>
        _loadedLandblockCount = loadedLandblockCount;

    public void Begin(
        string kind,
        long generation,
        uint destinationCell,
        in StreamingRevealWindow window)
    {
        _generation = generation;
        _kind = kind;
        int side = window.FarRadius * 2 + 1;
        _windowLandblocks = side * side;
        _render = false;
        _composites = false;
        _collision = false;
        _gateReady = false;
        _materialized = false;
        _summarized = false;
        _renderMs = -1;
        _compositesMs = -1;
        _collisionMs = -1;
        _gateReadyMs = -1;
        _materializedMs = -1;
        _lastProgressMs = 0;
        _clock.Restart();
        Console.WriteLine(
            $"[reveal-timing] event=begin kind={kind} gen={generation} "
            + $"cell=0x{destinationCell:X8} window={window.NearRadius}/"
            + $"{window.FarRadius} landblocks={_windowLandblocks} "
            + $"loaded={_loadedLandblockCount?.Invoke() ?? -1}");
    }

    public void Observe(
        in WorldRevealReadinessSnapshot readiness,
        in RuntimePortalSnapshot portal)
    {
        if (_generation == 0 || portal.Generation != _generation)
            return;

        long elapsed = _clock.ElapsedMilliseconds;
        if (!_render && readiness.IsRenderNeighborhoodReady)
        {
            _render = true;
            _renderMs = elapsed;
            Edge("render-ready", elapsed);
        }
        if (!_composites && readiness.AreCompositeTexturesReady)
        {
            _composites = true;
            _compositesMs = elapsed;
            Edge("composites-ready", elapsed);
        }
        if (!_collision && readiness.IsCollisionReady)
        {
            _collision = true;
            _collisionMs = elapsed;
            Edge("collision-ready", elapsed);
        }
        if (!_gateReady && readiness.IsReady)
        {
            _gateReady = true;
            _gateReadyMs = elapsed;
            Edge("gate-ready", elapsed);
        }
        if (!_materialized && portal.Materialized)
        {
            _materialized = true;
            _materializedMs = elapsed;
            Edge("materialized", elapsed);
        }

        if (!_summarized && portal.WorldViewportObserved)
        {
            _summarized = true;
            Console.WriteLine(
                $"[reveal-timing] SUMMARY kind={_kind} gen={_generation} "
                + $"totalMs={elapsed} renderMs={_renderMs} "
                + $"compositesMs={_compositesMs} collisionMs={_collisionMs} "
                + $"gateReadyMs={_gateReadyMs} "
                + $"materializedMs={_materializedMs} "
                + $"landblocks={_windowLandblocks}");
            return;
        }

        if (!_summarized && elapsed - _lastProgressMs >= 1000)
        {
            _lastProgressMs = elapsed;
            Console.WriteLine(
                $"[reveal-timing] elapsedMs={elapsed} "
                + $"render={(_render ? 1 : 0)} "
                + $"composites={(_composites ? 1 : 0)} "
                + $"collision={(_collision ? 1 : 0)} "
                + $"loaded={_loadedLandblockCount?.Invoke() ?? -1}"
                + $"/{_windowLandblocks}");
        }
    }

    private void Edge(string name, long elapsed) =>
        Console.WriteLine(
            $"[reveal-timing] event={name} kind={_kind} gen={_generation} "
            + $"elapsedMs={elapsed} "
            + $"loaded={_loadedLandblockCount?.Invoke() ?? -1}"
            + $"/{_windowLandblocks}");
}