using System.Diagnostics;
using System.Linq;
using System.Windows.Threading;
using AxCopilot.Models;
using AxCopilot.Services;

namespace AxCopilot.Views;

public partial class ChatWindow
{
    private int GetActiveTimelineRenderLimit()
    {
        if (!_isStreaming)
            return _timelineRenderLimit;

        var streamingLimit = IsLightweightLiveProgressMode()
            ? TimelineLightweightStreamingRenderLimit
            : TimelineStreamingRenderLimit;
        return Math.Min(_timelineRenderLimit, streamingLimit);
    }

    private void RenderMessages(bool preserveViewport = false)
    {
        // B-4: 비가시 상태일 때 렌더링 차단 — 최소화/숨김 시 불필요한 UI 재구축 방지
        if (this.WindowState == System.Windows.WindowState.Minimized || !IsVisible)
            return;

        var renderStopwatch = Stopwatch.StartNew();
        var previousScrollableHeight = GetTranscriptScrollableHeight();
        var previousVerticalOffset = GetTranscriptVerticalOffset();

        ChatConversation? conv;
        lock (_convLock) conv = _currentConversation;
        _appState.RestoreAgentRunHistory(conv?.AgentRunHistory);

        var visibleMessages = GetVisibleTimelineMessages(conv);
        var visibleEvents = GetVisibleTimelineEvents(conv);

        if (_isStreaming && preserveViewport
            && visibleMessages.Count == _lastRenderedMessageCount
            && visibleEvents.Count == _lastRenderedEventCount
            && (conv?.ShowExecutionHistory ?? true) == _lastRenderedShowHistory
            && string.Equals(_lastRenderedConversationId, conv?.Id, StringComparison.OrdinalIgnoreCase))
            return;

        if (conv == null || (visibleMessages.Count == 0 && visibleEvents.Count == 0))
        {
            ClearTranscriptElements();
            _runBannerAnchors.Clear();
            _lastRenderedTimelineKeys.Clear();
            _lastRenderedMessageCount = 0;
            _lastRenderedEventCount = 0;
            EmptyState.Visibility = System.Windows.Visibility.Visible;
            return;
        }

        if (!string.Equals(_lastRenderedConversationId, conv.Id, StringComparison.OrdinalIgnoreCase))
        {
            _lastRenderedConversationId = conv.Id;
            _timelineRenderLimit = TimelineRenderPageSize;
            _elementCache.Clear();
            _lastRenderedTimelineKeys.Clear();
            _lastRenderedMessageCount = 0;
            _lastRenderedEventCount = 0;
            InvalidateTimelineCache();
        }

        EmptyState.Visibility = System.Windows.Visibility.Collapsed;
        var renderPlan = BuildTranscriptRenderPlan(conv, visibleMessages, visibleEvents);

        // B-3: 스트리밍 전용 빠른 경로 → 일반 인크리멘탈 → 전체 재빌드
        if (!TryApplyStreamingAppendRender(renderPlan)
            && !TryApplyIncrementalTranscriptRender(renderPlan))
            ApplyFullTranscriptRender(renderPlan);
        PruneTranscriptElementCache(renderPlan.NewKeys);

        _lastRenderedMessageCount = visibleMessages.Count;
        _lastRenderedEventCount = visibleEvents.Count;
        _lastRenderedShowHistory = renderPlan.ShowHistory;
        renderStopwatch.Stop();
        if (renderStopwatch.ElapsedMilliseconds >= 24 || _isStreaming)
        {
            AgentPerformanceLogService.LogMetric(
                "transcript",
                "render_messages",
                conv.Id,
                _activeTab ?? "",
                renderStopwatch.ElapsedMilliseconds,
                new
                {
                    preserveViewport,
                    streaming = _isStreaming,
                    lightweight = IsLightweightLiveProgressMode(),
                    visibleMessages = visibleMessages.Count,
                    visibleEvents = visibleEvents.Count,
                    renderedItems = renderPlan.NewKeys.Count,
                    hiddenCount = renderPlan.HiddenCount,
                    transcriptElements = GetTranscriptElementCount(),
                    processFeedAppends = _processFeedAppendCount,
                    processFeedMerges = _processFeedMergeCount,
                    rowKindCounts = _transcriptRowKindCounts.ToDictionary(
                        pair => pair.Key.ToString(),
                        pair => pair.Value),
                });
        }

        if (!preserveViewport)
        {
            _ = Dispatcher.InvokeAsync(ScrollTranscriptToEnd, DispatcherPriority.Background);
            return;
        }

        _ = Dispatcher.InvokeAsync(() =>
        {
            if (_transcriptScrollViewer == null)
                return;

            var newScrollableHeight = GetTranscriptScrollableHeight();
            var delta = newScrollableHeight - previousScrollableHeight;
            var targetOffset = Math.Max(0, previousVerticalOffset + Math.Max(0, delta));
            ScrollTranscriptToVerticalOffset(targetOffset);
        }, DispatcherPriority.Background);
    }
}