using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Media;
using System.Windows.Threading;
using AxCopilot.Models;
using AxCopilot.Services;
using AxCopilot.Services.Agent;

namespace AxCopilot.Views;

public partial class ChatWindow
{
    // ─── V2 렌더 상태 ───────────────────────────────────────────────────
    private string? _v2LastRenderedConversationId;
    private int _v2LastRenderedMessageCount;
    private int _v2LastRenderedEventCount;
    private readonly List<string> _v2LastRenderedKeys = new();

    // V2 라이브 프로그레스 상태
    private StackPanel? _v2LiveContainer;
    private readonly Dictionary<string, Border> _v2LiveToolCards = new();
    private string? _v2LastLiveToolCallId;

    private void RenderMessagesV2(
        ChatConversation conv,
        IReadOnlyList<ChatMessage> visibleMessages,
        IReadOnlyList<ChatExecutionEvent> visibleEvents,
        bool preserveViewport,
        double previousScrollableHeight,
        double previousVerticalOffset,
        Stopwatch renderStopwatch,
        string? caller)
    {
        try
        {
            // 대화 전환 감지 → 캐시 초기화
            if (!string.Equals(_v2LastRenderedConversationId, conv.Id, StringComparison.OrdinalIgnoreCase))
            {
                _v2LastRenderedConversationId = conv.Id;
                _v2LastRenderedKeys.Clear();
                _v2LastRenderedMessageCount = 0;
                _v2LastRenderedEventCount = 0;
                _elementCache.Clear();
            }

            // ★ 패널이 비어있는데 V2 캐시가 남아있는 경우 강제 리셋
            //   탭 전환 시 ClearTranscriptElements()로 패널이 비워지지만
            //   빈 대화 탭을 거치면 V2가 호출되지 않아 캐시가 잔류하는 버그 방지
            if (GetTranscriptElementCount() == 0 && _v2LastRenderedKeys.Count > 0)
            {
                LogService.Info($"[V2Render] CACHE STALE RESET: panel=0 but cachedKeys={_v2LastRenderedKeys.Count}, forcing full rebuild");
                _v2LastRenderedKeys.Clear();
                _v2LastRenderedMessageCount = 0;
                _v2LastRenderedEventCount = 0;
            }

            // 통합 타임라인 빌드 (메시지 + 이벤트를 시간순 병합)
            var timeline = BuildV2Timeline(visibleMessages, visibleEvents);

            LogService.Info($"[V2Render] timeline={timeline.Count}, msgs={visibleMessages.Count}, evts={visibleEvents.Count}, convId={conv.Id[..Math.Min(8, conv.Id.Length)]}, caller={caller}");

            // 새 키 목록 생성
            var newKeys = new List<string>(timeline.Count);
            foreach (var item in timeline)
                newKeys.Add(item.Key);

            // 인크리멘탈 렌더 시도: 기존 키가 새 키의 접두사인 경우 추가분만 렌더
            // ★ 패널에 실제 엘리먼트가 있어야 인크리멘탈 가능 —
            //   탭 전환 시 ClearTranscriptElements()로 패널이 비워지지만
            //   V2 캐시(_v2LastRenderedKeys)는 유지되어 "이미 렌더됨"으로 오판하는 버그 방지
            var actualElementCount = GetTranscriptElementCount();
            var canIncremental = _v2LastRenderedKeys.Count > 0
                && actualElementCount > 0
                && newKeys.Count >= _v2LastRenderedKeys.Count
                && KeysArePrefixMatch(_v2LastRenderedKeys, newKeys);

            LogService.Info($"[V2Render] canIncremental={canIncremental}, prevKeys={_v2LastRenderedKeys.Count}, newKeys={newKeys.Count}, preElementCount={GetTranscriptElementCount()}");

            if (canIncremental)
            {
                // 라이브 컨테이너가 있으면 임시 제거 (맨 끝에 다시 추가)
                if (_v2LiveContainer != null && ContainsTranscriptElement(_v2LiveContainer))
                    RemoveTranscriptElement(_v2LiveContainer);

                for (int i = _v2LastRenderedKeys.Count; i < timeline.Count; i++)
                {
                    var item = timeline[i];
                    AddDeferredTranscriptElement(item.Key, () =>
                    {
                        if (_elementCache.TryGetValue(item.Key, out var cached))
                            return cached;
                        var element = item.CreateElement();
                        _elementCache[item.Key] = element;
                        return element;
                    });
                }

                // 라이브 컨테이너 재삽입
                if (_v2LiveContainer != null && _isStreaming)
                    AddTranscriptElement(_v2LiveContainer);
            }
            else
            {
                // 전체 재빌드
                ClearTranscriptElements();

                foreach (var item in timeline)
                {
                    var capturedItem = item;
                    AddDeferredTranscriptElement(capturedItem.Key, () =>
                    {
                        if (_elementCache.TryGetValue(capturedItem.Key, out var cached))
                            return cached;
                        var element = capturedItem.CreateElement();
                        _elementCache[capturedItem.Key] = element;
                        return element;
                    });
                }

                // 라이브 컨테이너 재삽입
                if (_v2LiveContainer != null && _isStreaming)
                    AddTranscriptElement(_v2LiveContainer);
            }

            _v2LastRenderedKeys.Clear();
            _v2LastRenderedKeys.AddRange(newKeys);
            _v2LastRenderedMessageCount = visibleMessages.Count;
            _v2LastRenderedEventCount = visibleEvents.Count;

            LogService.Info($"[V2Render] DONE postElementCount={GetTranscriptElementCount()}, savedKeys={_v2LastRenderedKeys.Count}");
        }
        catch (Exception ex)
        {
            LogService.Error($"[V2Render] 렌더링 예외: {ex.GetType().Name}: {ex.Message}\n{ex.StackTrace}");
        }

        _lastRenderTicks = Environment.TickCount64;
        _lastRenderedMessageCount = visibleMessages.Count;
        _lastRenderedEventCount = visibleEvents.Count;
        _lastRenderedShowHistory = conv?.ShowExecutionHistory ?? true;
        renderStopwatch.Stop();

        if (renderStopwatch.ElapsedMilliseconds >= (_isStreaming ? 100 : 24))
        {
            AgentPerformanceLogService.LogMetric(
                "transcript", "render_messages_v2", conv?.Id ?? "", _activeTab ?? "",
                renderStopwatch.ElapsedMilliseconds,
                new { preserveViewport, streaming = _isStreaming, visibleMessages = visibleMessages.Count, visibleEvents = visibleEvents.Count });
        }

        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);
    }

    private static bool KeysArePrefixMatch(List<string> oldKeys, List<string> newKeys)
    {
        for (int i = 0; i < oldKeys.Count; i++)
        {
            if (!string.Equals(oldKeys[i], newKeys[i], StringComparison.Ordinal))
                return false;
        }
        return true;
    }

    private sealed record V2TimelineItem(string Key, DateTime Timestamp, Func<UIElement> CreateElement);

    private List<V2TimelineItem> BuildV2Timeline(
        IReadOnlyList<ChatMessage> visibleMessages,
        IReadOnlyList<ChatExecutionEvent> visibleEvents)
    {
        var timeline = new List<V2TimelineItem>(visibleMessages.Count + visibleEvents.Count);

        // 1. 메시지 추가
        foreach (var msg in visibleMessages)
        {
            var capturedMsg = msg;
            var key = $"v2m_{msg.MsgId}";
            timeline.Add(new V2TimelineItem(key, msg.Timestamp, () => CreateV2MessageElement(capturedMsg)));
        }

        // 2. 실행 이벤트 추가 — ToolCall+ToolResult 쌍을 병합
        //    스트리밍 중이면 라이브 카드가 이미 표시하는 현재 실행 이벤트는 타임라인에서 제외
        var eventIndex = 0;
        var events = visibleEvents.ToList();
        var liveCardCutoff = (_isStreaming && _v2LiveContainer != null)
            ? _v2LiveStartTime
            : DateTime.MaxValue;

        for (int i = 0; i < events.Count; i++)
        {
            var executionEvent = events[i];

            // 스트리밍 중: 라이브 카드 시작 이후 이벤트는 라이브 카드에서 표시하므로 스킵
            if (executionEvent.Timestamp.ToUniversalTime() >= liveCardCutoff)
                continue;

            var agentEvent = ToAgentEvent(executionEvent);

            // SessionStart / UserPromptSubmit 숨김
            if (agentEvent.Type == AgentEventType.SessionStart || agentEvent.Type == AgentEventType.UserPromptSubmit)
                continue;

            var key = $"v2e_{executionEvent.Timestamp.Ticks}_{eventIndex++}";

            // ToolCall → 바로 다음 같은 도구의 ToolResult를 찾아 병합
            if (agentEvent.Type == AgentEventType.ToolCall && i + 1 < events.Count)
            {
                var nextEvent = ToAgentEvent(events[i + 1]);
                if (nextEvent.Type == AgentEventType.ToolResult
                    && string.Equals(nextEvent.ToolName, agentEvent.ToolName, StringComparison.OrdinalIgnoreCase))
                {
                    var capturedCall = agentEvent;
                    var capturedResult = nextEvent;
                    timeline.Add(new V2TimelineItem(key, executionEvent.Timestamp,
                        () => CreateV2ToolExecutionCard(capturedCall, capturedResult)));
                    i++; // ToolResult 스킵
                    continue;
                }
            }

            var capturedEvent = agentEvent;
            timeline.Add(new V2TimelineItem(key, executionEvent.Timestamp,
                () => CreateV2AgentEventElement(capturedEvent)));
        }

        // 시간순 정렬
        var needsSort = false;
        for (int i = 1; i < timeline.Count; i++)
        {
            if (timeline[i].Timestamp < timeline[i - 1].Timestamp)
            {
                needsSort = true;
                break;
            }
        }
        if (needsSort)
            timeline.Sort((a, b) => a.Timestamp.CompareTo(b.Timestamp));

        return timeline;
    }
}