using System.Drawing.Drawing2D;
using WorkCameraExport.Services;

namespace WorkCameraExport.Forms
{
    /// <summary>
    /// 图片查看器窗体 - 支持缩放、拖拽、轮播
    /// Requirements: 3.3, 3.4, 3.5, 3.6
    /// </summary>
    public partial class ImageViewerForm : Form
    {
        private readonly List<string> _imageUrls;
        private readonly Dictionary<string, Image?> _imageCache;
        private readonly ApiService? _apiService;
        
        private int _currentIndex;
        private float _zoomFactor = 1.0f;
        private PointF _imageOffset;
        private Point _lastMousePosition;
        private bool _isDragging;
        private Image? _currentImage;

        // 缩放限制
        private const float MinZoom = 0.1f;
        private const float MaxZoom = 10.0f;
        private const float ZoomStep = 0.1f;

        /// <summary>
        /// 当前图片索引
        /// </summary>
        public int CurrentIndex
        {
            get => _currentIndex;
            private set
            {
                if (_imageUrls.Count == 0) return;
                
                // 循环索引
                _currentIndex = WrapIndex(value, _imageUrls.Count);
                UpdateDisplay();
            }
        }

        /// <summary>
        /// 图片总数
        /// </summary>
        public int ImageCount => _imageUrls.Count;

        /// <summary>
        /// 构造函数
        /// </summary>
        /// <param name="imageUrls">图片 URL 列表</param>
        /// <param name="startIndex">起始索引</param>
        /// <param name="apiService">API 服务（用于下载图片）</param>
        public ImageViewerForm(List<string> imageUrls, int startIndex = 0, ApiService? apiService = null)
        {
            InitializeComponent();
            
            _imageUrls = imageUrls ?? new List<string>();
            _imageCache = new Dictionary<string, Image?>();
            _apiService = apiService;
            _currentIndex = WrapIndex(startIndex, Math.Max(1, _imageUrls.Count));
            _imageOffset = PointF.Empty;

            SetupEventHandlers();
            
            if (_imageUrls.Count > 0)
            {
                _ = LoadCurrentImageAsync();
            }
        }

        /// <summary>
        /// 设置事件处理器
        /// </summary>
        private void SetupEventHandlers()
        {
            // 图片面板事件
            panelImage.Paint += PanelImage_Paint;
            panelImage.MouseWheel += PanelImage_MouseWheel;
            panelImage.MouseDown += PanelImage_MouseDown;
            panelImage.MouseMove += PanelImage_MouseMove;
            panelImage.MouseUp += PanelImage_MouseUp;
            panelImage.Resize += PanelImage_Resize;

            // 键盘事件
            this.KeyPreview = true;
            this.KeyDown += ImageViewerForm_KeyDown;
        }

        #region 图片导航

        /// <summary>
        /// 显示下一张图片
        /// </summary>
        public void NextImage()
        {
            if (_imageUrls.Count <= 1) return;
            CurrentIndex = _currentIndex + 1;
        }

        /// <summary>
        /// 显示上一张图片
        /// </summary>
        public void PreviousImage()
        {
            if (_imageUrls.Count <= 1) return;
            CurrentIndex = _currentIndex - 1;
        }

        /// <summary>
        /// 显示指定索引的图片
        /// </summary>
        public void ShowImage(int index)
        {
            CurrentIndex = index;
        }

        /// <summary>
        /// 循环索引计算
        /// 确保索引始终在 [0, count-1] 范围内
        /// </summary>
        public static int WrapIndex(int index, int count)
        {
            if (count <= 0) return 0;
            
            // 处理负数索引
            index = index % count;
            if (index < 0) index += count;
            
            return index;
        }

        #endregion

        #region 图片加载

        /// <summary>
        /// 加载当前图片
        /// </summary>
        private async Task LoadCurrentImageAsync()
        {
            if (_imageUrls.Count == 0) return;

            var url = _imageUrls[_currentIndex];
            lblStatus.Text = $"正在加载图片 {_currentIndex + 1}/{_imageUrls.Count}...";
            lblStatus.ForeColor = Color.Blue;

            try
            {
                // 检查缓存
                if (_imageCache.TryGetValue(url, out var cachedImage) && cachedImage != null)
                {
                    _currentImage = cachedImage;
                    ResetView();
                    UpdateStatusLabel();
                    panelImage.Invalidate();
                    return;
                }

                // 下载图片
                byte[]? imageData = null;
                
                if (_apiService != null)
                {
                    var (success, data, _) = await _apiService.DownloadImageAsync(url, CancellationToken.None);
                    if (success) imageData = data;
                }
                else
                {
                    // 直接使用 HttpClient 下载
                    using var httpClient = new HttpClient { Timeout = TimeSpan.FromSeconds(30) };
                    imageData = await httpClient.GetByteArrayAsync(url);
                }

                if (imageData != null && imageData.Length > 0)
                {
                    using var ms = new MemoryStream(imageData);
                    var image = Image.FromStream(ms);
                    _imageCache[url] = image;
                    _currentImage = image;
                    ResetView();
                    UpdateStatusLabel();
                }
                else
                {
                    _currentImage = null;
                    lblStatus.Text = "图片加载失败";
                    lblStatus.ForeColor = Color.Red;
                }
            }
            catch (Exception ex)
            {
                _currentImage = null;
                lblStatus.Text = $"加载失败: {ex.Message}";
                lblStatus.ForeColor = Color.Red;
            }

            panelImage.Invalidate();
        }

        /// <summary>
        /// 更新显示
        /// </summary>
        private void UpdateDisplay()
        {
            _ = LoadCurrentImageAsync();
            UpdateNavigationButtons();
        }

        /// <summary>
        /// 更新状态标签
        /// </summary>
        private void UpdateStatusLabel()
        {
            if (_currentImage != null)
            {
                lblStatus.Text = $"图片 {_currentIndex + 1}/{_imageUrls.Count} | " +
                                $"尺寸: {_currentImage.Width}x{_currentImage.Height} | " +
                                $"缩放: {_zoomFactor:P0}";
                lblStatus.ForeColor = Color.FromArgb(51, 51, 51);
            }
        }

        /// <summary>
        /// 更新导航按钮状态
        /// </summary>
        private void UpdateNavigationButtons()
        {
            btnPrevious.Enabled = _imageUrls.Count > 1;
            btnNext.Enabled = _imageUrls.Count > 1;
            lblImageIndex.Text = _imageUrls.Count > 0 
                ? $"{_currentIndex + 1} / {_imageUrls.Count}" 
                : "0 / 0";
        }

        #endregion

        #region 缩放功能

        /// <summary>
        /// 放大图片
        /// </summary>
        public void ZoomIn()
        {
            SetZoom(_zoomFactor + ZoomStep);
        }

        /// <summary>
        /// 缩小图片
        /// </summary>
        public void ZoomOut()
        {
            SetZoom(_zoomFactor - ZoomStep);
        }

        /// <summary>
        /// 重置缩放
        /// </summary>
        public void ResetZoom()
        {
            _zoomFactor = 1.0f;
            _imageOffset = PointF.Empty;
            UpdateStatusLabel();
            panelImage.Invalidate();
        }

        /// <summary>
        /// 适应窗口大小
        /// </summary>
        public void FitToWindow()
        {
            if (_currentImage == null) return;

            var panelWidth = panelImage.ClientSize.Width;
            var panelHeight = panelImage.ClientSize.Height;
            var imageWidth = _currentImage.Width;
            var imageHeight = _currentImage.Height;

            var scaleX = (float)panelWidth / imageWidth;
            var scaleY = (float)panelHeight / imageHeight;
            
            _zoomFactor = Math.Min(scaleX, scaleY);
            _zoomFactor = Math.Clamp(_zoomFactor, MinZoom, MaxZoom);
            _imageOffset = PointF.Empty;
            
            UpdateStatusLabel();
            panelImage.Invalidate();
        }

        /// <summary>
        /// 设置缩放比例
        /// </summary>
        private void SetZoom(float zoom)
        {
            _zoomFactor = Math.Clamp(zoom, MinZoom, MaxZoom);
            UpdateStatusLabel();
            panelImage.Invalidate();
        }

        /// <summary>
        /// 重置视图
        /// </summary>
        private void ResetView()
        {
            _zoomFactor = 1.0f;
            _imageOffset = PointF.Empty;
            FitToWindow();
        }

        #endregion

        #region 绘制

        /// <summary>
        /// 绘制图片
        /// </summary>
        private void PanelImage_Paint(object? sender, PaintEventArgs e)
        {
            var g = e.Graphics;
            g.Clear(Color.FromArgb(30, 30, 30));
            g.InterpolationMode = InterpolationMode.HighQualityBicubic;
            g.SmoothingMode = SmoothingMode.HighQuality;

            if (_currentImage == null)
            {
                // 显示无图片提示
                using var font = new Font("Microsoft YaHei UI", 14f);
                using var brush = new SolidBrush(Color.Gray);
                var text = _imageUrls.Count == 0 ? "没有图片" : "图片加载中...";
                var size = g.MeasureString(text, font);
                var x = (panelImage.Width - size.Width) / 2;
                var y = (panelImage.Height - size.Height) / 2;
                g.DrawString(text, font, brush, x, y);
                return;
            }

            // 计算图片绘制位置和大小
            var scaledWidth = _currentImage.Width * _zoomFactor;
            var scaledHeight = _currentImage.Height * _zoomFactor;

            // 居中显示
            var centerX = (panelImage.Width - scaledWidth) / 2 + _imageOffset.X;
            var centerY = (panelImage.Height - scaledHeight) / 2 + _imageOffset.Y;

            var destRect = new RectangleF(centerX, centerY, scaledWidth, scaledHeight);
            var srcRect = new RectangleF(0, 0, _currentImage.Width, _currentImage.Height);

            g.DrawImage(_currentImage, destRect, srcRect, GraphicsUnit.Pixel);
        }

        #endregion

        #region 鼠标事件

        /// <summary>
        /// 鼠标滚轮缩放
        /// </summary>
        private void PanelImage_MouseWheel(object? sender, MouseEventArgs e)
        {
            if (_currentImage == null) return;

            var delta = e.Delta > 0 ? ZoomStep : -ZoomStep;
            SetZoom(_zoomFactor + delta);
        }

        /// <summary>
        /// 鼠标按下 - 开始拖拽
        /// </summary>
        private void PanelImage_MouseDown(object? sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left && _currentImage != null)
            {
                _isDragging = true;
                _lastMousePosition = e.Location;
                panelImage.Cursor = Cursors.Hand;
            }
        }

        /// <summary>
        /// 鼠标移动 - 拖拽图片
        /// </summary>
        private void PanelImage_MouseMove(object? sender, MouseEventArgs e)
        {
            if (_isDragging && _currentImage != null)
            {
                var deltaX = e.X - _lastMousePosition.X;
                var deltaY = e.Y - _lastMousePosition.Y;

                _imageOffset = new PointF(
                    _imageOffset.X + deltaX,
                    _imageOffset.Y + deltaY);

                _lastMousePosition = e.Location;
                panelImage.Invalidate();
            }
        }

        /// <summary>
        /// 鼠标释放 - 结束拖拽
        /// </summary>
        private void PanelImage_MouseUp(object? sender, MouseEventArgs e)
        {
            if (e.Button == MouseButtons.Left)
            {
                _isDragging = false;
                panelImage.Cursor = Cursors.Default;
            }
        }

        /// <summary>
        /// 面板大小改变
        /// </summary>
        private void PanelImage_Resize(object? sender, EventArgs e)
        {
            panelImage.Invalidate();
        }

        #endregion

        #region 键盘事件

        /// <summary>
        /// 键盘按键处理
        /// </summary>
        private void ImageViewerForm_KeyDown(object? sender, KeyEventArgs e)
        {
            switch (e.KeyCode)
            {
                case Keys.Left:
                case Keys.A:
                    PreviousImage();
                    e.Handled = true;
                    break;

                case Keys.Right:
                case Keys.D:
                    NextImage();
                    e.Handled = true;
                    break;

                case Keys.Add:
                case Keys.Oemplus:
                    ZoomIn();
                    e.Handled = true;
                    break;

                case Keys.Subtract:
                case Keys.OemMinus:
                    ZoomOut();
                    e.Handled = true;
                    break;

                case Keys.D0:
                case Keys.NumPad0:
                    ResetZoom();
                    e.Handled = true;
                    break;

                case Keys.F:
                    FitToWindow();
                    e.Handled = true;
                    break;

                case Keys.Escape:
                    this.Close();
                    e.Handled = true;
                    break;
            }
        }

        #endregion

        #region 按钮事件

        /// <summary>
        /// 上一张按钮点击
        /// </summary>
        private void btnPrevious_Click(object sender, EventArgs e)
        {
            PreviousImage();
        }

        /// <summary>
        /// 下一张按钮点击
        /// </summary>
        private void btnNext_Click(object sender, EventArgs e)
        {
            NextImage();
        }

        /// <summary>
        /// 放大按钮点击
        /// </summary>
        private void btnZoomIn_Click(object sender, EventArgs e)
        {
            ZoomIn();
        }

        /// <summary>
        /// 缩小按钮点击
        /// </summary>
        private void btnZoomOut_Click(object sender, EventArgs e)
        {
            ZoomOut();
        }

        /// <summary>
        /// 重置按钮点击
        /// </summary>
        private void btnReset_Click(object sender, EventArgs e)
        {
            ResetZoom();
        }

        /// <summary>
        /// 适应窗口按钮点击
        /// </summary>
        private void btnFit_Click(object sender, EventArgs e)
        {
            FitToWindow();
        }

        /// <summary>
        /// 关闭按钮点击
        /// </summary>
        private void btnClose_Click(object sender, EventArgs e)
        {
            this.Close();
        }

        #endregion

        #region 清理

        /// <summary>
        /// 窗体关闭时清理资源
        /// </summary>
        protected override void OnFormClosed(FormClosedEventArgs e)
        {
            base.OnFormClosed(e);

            // 清理图片缓存
            foreach (var image in _imageCache.Values)
            {
                image?.Dispose();
            }
            _imageCache.Clear();
            _currentImage = null;
        }

        #endregion
    }
}