namespace Xilium.CefGlue
{
    using System;
    using System.Collections.Generic;
    using System.Diagnostics;
    using System.Runtime.InteropServices;
    using Xilium.CefGlue.Interop;

    /// <summary>
    /// Implement this interface to handle events when window rendering is disabled.
    /// The methods of this class will be called on the UI thread.
    /// </summary>
    public abstract unsafe partial class CefRenderHandler
    {
        private static readonly CefRectangle[] s_emptyRectangleArray = new CefRectangle[0];


        private cef_accessibility_handler_t* get_accessibility_handler(cef_render_handler_t* self)
        {
            CheckSelf(self);
            var result = GetAccessibilityHandler();
            if (result == null) return null;
            return result.ToNative();
        }

        /// <summary>
        /// Return the handler for accessibility notifications. If no handler is
        /// provided the default implementation will be used.
        /// </summary>
        protected abstract CefAccessibilityHandler GetAccessibilityHandler();


        private int get_root_screen_rect(cef_render_handler_t* self, cef_browser_t* browser, cef_rect_t* rect)
        {
            CheckSelf(self);

            var m_browser = CefBrowser.FromNative(browser);
            var m_rect = new CefRectangle();

            var result = GetRootScreenRect(m_browser, ref m_rect);

            if (result)
            {
                rect->x = m_rect.X;
                rect->y = m_rect.Y;
                rect->width = m_rect.Width;
                rect->height = m_rect.Height;
                return 1;
            }
            else return 0;
        }

        /// <summary>
        /// Called to retrieve the root window rectangle in screen coordinates. Return
        /// true if the rectangle was provided. If this method returns false the
        /// rectangle from GetViewRect will be used.
        /// </summary>
        protected virtual bool GetRootScreenRect(CefBrowser browser, ref CefRectangle rect)
        {
            // TODO: return CefRectangle? (Nullable<CefRectangle>) instead of returning bool?
            return false;
        }


        private void get_view_rect(cef_render_handler_t* self, cef_browser_t* browser, cef_rect_t* rect)
        {
            CheckSelf(self);

            var m_browser = CefBrowser.FromNative(browser);
            CefRectangle m_rect;

            GetViewRect(m_browser, out m_rect);

            rect->x = m_rect.X;
            rect->y = m_rect.Y;
            rect->width = m_rect.Width;
            rect->height = m_rect.Height;
        }

        /// <summary>
        /// Called to retrieve the view rectangle which is relative to screen
        /// coordinates. This method must always provide a non-empty rectangle.
        /// </summary>
        protected abstract void GetViewRect(CefBrowser browser, out CefRectangle rect);


        private int get_screen_point(cef_render_handler_t* self, cef_browser_t* browser, int viewX, int viewY, int* screenX, int* screenY)
        {
            CheckSelf(self);

            var m_browser = CefBrowser.FromNative(browser);

            int m_screenX = 0;
            int m_screenY = 0;

            var result = GetScreenPoint(m_browser, viewX, viewY, ref m_screenX, ref m_screenY);

            if (result)
            {
                *screenX = m_screenX;
                *screenY = m_screenY;
                return 1;
            }
            else return 0;
        }

        /// <summary>
        /// Called to retrieve the translation from view coordinates to actual screen
        /// coordinates. Return true if the screen coordinates were provided.
        /// </summary>
        protected virtual bool GetScreenPoint(CefBrowser browser, int viewX, int viewY, ref int screenX, ref int screenY)
        {
            return false;
        }


        private int get_screen_info(cef_render_handler_t* self, cef_browser_t* browser, cef_screen_info_t* screen_info)
        {
            CheckSelf(self);

            var m_browser = CefBrowser.FromNative(browser);
            var m_screenInfo = new CefScreenInfo(screen_info);

            var result = GetScreenInfo(m_browser, m_screenInfo);

            m_screenInfo.Dispose();
            m_browser.Dispose();

            return result ? 1 : 0;
        }

        /// <summary>
        /// Called to allow the client to fill in the CefScreenInfo object with
        /// appropriate values. Return true if the |screen_info| structure has been
        /// modified.
        /// If the screen info rectangle is left empty the rectangle from GetViewRect
        /// will be used. If the rectangle is still empty or invalid popups may not be
        /// drawn correctly.
        /// </summary>
        protected abstract bool GetScreenInfo(CefBrowser browser, CefScreenInfo screenInfo);


        private void on_popup_show(cef_render_handler_t* self, cef_browser_t* browser, int show)
        {
            CheckSelf(self);

            var m_browser = CefBrowser.FromNative(browser);

            OnPopupShow(m_browser, show != 0);
        }

        /// <summary>
        /// Called when the browser wants to show or hide the popup widget. The popup
        /// should be shown if |show| is true and hidden if |show| is false.
        /// </summary>
        protected virtual void OnPopupShow(CefBrowser browser, bool show)
        {
        }


        private void on_popup_size(cef_render_handler_t* self, cef_browser_t* browser, cef_rect_t* rect)
        {
            CheckSelf(self);

            var m_browser = CefBrowser.FromNative(browser);
            var m_rect = new CefRectangle(rect->x, rect->y, rect->width, rect->height);

            OnPopupSize(m_browser, m_rect);
        }

        /// <summary>
        /// Called when the browser wants to move or resize the popup widget. |rect|
        /// contains the new location and size in view coordinates.
        /// </summary>
        protected abstract void OnPopupSize(CefBrowser browser, CefRectangle rect);


        private void on_paint(cef_render_handler_t* self, cef_browser_t* browser, CefPaintElementType type, UIntPtr dirtyRectsCount, cef_rect_t* dirtyRects, void* buffer, int width, int height)
        {
            CheckSelf(self);

            var m_browser = CefBrowser.FromNative(browser);

            // TODO: reuse arrays?
            var m_dirtyRects = new CefRectangle[(int)dirtyRectsCount];

            var count = (int)dirtyRectsCount;
            var rect = dirtyRects;
            for (var i = 0; i < count; i++)
            {
                m_dirtyRects[i].X = rect->x;
                m_dirtyRects[i].Y = rect->y;
                m_dirtyRects[i].Width = rect->width;
                m_dirtyRects[i].Height = rect->height;

                rect++;
            }

            OnPaint(m_browser, type, m_dirtyRects, (IntPtr)buffer, width, height);
        }

        /// <summary>
        /// Called when an element should be painted. Pixel values passed to this
        /// method are scaled relative to view coordinates based on the value of
        /// CefScreenInfo.device_scale_factor returned from GetScreenInfo. |type|
        /// indicates whether the element is the view or the popup widget. |buffer|
        /// contains the pixel data for the whole image. |dirtyRects| contains the set
        /// of rectangles in pixel coordinates that need to be repainted. |buffer| will
        /// be |width|*|height|*4 bytes in size and represents a BGRA image with an
        /// upper-left origin. This method is only called when CefWindowInfo::SharedTextureEnabled
        /// is set to false.
        /// </summary>
        protected abstract void OnPaint(CefBrowser browser, CefPaintElementType type, CefRectangle[] dirtyRects, IntPtr buffer, int width, int height);


        private void on_accelerated_paint(cef_render_handler_t* self, cef_browser_t* browser, CefPaintElementType type, UIntPtr dirtyRectsCount, cef_rect_t* dirtyRects, void* shared_handle)
        {
            CheckSelf(self);

            var m_browser = CefBrowser.FromNative(browser);

            // TODO: reuse arrays?
            var m_dirtyRects = new CefRectangle[(int)dirtyRectsCount];

            var count = (int)dirtyRectsCount;
            var rect = dirtyRects;
            for (var i = 0; i < count; i++)
            {
                m_dirtyRects[i].X = rect->x;
                m_dirtyRects[i].Y = rect->y;
                m_dirtyRects[i].Width = rect->width;
                m_dirtyRects[i].Height = rect->height;

                rect++;
            }

            OnAcceleratedPaint(m_browser, type, m_dirtyRects, (IntPtr)shared_handle);
        }

        /// <summary>
        /// Called when an element has been rendered to the shared texture handle.
        /// |type| indicates whether the element is the view or the popup widget.
        /// |dirtyRects| contains the set of rectangles in pixel coordinates that need
        /// to be repainted. |shared_handle| is the handle for a D3D11 Texture2D that
        /// can be accessed via ID3D11Device using the OpenSharedResource method. This
        /// method is only called when CefWindowInfo::SharedTextureEnabled is set to
        /// true, and is currently only supported on Windows.
        /// </summary>
        protected abstract void OnAcceleratedPaint(CefBrowser browser, CefPaintElementType type, CefRectangle[] dirtyRects, IntPtr sharedHandle);


        private int start_dragging(cef_render_handler_t* self, cef_browser_t* browser, cef_drag_data_t* drag_data, CefDragOperationsMask allowed_ops, int x, int y)
        {
            CheckSelf(self);

            var m_browser = CefBrowser.FromNative(browser);
            var m_dragData = CefDragData.FromNative(drag_data); // TODO dispose?

            var m_result = StartDragging(m_browser, m_dragData, allowed_ops, x, y);
            
            return m_result ? 1 : 0;
        }

        /// <summary>
        /// Called when the user starts dragging content in the web view. Contextual
        /// information about the dragged content is supplied by |drag_data|.
        /// (|x|, |y|) is the drag start location in screen coordinates.
        /// OS APIs that run a system message loop may be used within the
        /// StartDragging call.
        /// Return false to abort the drag operation. Don't call any of
        /// CefBrowserHost::DragSource*Ended* methods after returning false.
        /// Return true to handle the drag operation. Call
        /// CefBrowserHost::DragSourceEndedAt and DragSourceSystemDragEnded either
        /// synchronously or asynchronously to inform the web view that the drag
        /// operation has ended.
        /// </summary>
        protected virtual bool StartDragging(CefBrowser browser, CefDragData dragData, CefDragOperationsMask allowedOps, int x, int y)
        {
            return false;
        }


        private void update_drag_cursor(cef_render_handler_t* self, cef_browser_t* browser, CefDragOperationsMask operation)
        {
            CheckSelf(self);

            var m_browser = CefBrowser.FromNative(browser);

            UpdateDragCursor(m_browser, operation);
        }

        /// <summary>
        /// Called when the web view wants to update the mouse cursor during a
        /// drag &amp; drop operation. |operation| describes the allowed operation
        /// (none, move, copy, link).
        /// </summary>
        protected virtual void UpdateDragCursor(CefBrowser browser, CefDragOperationsMask operation)
        {
        }


        private void on_scroll_offset_changed(cef_render_handler_t* self, cef_browser_t* browser, double x, double y)
        {
            CheckSelf(self);

            var m_browser = CefBrowser.FromNative(browser);

            OnScrollOffsetChanged(m_browser, x, y);
        }

        /// <summary>
        /// Called when the scroll offset has changed.
        /// </summary>
        protected abstract void OnScrollOffsetChanged(CefBrowser browser, double x, double y);


        private void on_ime_composition_range_changed(cef_render_handler_t* self, cef_browser_t* browser, cef_range_t* selected_range, UIntPtr character_boundsCount, cef_rect_t* character_bounds)
        {
            CheckSelf(self);

            // TODO: reuse array/special list for rectange - this method called only from one thread and can be reused

            var m_browser = CefBrowser.FromNative(browser);
            var m_selectedRange = new CefRange(selected_range->from, selected_range->to);

            CefRectangle[] m_characterBounds;
            if (character_boundsCount == UIntPtr.Zero)
            {
                m_characterBounds = s_emptyRectangleArray;
            }
            else
            {
                var m_characterBoundsCount = checked((int)character_boundsCount);
                m_characterBounds = new CefRectangle[m_characterBoundsCount];
                for (var i = 0; i < m_characterBoundsCount; i++)
                {
                    m_characterBounds[i] = new CefRectangle(
                        character_bounds[i].x,
                        character_bounds[i].y,
                        character_bounds[i].width,
                        character_bounds[i].height
                        );
                }
            }

            OnImeCompositionRangeChanged(m_browser, m_selectedRange, m_characterBounds);
        }

        /// <summary>
        /// Called when the IME composition range has changed. |selected_range| is the
        /// range of characters that have been selected. |character_bounds| is the
        /// bounds of each character in view coordinates.
        /// </summary>
        protected abstract void OnImeCompositionRangeChanged(CefBrowser browser, CefRange selectedRange, CefRectangle[] characterBounds);


        private void on_text_selection_changed(cef_render_handler_t* self, cef_browser_t* browser, cef_string_t* selected_text, cef_range_t* selected_range)
        {
            CheckSelf(self);

            var m_browser = CefBrowser.FromNative(browser);
            var m_selected_text = cef_string_t.ToString(selected_text);
            var m_selected_range = new CefRange(selected_range->from, selected_range->to);

            OnTextSelectionChanged(m_browser, m_selected_text, m_selected_range);
        }

        /// <summary>
        /// Called when text selection has changed for the specified |browser|.
        /// |selected_text| is the currently selected text and |selected_range| is
        /// the character range.
        /// </summary>
        protected virtual void OnTextSelectionChanged(CefBrowser browser, string selectedText, CefRange selectedRange) { }


        private void on_virtual_keyboard_requested(cef_render_handler_t* self, cef_browser_t* browser, CefTextInputMode input_mode)
        {
            CheckSelf(self);

            var mBrowser = CefBrowser.FromNative(browser);
            OnVirtualKeyboardRequested(mBrowser, input_mode);
        }

        /// <summary>
        /// Called when an on-screen keyboard should be shown or hidden for the
        /// specified |browser|. |input_mode| specifies what kind of keyboard
        /// should be opened. If |input_mode| is CEF_TEXT_INPUT_MODE_NONE, any
        /// existing keyboard for this browser should be hidden.
        /// </summary>
        protected virtual void OnVirtualKeyboardRequested(CefBrowser browser, CefTextInputMode inputMode) { }
    }
}