import {
  OverlayIdentifier,
  type SurfaceBlockComponent,
} from '@blocksuite/affine-block-surface';
import {
  type LayoutType,
  type LocalConnectorElementModel,
  MindmapElementModel,
  type MindmapNode,
} from '@blocksuite/affine-model';
import type { Bound, IVec } from '@blocksuite/global/gfx';
import {
  type DragExtensionInitializeContext,
  type ExtensionDragEndContext,
  type ExtensionDragMoveContext,
  type ExtensionDragStartContext,
  type GfxModel,
  type GfxPrimitiveElementModel,
  isGfxGroupCompatibleModel,
  TransformExtension,
} from '@blocksuite/std/gfx';

import type { MindMapIndicatorOverlay } from '../indicator-overlay';
import { isMindmapNode, isSingleMindMapNode } from '../utils';
import { NODE_HORIZONTAL_SPACING, NODE_VERTICAL_SPACING } from '../view/layout';
import {
  containsNode,
  createFromTree,
  detachMindmap,
  findTargetNode,
  hideNodeConnector,
  tryMoveNode,
} from '../view/utils';
import { calculateResponseArea } from './drag-utils';

type DragMindMapCtx = {
  mindmap: MindmapElementModel;
  node: MindmapNode;
  /**
   * Whether the dragged node is the root node of the mind map
   */
  isRoot: boolean;
  originalMindMapBound: Bound;
};

export class MindMapDragExtension extends TransformExtension {
  static override key = 'mind-map-drag';
  /**
   * The response area of the mind map is calculated in real time.
   * It only needs to be calculated once when the mind map is dragged.
   */
  private readonly _responseAreaUpdated = new Set<MindmapElementModel>();

  private get _indicatorOverlay() {
    return this.std.getOptional(
      OverlayIdentifier('mindmap-indicator')
    ) as MindMapIndicatorOverlay | null;
  }

  private _calcDragResponseArea(mindmap: MindmapElementModel) {
    calculateResponseArea(mindmap);
    this._responseAreaUpdated.add(mindmap);
  }

  /**
   * Create handlers that can drag and drop mind map nodes
   * @param dragMindMapCtx
   * @param dragState
   * @returns
   */
  private _createManipulationHandlers(dragMindMapCtx: DragMindMapCtx): {
    onDragMove?: (context: ExtensionDragMoveContext) => void;
    onDragEnd?: (context: ExtensionDragEndContext) => void;
  } {
    let hoveredCtx: {
      mindmap: MindmapElementModel | null;
      node: MindmapNode | null;
      detach?: boolean;
      abort?: () => void;
      merge?: () => void;
    } | null = null;

    return {
      onDragMove: (context: ExtensionDragMoveContext) => {
        const { x, y } = context.dragLastPos;
        const hoveredMindMap = this._getHoveredMindMap([x, y], dragMindMapCtx);
        const indicator = this._indicatorOverlay;

        if (indicator) {
          indicator.currentDragPos = [x, y];
          indicator.refresh();
        }

        hoveredCtx?.abort?.();

        const hoveredNode = hoveredMindMap
          ? findTargetNode(hoveredMindMap, [x, y])
          : null;

        hoveredCtx = {
          mindmap: hoveredMindMap,
          node: hoveredNode,
        };

        // hovered on the currently dragged mind map but
        // 1. not hovered on any node or
        // 2. hovered on the node that is itself or its children (which is not allowed)
        // then consider user is trying to drop the node to its original position
        if (
          hoveredNode &&
          hoveredMindMap &&
          !containsNode(hoveredMindMap, hoveredNode, dragMindMapCtx.node)
        ) {
          const operation = tryMoveNode(
            hoveredMindMap,
            hoveredNode,
            dragMindMapCtx.mindmap,
            dragMindMapCtx.node,
            [x, y],
            options => this._drawIndicator(options)
          );

          if (operation) {
            hoveredCtx.abort = operation.abort;
            hoveredCtx.merge = operation.merge;
          }
        } else if (dragMindMapCtx.isRoot) {
          dragMindMapCtx.mindmap.layout();
          hoveredCtx.merge = () => {
            dragMindMapCtx.mindmap.layout();
          };
        } else {
          // if `hoveredMindMap` is not null
          // either the node is hovered on the dragged node's children
          // or the there is no hovered node at all
          // then consider user is trying to place the node to its original position
          if (hoveredMindMap) {
            const { node: draggedNode, mindmap } = dragMindMapCtx;
            const nodeBound = draggedNode.element.elementBound;

            hoveredCtx.abort = this._drawIndicator({
              targetMindMap: mindmap,
              target: draggedNode,
              sourceMindMap: mindmap,
              source: draggedNode,
              newParent: draggedNode.parent!,
              insertPosition: {
                type: 'sibling',
                layoutDir: mindmap.getLayoutDir(draggedNode) as Exclude<
                  LayoutType,
                  LayoutType.BALANCE
                >,
                position: y > nodeBound.y + nodeBound.h / 2 ? 'next' : 'prev',
              },
              path: mindmap.getPath(draggedNode),
            });
          } else {
            hoveredCtx.detach = true;

            const reset = (hoveredCtx.abort = hideNodeConnector(
              dragMindMapCtx.mindmap,
              dragMindMapCtx.node
            ));

            hoveredCtx.abort = () => {
              reset?.();
            };
          }
        }
      },
      onDragEnd: (dragEndContext: ExtensionDragEndContext) => {
        if (hoveredCtx?.merge) {
          hoveredCtx.merge();
        } else {
          hoveredCtx?.abort?.();

          if (hoveredCtx?.detach) {
            const { x: startX, y: startY } = dragEndContext.dragStartPos;
            const { x: endX, y: endY } = dragEndContext.dragLastPos;

            dragMindMapCtx.node.element.xywh =
              dragMindMapCtx.node.element.elementBound
                .moveDelta(endX - startX, endY - startY)
                .serialize();

            if (dragMindMapCtx.node !== dragMindMapCtx.mindmap.tree) {
              detachMindmap(dragMindMapCtx.mindmap, dragMindMapCtx.node);
              const mindmap = createFromTree(
                dragMindMapCtx.node,
                dragMindMapCtx.mindmap.style,
                dragMindMapCtx.mindmap.layoutType,
                this.gfx.surface!
              );

              mindmap.layout();
            } else {
              dragMindMapCtx.mindmap.layout();
            }
          }
        }

        hoveredCtx = null;
        this._responseAreaUpdated.clear();
      },
    };
  }

  /**
   * Create handlers that can translate entire mind map
   */
  private _createTranslationHandlers(ctx: {
    mindmaps: Set<MindmapElementModel>;
    nodes: Set<GfxModel>;
  }): {
    onDragStart?: (context: ExtensionDragStartContext) => void;
    onDragMove?: (context: ExtensionDragMoveContext) => void;
    onDragEnd?: (context: ExtensionDragEndContext) => void;
  } {
    return {
      onDragStart: () => {
        ctx.nodes.forEach(node => {
          node.stash('xywh');
        });
      },
      onDragEnd: () => {
        ctx.mindmaps.forEach(mindmap => {
          mindmap.layout();
        });
      },
    };
  }

  private _drawIndicator(options: {
    targetMindMap: MindmapElementModel;
    target: MindmapNode;
    sourceMindMap: MindmapElementModel;
    source: MindmapNode;
    newParent: MindmapNode;
    insertPosition:
      | {
          type: 'sibling';
          layoutDir: Exclude<LayoutType, LayoutType.BALANCE>;
          position: 'prev' | 'next';
        }
      | { type: 'child'; layoutDir: Exclude<LayoutType, LayoutType.BALANCE> };
    path: number[];
  }) {
    const indicatorOverlay = this._indicatorOverlay;

    if (!indicatorOverlay) {
      return () => {};
    }

    // draw the indicator at given position
    const { newParent, insertPosition, targetMindMap, target, source, path } =
      options;
    const children = newParent.children.filter(
      node => node.element.id !== source.id
    );

    indicatorOverlay.setIndicatorInfo({
      targetMindMap,
      target,
      parent: newParent,
      insertPosition,
      parentChildren: children,
      path,
    });

    return () => {
      indicatorOverlay.clear();
    };
  }

  private _getHoveredMindMap(
    position: IVec,
    dragMindMapCtx: DragMindMapCtx
  ): MindmapElementModel | null {
    const mindmap =
      (this.gfx
        .getElementByPoint(position[0], position[1], {
          all: true,
          responsePadding: [NODE_HORIZONTAL_SPACING, NODE_VERTICAL_SPACING * 2],
        })
        .find(el => {
          if (!(el instanceof MindmapElementModel)) {
            return false;
          }

          if (
            el === dragMindMapCtx.mindmap &&
            !dragMindMapCtx.originalMindMapBound.containsPoint(position)
          ) {
            return false;
          }

          return true;
        }) as MindmapElementModel) ?? null;

    if (
      mindmap &&
      (!this._responseAreaUpdated.has(mindmap) || !mindmap.tree.responseArea)
    ) {
      this._calcDragResponseArea(mindmap);
    }

    return mindmap;
  }

  private _setupDragNodeImage(
    mindmapNode: MindmapNode,
    pos: { x: number; y: number }
  ) {
    const surfaceBlock = this.gfx.surfaceComponent as SurfaceBlockComponent;
    const renderer = surfaceBlock?.renderer;
    const indicatorOverlay = this._indicatorOverlay;

    if (!renderer || !indicatorOverlay) {
      return;
    }

    const nodeBound = mindmapNode.element.elementBound;

    const canvas = renderer.getCanvasByBound(
      mindmapNode.element.elementBound,
      [mindmapNode.element],
      undefined,
      undefined,
      false
    );

    indicatorOverlay.dragNodePos = [nodeBound.x - pos.x, nodeBound.y - pos.y];
    indicatorOverlay.dragNodeImage = canvas;

    return () => {
      indicatorOverlay.dragNodeImage = null;
      indicatorOverlay.currentDragPos = null;
    };
  }

  private _updateNodeOpacity(
    mindmap: MindmapElementModel,
    mindNode: MindmapNode
  ) {
    const OPACITY = 0.3;
    const updatedNodes = new Set<
      GfxPrimitiveElementModel | LocalConnectorElementModel
    >();
    const traverse = (node: MindmapNode, parent: MindmapNode | null) => {
      node.element.opacity = OPACITY;
      updatedNodes.add(node.element);

      if (parent) {
        const connectorId = `#${parent.element.id}-${node.element.id}`;
        const connector = mindmap.connectors.get(connectorId);

        if (connector) {
          connector.opacity = OPACITY;
          updatedNodes.add(connector);
        }
      }

      if (node.children.length) {
        node.children.forEach(child => traverse(child, node));
      }
    };

    const parentNode = mindmap.getParentNode(mindNode.element.id) ?? null;

    traverse(mindNode, parentNode);

    return () => {
      updatedNodes.forEach(el => {
        el.opacity = 1;
      });
    };
  }

  override onDragInitialize(context: DragExtensionInitializeContext) {
    if (isSingleMindMapNode(context.elements)) {
      const mindmap = context.elements[0].group as MindmapElementModel;
      const mindmapNode = mindmap.getNode(context.elements[0].id)!;
      const mindmapBound = mindmap.elementBound;
      const isRoot = mindmapNode === mindmap.tree;

      mindmapBound.x -= NODE_HORIZONTAL_SPACING;
      mindmapBound.y -= NODE_VERTICAL_SPACING * 2;
      mindmapBound.w += NODE_HORIZONTAL_SPACING * 2;
      mindmapBound.h += NODE_VERTICAL_SPACING * 4;

      this._calcDragResponseArea(mindmap);

      const clearDragStatus = isRoot
        ? mindmap.stashTree(mindmapNode)
        : this._setupDragNodeImage(mindmapNode, context.dragStartPos);
      const clearOpacity = this._updateNodeOpacity(mindmap, mindmapNode);

      if (!isRoot) {
        context.elements.splice(0, 1);
      }

      const mindMapDragCtx: DragMindMapCtx = {
        mindmap,
        node: mindmapNode,
        isRoot,
        originalMindMapBound: mindmapBound,
      };

      return {
        ...this._createManipulationHandlers(mindMapDragCtx),
        clear() {
          clearOpacity();
          clearDragStatus?.();
          if (!isRoot) {
            context.elements.push(mindmapNode.element);
          }
        },
      };
    }

    const mindmapNodes = new Set<GfxModel>();
    const mindmaps = new Set<MindmapElementModel>();

    context.elements.forEach(el => {
      if (isMindmapNode(el)) {
        const mindmap =
          el.group instanceof MindmapElementModel
            ? el.group
            : (el as MindmapElementModel);

        mindmaps.add(mindmap);
        mindmap.childElements.forEach(child => mindmapNodes.add(child));
      } else if (isGfxGroupCompatibleModel(el)) {
        el.descendantElements.forEach(desc => {
          if (desc.group instanceof MindmapElementModel) {
            mindmaps.add(desc.group);
            desc.group.childElements.forEach(_el => mindmapNodes.add(_el));
          }
        });
      }
    });

    if (mindmapNodes.size > 1) {
      mindmapNodes.forEach(node => context.elements.push(node));
      return this._createTranslationHandlers({
        mindmaps,
        nodes: mindmapNodes,
      });
    }

    return {};
  }
}