Cursors and Enhancements

/**
 * Gap cursor selection type for positioning between blocks
 */
class GapCursor extends Selection {
  /**
   * Create a gap cursor at the given position
   */
  constructor(pos: ResolvedPos, side: -1 | 1);
  
  /**
   * Position of the gap cursor
   */
  $pos: ResolvedPos;
  
  /**
   * Side of the gap (-1 for before, 1 for after)
   */
  side: -1 | 1;
  
  /**
   * Check if gap cursor is valid at position
   */
  static valid($pos: ResolvedPos): boolean;
  
  /**
   * Find gap cursor near position
   */
  static findGapCursorFrom($pos: ResolvedPos, dir: -1 | 1, mustMove?: boolean): GapCursor | null;
}

/**
 * Create gap cursor plugin
 */
function gapCursor(): Plugin;

/**
 * Create drop cursor plugin
 */
function dropCursor(options?: DropCursorOptions): Plugin;

/**
 * Drop cursor configuration options
 */
interface DropCursorOptions {
  /**
   * Color of the drop cursor (default: black)
   */
  color?: string;
  
  /**
   * Width of the drop cursor line (default: 1px)
   */
  width?: number;
  
  /**
   * CSS class for the drop cursor
   */
  class?: string;
}

/**
 * Create trailing node plugin
 */
function trailingNode(options: TrailingNodeOptions): Plugin;

/**
 * Trailing node configuration options
 */
interface TrailingNodeOptions {
  /**
   * Node type to ensure at document end
   */
  node: string | NodeType;
  
  /**
   * Node types that should not be at document end
   */
  notAfter?: (string | NodeType)[];
}

/**
 * Represents a span of changed content
 */
class Span {
  /**
   * Create a change span
   */
  constructor(from: number, to: number, data?: any);
  
  /**
   * Start position
   */
  from: number;
  
  /**
   * End position  
   */
  to: number;
  
  /**
   * Associated metadata
   */
  data: any;
}

/**
 * Represents a specific change with content
 */
class Change {
  /**
   * Create a change
   */
  constructor(from: number, to: number, inserted: Fragment, data?: any);
  
  /**
   * Start position of change
   */
  from: number;
  
  /**
   * End position of change
   */
  to: number;
  
  /**
   * Inserted content
   */
  inserted: Fragment;
  
  /**
   * Change metadata
   */
  data: any;
}

/**
 * Tracks all changes in a document
 */
class ChangeSet {
  /**
   * Create change set from document comparison
   */
  static create(doc: Node, changes?: Change[]): ChangeSet;
  
  /**
   * Array of changes
   */
  changes: Change[];
  
  /**
   * Add a change to the set
   */
  addChange(change: Change): ChangeSet;
  
  /**
   * Map change set through transformation
   */
  map(mapping: Mappable): ChangeSet;
  
  /**
   * Simplify changes for presentation
   */
  simplify(): ChangeSet;
}

/**
 * Simplify changes by merging adjacent changes
 */
function simplifyChanges(changes: Change[], doc: Node): Change[];

import { 
  GapCursor, 
  gapCursor,
  dropCursor,
  trailingNode,
  ChangeSet,
  simplifyChanges 
} from "@tiptap/pm/gapcursor";
import "@tiptap/pm/dropcursor";
import "@tiptap/pm/trailing-node";
import "@tiptap/pm/changeset";

// Basic cursor enhancements setup
const enhancementPlugins = [
  // Gap cursor for block navigation
  gapCursor(),
  
  // Drop cursor for drag operations
  dropCursor({
    color: "#3b82f6",
    width: 2,
    class: "custom-drop-cursor"
  }),
  
  // Ensure document ends with paragraph
  trailingNode({
    node: "paragraph",
    notAfter: ["heading", "code_block"]
  })
];

// Create editor with enhancements
const state = EditorState.create({
  schema: mySchema,
  plugins: enhancementPlugins
});

// Custom gap cursor handling
class GapCursorManager {
  constructor(private view: EditorView) {
    this.setupKeyboardNavigation();
  }
  
  private setupKeyboardNavigation() {
    const plugin = keymap({
      "ArrowUp": this.navigateUp.bind(this),
      "ArrowDown": this.navigateDown.bind(this),
      "ArrowLeft": this.navigateLeft.bind(this),
      "ArrowRight": this.navigateRight.bind(this)
    });
    
    const newState = this.view.state.reconfigure({
      plugins: this.view.state.plugins.concat(plugin)
    });
    this.view.updateState(newState);
  }
  
  private navigateUp(state: EditorState, dispatch?: (tr: Transaction) => void): boolean {
    return this.navigateVertically(state, dispatch, -1);
  }
  
  private navigateDown(state: EditorState, dispatch?: (tr: Transaction) => void): boolean {
    return this.navigateVertically(state, dispatch, 1);
  }
  
  private navigateVertically(
    state: EditorState, 
    dispatch?: (tr: Transaction) => void, 
    dir: -1 | 1
  ): boolean {
    const { selection } = state;
    
    if (selection instanceof GapCursor) {
      // Find next gap cursor position
      const nextGap = GapCursor.findGapCursorFrom(selection.$pos, dir, true);
      if (nextGap && dispatch) {
        dispatch(state.tr.setSelection(nextGap));
        return true;
      }
    }
    
    return false;
  }
  
  private navigateLeft(state: EditorState, dispatch?: (tr: Transaction) => void): boolean {
    return this.navigateHorizontally(state, dispatch, -1);
  }
  
  private navigateRight(state: EditorState, dispatch?: (tr: Transaction) => void): boolean {
    return this.navigateHorizontally(state, dispatch, 1);
  }
  
  private navigateHorizontally(
    state: EditorState,
    dispatch?: (tr: Transaction) => void,
    dir: -1 | 1
  ): boolean {
    const { selection } = state;
    
    // Try to find gap cursor from current selection
    const $pos = dir === -1 ? selection.$from : selection.$to;
    const gap = GapCursor.findGapCursorFrom($pos, dir, false);
    
    if (gap && dispatch) {
      dispatch(state.tr.setSelection(gap));
      return true;
    }
    
    return false;
  }
}

// Enhanced drop cursor with custom behavior
class EnhancedDropCursor {
  private plugin: Plugin;
  
  constructor(options?: DropCursorOptions & { 
    onDrop?: (pos: number, data: any) => void;
    canDrop?: (pos: number, data: any) => boolean;
  }) {
    this.plugin = new Plugin({
      state: {
        init: () => null,
        apply: (tr, value) => {
          const meta = tr.getMeta("drop-cursor");
          if (meta !== undefined) {
            return meta;
          }
          return value;
        }
      },
      
      props: {
        decorations: (state) => {
          const dropPos = this.plugin.getState(state);
          if (dropPos) {
            return this.createDropDecoration(dropPos, options);
          }
          return null;
        },
        
        handleDrop: (view, event, slice, moved) => {
          if (options?.onDrop) {
            const pos = view.posAtCoords({
              left: event.clientX,
              top: event.clientY
            });
            
            if (pos && (!options.canDrop || options.canDrop(pos.pos, slice))) {
              options.onDrop(pos.pos, slice);
              return true;
            }
          }
          return false;
        },
        
        handleDOMEvents: {
          dragover: (view, event) => {
            const pos = view.posAtCoords({
              left: event.clientX,
              top: event.clientY
            });
            
            if (pos) {
              view.dispatch(
                view.state.tr.setMeta("drop-cursor", pos.pos)
              );
            }
            
            return false;
          },
          
          dragleave: (view) => {
            view.dispatch(
              view.state.tr.setMeta("drop-cursor", null)
            );
            return false;
          }
        }
      }
    });
  }
  
  private createDropDecoration(pos: number, options?: DropCursorOptions): DecorationSet {
    const widget = document.createElement("div");
    widget.className = `drop-cursor ${options?.class || ""}`;
    widget.style.position = "absolute";
    widget.style.width = `${options?.width || 1}px`;
    widget.style.backgroundColor = options?.color || "black";
    widget.style.height = "1.2em";
    widget.style.pointerEvents = "none";
    
    return DecorationSet.create(document, [
      Decoration.widget(pos, widget, { side: 1 })
    ]);
  }
  
  getPlugin(): Plugin {
    return this.plugin;
  }
}

// Advanced trailing node with custom rules
class SmartTrailingNode {
  constructor(options: {
    trailingNode: NodeType;
    rules?: Array<{
      after: NodeType[];
      insert: NodeType;
      attrs?: Attrs;
    }>;
  }) {
    this.setupPlugin(options);
  }
  
  private setupPlugin(options: any) {
    const plugin = new Plugin({
      appendTransaction: (transactions, oldState, newState) => {
        const lastTransaction = transactions[transactions.length - 1];
        if (!lastTransaction?.docChanged) return null;
        
        return this.ensureTrailingNode(newState, options);
      }
    });
    
    // Add plugin to existing state
    // Implementation depends on specific usage
  }
  
  private ensureTrailingNode(state: EditorState, options: any): Transaction | null {
    const { doc } = state;
    const lastChild = doc.lastChild;
    
    if (!lastChild) {
      // Empty document - add trailing node
      const tr = state.tr;
      const trailingNode = options.trailingNode.createAndFill();
      tr.insert(doc.content.size, trailingNode);
      return tr;
    }
    
    // Check custom rules
    if (options.rules) {
      for (const rule of options.rules) {
        if (rule.after.includes(lastChild.type)) {
          const tr = state.tr;
          const insertNode = rule.insert.create(rule.attrs);
          tr.insert(doc.content.size, insertNode);
          return tr;
        }
      }
    }
    
    // Default trailing node check
    if (lastChild.type !== options.trailingNode) {
      const tr = state.tr;
      const trailingNode = options.trailingNode.createAndFill();
      tr.insert(doc.content.size, trailingNode);
      return tr;
    }
    
    return null;
  }
}

class BlockSelection extends Selection {
  constructor($pos: ResolvedPos) {
    super($pos, $pos);
  }
  
  static create(doc: Node, pos: number): BlockSelection {
    const $pos = doc.resolve(pos);
    return new BlockSelection($pos);
  }
  
  map(doc: Node, mapping: Mappable): Selection {
    const newPos = mapping.map(this.from);
    return BlockSelection.create(doc, newPos);
  }
  
  eq(other: Selection): boolean {
    return other instanceof BlockSelection && other.from === this.from;
  }
  
  getBookmark(): SelectionBookmark {
    return new BlockBookmark(this.from);
  }
}

class BlockBookmark implements SelectionBookmark {
  constructor(private pos: number) {}
  
  map(mapping: Mappable): SelectionBookmark {
    return new BlockBookmark(mapping.map(this.pos));
  }
  
  resolve(doc: Node): Selection {
    return BlockSelection.create(doc, this.pos);
  }
}

class VisualEnhancementPlugin {
  static createReadingGuide(): Plugin {
    return new Plugin({
      state: {
        init: () => null,
        apply: (tr, value) => {
          const meta = tr.getMeta("reading-guide");
          if (meta !== undefined) return meta;
          return value;
        }
      },
      
      props: {
        decorations: (state) => {
          const linePos = this.getState(state);
          if (linePos) {
            return this.createReadingGuide(linePos);
          }
          return null;
        },
        
        handleDOMEvents: {
          mousemove: (view, event) => {
            const pos = view.posAtCoords({
              left: event.clientX,
              top: event.clientY
            });
            
            if (pos) {
              view.dispatch(
                view.state.tr.setMeta("reading-guide", pos.pos)
              );
            }
            
            return false;
          }
        }
      }
    });
  }
  
  private static createReadingGuide(pos: number): DecorationSet {
    // Create horizontal line decoration
    const guide = document.createElement("div");
    guide.className = "reading-guide";
    guide.style.cssText = `
      position: absolute;
      width: 100%;
      height: 1px;
      background: rgba(0, 100, 200, 0.3);
      pointer-events: none;
      z-index: 1;
    `;
    
    return DecorationSet.create(document, [
      Decoration.widget(pos, guide, { side: 0 })
    ]);
  }
  
  static createFocusMode(): Plugin {
    return new Plugin({
      state: {
        init: () => ({ focused: false, paragraph: null }),
        apply: (tr, value) => {
          const selection = tr.selection;
          const $pos = selection.$from;
          const currentParagraph = $pos.node($pos.depth);
          
          return {
            focused: selection.empty,
            paragraph: currentParagraph
          };
        }
      },
      
      props: {
        decorations: (state) => {
          const pluginState = this.getState(state);
          if (pluginState.focused && pluginState.paragraph) {
            return this.createFocusDecorations(state, pluginState.paragraph);
          }
          return null;
        }
      }
    });
  }
  
  private static createFocusDecorations(state: EditorState, focusedNode: Node): DecorationSet {
    const decorations: Decoration[] = [];
    
    // Dim all other paragraphs
    state.doc.descendants((node, pos) => {
      if (node.type.name === "paragraph" && node !== focusedNode) {
        decorations.push(
          Decoration.node(pos, pos + node.nodeSize, {
            class: "dimmed-paragraph",
            style: "opacity: 0.4; transition: opacity 0.2s;"
          })
        );
      }
    });
    
    return DecorationSet.create(state.doc, decorations);
  }
}

class ChangeTracker {
  private changeSet: ChangeSet;
  private baseDoc: Node;
  
  constructor(baseDoc: Node) {
    this.baseDoc = baseDoc;
    this.changeSet = ChangeSet.create(baseDoc);
  }
  
  trackChanges(oldState: EditorState, newState: EditorState): ChangeSet {
    if (!newState.tr.docChanged) {
      return this.changeSet;
    }
    
    const changes: Change[] = [];
    
    // Extract changes from transaction steps
    newState.tr.steps.forEach((step, index) => {
      if (step instanceof ReplaceStep) {
        const change = new Change(
          step.from,
          step.to,
          step.slice.content,
          {
            timestamp: Date.now(),
            user: this.getCurrentUser(),
            type: "replace"
          }
        );
        changes.push(change);
      }
      
      if (step instanceof AddMarkStep) {
        const change = new Change(
          step.from,
          step.to,
          Fragment.empty,
          {
            timestamp: Date.now(),
            user: this.getCurrentUser(),
            type: "add-mark",
            mark: step.mark
          }
        );
        changes.push(change);
      }
    });
    
    // Update change set
    let newChangeSet = this.changeSet;
    for (const change of changes) {
      newChangeSet = newChangeSet.addChange(change);
    }
    
    this.changeSet = newChangeSet.simplify();
    return this.changeSet;
  }
  
  createChangeDecorations(): DecorationSet {
    const decorations: Decoration[] = [];
    
    for (const change of this.changeSet.changes) {
      const className = `change-${change.data.type}`;
      const title = `${change.data.user} at ${new Date(change.data.timestamp).toLocaleString()}`;
      
      decorations.push(
        Decoration.inline(change.from, change.to, {
          class: className,
          title
        })
      );
    }
    
    return DecorationSet.create(this.baseDoc, decorations);
  }
  
  acceptChanges(from?: number, to?: number): ChangeSet {
    const filteredChanges = this.changeSet.changes.filter(change => {
      if (from !== undefined && to !== undefined) {
        return !(change.from >= from && change.to <= to);
      }
      return false;
    });
    
    this.changeSet = ChangeSet.create(this.baseDoc, filteredChanges);
    return this.changeSet;
  }
  
  rejectChanges(from?: number, to?: number): Node {
    // Revert changes in the specified range
    // This would require more complex implementation
    return this.baseDoc;
  }
  
  private getCurrentUser(): string {
    // Get current user identifier
    return "current-user";
  }
}

class AccessibilityEnhancer {
  static createAriaLiveRegion(): Plugin {
    return new Plugin({
      view: () => {
        const liveRegion = document.createElement("div");
        liveRegion.setAttribute("aria-live", "polite");
        liveRegion.setAttribute("aria-atomic", "true");
        liveRegion.style.cssText = `
          position: absolute;
          left: -10000px;
          width: 1px;
          height: 1px;
          overflow: hidden;
        `;
        document.body.appendChild(liveRegion);
        
        return {
          update: (view, prevState) => {
            if (prevState.selection.eq(view.state.selection)) return;
            
            const announcement = this.createSelectionAnnouncement(view.state.selection);
            if (announcement) {
              liveRegion.textContent = announcement;
            }
          },
          
          destroy: () => {
            liveRegion.remove();
          }
        };
      }
    });
  }
  
  private static createSelectionAnnouncement(selection: Selection): string {
    if (selection instanceof GapCursor) {
      return "Gap cursor between blocks";
    }
    
    if (selection.empty) {
      return `Cursor at position ${selection.from}`;
    }
    
    const length = selection.to - selection.from;
    return `Selected ${length} character${length === 1 ? "" : "s"}`;
  }
  
  static createKeyboardNavigation(): Plugin {
    return keymap({
      "Alt-ArrowUp": (state, dispatch) => {
        // Move to previous block
        return this.navigateToBlock(state, dispatch, -1);
      },
      
      "Alt-ArrowDown": (state, dispatch) => {
        // Move to next block
        return this.navigateToBlock(state, dispatch, 1);
      },
      
      "Ctrl-Home": (state, dispatch) => {
        // Move to document start
        if (dispatch) {
          dispatch(state.tr.setSelection(Selection.atStart(state.doc)));
        }
        return true;
      },
      
      "Ctrl-End": (state, dispatch) => {
        // Move to document end
        if (dispatch) {
          dispatch(state.tr.setSelection(Selection.atEnd(state.doc)));
        }
        return true;
      }
    });
  }
  
  private static navigateToBlock(
    state: EditorState,
    dispatch?: (tr: Transaction) => void,
    direction: -1 | 1
  ): boolean {
    const { selection } = state;
    const $pos = selection.$from;
    
    // Find next block element
    let depth = $pos.depth;
    while (depth > 0) {
      const node = $pos.node(depth);
      if (node.isBlock) {
        const nodePos = $pos.start(depth);
        const nextPos = direction === -1 
          ? nodePos - 1 
          : nodePos + node.nodeSize;
        
        try {
          const $nextPos = state.doc.resolve(nextPos);
          const nextBlock = direction === -1 
            ? $nextPos.nodeBefore 
            : $nextPos.nodeAfter;
          
          if (nextBlock?.isBlock && dispatch) {
            const targetPos = direction === -1 
              ? nextPos - nextBlock.nodeSize + 1
              : nextPos + 1;
            
            dispatch(
              state.tr.setSelection(
                Selection.near(state.doc.resolve(targetPos))
              )
            );
            return true;
          }
        } catch (error) {
          // Position out of bounds
          break;
        }
      }
      depth--;
    }
    
    return false;
  }
}

/**
 * Drop cursor configuration options
 */
interface DropCursorOptions {
  color?: string;
  width?: number;
  class?: string;
}

/**
 * Trailing node configuration options
 */
interface TrailingNodeOptions {
  node: string | NodeType;
  notAfter?: (string | NodeType)[];
}

/**
 * Change metadata interface
 */
interface ChangeData {
  timestamp: number;
  user: string;
  type: string;
  [key: string]: any;
}

/**
 * Selection bookmark interface
 */
interface SelectionBookmark {
  map(mapping: Mappable): SelectionBookmark;
  resolve(doc: Node): Selection;
}