/**
 * YjsDocument – Manages a Y.Doc with shared maps for CAD elements, layers, and blocks.
 * Provides helpers to sync local state with the CRDT document.
 */
import * as Y from 'yjs';
import type { CADElement, CADLayer, BlockDefinition } from '../types/cad.types';
import type { ElementGroup } from '../tools/modification/GroupTool';
import type { BackgroundConfig } from '../services/backgroundService';
import type { LayoutDefinition } from '../types/cad.types';

export interface YjsDocumentData {
  elements: Y.Map<CADElement>;
  layers: Y.Map<CADLayer>;
  blocks: Y.Map<BlockDefinition>;
  meta: Y.Map<unknown>;
  groups: Y.Map<ElementGroup>;
  bgConfig: Y.Map<BackgroundConfig>;
  layouts: Y.Map<LayoutDefinition>; // Task G1
}

export class YjsDocument {
  readonly doc: Y.Doc;
  readonly data: YjsDocumentData;

  constructor() {
    this.doc = new Y.Doc();
    this.data = {
      elements: this.doc.getMap<CADElement>('elements'),
      layers: this.doc.getMap<CADLayer>('layers'),
      blocks: this.doc.getMap<BlockDefinition>('blocks'),
      meta: this.doc.getMap<unknown>('meta'),
      groups: this.doc.getMap<ElementGroup>('groups'),
      bgConfig: this.doc.getMap<BackgroundConfig>('bgConfig'),
      layouts: this.doc.getMap<LayoutDefinition>('layouts'),
    };
  }

  /** Get all elements as a plain array */
  getElements(): CADElement[] {
    return Array.from(this.data.elements.values());
  }

  /** Get all layers as a plain array */
  getLayers(): CADLayer[] {
    return Array.from(this.data.layers.values());
  }

  /** Get all blocks as a plain array */
  getBlocks(): BlockDefinition[] {
    return Array.from(this.data.blocks.values());
  }

  /** Get all groups as a plain array */
  getGroups(): ElementGroup[] {
    return Array.from(this.data.groups.values());
  }

  /** Get all background configs as a plain array */
  getBgConfigs(): BackgroundConfig[] {
    return Array.from(this.data.bgConfig.values());
  }

  /** Get all layouts as a plain array (Task G1) */
  getLayouts(): LayoutDefinition[] {
    return Array.from(this.data.layouts.values());
  }

  /** Add or update a single element */
  setElement(el: CADElement): void {
    this.doc.transact(() => {
      this.data.elements.set(el.id, el);
    });
  }

  /** Remove an element by id */
  deleteElement(id: string): void {
    this.data.elements.delete(id);
  }

  /** Add or update a layer */
  setLayer(layer: CADLayer): void {
    this.data.layers.set(layer.id, layer);
  }

  /** Remove a layer by id */
  deleteLayer(id: string): void {
    this.data.layers.delete(id);
  }

  /** Add or update a block definition */
  setBlock(block: BlockDefinition): void {
    this.data.blocks.set(block.id, block);
  }

  /** Remove a block by id */
  deleteBlock(id: string): void {
    this.data.blocks.delete(id);
  }

  /** Add or update a group */
  setGroup(group: ElementGroup): void {
    this.doc.transact(() => {
      this.data.groups.set(group.id, group);
    });
  }

  /** Remove a group by id */
  deleteGroup(id: string): void {
    this.data.groups.delete(id);
  }

  /** Add or update a background config */
  setBgConfig(id: string, config: BackgroundConfig): void {
    this.doc.transact(() => {
      this.data.bgConfig.set(id, config);
    });
  }

  /** Remove a background config by id */
  deleteBgConfig(id: string): void {
    this.data.bgConfig.delete(id);
  }

  /** Bulk-load local state into the Y.Doc (replaces all content) */
  loadFromState(state: {
    elements: CADElement[];
    layers: CADLayer[];
    blocks: BlockDefinition[];
    groups?: ElementGroup[];
    bgConfigs?: BackgroundConfig[];
  }): void {
    this.doc.transact(() => {
      // Issue #7: Only clear and replace a map if the incoming array is non-empty.
      // Clearing maps when data is empty wipes CRDT data from other connected clients.
      if (state.elements.length > 0) {
        this.data.elements.clear();
        for (const el of state.elements) {
          this.data.elements.set(el.id, el);
        }
      }
      if (state.layers.length > 0) {
        this.data.layers.clear();
        for (const layer of state.layers) {
          this.data.layers.set(layer.id, layer);
        }
      }
      if (state.blocks.length > 0) {
        this.data.blocks.clear();
        for (const block of state.blocks) {
          this.data.blocks.set(block.id, block);
        }
      }
      if (state.groups && state.groups.length > 0) {
        this.data.groups.clear();
        for (const group of state.groups) {
          this.data.groups.set(group.id, group);
        }
      }
      if (state.bgConfigs && state.bgConfigs.length > 0) {
        this.data.bgConfig.clear();
        for (const cfg of state.bgConfigs) {
          // Use 'default' as the key since there is typically one background config
          this.data.bgConfig.set(cfg.name || 'default', cfg);
        }
      }
    });
  }

  /** Export current state as a plain object */
  toState(): {
    elements: CADElement[];
    layers: CADLayer[];
    blocks: BlockDefinition[];
    groups: ElementGroup[];
    bgConfigs: BackgroundConfig[];
  } {
    return {
      elements: this.getElements(),
      layers: this.getLayers(),
      blocks: this.getBlocks(),
      groups: this.getGroups(),
      bgConfigs: this.getBgConfigs(),
    };
  }

  /** Encode full document state as update binary */
  encodeState(): Uint8Array {
    return Y.encodeStateAsUpdate(this.doc);
  }

  /** Apply a remote update binary */
  applyUpdate(update: Uint8Array): void {
    Y.applyUpdate(this.doc, update);
  }

  /** Register a callback for document changes */
  onChange(callback: () => void): () => void {
    this.doc.on('update', callback);
    return () => this.doc.off('update', callback);
  }

  /** Destroy the document */
  destroy(): void {
    this.doc.destroy();
  }
}