// https://github.com/microsoft/tabster/blob/a89fc5d7e332d48f68d03b1ca6e344489d1c3898/src/Shadowdomize/ShadowTreeWalker.ts

import {nodeContains} from './DOMFunctions';
import {shadowDOM} from '@react-stately/flags';

export class ShadowTreeWalker implements TreeWalker {
  public readonly filter: NodeFilter | null;
  public readonly root: Node;
  public readonly whatToShow: number;

  private _doc: Document;
  private _walkerStack: Array<TreeWalker> = [];
  private _currentNode: Node;
  private _currentSetFor: Set<TreeWalker> = new Set();

  constructor(
      doc: Document,
      root: Node,
      whatToShow?: number,
      filter?: NodeFilter | null
    ) {
    this._doc = doc;
    this.root = root;
    this.filter = filter ?? null;
    this.whatToShow = whatToShow ?? NodeFilter.SHOW_ALL;
    this._currentNode = root;

    this._walkerStack.unshift(
      doc.createTreeWalker(root, whatToShow, this._acceptNode)
    );

    const shadowRoot = (root as Element).shadowRoot;

    if (shadowRoot) {
      const walker = this._doc.createTreeWalker(
        shadowRoot,
        this.whatToShow,
        {acceptNode: this._acceptNode}
      );

      this._walkerStack.unshift(walker);
    }
  }

  private _acceptNode = (node: Node): number => {
    if (node.nodeType === Node.ELEMENT_NODE) {
      const shadowRoot = (node as Element).shadowRoot;

      if (shadowRoot) {
        const walker = this._doc.createTreeWalker(
          shadowRoot,
          this.whatToShow,
          {acceptNode: this._acceptNode}
        );

        this._walkerStack.unshift(walker);

        return NodeFilter.FILTER_ACCEPT;
      } else {
        if (typeof this.filter === 'function') {
          return this.filter(node);
        } else if (this.filter?.acceptNode) {
          return this.filter.acceptNode(node);
        } else if (this.filter === null) {
          return NodeFilter.FILTER_ACCEPT;
        }
      }
    }

    return NodeFilter.FILTER_SKIP;
  };

  public get currentNode(): Node {
    return this._currentNode;
  }

  public set currentNode(node: Node) {
    if (!nodeContains(this.root, node)) {
      throw new Error(
        'Cannot set currentNode to a node that is not contained by the root node.'
      );
    }

    const walkers: TreeWalker[] = [];
    let curNode: Node | null | undefined = node;
    let currentWalkerCurrentNode = node;

    this._currentNode = node;

    while (curNode && curNode !== this.root) {
      if (curNode.nodeType === Node.DOCUMENT_FRAGMENT_NODE) {
        const shadowRoot = curNode as ShadowRoot;

        const walker = this._doc.createTreeWalker(
          shadowRoot,
          this.whatToShow,
          {acceptNode: this._acceptNode}
        );

        walkers.push(walker);

        walker.currentNode = currentWalkerCurrentNode;

        this._currentSetFor.add(walker);

        curNode = currentWalkerCurrentNode = shadowRoot.host;
      } else {
        curNode = curNode.parentNode;
      }
    }

    const walker = this._doc.createTreeWalker(
      this.root,
      this.whatToShow,
      {acceptNode: this._acceptNode}
    );

    walkers.push(walker);

    walker.currentNode = currentWalkerCurrentNode;

    this._currentSetFor.add(walker);

    this._walkerStack = walkers;
  }

  public get doc(): Document {
    return this._doc;
  }

  public firstChild(): Node | null {
    let currentNode = this.currentNode;
    let newNode = this.nextNode();
    if (!nodeContains(currentNode, newNode)) {
      this.currentNode = currentNode;
      return null;
    }
    if (newNode) {
      this.currentNode = newNode;
    }
    return newNode;
  }

  public lastChild(): Node | null {
    let walker = this._walkerStack[0];
    let newNode = walker.lastChild();
    if (newNode) {
      this.currentNode = newNode;
    }
    return newNode;
  }

  public nextNode(): Node | null {
    const nextNode = this._walkerStack[0].nextNode();

    if (nextNode) {
      const shadowRoot = (nextNode as Element).shadowRoot;

      if (shadowRoot) {
        let nodeResult: number | undefined;

        if (typeof this.filter === 'function') {
          nodeResult = this.filter(nextNode);
        } else if (this.filter?.acceptNode) {
          nodeResult = this.filter.acceptNode(nextNode);
        }

        if (nodeResult === NodeFilter.FILTER_ACCEPT) {
          this.currentNode = nextNode;
          return nextNode;
        }

        // _acceptNode should have added new walker for this shadow,
        // go in recursively.
        let newNode = this.nextNode();
        if (newNode) {
          this.currentNode = newNode;
        }
        return newNode;
      }

      if (nextNode) {
        this.currentNode = nextNode;
      }
      return nextNode;
    } else {
      if (this._walkerStack.length > 1) {
        this._walkerStack.shift();

        let newNode = this.nextNode();
        if (newNode) {
          this.currentNode = newNode;
        }
        return newNode;
      } else {
        return null;
      }
    }
  }

  public previousNode(): Node | null {
    const currentWalker = this._walkerStack[0];

    if (currentWalker.currentNode === currentWalker.root) {
      if (this._currentSetFor.has(currentWalker)) {
        this._currentSetFor.delete(currentWalker);

        if (this._walkerStack.length > 1) {
          this._walkerStack.shift();
          let newNode = this.previousNode();
          if (newNode) {
            this.currentNode = newNode;
          }
          return newNode;
        } else {
          return null;
        }
      }

      return null;
    }

    const previousNode = currentWalker.previousNode();

    if (previousNode) {
      const shadowRoot = (previousNode as Element).shadowRoot;

      if (shadowRoot) {
        let nodeResult: number | undefined;

        if (typeof this.filter === 'function') {
          nodeResult = this.filter(previousNode);
        } else if (this.filter?.acceptNode) {
          nodeResult = this.filter.acceptNode(previousNode);
        }

        if (nodeResult === NodeFilter.FILTER_ACCEPT) {
          if (previousNode) {
            this.currentNode = previousNode;
          }
          return previousNode;
        }

        // _acceptNode should have added new walker for this shadow,
        // go in recursively.
        let newNode = this.lastChild();
        if (newNode) {
          this.currentNode = newNode;
        }
        return newNode;
      }

      if (previousNode) {
        this.currentNode = previousNode;
      }
      return previousNode;
    } else {
      if (this._walkerStack.length > 1) {
        this._walkerStack.shift();

        let newNode = this.previousNode();
        if (newNode) {
          this.currentNode = newNode;
        }
        return newNode;
      } else {
        return null;
      }
    }
  }

    /**
     * @deprecated
     */
  public nextSibling(): Node | null {
    // if (__DEV__) {
    //     throw new Error("Method not implemented.");
    // }

    return null;
  }

    /**
     * @deprecated
     */
  public previousSibling(): Node | null {
    // if (__DEV__) {
    //     throw new Error("Method not implemented.");
    // }

    return null;
  }

    /**
     * @deprecated
     */
  public parentNode(): Node | null {
    // if (__DEV__) {
    //     throw new Error("Method not implemented.");
    // }

    return null;
  }
}

/**
 * ShadowDOM safe version of document.createTreeWalker.
 */
export function createShadowTreeWalker(
    doc: Document,
    root: Node,
    whatToShow?: number,
    filter?: NodeFilter | null
) {
  if (shadowDOM()) {
    return new ShadowTreeWalker(doc, root, whatToShow, filter);
  }
  return doc.createTreeWalker(root, whatToShow, filter);
}