# All files / src/plugins/default markbind-plugin-tree.ts

93.93% Statements 62/66
66.66% Branches 16/24
93.33% Functions 14/15
93.75% Lines 60/64

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     /**
     * Creates tree-like visualisations.
     * Transforms the content in <tree> tags into corresponding textual representations
     * that are easier to visualise the relationships.
     * A common use case is folder structures visualisations.
     */
    import has from 'lodash/has';
    import { MbNode } from '../../utils/node';
    import { PluginContext } from '../Plugin';

    import md from '../../lib/markdown-it';

    const _ = { has };

    const CSS_FILE_NAME = 'markbind-plugin-tree.css';

    const TOKEN = {
      child: '├── ',
      lastChild: '└── ',
      connector: '│   ',
      space: '    ',
    };

    class TreeNode {
      content: string;
      parent: TreeNode | null;
      children: TreeNode[];
      level: number;

      constructor(content: string, parent: TreeNode | null, children: TreeNode[], level: number) {
        this.content = content;
        this.parent = parent;
        this.children = children;
        this.level = level;
      }

      /**
       * Returns true if this node is the last child of its parent.
       * A root node is considered to be the last child.
       * This is used to determine the correct connector to use.
       */
      isLastChild(): boolean {
        Iif (this.parent === null) {
          return true;
        }
        return this.parent.children[this.parent.children.length - 1] === this;
      }

      /**
       * Returns the token to append before the content.
       */
      getPositionalToken(): string {
        return this.isLastChild() ? TOKEN.lastChild : TOKEN.child;
      }

      /**
       * Determines the level of a line.
       * Every 2 spaces from the start of the line means 1 level.
       * The root node is level 0.
       */
      static levelize(line: string): number {
        const lineMatch = line.match(/^\s*/) ?? [''];
        return Math.floor(lineMatch[0].length / 2);
      }

      /**
       * Returns formatted TreeNode content.
       * Removes dashes (-), asterisks (*), or plus signs (+) at the beginning of the line
       */
      static getContent(raw: string): string {
        return raw.trim().replace(/^[-+*]\s/, '');
      }

      /**
       * Creates TreeNode objects from the raw text.
       * @param raw - The raw text to parse.
       * @return The dummy root node of the tree.
       */
      static parse(raw: string): TreeNode {
        const lines = raw.split('\n').filter(line => line.trim() !== '');
        const rootNode = new TreeNode('.', null, [], -1); // dummy root node
        const prevParentStack = [rootNode];
        let prevLevel = rootNode.level;
        let prevParent = rootNode;
        let prevNode = rootNode;
        lines
          .forEach((line) => {
            const level = TreeNode.levelize(line);
            const content = TreeNode.getContent(line);

            if (level > prevLevel) {
              prevParentStack.push(prevNode);
              prevParent = prevNode;
            } else if (level < prevLevel) {
              for (let i = 0; i < prevLevel - level; i += 1) {
                prevParentStack.pop();
              }
              prevParent = prevParentStack[prevParentStack.length - 1];
            }

            const newNode = new TreeNode(content, prevParent, [], level);
            prevParent.children.push(newNode);
            prevLevel = level;
            prevNode = newNode;
          });
        return rootNode;
      }

      /**
       * Traverses the tree and appends the tokens to the given array.
       * @param currNode - The node to traverse.
       * @param result - The array to append the tokens to.
       */
      static traverse(currNode: TreeNode, result: string[]) {
        Iif (!currNode.children) {
          return;
        }
        if (currNode.parent === null) {
          result.push(md.renderInline(`${currNode.content}\n`));
        } else {
          const tokens = [
            '\n',
            md.renderInline(currNode.content),
            currNode.getPositionalToken(),
          ];

          // computes the strings appended to the content of the TreeNode
          let curr: TreeNode | null = currNode.parent;
          while (curr && _.has(curr, 'parent.parent')) {
            tokens.push(curr.isLastChild() ? TOKEN.space : TOKEN.connector);
            curr = curr.parent;
          }

          result.push(tokens.reverse().join(''));
        }
        currNode.children.forEach((child: TreeNode) => {
          TreeNode.traverse(child, result);
        });
      }

      /**
       * Returns the TreeNode as a string.
       * This assumes that the node is a root node.
       */
      toString(): string {
        const treeTokens: string[] = [];
        TreeNode.traverse(this, treeTokens);
        return treeTokens.join('');
      }

      /**
       * Returns the rendered tree.
       * @param raw - The raw text to parse.
       */
      static visualize(raw: string): string {
        const dummyRootNode = TreeNode.parse(raw);
        return dummyRootNode.children
          .reduce((prev, curr) => {
            curr.parent = null;
            return prev + curr.toString();
          }, '');
      }
    }

    export = {
      tagConfig: {
        tree: {
          isSpecial: true,
        },
      },
      getLinks: () => [`<link rel="stylesheet" href="${CSS_FILE_NAME}">`],
      processNode: (_pluginContext: PluginContext, node: MbNode) => {
        Iif (node.name !== 'tree') {
          return;
        }
        node.name = 'div';
        node.attribs.class = node.attribs.class ? `${node.attribs.class} tree` : 'tree';
        node.children = node.children ?? [];
        node.children[0].data = TreeNode.visualize(node.children[0].data);
      },
    };