feat: add merge function

Able to deal with:
1.  merge a subtree

.vscode/launch.json

@@ -0,0 +1,15 @@
+{
+  "version": "0.2.0",
+  "configurations": [
+    {
+      "type": "node",
+      "request": "launch",
+      "name": "File Graph Yarn Jest",
+      "runtimeExecutable": "yarn",
+      "args": ["test", "--runInBand"],
+      "cwd": "${workspaceFolder}/packages/file-graph",
+      "console": "integratedTerminal",
+      "internalConsoleOptions": "neverOpen"
+    }
+  ]
+}

packages/file-graph/file.js

@@ -1,7 +1,9 @@
+import { basename } from './utils'
+
 export default class File {
-  constructor({ path, name, type, discovered }) {
+  constructor({ path, type, discovered }) {
     this.path = path
-    this.name = name
+    this.name = basename(path)
     this.type = type
     this.discovered = discovered
   }

packages/file-graph/fileNode.js

@@ -11,11 +11,15 @@ export default class FileNode extends File {
   addChild(fileInput, { makeParents } = {}) {
     const file = new FileNode(fileInput)
     if (file.path === this.path) {
-      throw new DuplicateItemError('File already exists in the tree')
+      throw new DuplicateItemError(
+        `File ${file.path} already exists in the tree: ${this.toString()}`
+      )
     }
 
     if (this.children.some((child) => child.path === file.path)) {
-      throw new DuplicateItemError('File already exists in the tree')
+      throw new DuplicateItemError(
+        `File ${file.path} already exists in the tree: ${this.toString()}`
+      )
     }
 
     const parentPath = dirname(file.path)
@@ -37,11 +41,47 @@ export default class FileNode extends File {
         })
         this.addChild(parent, { makeParents })
       } else {
-        throw new ParentNotExistsError('Parent path not found in the tree')
+        throw new ParentNotExistsError(
+          `Parent path not found in the tree, ${file.path}, ${this.path}`
+        )
       }
     }
   }
 
+  merge(fileNode) {
+    // Merge the children of the provided file node into this node
+    // If a child already exists, merge the children of that child
+    // If a child does not exist, add it to this node
+    if (fileNode.path === this.path) {
+      fileNode.children.forEach((child) => {
+        const existingChild = this.children.find((c) => c.path === child.path)
+        if (existingChild) {
+          existingChild.merge(child)
+        } else {
+          this.children.push(child)
+        }
+      })
+
+      // If a child exists in this node but not in the provided node, remove it
+      this.children = this.children.filter((child) =>
+        fileNode.children.some((c) => c.path === child.path)
+      )
+    } else if (this.contains(fileNode)) {
+      const childNode = this.children.find((child) => child.contains(fileNode))
+      if (childNode) {
+        childNode.merge(fileNode)
+      } else {
+        this.addChild(fileNode)
+      }
+    } else {
+      throw new Error(
+        'Cannot merge file nodes with different paths',
+        this.path,
+        fileNode.path
+      )
+    }
+  }
+
   toString() {
     const indent = '    '.repeat(this.path.split('/').length - 1)
     const suffix = this.isDirectory() ? '/' : ''

packages/file-graph/fileNode.test.js

@@ -93,4 +93,53 @@ describe('FileNode', () => {
       currentNode = currentNode.children[0]
     }
   })
+
+  test('merge-two-trees', () => {
+    const root = {
+      path: '/',
+      type: 'folder',
+    }
+    const files1 = [
+      { path: '/a', type: 'file' },
+      { path: '/b', type: 'folder' },
+      { path: '/b/c', type: 'folder' },
+      { path: '/b/d', type: 'file' },
+      { path: '/b/c/f', type: 'file' },
+    ]
+
+    const files2 = [
+      { path: '/b', type: 'folder' },
+      { path: '/b/c', type: 'folder' },
+      { path: '/b/e', type: 'file' },
+      { path: '/b/c/g', type: 'file' },
+    ]
+
+    const expected = [
+      { path: '/a', type: 'file' },
+      { path: '/b', type: 'folder' },
+      { path: '/b/c', type: 'folder' },
+      { path: '/b/e', type: 'file' },
+      { path: '/b/c/g', type: 'file' },
+    ]
+
+    const node1 = new FileNode(root)
+    files1.forEach((file) => node1.addChild(file))
+
+    const node2 = new FileNode(files2[0])
+    files2.slice(1).forEach((file) => node2.addChild(file))
+
+    console.log('node1', node1.toString())
+    console.log('node2', node2.toString())
+
+    const expectedNode = new FileNode(root)
+    expected.forEach((file) => expectedNode.addChild(file))
+
+    console.log('expected', expectedNode.toString())
+
+    node1.merge(node2)
+
+    console.log('node1-after', node1.toString())
+
+    expect(node1.toString()).toBe(expectedNode.toString())
+  })
 })

packages/file-graph/utils.js

@@ -1,5 +1,8 @@
 export function dirname(path) {
   const parts = path.split('/')
+  if (parts.length <= 2) {
+    return '/'
+  }
   parts.pop()
   return parts.join('/')
 }