How to create a file from a snippet using vscode-extention

I would like to create files and apply snippets from an extension.

Expected process flow(All processes are done by extensions)

1. retrieve the snippet
2. create new file
3. apply the snippet to the created file
4. repeat steps 2~3

What I have done

• Create a custom snippet custom.code-snippets under the .vscode folder.
• Execute the created snippet from the command palette or from a text editor input.
• Build and run the extension
• Create files from the extension
• Retrieving the contents of a snippet file.

What I looked into

• Check for functions like executeSnippet.
• Check for functions like vscode.TextDocument.insertText

There is a SnippetString in the API, so there seems to be a way to apply snippets.

Search VSCode API page with the word snippet

29hits

• 1~2 : CompletionItem
  • on typing
• 3~4 : DocumentDropEdit
  • on drop
• 5~7 : InlineCompletionItem
  • on typing
• 8 : MarkedString
  • have nothing to do with this issue.
• 9 : ProviderResult
  • have nothing to do with this issue.
• 10~25 : SnippetString
  • Use this to assemble snippets.
• 26~28 : TextEditor
  • Processing "opened" documents
• 29 : WorkspaceConfiguration
  • have nothing to do with this issue.

I could only find something that could do something about user behavior.

This is my first time developing a VSCode extension and I don't know how to do it. Can you just tell me which functionality I should use? If it's not possible, I'll give up and use Nodejs.