Feature: Commands should be able to request input from user

[Huy-DNA]

Description

• The frontend hardwires the logic to show previous lines + current editable lines.
• There's no way for a command to request an input from user, because command is sandboxed from the UI, but the UI is needed to add an editable lines.
• Current workaround is that a command must require the user to pass all of the inputs as arguments to the command, which is awkward.

Suggestion

• The UI and the command execution should still be decoupled.

• The command should be passed some kind of callbacks, like read() and write() to signals that it wants to do I/O.

• The UI contains:

  • Rendering logic (so that the user can read whatever) based on the input it's passed, for example, it should interpret ANSI escape code.
  • Input logic (so that user can type whatever).

• Likely solution: A simulated terminal driver like in Linux terminals.

  • Input queue: User types -> input goes into input buffer.
  • Output queue:

• The flow:

     User types -> Terminal driver interprets (normal characters or special characters like `Ctrl+C`) -> Terminal driver pushes to the input queue (also the output queue for the "input echoing" effect) or sends some signal to the command (how to deal with signals?).
     <If a command is running> -> Command performs a `read()` some time -> Take characters from the input queue. -> Command performs a `write()` some time -> Append to the input queue.