# deck.chat: T-Deck generic chat UI helper library for CircuitPython
# Depends on tdeck_repl for providing working input on T-Decks
#
# Created by Luxferre in 2025, released into public domain

from deck.input import input

class DeckChat:
  def __init__(self, start_state={}, chat_prefix='> ', command_prefix='/', paginate=0):
    """Init the chat class"""
    self.command_prefix = command_prefix # prefix that commands start with
    self.chat_prefix = chat_prefix       # prefix to write before input
    self.command_handlers = {            # command handler storage
      'default': lambda m,s: (m,s)       # echo handler by default
    }
    self.state = start_state             # internal state object (impl-specific)
    self.paginate_n = paginate           # paginate the responses exceeding N>0 lines

  def command(self, command, handler):
    """
    Register a new handler inside the chat instance.
    The handler accepts two parameters: a message and a state object,
    and returns the response and the new state object.
    If the returned state object is None, then the chat loop exits.
    Non-command handler is registered under the 'default' command.
    """
    cmd = command.strip().lower()
    if cmd.startswith(self.command_prefix):
      cmd = cmd[1:]
    self.command_handlers[cmd] = handler

  def _detect_command(self, msg):
    """
    Split a chat line into the command (or 'default' if none detected)
    and the rest of the message.
    """
    res = ('default', msg)
    if msg.startswith(self.command_prefix):
      parts = msg.split(' ')
      cmd = parts[0].lower().strip()[1:]
      arg = ' '.join(parts[1:]).strip() if len(parts) > 1 else None
      if cmd in self.command_handlers:
        res = (cmd, arg)
    return res

  def _paginate_output(self, text):
    """Splits output for small terminals."""
    lines = text.split('\n')
    for i in range(0, len(lines), self.paginate_n):
      chunk = lines[i:i + self.paginate_n]
      for line in chunk: print(line)
      if i + self.paginate_n < len(lines):
        input("-- Press Enter --")

  def start(self):
    """Start the chat loop"""
    while True:
      try:
        input_msg = input(self.chat_prefix).strip()
        if len(input_msg) == 0: continue
        cmd, msg = self._detect_command(input_msg)
        output, self.state = self.command_handlers[cmd](msg, self.state)
        if self.paginate_n > 0:
          self._paginate_output(output.strip())
        else:
          print(output)  
        if self.state is None:
          break
      except (KeyboardInterrupt, EOFError):
        print()
        break