#!/usr/bin/env python3
# Convert ILDEC .oct format files to PDP-8 .rim format
# Created by Luxferre in 2026, released into the public domain

import sys

def print_error(msg):
  sys.stderr.write(f"Error: {msg}\n")

def convert_octaddr_to_rim(input_path, output_path):
  pairs = []
  line_num = 0
  try:
    with open(input_path, 'r') as f:
      for line in f:
        line_num += 1
        # Strip comments starting with /, #, ;
        clean_line = line
        for comment_char in ('/', '#', ';'):
          if comment_char in clean_line:
            clean_line = clean_line.split(comment_char, 1)[0]
        
        clean_line = clean_line.strip()
        if not clean_line:
          continue

        if ':' not in clean_line:
          print_error(f"Line {line_num}: Missing colon separator (format is 'addr: data').")
          return False

        parts = clean_line.split(':', 1)
        addr_str = parts[0].strip()
        data_str = parts[1].strip()

        try:
          addr = int(addr_str, 8)
        except ValueError:
          print_error(f"Line {line_num}: Invalid octal address '{addr_str}'.")
          return False

        try:
          data = int(data_str, 8)
        except ValueError:
          print_error(f"Line {line_num}: Invalid octal data '{data_str}'.")
          return False

        if not (0 <= addr <= 0o7777):
          print_error(f"Line {line_num}: Address '{addr_str}' ({oct(addr)}) out of 12-bit range (0-7777).")
          return False

        if not (0 <= data <= 0o7777):
          print_error(f"Line {line_num}: Data '{data_str}' ({oct(data)}) out of 12-bit range (0-7777).")
          return False

        pairs.append((addr, data))
  except Exception as e:
    print_error(f"Failed to read input file '{input_path}': {e}")
    return False

  if not pairs:
    print_error("No valid address:data pairs found in the input file.")
    return False

  # Write RIM format
  # Leader: 2 bytes of 0xFF
  # For each pair:
  #   addr high: ((addr >> 6) & 0x3F) | 0x40
  #   addr low:  addr & 0x3F
  #   data high: (data >> 6) & 0x3F
  #   data low:  data & 0x3F
  # Trailer: 2 bytes of 0xFF
  try:
    with open(output_path, 'wb') as f:
      # Write leader
      f.write(bytes([0xFF] * 2))
      
      for addr, data in pairs:
        addr_hi = ((addr >> 6) & 0x3F) | 0x40
        addr_lo = addr & 0x3F
        data_hi = (data >> 6) & 0x3F
        data_lo = data & 0x3F
        f.write(bytes([addr_hi, addr_lo, data_hi, data_lo]))
      
      # Write trailer
      f.write(bytes([0xFF] * 2))
  except Exception as e:
    print_error(f"Failed to write output file: {e}")
    return False

  print(f"Successfully converted '{input_path}' to '{output_path}' ({len(pairs)} words).")
  return True

def main():
  args = sys.argv if hasattr(sys, 'argv') else []
  if len(args) < 2 or len(args) > 3:
    print("Usage: python3 oct2rim.py <input_octaddr_file> [output_rim_file]")
    sys.exit(1)

  input_path = args[1]
  if len(args) == 3:
    output_path = args[2]
  else:
    # Generate default output name by replacing extension with .rim
    dot_idx = input_path.rfind('.')
    slash_idx = max(input_path.rfind('/'), input_path.rfind('\\'))
    if dot_idx > slash_idx:
      output_path = input_path[:dot_idx] + ".rim"
    else:
      output_path = input_path + ".rim"

  success = convert_octaddr_to_rim(input_path, output_path)
  if not success:
    sys.exit(1)

if __name__ == '__main__':
  main()