changeling

#!/usr/bin/env python3

import shapescript, sys

def error(adjective):
	print('This shape is %s.' % adjective)
	exit(1)

try:
	changeling = open(sys.argv[1]).read().split('\n')
except IndexError:
	print('Syntax: %s source-file' % argv[0], file = sys.stderr)
	exit(1)

if changeling.pop() != '' or any(len(line) != len(changeling) for line in changeling):
	error('unpleasant')

source = ''

for line in changeling:
	if not line or min(line) < ' ' or max(line) > '~':
		error('unpleasant')

	accumulator = 0

	for char in line + '\n':
		value = ord(char)

		try:
			source += chr(value ^ (accumulator >> 1))
		except:
			error('unpleasant')

		accumulator += value - 32

try:
	for item in shapescript.interpret(source):
		print(item, end = '')
except SyntaxError:
	error('unpurposed')
except:
	error('inadequate')