#!/usr/bin/env python
"""
be93.py - A Befunge Interpreter for Python
License: GPL 2; share and enjoy!
Author: Sean B. Palmer, inamidst.com

Usage: 
   ./be93.py <script>   # runs script as befunge-93
   ./be93.py --help     # prints out this message
"""

import sys, re

class Befunge: 
   def __init__(self, fpout=None): 
      self.grid = []
      self.stack = []
      self.direction = '>'
      self.stringmode = 0
      self.skip = 0
      self.pos = [0, 0]

      if fpout: self.fpout = fpout
      else: self.fpout = sys.stdout

      for i in range(25): 
         self.grid.append(list(' ' * 75))

   def push(self, obj): 
      if type(obj) is type(''): 
         assert len(obj) == 1
         obj = ord(obj)
      self.stack.append(obj)

   def pop(self): 
      if self.stack: 
         return self.stack.pop()
      else: return 0

   def step(self): 
      command = self.grid[self.pos[1]][self.pos[0]]
      if self.stringmode: 
         if command == '"': 
            self.stringmode = 0
         else: self.push(ord(command))
      elif command == ' ': pass
      elif command == '+': 
         v2 = self.pop()
         v1 = self.pop()
         self.push(v1 + v2)
      elif command == '-': 
         v2 = self.pop()
         v1 = self.pop()
         self.push(v1 - v2)
      elif command == '*': 
         v2 = self.pop()
         v1 = self.pop()
         self.push(v1 * v2)
      elif command == '/': 
         v2 = self.pop()
         v1 = self.pop()
         self.push(int(v1 / v2))
      elif command == '%': 
         v2 = self.pop()
         v1 = self.pop()
         self.push(v1 % v2)
      elif command == '!': 
         v = self.pop()
         if v != 0: self.push(0)
         else: self.push(1)
      elif command == '`': 
         v2 = self.pop()
         v1 = self.pop()
         if v1 > v2: self.push(1)
         else: self.push(0)
      elif command in ('>', '<', '^', 'v'): 
         self.direction = command
      elif command == '?': 
         self.direction = random.choice(('>', '<', '^', 'v'))
      elif command == '_': 
         v = self.pop()
         if v: self.direction = '<'
         else: self.direction = '>'
      elif command == '|': 
         v = self.pop()
         if v: self.direction = '^'
         else: self.direction = 'v'
      elif command == '"': 
         self.stringmode = 1
      elif command == ':': 
         v = self.pop()
         self.push(v)
         self.push(v)
      elif command == '\\': 
         v2 = self.pop()
         v1 = self.pop()
         self.push(v2)
         self.push(v1)
      elif command == '$': 
         v = self.pop()
      elif command == '.': 
         v = self.pop()
         self.output(v)
      elif command == ',': 
         v = self.pop()
         self.output(chr(v))
      elif command == '#': 
         self.skip = 1
      elif command == 'g': 
         y = self.pop()
         x = self.pop()
         v = self.grid[y][x]
         self.push(v)
      elif command == 'p': 
         y = self.pop()
         x = self.pop()
         v = self.pop()
         self.grid[y][x] = chr(v)
      elif command == '&': 
         sys.stderr.write('Input: ')
         v = get_input()
         self.push(int(v))
      elif command == '~': 
         sys.stderr.write('Input: ')
         v = get_input()
         while len(v) == 0: 
            v = get_input()
         v = v[0]
         self.push(ord(v))
      elif command == '@': 
         return 0
      elif command in '0123456789': 
         self.push(int(command))
      else: raise "Unidentified command %s at %s" % (command, self.pos)
      return 1

   def output(self, obj): 
      if type(obj) == type(1): 
         obj = '%s ' % obj
      self.fpout.write(obj)

   def movePointer(self): 
      x, y = 0, 1
      m = 1
      if self.skip: 
         m += 1
         self.skip = 0
      if self.direction == '>': 
         self.pos[x] += m
         if self.pos[x] > 75: 
            self.pos[x] = self.pos[x] - 75
      elif self.direction == '<': 
         self.pos[x] -= m
         if self.pos[x] < 0: 
            self.pos[x] = 75 + self.pos[x]
      elif self.direction == '^': 
         self.pos[y] -= m
         if self.pos[y] < 0: 
            self.pos[y] = 25 + self.pos[y]
      elif self.direction == 'v': 
         self.pos[y] += m
         if self.pos[y] > 25: 
            self.pos[y] = self.pos[y] - 25

   def reset(self, fpout=None): 
      self.__init__(fpout)

   def read(self, s): 
      lines = s.splitlines()
      for y in range(len(lines)): 
         for x in range(len(lines[y])): 
            self.grid[y][x] = lines[y][x]

   def printGrid(self): 
      result = ''
      for line in self.grid: 
         result += ''.join(line) + '\n'
      result = result[:-1]
      result = re.sub('[\x00-\x09\x0e-\x1f]', ' ', result)
      return result

   def run(self): 
      while 1: 
         x = self.step()
         if not x: break
         self.movePointer()

def main(args=None): 
   if args is None: 
      args = sys.argv[1:]

   if args: 
      if args[0] == '--help': 
         print __doc__
         sys.exit()
      input = open(args[0])
   else: input = sys.stdin
   s = input.read()
   if not (input is sys.stdin): 
      input.close()
   
   lines = s.splitlines()
   if lines: 
      if lines[0].startswith('#!/'): 
         lines = lines[1:]
   s = '\n'.join(lines)

   b = Befunge()
   b.read(s)
   b.run()

if __name__=="__main__": 
   main()