#!/usr/bin/env python
# -*- coding: utf-8 -*-

import random
import urwid

level_map = """
                                            
                                        ..      
                                       .....        
                                         ..             
          ...........                             ..........
       .....○..........                        .................
     ..............................................%..┏━━━.━┓.....
   ......┏━━━━━┓......................................┃✚...☣┃......
  .......┃☢...✚┃....                    .............☻...█⚑.┃.......
  .......┃.⚐█....⛨............                    ....┃.....┃.......
   ......┃☣...✚┃....☺.................................┗━━━━━┛......
    .....┗━.━━━┛..................................................
      ..................                       ..........●......
         ...........                                 ........
                            ..                            
                           ....                        
                            ..                      

"""

global offset_x
offset_x = random.randint(0, 20)

global offset_y
offset_y = random.randint(0, 10)

def pad_line(line, maxcol):
    line_bytes = (u'→' * (-offset_x)) + line.decode('utf-8')
    if offset_x >= 0:
        line_bytes_visible = line_bytes[offset_x:maxcol+offset_x]
    else:
        line_bytes_visible = line_bytes[:maxcol]
    result = line_bytes_visible.encode('utf-8') \
             + ('←' * (maxcol-len(line_bytes_visible))) 
    return result

class Map(urwid.Widget):
    _sizing = frozenset(['box'])

    def render(self, size, focus=False):
        (maxcol, maxrow) = size

        visible_map = []
        if offset_y < 0:
            visible_map = [ '↓' * maxcol ] * -offset_y  # top padding    

        # transform map to lines
        visible_level_map = [
            pad_line(line, maxcol)
            for line
            in level_map.split('\n')
        ]

        visible_map.extend(visible_level_map)

        # cut off invisible lines from top:
        if offset_y > 0:
            visible_map = visible_map[offset_y:]

        # cut off invisible lines from bottom
        visible_map = visible_map[:maxrow]

        # bottom padding
        missing_rows = maxrow - len(visible_map)
        if missing_rows > 0:
            for i in range(missing_rows):
                visible_map.append('↑' * (maxcol))

        return urwid.TextCanvas(
            visible_map,
            maxcol=maxcol
        )

global map
map = Map()

def handle_input(key):
    if key == 'q':
        raise urwid.ExitMainLoop()

    global offset_x
    if key == 'left':
        offset_x -= 1
    elif key == 'right':
        offset_x += 1

    global offset_y
    if key == 'up':
        offset_y -= 1
    elif key == 'down':
        offset_y += 1

    map._invalidate()

global loop
loop = urwid.MainLoop(
    map,
    [],
    unhandled_input=handle_input
)
loop.run()