# A program that draws a maze for the user to solve with the turtle
# Author: Nicholas Coleman
#
# The maze map is set up as a list of lists of one-digit hexadecimals.
# Each hexadecimal digit corresponds to a 4-bit encoding of a particular
# cell configuration:
#  * 1-bit: east wall
#  * 2-bit: north wall
#  * 4-bit: west wall
#  * 8-bit: south wall
# For example, 0xB = 11 = 8 + 2 + 1 = south, north, and east walls
# 
# The program is currently set up to draw a hard-coded maze, move the
# turtle to the entrance, then allow the user to use the arrow keys to
# move the turtle through the maze.
# If the user clicks the window it will exit.
# It does not currently prevent the user from moving through walls, and
# it does not tell the user if they have successfully completed the maze.

from turtle import *

def main():
    cellWidth = 50
    startPos = 1
    mazeMap = [[0xE, 0xD, 0x6, 0xC, 0x6],
               [0x2, 0xC, 0x3, 0xB, 0xA],
               [0x8, 0x1, 0x6, 0xE, 0xA],
               [0xB, 0xE, 0x9, 0x1, 0x2],
               [0xC, 0x1, 0x5, 0x6, 0x9],
               [0xB, 0xD, 0x5, 0x1, 0x7]]
    drawMaze(mazeMap, cellWidth, startPos)
    shape("turtle")
    listen()
    onkey(moveUp, "Up")
    onkey(moveDown, "Down")
    onkey(moveLeft, "Left")
    onkey(moveRight, "Right")
    
    exitonclick()

def drawCell(cellNum, cellWidth):
    for side in [0x1, 0x2, 0x4, 0x8]:
        if cellNum & side:
            pendown()
        else:
            penup()
        forward(cellWidth)
        left(90)

def drawMaze(mazeMap, cellWidth, startPos):
    # number of rows and columns
    numRows = len(mazeMap)
    numCols = len(mazeMap[0])

    # where start drawing the upper-left cell
    xPosUL = -(numCols / 2 * cellWidth)
    yPosUL = (numRows / 2 - 1) * cellWidth

    # where to put the turtle after drawing the maze.
    xPosStart = xPosUL - cellWidth / 2
    yPosStart = yPosUL - startPos * cellWidth + cellWidth / 2 

    # go to the lower-left corner of the upper-left cell
    penup()
    goto(xPosUL, yPosUL)

    # draw each cell in the maze using the map given
    for row in range(numRows):
        for col in range(numCols):
            drawCell(mazeMap[row][col], cellWidth)
            penup()
            forward(cellWidth)
        if numRows - row > 1:
            goto(xcor() - cellWidth * numCols, ycor() - cellWidth)
        else:
            goto(xPosStart, yPosStart)

def moveUp():
    goto(xcor(), ycor() + 50)

def moveDown():
    goto(xcor(), ycor() - 50)

def moveLeft():
    goto(xcor() - 50, ycor())

def moveRight():
    goto(xcor() + 50, ycor())

main()