# tile_grid.py
# ------------
# By MWC Contributors
#
# Implements `draw_tile_grid`, which draws a grid of tiles. 

from turtle import *
from tile import fly

def draw_tile_grid(width, height, tile_size, tile_function):
    """Draws a (width x height) grid, with tile_function drawn on each tile.

    For each height, or row of the grid, the computer draws (width) tiles from left to right, and then returns to the left side and moves up one row to draw another row of tiles until all rows have been drawn, and then the cursor returns to the start.
    """
    for y in range(height):
        for x in range(width):
            tile_function(tile_size)
            fly(tile_size)
        return_to_x_origin(tile_size, width)
        move_up_one_row(tile_size)
    return_to_y_origin(tile_size, height)

def return_to_x_origin(tile_size, width):
    "After drawing a row of tiles, returns the turtle to the starting x position"
    fly(-1 * tile_size * width)

def return_to_y_origin(tile_size, height):
    "After drawing all rows of tiles, returns the turtle to the starting y position"
    right(90)
    fly(tile_size * height)
    left(90)

def move_up_one_row(tile_size):
    "Moves the turtle up one row"
    left(90)
    fly(tile_size)
    right(90)