path_finding.py

from copyreg import constructor
import pygame
import math
from queue import PriorityQueue

WIN_WIDTH = 800
WIN = pygame.display.set_mode((WIN_WIDTH, WIN_WIDTH)) 
pygame.display.set_caption("A-Star Path Finding Algorithm")

RED = (255, 0, 0)
GREEN = (0, 255, 0)
BLUE = (0, 255, 0)
YELLOW = (255, 255, 0)
WHITE = (255, 255, 255)
BLACK = (0, 0, 0)
PURPLE = (128, 0, 128)
ORANGE = (255, 165 ,0)
GREY = (128, 128, 128)
TURQUOISE = (64, 224, 208)

class Node:
    def __init__(self, row, col, width, total_rows):
        self.row = row
        self.col = col
        # Caluculate coords of node
        self.x = row * width
        self.y = col * width
        self.color = WHITE # start with all white nodes
        self.neighbors = []
        self.width = width
        self.total_rows = total_rows

    def get_pos(self):
        return self.row, self.col
    
    def is_closed(self):
        return self.color == RED
    
    def is_opne(self):
        return self.color == GREEN
    
    def is_barrier(self):
        return self.color == BLACK

    def is_start(self):
        return self.color == ORANGE

    def is_end(self):
        return self.color == TURQUOISE
    
    def reset(self):
        self.color = WHITE
    
    def make_closed(self):
        self.color = RED

    def make_open(self):
        self.color = GREEN

    def make_barrier(self):
        self.color = BLACK

    def make_start(self):
        self.color = ORANGE

    def make_end(self):
        self.color = TURQUOISE

    def make_path(self):
        self.color = PURPLE
    
    def draw(self, win):
        pygame.draw.rect(win, self.color, (self.x, self.y, self.width, self.width))

    def update_neighbors(self, grid):
        self.neighbors = []
        if self.row < self.total_rows-1 and not grid[self.row + 1][self.col].is_barrier(): # DOWN
            self.neighbors.append(grid[self.row + 1][self.col])
        if self.row > 0 and not grid[self.row - 1][self.col].is_barrier(): # UP
            self.neighbors.append(grid[self.row - 1][self.col])
        if self.col < self.total_rows-1 and not grid[self.row][self.col + 1].is_barrier(): # RIGHT
            self.neighbors.append(grid[self.row][self.col + 1])
        if self.col > 0 and not grid[self.row][self.col - 1].is_barrier(): # LEFT
            self.neighbors.append(grid[self.row][self.col - 1])

    def __lt__(self, other): # Compare nodes and return false if less than
        return False

def h(point1, point2): #heuristic Function to get distance using manhattan distance
    x1, y1 = point1
    x2, y2 = point2
    return abs(x1 - x2) + abs(y1 - y2)

def construct_path(came_from, current, draw):
    while current in came_from:
        current = came_from[current]
        current.make_path()
        draw()


def astar(draw, grid, start, end):
    count = 0
    open_set = PriorityQueue()
    open_set.put((0, count, start))
    came_from = {}
    g_score = {node: float("inf") for row in grid for node in row} # dict comprehension
    g_score[start] = 0
    f_score = {node: float("inf") for row in grid for node in row}
    f_score[start] = h(start.get_pos(), end.get_pos())

    open_set_hash = {start}

    while not open_set.empty():
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                pygame.quit()
        current = open_set.get()[2] # get node from (0, count, start->node)
        open_set_hash.remove(current)

        if current == end: # make path and exit
            construct_path(came_from, end, draw)
            end.make_end()
            return True
        
        for neighbor in current.neighbors:
            temp_g_score = g_score[current] + 1
            if temp_g_score < g_score[neighbor]:
                came_from[neighbor] = current
                g_score[neighbor] = temp_g_score
                f_score[neighbor] = temp_g_score + h(neighbor.get_pos(), end.get_pos())
                if neighbor not in open_set_hash:
                    count += 1
                    open_set.put((f_score[neighbor], count, neighbor))
                    open_set_hash.add(neighbor)
                    neighbor.make_open()
        draw()

        if current != start: #  
            current.make_closed()
    return False

def make_grid(rows, width):
    grid = []
    gap = width // rows # Integer Division returns height of each node
    for i in range(rows):
        grid.append([])
        for j in range(rows):
            node = Node(i, j, gap, rows)
            grid[i].append(node)
    return grid

def draw_grid(win, rows, width): # Draw grid lines
    gap = width // rows
    for i in range(rows):
        pygame.draw.line(win, GREY, (0, i * gap), (width, i * gap))
        for j in range(rows):
            pygame.draw.line(win, GREY, (j * gap, 0), (j * gap, width))

def draw(win, grid, rows, width):
    win.fill(WHITE)
    for row in grid:
        for node in row:
            node.draw(win)
    draw_grid(win, rows, width)
    pygame.display.update()

def get_clicked_pos(pos, rows, width):
    gap = width // rows
    y ,x = pos
    row = y // gap
    col = x // gap
    return row, col

def main(win, width):
    _ROWS = 50 # How many nodes to draw
    grid = make_grid(_ROWS, width)

    start = None
    end = None

    run = True
    started = False

    while run:
        draw(win, grid, _ROWS, width)
        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                run = False
            
            if started:
                continue
            if pygame.mouse.get_pressed()[0]: # LEFT mouse button - DRAW
                pos = pygame.mouse.get_pos()
                row, col = get_clicked_pos(pos, _ROWS, width)
                node = grid[row][col]
                if not start and end != node:
                    start = node
                    start.make_start()
                elif not end and start != node:
                    end = node
                    end.make_end()
                elif node != end and node != start:
                    node.make_barrier()

            elif pygame.mouse.get_pressed()[2]: # Right mouse button - RESET
                pos = pygame.mouse.get_pos()
                row, col = get_clicked_pos(pos, _ROWS,  WIN_WIDTH)
                node = grid[row][col]
                node.reset()
                if node == start:
                    start = None
                elif node == end:
                    end = None

            if event.type == pygame.KEYDOWN:
                if event.key == pygame.K_SPACE and not started:
                    for row in grid:
                        for node in row:
                            node.update_neighbors(grid)
                    
                    astar(lambda: draw(win, grid, _ROWS, width), grid, start, end)

                # Reset the game
                if event.key == pygame.K_c:
                    start = None
                    end = None
                    grid = make_grid(_ROWS, width)
                    
    pygame.quit()

main(WIN, WIN_WIDTH)