main.py

import pygame
import math
import colorspy as colors
from queue import PriorityQueue

WIDTH = 800
WIN = pygame.display.set_mode((WIDTH, WIDTH))
pygame.display.set_caption("Path Finding Algorithm")

# Defining a node in the grid and assigning the values to the node
class Node:
    def __init__(self, row, col, width, total_rows):
        self.row = row
        self.col = col
        self.x = row * width
        self.y = col * width
        self.color = colors.white
        self.neighbors = []
        self.width = width
        self.total_rows = total_rows

    def get_position(self):
        return self.row, self.col

    def is_closed(self):
        return self.color == colors.red

    def is_open(self):
        return self.color == colors.green

    def is_barrier(self):
        return self.color == colors.black

    def is_start(self):
        return self.color == colors.purple

    def is_end(self):
        return self.color == colors.orange

    def reset(self):
        self.color = colors.white

    def make_start(self):
        self.color = colors.purple

    def make_closed(self):
        self.color = colors.red

    def make_open(self):
        self.color = colors.green

    def make_barrier(self):
        self.color = colors.black

    def make_end(self):
        self.color = colors.orange

    def make_path(self):
        self.color = colors.blue

    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 a row
            self.neighbors.append(grid[self.row + 1][self.col])

        if self.row > 0 and not grid[self.row - 1][self.col].is_barrier(): # up a row 
            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 a column
            self.neighbors.append(grid[self.row][self.col + 1])

        if self.col > 0 and not grid[self.row][self.col - 1].is_barrier(): # left a column
            self.neighbors.append(grid[self.row][self.col - 1])

    def __lt__(self, other):
        return False

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


# Defining the  A* algorithm to find the shortest path
def algorithm(draw, grid, start, end):
    count = 0
    open_set = PriorityQueue() # Priority Queue to store the nodes that are yet to be explored
    open_set.put((0, count, start)) # putting the starting node in the priority queue
    came_from = {} # Dictionary to store the path
    g_score = {node: float("inf") for row in grid for node in row} # Dictionary to store the cost of the path
    g_score[start] = 0 # Cost of the path from the starting node to the current node
    f_score = {node: float("inf") for row in grid for node in row} 
    f_score[start] = hueristic(start.get_position(), end.get_position())

    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]
        open_set_hash.remove(current)

        if current == end:
            reconstruct_path(came_from, end, draw)
            end.make_end()
            start.make_start()
            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 + hueristic(neighbor.get_position(), end.get_position())
                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

# Defining the hueristic function using manhanttan distance
def hueristic(p1, p2):
    x1, y1 = p1
    x2, y2 = p2
    return abs(x1 - x2) + abs(y1 - y2)

def make_grid(rows, width):
    # Creating a grid of nodes. Width is the width of the entire window
    grid = []
    gap = width // rows
    for i in range(rows):
        grid.append([])
        for j in range(rows):
            node = Node(i, j, gap, rows)
            grid[i].append(node)

    return grid

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

# Function to draw all the nodes in the grid
def draw(win, grid, rows, width):
    win.fill(colors.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 = 60
    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 is pressed
                pos = pygame.mouse.get_pos()
                row, col = get_clicked_pos(pos, ROWS, width)
                node = grid[row][col]

                if not start and node != end:
                    start = node
                    start.make_start()

                elif not end and node != start:
                    end = node
                    end.make_end()

                elif node != start and node != end:
                    node.make_barrier()

            elif pygame.mouse.get_pressed()[2]: # Right mouse button is pressed
                pos = pygame.mouse.get_pos()
                row, col = get_clicked_pos(pos, ROWS, 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 start and end:
                    for row in grid:
                        for node in row:
                            node.update_neighbors(grid)

                    algorithm(lambda: draw(win, grid, ROWS, width), grid, start, end)

                if event.key == pygame.K_c:
                    start = None
                    end = None
                    grid = make_grid(ROWS, width)

    pygame.quit()

main(WIN, WIDTH)