import sys
import os
from collections import deque
import heapq
import time

class GridPoint:
    def __init__(self, x, y):
        self.x = x
        self.y = y
        self.blocked = False
        self.is_start = False
        self.is_exit = False

    def can_step(self):
        return not self.blocked

class Labyrinth:
    def __init__(self, w, h):
        self.w = w
        self.h = h
        self.grid = [[GridPoint(x, y) for x in range(w)] for y in range(h)]
        self.start_point = None
        self.exit_point = None

    def get_point(self, x, y):
        if 0 <= x < self.w and 0 <= y < self.h:
            return self.grid[y][x]
        return None

    def set_point(self, x, y, typ):
        p = self.get_point(x, y)
        if not p:
            return
        if typ == 'wall':
            p.blocked = True
        elif typ == 'start':
            if self.start_point:
                self.start_point.is_start = False
            p.is_start = True
            p.blocked = False
            self.start_point = p
        elif typ == 'exit':
            if self.exit_point:
                self.exit_point.is_exit = False
            p.is_exit = True
            p.blocked = False
            self.exit_point = p
        elif typ == 'path':
            p.blocked = False

    def neighbors(self, p):
        dirs = [(0, -1), (0, 1), (-1, 0), (1, 0)]
        res = []
        for dx, dy in dirs:
            nx, ny = p.x + dx, p.y + dy
            nb = self.get_point(nx, ny)
            if nb and nb.can_step():
                res.append(nb)
        return res

class MazeLoader:
    def load(self, filename):
        raise NotImplementedError

class TextMazeLoader(MazeLoader):
    def load(self, filename):
        with open(filename, 'r') as f:
            lines = [line.rstrip('\n') for line in f]
        h = len(lines)
        w = max(len(line) for line in lines) if h > 0 else 0
        start_cnt = 0
        exit_cnt = 0
        lab = Labyrinth(w, h)

        for y, line in enumerate(lines):
            for x, ch in enumerate(line):
                if ch == '#':
                    lab.set_point(x, y, 'wall')
                elif ch == 'S':
                    lab.set_point(x, y, 'start')
                    start_cnt += 1
                elif ch == 'E':
                    lab.set_point(x, y, 'exit')
                    exit_cnt += 1
                else:
                    lab.set_point(x, y, 'path')
        if start_cnt != 1 or exit_cnt != 1:
            raise ValueError(f"Need exactly one S and one E. Found S={start_cnt}, E={exit_cnt}")
        return lab

class SearchAlgorithm:
    def find_way(self, lab, start, goal):
        raise NotImplementedError

    def _build_path(self, prev, start, goal):
        path = []
        cur = goal
        while cur:
            path.append(cur)
            cur = prev.get(cur)
        path.reverse()
        return path

    def get_visited(self):
        return getattr(self, '_visited', 0)

class BreadthFirst(SearchAlgorithm):
    def find_way(self, lab, start, goal):
        q = deque([start])
        prev = {start: None}
        seen = {start}
        while q:
            cur = q.popleft()
            if cur == goal:
                self._visited = len(seen)
                return self._build_path(prev, start, goal)
            for nb in lab.neighbors(cur):
                if nb not in seen:
                    seen.add(nb)
                    prev[nb] = cur
                    q.append(nb)
        self._visited = len(seen)
        return []

class DepthFirst(SearchAlgorithm):
    def find_way(self, lab, start, goal):
        stack = [start]
        prev = {start: None}
        seen = {start}
        while stack:
            cur = stack.pop()
            if cur == goal:
                self._visited = len(seen)
                return self._build_path(prev, start, goal)
            for nb in lab.neighbors(cur):
                if nb not in seen:
                    seen.add(nb)
                    prev[nb] = cur
                    stack.append(nb)
        self._visited = len(seen)
        return []

class AStar(SearchAlgorithm):
    def _dist(self, a, b):
        return abs(a.x - b.x) + abs(a.y - b.y)

    def find_way(self, lab, start, goal):
        heap = []
        cnt = 0
        start_f = self._dist(start, goal)
        heapq.heappush(heap, (start_f, cnt, start))
        cnt += 1
        prev = {}
        g = {start: 0}
        f = {start: start_f}
        seen = set()
        while heap:
            cur_f, _, cur = heapq.heappop(heap)
            seen.add(cur)
            if cur == goal:
                self._visited = len(seen)
                return self._build_path(prev, start, goal)
            if cur_f > f.get(cur, float('inf')):
                continue
            for nb in lab.neighbors(cur):
                new_g = g[cur] + 1
                if new_g < g.get(nb, float('inf')):
                    prev[nb] = cur
                    g[nb] = new_g
                    new_f = new_g + self._dist(nb, goal)
                    f[nb] = new_f
                    heapq.heappush(heap, (new_f, cnt, nb))
                    cnt += 1
        self._visited = len(seen)
        return []

class LabyrinthSolver:
    def __init__(self, lab):
        self.lab = lab
        self.algorithm = None

    def set_algorithm(self, algo):
        self.algorithm = algo

    def solve(self):
        if not self.algorithm:
            return None
        t0 = time.perf_counter()
        path = self.algorithm.find_way(self.lab, self.lab.start_point, self.lab.exit_point)
        t1 = time.perf_counter()
        ms = (t1 - t0) * 1000
        return ms, self.algorithm.get_visited(), len(path)

def run_experiment(maze_file, algo, runs=5):
    loader = TextMazeLoader()
    lab = loader.load(maze_file)
    total_ms = 0
    total_visited = 0
    total_len = 0
    for _ in range(runs):
        solver = LabyrinthSolver(lab)
        solver.set_algorithm(algo)
        stats = solver.solve()
        if stats:
            ms, vis, plen = stats
            total_ms += ms
            total_visited += vis
            total_len += plen
    return total_ms / runs, total_visited / runs, total_len / runs

class TextView:
    def display(self, lab):
        os.system('cls' if os.name == 'nt' else 'clear')
        print("=" * (lab.w * 2 + 4))
        print("   LABYRINTH")
        print("=" * (lab.w * 2 + 4))
        for y in range(lab.h):
            print("  ", end='')
            for x in range(lab.w):
                p = lab.get_point(x, y)
                if p == lab.start_point:
                    print('S', end=' ')
                elif p == lab.exit_point:
                    print('E', end=' ')
                elif p.blocked:
                    print('#', end=' ')
                else:
                    print('.', end=' ')
            print()
        print("=" * (lab.w * 2 + 4))
        print("  S - start  E - exit  # - wall  . - path")

if __name__ == "__main__":
    # quick demo
    loader = TextMazeLoader()
    lab = loader.load("maze/maze1.txt")
    view = TextView()
    view.display(lab)
    print("\nRunning experiment on maze1.txt with BFS...")
    bfs = BreadthFirst()
    avg_t, avg_v, avg_l = run_experiment("maze/maze1.txt", bfs, runs=3)
    print(f"BFS: time={avg_t:.3f}ms visited={avg_v:.0f} length={avg_l:.0f}")