# --- Day 8: Treetop Tree House ---

# The expedition comes across a peculiar patch of tall trees all planted
# carefully in a grid. The Elves explain that a previous expedition planted
# these trees as a reforestation effort. Now, they're curious if this would be
# a good location for a tree house.

# First, determine whether there is enough tree cover here to keep a tree house
# hidden. To do this, you need to count the number of trees that are visible
# from outside the grid when looking directly along a row or column.

# The Elves have already launched a quadcopter to generate a map with the
# height of each tree (your puzzle input). For example:

# 30373
# 25512
# 65332
# 33549
# 35390

# Each tree is represented as a single digit whose value is its height, where 0
# is the shortest and 9 is the tallest.

# A tree is visible if all of the other trees between it and an edge of the
# grid are shorter than it. Only consider trees in the same row or column; that
# is, only look up, down, left, or right from any given tree.

# All of the trees around the edge of the grid are visible - since they are
# already on the edge, there are no trees to block the view. In this example,
# that only leaves the interior nine trees to consider:

#     The top-left 5 is visible from the left and top. (It isn't visible from
# the right or bottom since other trees of height 5 are in the way.)
#     The top-middle 5 is visible from the top and right.
#     The top-right 1 is not visible from any direction; for it to be visible,
# there would need to only be trees of height 0 between it and an edge.
#     The left-middle 5 is visible, but only from the right.
#     The center 3 is not visible from any direction; for it to be visible,
# there would need to be only trees of at most height 2 between it and an edge.
#     The right-middle 3 is visible from the right.
#     In the bottom row, the middle 5 is visible, but the 3 and 4 are not.

# With 16 trees visible on the edge and another 5 visible in the interior, a
# total of 21 trees are visible in this arrangement.

# Consider your map; how many trees are visible from outside the grid?

import numpy as np

with open("/home/xfeluser/AoC_2022/P8.txt") as f:
    grid = [int(num) for line in f.read().strip().split() for num in line]

grid_arr = np.array(grid).reshape(int(len(grid) ** 0.5), int(len(grid) ** 0.5))

perimeter = grid_arr.shape[0] * 2 + (grid_arr.shape[0] - 2) * 2


def is_visible(arr, x, y):
    point = arr[x, y]
    top = arr[:x, y]
    bottom = arr[x + 1 :, y]
    left = arr[x, :y]
    right = arr[x, y + 1 :]

    return np.any(
        [1 for pos in [top, bottom, left, right] if np.all(point - pos > 0)]
    )


total = 0
for idx, element in enumerate(np.nditer(grid_arr[1:-1, 1:-1])):
    x = 1 + (idx // grid_arr[1:-1, 1:-1].shape[0])
    y = 1 + (idx % grid_arr[1:-1, 1:-1].shape[0])
    if is_visible(grid_arr, x, y):
        total += 1

print(perimeter + total)


# --- Part Two ---

# Content with the amount of tree cover available, the Elves just need to know
# the best spot to build their tree house: they would like to be able to see a
# lot of trees.

# To measure the viewing distance from a given tree, look up, down, left, and
# right from that tree; stop if you reach an edge or at the first tree that is
# the same height or taller than the tree under consideration. (If a tree is
# right on the edge, at least one of its viewing distances will be zero.)

# The Elves don't care about distant trees taller than those found by the rules
# above; the proposed tree house has large eaves to keep it dry, so they
# wouldn't be able to see higher than the tree house anyway.

# In the example above, consider the middle 5 in the second row:

# 30373
# 25512
# 65332
# 33549
# 35390

#     Looking up, its view is not blocked; it can see 1 tree (of height 3).
#     Looking left, its view is blocked immediately; it can see only 1 tree
# (of height 5, right next to it).
#     Looking right, its view is not blocked; it can see 2 trees.
#     Looking down, its view is blocked eventually; it can see 2 trees (one of
# height 3, then the tree of height 5 that blocks its view).

# A tree's scenic score is found by multiplying together its viewing distance
# in each of the four directions. For this tree, this is 4 (found by
# multiplying 1 * 1 * 2 * 2).

# However, you can do even better: consider the tree of height 5 in the middle
# of the fourth row:

# 30373
# 25512
# 65332
# 33549
# 35390

#     Looking up, its view is blocked at 2 trees (by another tree with a height
# of 5).
#     Looking left, its view is not blocked; it can see 2 trees.
#     Looking down, its view is also not blocked; it can see 1 tree.
#     Looking right, its view is blocked at 2 trees (by a massive tree of
# height 9).

# This tree's scenic score is 8 (2 * 2 * 1 * 2); this is the ideal spot for the
# tree house.

# Consider each tree on your map. What is the highest scenic score possible for
# any tree?

from math import prod


def visibility(arr, x, y):
    point = arr[x, y]
    top = arr[:x, y]
    bottom = arr[x + 1 :, y]
    left = arr[x, :y]
    right = arr[x, y + 1 :]

    return prod(
        (
            length_path(point, direction)
            for direction in [top[::-1], bottom, left[::-1], right]
        )
    )


def length_path(p, direction):
    path_length = 0
    for pos in direction:
        if p - pos >= 0:
            path_length += 1
            if p - pos == 0:
                break
        else:
            path_length += 1
            break

    return path_length


total = 0
maximum_path = 0
for idx, element in enumerate(np.nditer(grid_arr[1:-1, 1:-1])):
    x = 1 + (idx // grid_arr[1:-1, 1:-1].shape[0])
    y = 1 + (idx % grid_arr[1:-1, 1:-1].shape[0])
    maximum_path = max(visibility(grid_arr, x, y), maximum_path)

print(maximum_path)