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-- -----------------------------------------------------------------------
-- dng
-- ------------------------------------------------------------------------
-- Copyright (c) 2022 Steph Enders <steph@senders.io>
--
-- This software is provided 'as-is', without any express or implied
-- warranty. In no event will the authors be held liable for any damages
-- arising from the use of this software.
--
-- Permission is granted to anyone to use this software for any purpose,
-- including commercial applications, and to alter it and redistribute it
-- freely, subject to the following restrictions:
--
-- 1. The origin of this software must not be misrepresented; you must not
-- claim that you wrote the original software. If you use this software
-- in a product, an acknowledgment in the product documentation would
-- be appreciated but is not required.
--
-- 2. Altered source versions must be plainly marked as such, and must not
-- be misrepresented as being the original software.
--
-- 3. This notice may not be removed or altered from any source
-- distribution.
--
-- -----------------------------------------------------------------------
package.path="./?.lua;" .. package.path
require "dnglib.constants"
local Queue = require "dnglib.queue"
---@param map table
local function print_map(map)
for i = 1, #map do
row = map[i]
line = ""
for j = 1, #row do
if row[j] == MAP_WALL then
line = line .. "# "
elseif row[j] == MAP_VISITED then
line = line .. "x "
else
line = line .. " "
end
end
print(line)
end
end
local function can_move(x, y, map)
return map[y][x] == MAP_SPACE
end
---@param x number
---@param y number
---@param origin table
---@param map table
---@param queue table
---@return boolean found goal
local function push_moves(x, y, origin, map, queue, target_pos)
map[y][x] = MAP_VISITED -- should be but just in case
-- UP
if can_move(x, y - 1, map) then
pos = {
x = x,
y = y - 1,
origin = origin
}
map[pos.y][pos.x] = MAP_VISITED
if (pos.x == target_pos.x and pos.y == target_pos.y) then
return true
end
queue:push(pos)
end
-- DOWN
if can_move(x, y + 1, map) then
pos = {
x = x,
y = y + 1,
origin = origin
}
map[pos.y][pos.x] = MAP_VISITED
if (pos.x == target_pos.x and pos.y == target_pos.y) then
return true
end
queue:push(pos)
end
-- LEFT
if can_move(x - 1, y, map) then
pos = {
x = x - 1,
y = y,
origin = origin
}
map[pos.y][pos.x] = MAP_VISITED
if (pos.x == target_pos.x and pos.y == target_pos.y) then
return true
end
queue:push(pos)
end
-- RIGHT
if can_move(x + 1, y, map) then
pos = {
x = x + 1,
y = y,
origin = origin
}
map[pos.y][pos.x] = MAP_VISITED
if (pos.x == target_pos.x and pos.y == target_pos.y) then
return true
end
queue:push(pos)
end
return false
end
---
---@param start_pos table [x, y]
---@param target_pos table [x, y]
---@param map table 2D map array
---@return table best move to target [x, y]
---
local function best_effort_move(start_pos, target_pos, map)
local diff_x = target_pos.x - start_pos.x
local diff_y = target_pos.y - start_pos.y
local move = { dx = 0, dy = 0 }
if diff_x > 0 and can_move(start_pos.x + 1, start_pos.y, map) then
move.dx = 1
return move
elseif diff_x < 0 and can_move(start_pos.x - 1, start_pos.y, map) then
move.dx = -1
return move
end
if diff_y > 0 and can_move(start_pos.x, start_pos.y + 1, map) then
move.dy = 1
return move
elseif diff_y < 0 and can_move(start_pos.x, start_pos.y - 1, map) then
move.dy = -1
return move
end
-- return 0, 0 move
return move
end
---
---@param start_pos table [x, y]
---@param target_pos table [x, y]
-- @param enemies list of enemy positions (cannot pass thru enemy)
-- @param treasures list of treasure positions (cannot pass thru treasure)
---@param map table 2D map array
---@return table best move to target [x, y]
---
local function pathfind(start_pos, target_pos, enemies, treasures, map)
local queue = Queue:new()
local visit_map = {}
for k, v in ipairs(map) do
row = {}
for ik, iv in ipairs(v) do
row[ik] = iv
end
visit_map[k] = row
end
for _, e in ipairs(enemies) do
if e ~= start_pos then
visit_map[e.y][e.x] = MAP_WALL -- use wall value for impass
end
end
for _, t in ipairs(treasures) do
visit_map[t.y][t.x] = MAP_WALL -- use wall value for impass
end
-- since we mutate the visit_map let's calc this early if need be
local best_effort = best_effort_move(start_pos, target_pos, visit_map)
if (push_moves(start_pos.x, start_pos.y, nil, visit_map, queue, target_pos)) then
return { dx = target_pos.x - start_pos.x, dy = target_pos.y - start_pos.y }
end
while queue:empty() ~= true do
local pos = queue:pop()
origin = pos.origin or { x = pos.x, y = pos.y }
hit_target = push_moves(pos.x, pos.y, origin, visit_map, queue, target_pos)
if hit_target then
return { dx = origin.x - start_pos.x, dy = origin.y - start_pos.y }
end
end
--- cannot find path - just move "towards" player
return best_effort
end
return {
pathfind = pathfind,
print_map = print_map,
}
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