main.lua

--[[
    Lua star example - Run with love (https://love2d.org/)
    Copyright 2018 Wesley Werner <wesley.werner@gmail.com>

    Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

    The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
]]--

local luastar = require("lua-star")

-- a 2D map where true is open and false is blocked
local map = { }
local mapsize = 25
local screensize = 500
local tilesize = screensize / mapsize

-- path start and end
local path = nil
local start = { x = 1, y = mapsize }
local goal = { x = mapsize, y = 1 }

-- remember the tile the mouse is hovered over
local hoveredTile

-- fonts
local largeFont = love.graphics.newFont (30)
local smallFont = love.graphics.newFont (10)

-- save a screenshot
local saveScreenshot = false

function randomizeMap ()

    -- build an open map
    for x=1, mapsize do
        map[x] = {}
        for y=1, mapsize do
            map[x][y] = true
        end
    end

    -- add random walls
    math.randomseed (os.clock ())
    for i = 1, 45 do
        -- start point
        local x = math.random (1, mapsize-2)
        local y = math.random (1, mapsize-2)
        -- vertical or horizontal
        if math.random() > .5 then
            for n = 1, 5 do
                map[x][math.min (mapsize, y+n)] = false
            end
        else
            for n = 1, 5 do
                map[math.min (mapsize, x+n)][y] = false
            end
        end
    end

    requestPath()
    --saveScreenshot = true

end

function love.load ()

    love.window.setMode (screensize, screensize)
    randomizeMap()

end

function love.keypressed (key)

    if key == "escape" then
        love.event.quit()
    elseif key == "space" then
        randomizeMap()
    end

end

function love.draw ()

    -- draw walls
    love.graphics.setColor(.6, .6, .6)
    for x=1, mapsize do
        for y=1, mapsize do
            local fillstyle = "line"
            if map[x][y] == false then fillstyle = "fill" end
            love.graphics.rectangle(fillstyle, (x-1)*tilesize, (y-1)*tilesize, tilesize, tilesize)
        end
    end

    -- draw the path
    love.graphics.setFont (smallFont)
    if path then
        for i, p in ipairs(path) do
            love.graphics.setColor(0, 1, 0)
            love.graphics.rectangle("fill", (p.x-1)*tilesize, (p.y-1)*tilesize, tilesize, tilesize)
            love.graphics.setColor(0, 0, 0)
            love.graphics.print(i, (p.x-1) * tilesize, (p.y-1) * tilesize)
        end
    end

    -- draw start and end
    love.graphics.setColor(1, 0, 0)
    love.graphics.setFont (largeFont)
    love.graphics.print("*", (start.x-1) * tilesize, (start.y-1) * tilesize)
    love.graphics.print("*", (goal.x-1) * tilesize, (goal.y-1) * tilesize)

    if saveScreenshot then
        saveScreenshot = false
        local filename = string.format("screenshot-%d.png", os.time())
        love.graphics.captureScreenshot(filename)
        print (string.format("written %s", filename))
    end

end

function love.mousemoved (x, y, dx, dy, istouch)

    local dx = math.floor(x / tilesize) + 1
    local dy = math.floor(y / tilesize) + 1

    if hoveredTile then
        if hoveredTile.dx == dx and hoveredTile.dy == dy then
            return
        end
    end

    hoveredTile = { dx = dx, dy = dy }
    if love.mouse.isDown (1) then
        map[dx][dy] = not map[dx][dy]
        requestPath()
    end

end

function love.mousepressed (x, y, button, istouch)

    local dx = math.floor(x / tilesize) + 1
    local dy = math.floor(y / tilesize) + 1
    map[dx][dy] = not map[dx][dy]
    requestPath()

end

function positionIsOpenFunc (x, y)

    -- should return true if the position is open to walk
    return map[x][y]

end

function requestPath ()

    path = luastar:find(mapsize, mapsize, start, goal, positionIsOpenFunc)

end