-- Simple TerraME model of the game of life

--[[ 
The Game of Life, also known simply as Life, is a cellular automaton devised by the British mathematician John Horton Conway in 1970.

One interacts with the Game of Life by creating an initial configuration and observing how it evolves or, for advanced players, by creating patterns with particular properties.

The universe of the Game of Life is an infinite two-dimensional orthogonal grid of square cells, each of which is in one of two possible states, alive or dead. Every cell interacts with its eight neighbours, which are the cells that are horizontally, vertically, or diagonally adjacent. 

At each step in time, the following transitions occur:

Any live cell with fewer than two live neighbours dies, as if caused by under-population.
Any live cell with two or three live neighbours lives on to the next generation.
Any live cell with more than three live neighbours dies, as if by over-population.
Any dead cell with exactly three live neighbours becomes a live cell, as if by reproduction.

The initial pattern constitutes the seed of the system. The first generation is created by applying the above rules simultaneously to every cell in the seed. Births and deaths occur simultaneously, and the discrete moment at which this happens is sometimes called a tick (in other words, each generation is a pure function of the preceding one). The rules continue to be applied repeatedly to create further generations.

]]--

-- What do I need?  
-- A cell space 
-- timer to implement the dynamics 
-- rules to get the next stage
-- starting configuration 



-- cs = CellularSpace{xdim = 10}
-- insertPattern(cs, getLife("glider"), 0, 0)
function insertPattern(cs1, cs2, x0, y0)
	for i = 0, (cs2.ydim - 1) do
		for j = 0, (cs2.xdim - 1) do
			cs1:get(x0 + j, y0 + i).state = cs2:get(j, i).state
		end
	end
end

--- Return a CellularSpace from a data file available in the ca package.
-- It works with .life files, where the CellularSpace is stored as spaces
-- (dead) or Xs (alive).
-- @arg pattern A string with a file name without .file.
-- @usage import("ca")
-- 
-- glider = getLife("glider")
function getLife(pattern)
	local mfile = file(pattern..".life", "ca")

	local lines = {}
	for line in io.lines(mfile) do 
		lines[#lines + 1] = line
	end

	local xdim = string.len(lines[1])
	local ydim = #lines

	if ydim == xdim then ydim = nil end

	local cs = CellularSpace{
		xdim = xdim,
		ydim = ydim
	}

	local ydim = #lines

	forEachElement(lines, function(y, line)
		if xdim ~= string.len(line) then
			customError("Line "..y.." of file "..mfile.." does not have the same length ("
				..string.len(line)..") of the first line ("..xdim..").")
		end

		for x = 1, xdim do
			if string.sub(line, x, x) == "X" then
				cs:get(x - 1, y - 1).state = "alive"
			elseif string.sub(line, x, x) == " " then
				cs:get(x - 1, y - 1).state = "dead"
			else
				customError("Invalid character '"..string.sub(line, x, x)
					.."' in file "..mfile.." (line "..y..").")
			end
		end
	end)

	return cs
end

--- main program 
random = Random{seed = os.time()}

Life = Model { 
    dim       =  50,
    prob      =  0.2,
    x0        =  20,
    y0        =  20,
    pattern   =  "heavySpaceship",
    init      = function (model)
        model.finalTime = 500
        
        model.myCell = Cell { 
            -- starting configuration (random)
            init = function (cell)
                    cell.state = "dead"
            end,
            
            countLiveNeighbors = function (cell)
                local liveNeigh = 0 
                
                forEachNeighbor (cell, function (cell, neigh) 
                        if (neigh.past.state == "alive") then liveNeigh = liveNeigh + 1 end
                    end)
                return liveNeigh 
            end,
            
            -- rules to implement the game
            execute = function (cell)
                
                local liveNeigh = cell:countLiveNeighbors()
                
                -- Any live cell with fewer than two live neighbours dies
                if cell.past.state == "alive" and liveNeigh < 2 then cell.state = "dead" end
                
                -- Any live cell with two or three live neighbours lives 
                if cell.past.state == "alive" and (liveNeigh == 2 or liveNeigh == 3) then
                    cell.state = "alive" 
                end
            
                -- Any live cell with more than three live neighbours dies
                if cell.past.state == "alive" and liveNeigh > 3 then cell.state = "dead" end
                
                -- Any dead cell with exactly three live neighbours becomes a live cell
                if cell.past. state == "dead" and liveNeigh == 3 then cell.state = "alive" end
            end
            
        }
        model.cells = CellularSpace {
            xdim     = model.dim,
            instance = model.myCell,
        }
        
        model.cs2 = getLife(model.pattern) -- this is the small cell space with the pattern
        
        insertPattern(model.cells, model.cs2, model.x0, model.y0)
        
        model.cells:createNeighborhood {            
            strategy = "moore",
            wrap     = true
        }
        
        model.timer = Timer {
            Event{action = function ()
                    model.cells:synchronize()
                    model.cells:execute()
                    model.cells:notify()
                end}
        }
        
        model.map = Map{
            target = model.cells,
            select = "state",
            color = "Blues",
            value = {"dead", "alive"}
        }
    end
}


mylife = Life{
    pattern = "glider"
}

mylife:execute()