--
--------------------------------------------------------------------------------
--         FILE:  life.lua
--        USAGE:  ./life.lua 
--  DESCRIPTION:  Conway's Game of Life?
--      OPTIONS:  ---
-- REQUIREMENTS:  ---
--         BUGS:  ---
--        NOTES:  ---
--       AUTHOR:  Philipp Gesang (Phg), <megas.kapaneus@gmail.com>
--      COMPANY:  
--      VERSION:  1.0
--      CREATED:  05/08/10 12:03:11 CEST
--     REVISION:  ---
--------------------------------------------------------------------------------
--

gol = {}

gol.helpers = {}

local C, Cs, Ct, P, R, S, match = lpeg.C, lpeg.Cs, lpeg.Ct, lpeg.P, lpeg.R, lpeg.S, lpeg.match


-- http://lua-users.org/lists/lua-l/2009-06/msg00343.html
gol.helpers.utfchar = R("\000\127") +
    R("\194\223") * R("\128\191") + 
    R("\224\240") * R("\128\191") * R("\128\191") + 
    R("\241\244") * R("\128\191") * R("\128\191") * R("\128\191")


-- by Roberto, captures everything in a table
-- http://www.inf.puc-rio.br/~roberto/lpeg/lpeg.html
function gol.helpers.split (s, sep)
  sep = P(sep)
  local elem = C((1 - sep)^0)
  local p = Ct(elem * (sep * elem)^0)   -- make a table capture
  return match(p, s)
end

-- Modified to match left and right of one separator only.
function gol.helpers.split_once (s, sep) 
    local utfchar = gol.helpers.utfchar
    sep = P(sep)
    local left  = C((1 - sep)^0)
    local right = C((utfchar)^0)
    local p = Ct(left * sep * right)
    return p:match(s)
end

-- Modified stripper from Roberto to support trimming other chars than whitespace
function gol.helpers.strip(str, chars)
    local chars = chars or " \t\v\n"
    chars = S(chars)
    local nochars = 1 - chars
    local stripper = chars^0 * C((chars^0 * nochars^1)^0)

    return match(stripper,str) or ""
end

function gol.helpers.dead_row(len)
    local row  = ""
    local dead = "0"
    for i=1, len, 1 do
        row = row .. dead
    end
    return row
end

-- Read rules of type "B3/S23"
-- => “birth” of a new cell if exactly 3 adjacent cells are “alive”
-- => “staying alive” of cells with two or three adjacent “live” cells
function gol.parse_rule (raw_rule)
    local help = gol.helpers
    local b_s = help.split_once (raw_rule, "/")
    local tmp_b = help.strip(b_s[1], "B")
    local tmp_s = help.strip(b_s[2], "S")

    local b, s = {}, {}

    -- single digits express birth/stay conditions
    local n = 1
    repeat
        table.insert( b, tonumber(tmp_b:sub(n,n)) )
        n = n + 1
    until n > string.len(tmp_b)

    n = 1
    repeat
        table.insert( s, tonumber(tmp_s:sub(n,n)) )
        n = n + 1
    until n > string.len(tmp_s)

    return { birth = b, stay = s }
end

function gol.apply_rule (cell, cnt, rule, fade, keep)
    --local live, dead = "1", "0"
    --local new = dead
    local new = 0
    local live = "1"
    local stay  = rule.stay
    local birth = rule.birth

    -- checking if cnt matches the numbers from the conditions list
    if cell == live then
        for _, cond in ipairs(stay) do
            if cnt == cond then
                new = "1"
                break
            end
        end
    else -- ==dead
        for _, cond in ipairs(birth) do
            if cnt == cond then
                new = "1"
                break
            end
        end
    end

    if fade then
        if not (live == new) then
            local add = tonumber (cell)
            if not add then -- == "D"
                add = "D"
            else
                if add and add < 9 and add ~= 0 then
                    add = add + 1
                elseif keep and add and add == 9 then -- marking dead cells once alive
                    add = "D"
                else 
                    add = 0
                end
            end
            new = tostring(add)
        end
    end

    return new
end
    

function gol.parse_file (fname)
    local tmp = {} -- return an array
    local len      -- check for equal line length

    local file = assert(io.open(fname, "r"), "Not a file: " .. fname)
    for line in file:lines() do
        if not len then len = string.len(line) end

        if len ~= string.len(line) then
            -- inconsistent horizontal sizes; kill off program
            return nil
        else
            table.insert(tmp, line)
        end
    end
    file:close()

    return tmp
end

--- Computing single lines and whole frames and intervals thereof

function gol.next_line (rows, rule)
    local live = "1"

    local fade = false
    if mplife then
        fade = mplife.setup.current.fade
    end

    local n = 1
    local max = string.len(rows[2])

    local cell = R("09") + P("D")
    local nocell = 1-cell
    local ce = Cs(cell) / function (current) 

        local env = {}
        local lpos, rpos -- positions left of / right of current

        -- toroidal, flips over at borders
        if n == 1 then
            lpos = max
        else
            lpos = n - 1
        end

        if n == max then
            rpos = 1
        else
            rpos = n + 1
        end

        --     +---+---+---+
        --     |nw | n | ne|
        --     +---+---+---+
        --     |w  | c |  e| env[ironment] of current
        --     +---+---+---+
        --     |sw | s | se|
        --     +---+---+---+

        env.nw = string.sub( rows[1], lpos, lpos )
        env.n  = string.sub( rows[1], n   , n    )
        env.ne = string.sub( rows[1], rpos, rpos )

        env.w  = string.sub( rows[2], rpos, rpos )
        env.e  = string.sub( rows[2], lpos, lpos )

        env.sw = string.sub( rows[3], lpos, lpos )
        env.s  = string.sub( rows[3], n   , n    )
        env.se = string.sub( rows[3], rpos, rpos )

        -- counting live cells in the environment
        local cnt = 0
        for _, chr in pairs(env) do
            if chr == live then
                cnt = cnt + 1
            end
        end

        n = n + 1
        --
        -- adding new cell according to ruleset
        return gol.apply_rule(current, cnt, rule, fade, true)
    end

    local noce = Cs(nocell) / ""
    local c = Cs(ce * (noce + ce)^0)

    return c:match(rows[2])
end

function gol.next_frame (old, rule)
    local new = {}
    
    local n = 1

    repeat
        local rows = {}

        rows[2] = old[n] -- current

        -- toroidal
        rows[1] = old[n-1] or old[#old]  -- last
        rows[3] = old[n+1] or old[1]     -- next

        new[n] = gol.next_line( rows, rule )

        n = n + 1
    until n > #old

    return new
end

-- get the nth frame starting from init
function gol.frame (init, rule, n)
    local frame = init
    local gnext = gol.next_frame

    for i=1, n, 1 do
        frame = gnext( frame, rule )
    end

    return frame
end

-- get array of frames until nth [from offset]
function gol.frames (init, rule, n, offset)
    local frames = {}
    local last
    local gnext = gol.next_frame

    -- “fast forward”
    if offset then
        last = gol.frame( init, rule, offset )
    else
        last = init
    end

    for i=1, n, 1 do
        frames[i] = last
        last = gnext( last, rule )
    end

    return frames
end

--- pretty printing frames (ascii)

-- pp a heading: len should exceed length of mark + 4
function gol.pre_section (len, mark)
    local mark = mark or "Frame"
    local t = "-"

    local s = t..t.." "..mark.." "
    if s:len() < len then
        for n=1, len - s:len(), 1 do
            s = s..t
        end
    end

    io.write ("\n\n"..s.."\n")
end

function gol.pre_frame (frame)
    local repl = {
        ["0"] = "·",
        ["1"] = "O",
        ["2"] = "2",
        ["3"] = "3",
        ["4"] = "4",
        ["5"] = "5",
        ["6"] = "6",
        ["7"] = "7",
        ["8"] = "8",
        ["9"] = "9",
    }

    local cell = R"09" + P"D"
    local nocell = 1-cell
    local ce = Cs(cell) / repl
    local noce = Cs(nocell) / ""
    local c = Cs(ce * (noce + ce)^0)

    for j, row in ipairs(frame) do
        io.write("\n" .. c:match(row))
    end
end

function gol.pre_movie (frames, section)
    for i, frame in ipairs(frames) do
        if section then
            local l = string.len(frame[1])
            gol.pre_section( l, "Nr. " .. tostring(i) )
        end
        gol.pre_frame( frame )
    end
    io.write("\n")
end

return gol