autogrid.lua

local ag =
    {grid = {}
    ,fns = {}}

function ag.init(tab_or_g, fns)
    if type(tab_or_g) == 'table' then
        -- TODO for version with switchable layers
        ag.grid = tab_or_g.grid
        ag.fns = tab_or_g.fns
    else -- assume grid obj
        ag.grid = tab_or_g
        ag.fns = fns -- save user provided table of actions
    end
    -- hook autogrid up to grid interface
    ag.grid.key = ag.key
end

local function apply(f, ...)
    return f(...)
end

local function maybe_fn_table(obj,...)
    -- false signals the obj doesn't exist
    if obj == nil then return false end

    local typ = type(obj)
    if typ == 'function' then
        obj(...)
    elseif typ == 'table' then
        apply(unpack(obj),...)
    end
    -- true signals this mapping was eval'd
    return true
end

function ag.key(x,y,z)
    if     maybe_fn_table(ag.fns[x .. ',' .. y],z) then return -- individual key
    elseif maybe_fn_table(ag.fns['x' .. x],y,z) then return -- column
    elseif maybe_fn_table(ag.fns['y' .. y],x,z) then return -- row
    end
end

return ag