cash-register/stratumBackend/stratumDBlib.lua

local stratum = {}

-- Source - https://stackoverflow.com/a/1579673
-- Posted by Faisal Hanif, modified by community. See post 'Timeline' for change history
-- Retrieved 2026-04-05, License - CC BY-SA 3.0

---splits a string by a pattern
---@param pString string
---@param pPattern string
---@return string[]
local function split(pString, pPattern)
   local Table = {}  -- NOTE: use {n = 0} in Lua-5.0
   local fpat = "(.-)" .. pPattern
   local last_end = 1
   local s, e, cap = pString:find(fpat, 1)
   while s do
      if s ~= 1 or cap ~= "" then
     table.insert(Table,cap)
      end
      last_end = e+1
      s, e, cap = pString:find(fpat, last_end)
   end
   if last_end <= #pString then
      cap = pString:sub(last_end)
      table.insert(Table, cap)
   end
   return Table
end



---applys macros to code
---@param code string
---@return string
function stratum.applyMacros(code,libpath)
    local import_name = ""
    local alphabet = {"A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"}
    for _ = 1,10 do
        import_name = import_name..alphabet[math.random(1,#alphabet)]
    end
    local import_string = "local "..import_name.." = require(\""..libpath.."\")\n"
    local splits = split(" "..code,"%-%-#")
    for instanceIndex = 2,#splits do
        local instance = splits[instanceIndex]
        local lines = split(instance:gsub("\n"," \n").." ","\n")
        local nonSpacedLines = split(instance,"\n")
        local contextDepth = 0
        local finalCodeLines = {}
        for lineIndex = 2,#lines do
            local line = lines[lineIndex]
            local _,dos = line:gsub("do ","")
            local _,funcs = line:gsub("function ","")
            local _,thens = line:gsub("then ","")
            local _,ends = line:gsub("end ","")
            contextDepth = contextDepth+dos+funcs+thens-ends
            finalCodeLines[#finalCodeLines+1] = nonSpacedLines[lineIndex]
            if contextDepth <= 0 then
                break
            end
        end
        local replaceSub = table.concat(finalCodeLines,"\n")
        local opcount = 0
        ---@type string
        local funcdef = table.remove(finalCodeLines,1)
        table.remove(finalCodeLines)
        local body = table.concat(finalCodeLines,"\n")
        local replace = funcdef

        if nonSpacedLines[1] == "data_transform" and string.find(funcdef,"function ") then
            funcdef,opcount = funcdef:gsub("function ",""):gsub("local ", "")
            local defsplit = split(funcdef, "%(")
            defsplit[2] = split(defsplit[2],"%)")[1] or "_"
            replace = defsplit[1].." = "..import_name..".createTransform(\""..defsplit[1].."\",\"local data,"..defsplit[2].." = ...\\n"..body:gsub("\n","\\n"):gsub("\"","\\\"").."\")"
            if opcount > 0 then
                replace = "local "..replace
            end
        elseif nonSpacedLines[1] == "common_transform" and string.find(funcdef,"function ") then
            funcdef = funcdef:gsub("function ",""):gsub("local ", "")
            local defsplit = split(funcdef, "%(")
            defsplit[2] = split(defsplit[2],"%)")[1] or "_"
            replace = replaceSub.."\n"..(import_name..".createTransform(\""..defsplit[1].."\",\"local data,"..defsplit[2].." = ...\\n"..body:gsub("\n","\\n"):gsub("\"","\\\"").."\")")
        end
        code = code:gsub(replaceSub:gsub("([%(%)%.%%%+%-%*%?%[%]%^%$])", "%%%1"),replace)
    end
    return import_string..code
end

function stratum.loadTransforms(modules,libpath)
    local file,err = package.searchpath(shell.dir(),modules)
    if not file then
        file,err = package.searchpath(shell.dir(),modules..".lua")
    end
    if not file then error("failed to find package: "..err,2) end
    local file = fs.open(file,"r")
    if not file then error("failed to open file",2) end
    local contents = file.readAll()
    file.close()
    if not contents then error("failed to read file",2) end
    contents = stratum.applyMacros(contents,libpath)
    local trans, err = load(contents,"transforms","t",_ENV)
    if not trans then error(err,2) end
    return trans()
end

function stratum.setBackend(backend)
    if backend.sendMessage and backend.receiveMessage then
        _G._STRATUMBACKEND = backend
    end
end

function stratum.createTransform(name,func)
    local backend = _STRATUMBACKEND
    if not backend or not (backend.sendMessage and backend.receiveMessage) then error("stratum backend not defined or defined incorrectly",2) end
    backend.sendMessage({protocol="RegisterTransform",name=name,functionBody=func})
    while true do
        local message = backend.receiveMessage()
        if message.protocol == "TransformRegistered" and message.name == name then
            return function (...)
                backend.sendMessage({protocol = "CallTransform", name=name,params={...}})
                while true do
                local message = backend.receiveMessage()
                    if message.protocol == "TransformResult" and message.name == name then
                        return table.unpack(message.result)
                    elseif message.protocol == "TransformError" and message.name == name then
                        error(message.error,2)
                    end
                end
            end
        end
    end
end

return stratum