NanoDatabase v3.0

local defaultFolder="databases/"
local defaultFolderName=string.gsub(defaultFolder,"%/","")
local defaultFileName="database.txt"
local readOnly=false
local debugMode=false

if fs.isDir(defaultFolderName)==false then
    fs.makeDir(defaultFolderName)
end

function createDataFile(fileName)
    databaseFileName=defaultFolder..fileName or defaultFileName
    if fs.exists(databaseFileName) then
        debugMessage("A file with that name already exists.")
        return false,"A file with that name already exists."
    else
        file=fs.open(databaseFileName,"w")
        if file==nil then
            debugMessage("Unable to create the file")
            return false,"Unable to create the file."
        else
             file.write("Beginning of file.\n\n<Empty Entry>\n\nEnd of file")
             file.close()
             return databaseFileName
        end
    end
end

function setData(fileName,key,value)
    if fs.exists(defaultFolder..fileName) then
        file=fs.open(defaultFolder..fileName,"r")
        fullFile=file.readAll()
        file.close()
        start,stop=string.find(fullFile,"<<"..key..">")
        if start==nil then
            start,stop=string.find(fullFile,"<Empty Entry>")
            newFile=string.gsub(fullFile,"<Empty Entry>","<<"..key..">=<"..value..">>".."\n<Empty Entry>")
            file=fs.open(defaultFolder..fileName,"w")
            file.write(newFile)
            file.close()
            return true
        else
            file.close()
            local oldData=getData(fileName,key)
            newFile=string.gsub(fullFile,"<<"..key..">=<"..oldData..">>","<<"..key..">=<"..value..">>")
            file=fs.open(defaultFolder..fileName,"w")
            file.write(newFile)
            file.close()
            return true
        end
    else
        debugMessage("A file with the name "..fileName.." does not yet exist (failed to setData).")
        return false,"A file with the name "..fileName.." does not yet exist (failed to setData)."
    end
end

function getData(fileName,key)
    if fs.exists(defaultFolder..fileName) then
        file=fs.open(defaultFolder..fileName,"r")
        fullFile=file.readAll()
        file.close()
        start,stop=string.find(fullFile,"<<"..key..">")
        if start==nil then
            debugMessage("No data found under that key.")
            return false,"No data found under that key."
        else
            local line=getLine(fullFile,key)
            local __,stop=string.find(line,"%>=<")
            local start=stop+1
            local tempLine=string.sub(line,start,string.len(line))
            local stop,__=string.find(tempLine,"%>>")
            local data=string.sub(tempLine,0,stop-1)
            return data
        end
    else
        debugMessage("A file with the name "..fileName.." does not yet exist (failed to getData).")
        return false,"A file with the name "..fileName.." does not yet exist (failed to getData)."
    end
end

function getLine(fullString,key)
    local start,__=string.find(fullString,"<<"..key..">=<")
    local temp=string.sub(fullString,start,string.len(fullString))
    local __,stop=string.find(temp,"%>>")
    local line=string.sub(temp,0,stop)
    return line
end

function debugMessage(message)
    if debugMode then
        print("*DATABASE* "..message)
    end
end