implement

--[[
    Author: Kingdaro
    doughnut steel

    Description:
    implements the code of another file
    into the top of whatever file(s) you choose
    useful for, as an example, storing a checkFuel() function
    and implementing it into turtle programs
    as opposed to rewriting it every time
]]

local args = {...}

local function implement( source, ... )
    local dir = shell.dir()
    source = source..dir

    local sourceFile = fs.open(source, 'r')
    if not sourceFile then
        return false, 'could not open source file'
    end
    local code = sourceFile.readAll()
    sourceFile.close()

    -- format code for reimplementation if already implemented, for easy updating
    code = '--IMPLEMENT '..source..'\n'..
    code..
    '\n--END'

    local files = {...}
    for i=1,#files do
        files[i] = dir .. files[i]
        local file = fs.open(files[i], 'r')
        if file then
            local fileContent = file.readAll()
            file.close()

            -- remove current implementation if it exists
            fileContent = fileContent:gsub('%-%-IMPLEMENT '..source..'.-%-%-END\n*', '')

            file = fs.open(files[i], 'w')
            file.write(code .. '\n\n' .. fileContent)
            file.close()

            print ('successfully written ', files[i])
        else
            print ('could not open ', files[i])
        end
    end
end

if #args >= 3 and args[2] == 'into' then
    table.remove(args, 2)
    implement(unpack(args))
else
    print 'Usage: implement <source> into <file> (<file2> <file3> ...)'
end