gitget - An updater for ComputerCraft scripts stored on a github.com

--[[ gitget
  An updater for ComputerCraft scripts stored on a github.com
]]--

-- Configuration variables
local sConfigName = "gitget.cfg"

-- Returns full GitHub address
function createAddress(tConfig)
  local sUrl = "https://raw.github.com"
  return (sUrl .. "/" .. tConfig["user"] .. "/" .. tConfig["project"] .. "/" .. tConfig["branch"] .. "/" .. tConfig["filename"])
end

-- Loads a table from file
function loadTable(sPath)
  if not fs.exists(sPath) then
	error("loadTable() file not found: " .. sPath)
  end
  
  if fs.isDir(sPath) then
	error("loadTable() cannot open a directory")
  end
  
  local file = fs.open(sPath, "r")
  local sTable = file.readAll()
  file.close()
  return textutils.unserialize(sTable)
end

-- Saves a table to file
-- Uses saveString()
function saveTable(tData, sPath)
  local sSerializedData = textutils.serialize(tData)
  return saveString(sSerializedData, sPath)
end

-- Saves a string to file
function saveString(sData, sPath)
  if fs.isDir(sPath) then
	error("saveString() cannot save over a directory")
  end
  
  local file = fs.open(sPath, "w")
  file.write(sData)
  file.close()
  return true
end

-- Downloads a file from url provided
function download(sUrl, sPath)
  print("Downloading: " .. sUrl)
  if http then
	local sData = http.get(sUrl)
	
	if sData then
	  print("Fetched file")
	  return saveString(sData.readAll(), sPath)
	else
	  print("Failed to fetch file: " .. sUrl)
	  return false
	end
	
  else
	error("download() needs http api enabled to fetch files")
  end
end

-- Writes a prompt at pos
function promptPos(sPrompt, nX, nY)
  term.setCursorPos(nX, nY)
  term.clearLine()
  term.write(sPrompt)
  return true
end

function assemblePromptTable(tConfig)
  tPrompt = {
	"Gitget - a github file fetcher.",
	"Filename [" .. tConfig["filename"] .. "] :",
	"Branch [" .. tConfig["branch"] .. "] :",
	"Project [" .. tConfig["project"] .. "] :",
	"User [" .. tConfig["user"] .. "] :",
	"Press enter with no input to download.",
  }
  return tPrompt
end

-- Draws the config settings on the screen
-- returns prompt table
function drawPrompt(tPrompt)
  for nKey, sValue in ipairs(tPrompt) do
	promptPos(sValue, 1, nKey)
  end
  return true
end

-- Invokes read() after the line given
function userInput(nPos, tPrompt)
  term.setCursorPos((#tPrompt[nPos] + 1), nPos)
  return read()
end

-- Checks for first run and creates config file
function checkFirstInit()
  if not fs.exists(sConfigName) then
	tInit = {["filename"] = " ", ["branch"] = " ", ["project"] = " ", ["user"] = " ",}
	saveTable(tInit, sConfigName)
  end
end

-- Set some global variables
local nInputPos = 2
local tConfig
local tPrompt
local sInput
local tInputRow = {"prompt", "filename", "branch", "project", "user"}

-- Runtime section
checkFirstInit()
term.clear()
while true do
  tConfig = loadTable(sConfigName)
  tPrompt = assemblePromptTable(tConfig)
  drawPrompt(tPrompt)
  sInput = userInput(nInputPos, tPrompt)
  
  if sInput == "" then
	sInput = tConfig[tInputRow[nInputPos]]
	break
  else
	tConfig[tInputRow[nInputPos]] = sInput
	saveTable(tConfig, sConfigName)
	nInputPos = nInputPos + 1
	if nInputPos > #tInputRow then nInputPos = 2 end
  end
end

term.setCursorPos(1, (#tPrompt + 1))
download(createAddress(tConfig), tConfig["filename"])