Code-block retriever

local function getInfo(label)
 local id
 while true do
  term.clear()
  term.setCursorPos(1, 1)
  print("Enter the " .. label .. " of the post to get code from:")
  id = tonumber(read())
  if id then break end
  print("Error: That is not a number. Please try again.")
  sleep(3)
 end
 term.clear()
 term.setCursorPos(1, 1)
 return id
end

local function hasError(page)
 return string.find(page, "<h1 class='ipsType_pagetitle'>An Error Occurred</h1>") and true
end

local function getPage(url)
 local page
 for attempts=1,3 do
  print("Downloading Page: Attempt " .. attempts)
  page = http.get(url)
  if page then print("Download Successful!") break
  else print("Download Failed!") end
  if attempts < 3 then print("Retrying...") end
 end
 if not page then return end
 local html = page.readAll()
 page.close()
 return html
end

local function contains(tabl, item)
 for _,value in ipairs(tabl) do
  if value == item then return true end
 end
 return false
end

local function extractCode(page)
 local codes = {}
 local matches = 0
 print("Extracting Codes.")
 for code in string.gmatch(page, "<pre class='prettyprint'>(.-)</pre>") do
  if not contains(codes, code) then
   table.insert(codes, code)
  end
 end
 print(#codes .. " Code Blocks Found")
 return codes
end

local function makeURL(id, pageNum)
 return "http://www.computercraft.info/forums2/index.php?/topic/"..id.."-/page__st_" .. 20*(pageNum-1)
end

function unescape(codes)
 replace = {["quot"] = [["]], ["apos"] = [[']], ["amp"] = "&", ["lt"] = "<", ["gt"] = ">"}
 newcodes = {}
 for i,code in ipairs(codes) do
  table.insert(newcodes, ({string.gsub(code, "&#?(%w-);", function(word) return replace[word] or string.char(tonumber(word)) end)})[1])
  newcodes[#newcodes] = string.gsub(newcodes[#newcodes], "<br />", "\n")
 end
 return newcodes
end

local function displayCodes(codes)
 local codeLines = {}
 local termHeight = ({term.getSize()})[2]
 local lineUp = 0
 local lineDown = termHeight+1
 local menuOpen = false
 local codeNumber = 1
 local option = 1
 local options = {"[Save]  Delete   Exit", " Save  [Delete]  Exit", " Save   Delete  [Exit]"}
 for _,codeString in ipairs(codes) do
  local code={}
  codeString = "\n"..codeString.."\n"
  while true do
   local line, subPos = string.match(codeString, "\n(.-)()\n")
   if not line then break end
   table.insert(code, line)
   codeString = string.sub(codeString, subPos)
  end
  table.insert(codeLines, code)
 end
 loadDisplay(codeLines[codeNumber])
 while true do
  e,p = os.pullEvent("key")
  if not menuOpen then
   if p == keys.up then
    if lineUp >= 0 then
     term.scroll(-1)
     term.setCursorPos(1, 1)
     term.write(codeLines[codeNumber][lineUp])
     lineDown = lineDown - 1
     lineUp = lineUp - 1
    end
   elseif p == keys.down then
    if lineDown <= #codeLines[codeNumber] then
     term.scroll(1)
     term.setCursorPos(1, termHeight)
     term.write(codeLines[codeNumber][lineDown])
     lineDown = lineDown + 1
     lineUp = lineUp + 1
    end
   elseif p == keys.left then
    if codeNumber > 1 then
     codeNumber = codeNumber - 1
     loadDisplay(codeLines[codeNumber])
     lineUp = 0
     lineDown = termHeight+1
    end
   elseif p == keys.right then
    if codeNumber < #codeLines then
     codeNumber = codeNumber + 1
     loadDisplay(codeLines[codeNumber])
     lineUp = 0
     lineDown = termHeight+1
    end
   elseif p == keys.rightCtrl or p == keys.leftCtrl then
    term.setCursorPos(1, termHeight)
    option = 1
    term.clearLine()
    term.write(options[option])
    menuOpen = true
   end
  else
   if p == keys.leftCtrl or p == keys.rightCtrl then
    term.setCursorPos(1, termHeight)
    term.clearLine()
    if codeLines[codeNumber][lineDown-1] then term.write(codeLines[codeNumber][lineDown-1]) end
    menuOpen = false
   elseif p == keys.left then
    option = ((option-2)%3)+1
    term.setCursorPos(1, termHeight)
    term.clearLine()
    term.write(options[option])
   elseif p == keys.right then
    option = ((option)%3)+1
    term.setCursorPos(1, termHeight)
    term.clearLine()
    term.write(options[option])
   elseif p == keys.enter then
    if option == 1 then
     save(codeLines[codeNumber])
     table.remove(codeLines, codeNumber)
     codeNumber = 1
     if #codeLines < 1 then
      return true
     end
     loadDisplay(codeLines[codeNumber])
     menuOpen = false
    elseif option == 2 then
     table.remove(codeLines, codeNumber)
     codeNumber = 1
     if #codeLines < 1 then
      return true
     end
     loadDisplay(codeLines[codeNumber])
     lineUp = 0
     lineDown = termHeight+1
     menuOpen = false
    elseif option == 3 then return false
    end
   end
  end
 end
end

function loadDisplay(lines, offset)
 term.clear()
 term.setCursorPos(1, 1)
 offset = offset or 0
 local height = ({term.getSize()})[2]
 term.clear()
 term.setCursorPos(1, 1)
 for index = 1,height do
  term.setCursorPos(1, index)
  if lines[index+offset] then term.write(lines[index+offset]) else break end
 end
end

function save(lines)
 local saved = false
 while not saved do
  while not saved do
   term.clear()
   term.setCursorPos(1, 1)
   print("Please enter a valid filepath:")
   local path = read()
   if string.find(path, "[^%w%-_/]+") or string.find(path, "//") then print("Error: path contains invalid characters") sleep(3) break end
   if string.sub(path, 1, 1) ~= "/" then path = "/"..path end
   if string.sub(path, path:len()) ~= "/" then path = path.."/" end
   local pathParts = {}
   while true do
    local part, subPos = string.match(path, "/(.-)()/")
    if not part then break end
    table.insert(pathParts, part)
    path = string.sub(path, subPos)
   end
   local constructedPath = ""
   if #pathParts < 1 then print("Error: No file specified") sleep(3) end
   for i,pathPart in ipairs(pathParts) do
    if pathPart == "" then
     print("Error: Missing directory in path")
     sleep(3)
     break
    end
    constructedPath = constructedPath .. "/" .. pathPart
    if (not fs.exists(constructedPath)) and (i<#pathParts) then fs.makeDir(constructedPath)
    elseif fs.exists(constructedPath) and (not fs.isDir(constructedPath)) then print("Error: directory\n", constructedPath, "\nis already a file.") sleep(3) break
    elseif fs.exists(constructedPath) and i==#pathParts then print("Error: file\n", constructedPath, "\nalready exists.") sleep(3) break
    else
     print("Path: "..constructedPath)
     local file = fs.open(constructedPath, "w")
     if not file then print("An unknown error occured while opening the file.") sleep(3) break end
     file.write(table.concat(lines, "\n"))
     file.close()
     saved = true
     term.clear()
     term.setCursorPos(1, 1)
     print("Successfully saved code to:")
     print(constructedPath)
     sleep(3)
     break
    end
   end
  end
 end
end

local function main()
 local html
 repeat
  local url = makeURL(getInfo("ID#"), getInfo("page"))
  html = getPage(url)
  if not html then print("Too many failed attemps, try again later.") return false end
  local valid = not hasError(html)
  if not valid then print("An error occured. Your ID may be invalid.") end
 until valid
 local codes = extractCode(html)
 local codes = unescape(codes)
 if #codes == 0 then print("There is no code on that page") return true end
 print("Press any key to view collected code.")
 while true do local e,p = os.pullEvent("key") if p~=keys.escape then break end end
 if displayCodes(codes) then
  term.clear()
  term.setCursorPos(1, 1)
  print("There is no code left to display")
  print("Press any key to exit")
  while true do local e,p = os.pullEvent("key") if p~=keys.escape then break end end sleep(0)
 end
 term.clear()
 term.setCursorPos(1, 1)
 return true
end

main()