MBS as default shell

4 files changed, 1350 insertions, 0 deletions

diff --git a/.mbs/lib/blit_window.lua b/.mbs/lib/blit_window.lua
new file mode 100644
index 0000000..39cd843
--- /dev/null
+++ b/.mbs/lib/blit_window.lua
@@ -0,0 +1,297 @@
+local colour_lookup = {}
+for i = 0, 16 do
+  colour_lookup[2 ^ i] = string.format("%x", i)
+end
+
+function create(original)
+  if not original then original = term.current() end
+
+  local text = {}
+  local text_colour = {}
+  local back_colour = {}
+  local palette = {}
+
+  local cursor_x, cursor_y = 1, 1
+
+  local cursor_blink = false
+  local cur_text_colour = "0"
+  local cur_back_colour = "f"
+
+  local sizeX, sizeY = original.getSize()
+  local color = original.isColor()
+
+  local bubble = true
+
+  local redirect = {}
+
+  if original.getPaletteColour then
+    for i = 0, 15 do
+      local c = 2 ^ i
+      palette[c] = { original.getPaletteColour(c) }
+    end
+  end
+
+  function redirect.write(writeText)
+    writeText = tostring(writeText)
+    if bubble then original.write(writeText) end
+
+    local pos = cursor_x
+
+    -- If we're off the screen then just emulate a write
+    if cursor_y > sizeY or cursor_y < 1 then
+      cursor_x = pos + #writeText
+      return
+    end
+
+    if pos + #writeText <= 1 or pos > sizeX then
+      -- If we're too far off the left then skip.
+      cursor_x = pos + #writeText
+      return
+    elseif pos < 1 then
+      -- Adjust text to fit on screen starting at one.
+      writeText = string.sub(writeText, math.abs(cursor_x) + 2)
+      pos = 1
+    end
+
+    local lineText = text[cursor_y]
+    local lineColor = text_colour[cursor_y]
+    local lineBack = back_colour[cursor_y]
+    local preStop = pos - 1
+    local preStart = math.min(1, preStop)
+    local postStart = pos + string.len(writeText)
+    local postStop = sizeX
+    local sub, rep = string.sub, string.rep
+
+    text[cursor_y] = sub(lineText, preStart, preStop)..writeText..sub(lineText, postStart, postStop)
+    text_colour[cursor_y] = sub(lineColor, preStart, preStop)..rep(cur_text_colour, #writeText)..sub(lineColor, postStart, postStop)
+    back_colour[cursor_y] = sub(lineBack, preStart, preStop)..rep(cur_back_colour, #writeText)..sub(lineBack, postStart, postStop)
+    cursor_x = pos + string.len(writeText)
+  end
+
+  function redirect.blit(writeText, writeFore, writeBack)
+    if type(writeText) ~= "string" then error("bad argument #1 (expected string, got " .. type(writeText) .. ")", 2) end
+    if type(writeFore) ~= "string" then error("bad argument #2 (expected string, got " .. type(writeFore) .. ")", 2) end
+    if type(writeBack) ~= "string" then error("bad argument #3 (expected string, got " .. type(writeBack) .. ")", 2) end
+    if #writeFore ~= #writeText or #writeBack ~= #writeText then error("Arguments must be the same length", 2) end
+
+    if bubble then original.blit(writeText, writeFore, writeBack) end
+    local pos = cursor_x
+
+    -- If we're off the screen then just emulate a write
+    if cursor_y > sizeY or cursor_y < 1 then
+      cursor_x = pos + #writeText
+      return
+    end
+
+    if pos + #writeText <= 1 then
+      --skip entirely.
+      cursor_x = pos + #writeText
+      return
+    elseif pos < 1 then
+      --adjust text to fit on screen starting at one.
+      writeText = string.sub(writeText, math.abs(cursor_x) + 2)
+      writeFore = string.sub(writeFore, math.abs(cursor_x) + 2)
+      writeBack = string.sub(writeBack, math.abs(cursor_x) + 2)
+      cursor_x = 1
+    elseif pos > sizeX then
+      --if we're off the edge to the right, skip entirely.
+      cursor_x = pos + #writeText
+      return
+    end
+
+    local lineText = text[cursor_y]
+    local lineColor = text_colour[cursor_y]
+    local lineBack = back_colour[cursor_y]
+    local preStop = cursor_x - 1
+    local preStart = math.min(1, preStop)
+    local postStart = cursor_x + string.len(writeText)
+    local postStop = sizeX
+    local sub = string.sub
+
+    text[cursor_y] = sub(lineText, preStart, preStop)..writeText..sub(lineText, postStart, postStop)
+    text_colour[cursor_y] = sub(lineColor, preStart, preStop)..writeFore..sub(lineColor, postStart, postStop)
+    back_colour[cursor_y] = sub(lineBack, preStart, preStop)..writeBack..sub(lineBack, postStart, postStop)
+    cursor_x = pos + string.len(writeText)
+  end
+
+  function redirect.clear()
+    for i = 1, sizeY do
+      text[i] = string.rep(" ", sizeX)
+      text_colour[i] = string.rep(cur_text_colour, sizeX)
+      back_colour[i] = string.rep(cur_back_colour, sizeX)
+    end
+
+    if bubble then return original.clear() end
+  end
+
+  function redirect.clearLine()
+    -- If we're off the screen then just emulate a clearLine
+    if cursor_y > sizeY or cursor_y < 1 then
+      return
+    end
+
+    text[cursor_y] = string.rep(" ", sizeX)
+    text_colour[cursor_y] = string.rep(cur_text_colour, sizeX)
+    back_colour[cursor_y] = string.rep(cur_back_colour, sizeX)
+
+    if bubble then return original.clearLine() end
+  end
+
+  function redirect.getCursorPos()
+    return cursor_x, cursor_y
+  end
+
+  function redirect.setCursorPos(x, y)
+    if type(x) ~= "number" then error("bad argument #1 (expected number, got " .. type(x) .. ")", 2) end
+    if type(y) ~= "number" then error("bad argument #2 (expected number, got " .. type(y) .. ")", 2) end
+
+    cursor_x = math.floor(x)
+    cursor_y = math.floor(y)
+    if bubble then return original.setCursorPos(x, y) end
+  end
+
+  function redirect.setCursorBlink(b)
+    cursor_blink = b
+    if bubble then return original.setCursorBlink(b) end
+  end
+
+  function redirect.getSize()
+    return sizeX, sizeY
+  end
+
+  function redirect.scroll(n)
+    if type(n) ~= "number" then error("bad argument #1 (expected number, got " .. type(n) .. ")", 2) end
+
+    local empty_text = string.rep(" ", sizeX)
+    local empty_text_colour = string.rep(cur_text_colour, sizeX)
+    local empty_back_colour = string.rep(cur_back_colour, sizeX)
+    if n > 0 then
+      for i = 1, sizeY do
+        text[i] = text[i + n] or empty_text
+        text_colour[i] = text_colour[i + n] or empty_text_colour
+        back_colour[i] = back_colour[i + n] or empty_back_colour
+      end
+    elseif n < 0 then
+      for i = sizeY, 1, -1 do
+        text[i] = text[i + n] or empty_text
+        text_colour[i] = text_colour[i + n] or empty_text_colour
+        back_colour[i] = back_colour[i + n] or empty_back_colour
+      end
+    end
+
+    if bubble then return original.scroll(n) end
+  end
+
+  function redirect.setTextColour(clr)
+    if type(clr) ~= "number" then error("bad argument #1 (expected number, got " .. type(clr) .. ")", 2) end
+    cur_text_colour = colour_lookup[clr] or error("Invalid colour (got " .. clr .. ")" , 2)
+    if bubble then return original.setTextColour(clr) end
+  end
+  redirect.setTextColor = redirect.setTextColour
+
+  function redirect.setBackgroundColour(clr)
+    if type(clr) ~= "number" then error("bad argument #1 (expected number, got " .. type(clr) .. ")", 2) end
+    cur_back_colour = colour_lookup[clr] or error("Invalid colour (got " .. clr .. ")" , 2)
+    if bubble then return original.setBackgroundColour(clr) end
+  end
+  redirect.setBackgroundColor = redirect.setBackgroundColour
+
+  function redirect.isColour()
+    return color == true
+  end
+  redirect.isColor = redirect.isColour
+
+  function redirect.getTextColour()
+    return 2 ^ tonumber(cur_text_colour, 16)
+  end
+  redirect.getTextColor = redirect.getTextColour
+
+  function redirect.getBackgroundColour()
+    return 2 ^ tonumber(cur_back_colour, 16)
+  end
+  redirect.getBackgroundColor = redirect.getBackgroundColour
+
+  if original.getPaletteColour then
+    function redirect.setPaletteColour(colour, r, g, b)
+      local palcol = palette[colour]
+      if not palcol then error("Invalid colour (got " .. tostring(colour) .. ")", 2) end
+      if type(r) == "number" and g == nil and b == nil then
+          palcol[1], palcol[2], palcol[3] = colours.rgb8(r)
+      else
+          if type(r) ~= "number" then error("bad argument #2 (expected number, got " .. type(r) .. ")", 2) end
+          if type(g) ~= "number" then error("bad argument #3 (expected number, got " .. type(g) .. ")", 2) end
+          if type(b) ~= "number" then error("bad argument #4 (expected number, got " .. type(b) .. ")", 2) end
+
+          palcol[1], palcol[2], palcol[3] = r, g, b
+      end
+
+      if bubble then return original.setPaletteColour(colour, r, g, b) end
+    end
+    redirect.setPaletteColor = redirect.setPaletteColour
+
+    function redirect.getPaletteColour(colour)
+      local palcol = palette[colour]
+      if not palcol then error("Invalid colour (got " .. tostring(colour) .. ")", 2) end
+      return palcol[1], palcol[2], palcol[3]
+    end
+    redirect.getPaletteColor = redirect.getPaletteColour
+  end
+
+  function redirect.draw(target)
+    if not target then target = original end
+
+    if target.getPaletteColour then
+      for colour, pal in pairs(palette) do
+        target.setPaletteColour(colour, pal[1], pal[2], pal[3])
+      end
+    end
+
+    for i=1, sizeY do
+      target.setCursorPos(1,i)
+      target.blit(text[i], text_colour[i], back_colour[i])
+    end
+
+    target.setCursorPos(cursor_x, cursor_y)
+    target.setTextColour(2 ^ tonumber(cur_text_colour, 16))
+    target.setBackgroundColor(2 ^ tonumber(cur_back_colour, 16))
+    target.setCursorBlink(cursor_blink)
+  end
+
+  function redirect.bubble(b)
+    bubble = b
+  end
+
+  function redirect.updateSize()
+    local new_x, new_y = original.getSize()
+    if new_x == sizeX and new_y == sizeY then return end
+
+    -- For any existing lines, trim them
+    for y = 1, sizeY do
+      if new_x < sizeX then
+        text[y] = text[y]:sub(1, new_x)
+        text_colour[y] = text_colour[y]:sub(1, new_x)
+        back_colour[y] = back_colour[y]:sub(1, new_x)
+      elseif new_x > sizeX then
+        text[y] = text[y] .. (" "):rep(new_x - sizeX)
+        text_colour[y] = text_colour[y] .. (cur_text_colour):rep(new_x - sizeX)
+        back_colour[y] = back_colour[y] .. (cur_back_colour):rep(new_x - sizeX)
+      end
+    end
+
+    -- Add any new lines we might need.
+    local text_line = (" "):rep(new_x)
+    local fore_line = (cur_text_colour):rep(new_x)
+    local back_line = (cur_back_colour):rep(new_x)
+    for y = sizeY + 1, new_y do
+      text[y] = text_line
+      text_colour[y] = fore_line
+      back_colour[y] = back_line
+    end
+
+    sizeX = new_x
+    sizeY = new_y
+  end
+
+  redirect.clear()
+  return redirect
+end
\ No newline at end of file
diff --git a/.mbs/lib/readline.lua b/.mbs/lib/readline.lua
new file mode 100644
index 0000000..ba322a6
--- /dev/null
+++ b/.mbs/lib/readline.lua
@@ -0,0 +1,506 @@
+
+--- A mapping of colours, to aid reading settings.
+local colour_table = { }
+
+for k, v in pairs(colours) do
+  if type(v) == "number" then colour_table[k] = v end
+end
+
+for k, v in pairs(colors) do
+  if type(v) == "number" then colour_table[k] = v end
+end
+
+--- Keys which are used in combinations involving the "meta" key.
+local meta_keys = "ulcdbf"
+
+--- Clamp a [value] within a range
+local function clamp(value, min, max)
+  if value < min then return min end
+  if value > max then return max end
+  return value
+end
+
+--- Verify a [tbl] has a [key] of nil or the given [type]
+local type = type
+local function check_key(tbl, key, ty)
+   local actual_type = type(tbl[key])
+   if actual_type ~= "nil" and actual_type ~= ty then
+    error(("bad key %s (expected %s, got %s)"):format(key, ty, actual_type), 3)
+  end
+end
+
+function read(opts)
+  if opts == nil then
+    opts = {}
+  elseif type(opts) ~= "table" then
+    error("bad argument #1 (expected table, got " .. type(opts) .. ")", 2)
+  end
+
+  check_key(opts, "replace_char", "string") -- Character to show instead
+  check_key(opts, "history", "table") -- List of previous items
+  check_key(opts, "complete", "function") -- Completion function
+  check_key(opts, "default", "string") -- Initial string
+  check_key(opts, "complete_fg", "number") -- Foreground for completion
+  check_key(opts, "complete_bg", "number") -- Background for completion
+
+  -- Highlight function: (line: string, start: number) -> (end: number, colour:colour)
+  check_key(opts, "highlight", "function")
+
+  local w = term.getSize()
+  local sx = term.getCursorPos()
+
+  local sLine = opts.default or ""
+  local nPos, nScroll = #sLine, 0
+  local tKillRing, nKillRing = {}, 0
+
+  local nHistoryPos
+  local tDown = {}
+  local nMod = 0
+  local replace_char = opts.replace_char and opts.replace_char:sub(1, 1)
+  local complete_fg = opts.complete_fg or colour_table[settings.get("mbs.readline.complete_fg")] or -1
+  local complete_bg = opts.complete_bg or colour_table[settings.get("mbs.readline.complete_bg")] or -1
+
+  local tCompletions
+  local nCompletion
+  local function recomplete()
+    if opts.complete and nPos == #sLine then
+      tCompletions = opts.complete(sLine)
+      if tCompletions and #tCompletions > 0 then
+        nCompletion = 1
+      else
+        nCompletion = nil
+      end
+    else
+      tCompletions = nil
+      nCompletion = nil
+    end
+  end
+
+  local function uncomplete()
+    tCompletions = nil
+    nCompletion = nil
+  end
+
+  local function updateModifier()
+    nMod = 0
+    if tDown[keys.leftCtrl] or tDown[keys.rightCtrl] then nMod = nMod + 1 end
+    if tDown[keys.leftAlt] or tDown[keys.rightAlt]   then nMod = nMod + 2 end
+  end
+
+  local function nextWord()
+    -- Attempt to find the position of the next word
+    local nOffset = sLine:find("%w%W", nPos + 1)
+    if nOffset then return nOffset else return #sLine end
+  end
+
+  local function prevWord()
+    -- Attempt to find the position of the previous word
+    local nOffset = 1
+    while nOffset <= #sLine do
+      local nNext = sLine:find("%W%w", nOffset)
+      if nNext and nNext < nPos then
+        nOffset = nNext + 1
+      else
+        break
+      end
+    end
+    return nOffset - 1
+  end
+
+  local function redraw(_bClear)
+    local cursor_pos = nPos - nScroll
+    if sx + cursor_pos >= w then
+      -- We've moved beyond the RHS, ensure we're on the edge.
+      nScroll = sx + nPos - w
+    elseif cursor_pos < 0 then
+      -- We've moved beyond the LHS, ensure we're on the edge.
+      nScroll = nPos
+    end
+
+    local _, cy = term.getCursorPos()
+    term.setCursorPos(sx, cy)
+    local sReplace = (_bClear and " ") or replace_char
+
+    if opts.highlight and not _bClear then
+      -- We've a highlighting function: step through each line of input
+      local old_col = term.getTextColor()
+      local hl_pos, hl_max, hl_col = 1, #sLine, old_col
+      while hl_pos <= hl_max do
+        local next_pos, next_col = opts.highlight(sLine, hl_pos)
+        if next_pos < hl_pos then error("Highlighting function consumed no input") end
+
+        if next_pos >= nScroll + 1 then
+          if next_col ~= hl_col then term.setTextColor(next_col) hl_col = next_col end
+          if sReplace then
+            term.write(string.rep(sReplace, next_pos - math.max(nScroll + 1, hl_pos) + 1))
+          else
+            term.write(string.sub(sLine, math.max(nScroll + 1, hl_pos), next_pos))
+          end
+        end
+
+        hl_pos = next_pos + 1
+      end
+      term.setTextColor(old_col)
+    else
+      -- If we've no highlighting function, we can go the "fast" path.
+      if sReplace then
+        term.write(string.rep(sReplace, math.max(#sLine - nScroll, 0)))
+      else
+        term.write(string.sub(sLine, nScroll + 1))
+      end
+    end
+
+    if nCompletion then
+      local sCompletion = tCompletions[ nCompletion ]
+      local oldText, oldBg
+      if not _bClear then
+        oldText = term.getTextColor()
+        oldBg = term.getBackgroundColor()
+        if complete_fg > -1 then term.setTextColor(complete_fg) end
+        if complete_bg > -1 then term.setBackgroundColor(complete_bg) end
+      end
+      if sReplace then
+        term.write(string.rep(sReplace, #sCompletion))
+      else
+        term.write(sCompletion)
+      end
+      if not _bClear then
+        term.setTextColor(oldText)
+        term.setBackgroundColor(oldBg)
+      end
+    end
+
+    term.setCursorPos(sx + nPos - nScroll, cy)
+  end
+
+  local function nsub(start, fin)
+    if start < 1 or fin < start then return "" end
+    return sLine:sub(start, fin)
+  end
+
+  local function clear()
+    redraw(true)
+  end
+
+  local function kill(text)
+    if #text == "" then return end
+    nKillRing = nKillRing + 1
+    tKillRing[nKillRing] = text
+  end
+
+  local function acceptCompletion()
+    if nCompletion then
+      -- Clear
+      clear()
+
+      -- Find the common prefix of all the other suggestions which start with the same letter as the current one
+      local sCompletion = tCompletions[ nCompletion ]
+      sLine = sLine .. sCompletion
+      nPos = #sLine
+
+      -- Redraw
+      recomplete()
+      redraw()
+    end
+  end
+
+  term.setCursorBlink(true)
+  recomplete()
+  redraw()
+  while true do
+    local sEvent, param, param1, param2 = os.pullEvent()
+    if sEvent == "char" and (nMod == 0 or nMod == 3 or (nMod == 2 and not meta_keys:find(param, 1, true))) then
+      -- Typed key
+      -- Alt+X will queue a char event, so we limit ourselves to cases where
+      -- no modifier is used, or Ctrl+Alt are (equivalent to AltGr), or the Alt
+      -- key is used and we have no known combination.
+      clear()
+      sLine = string.sub(sLine, 1, nPos) .. param .. string.sub(sLine, nPos + 1)
+      nPos = nPos + 1
+      recomplete()
+      redraw()
+    elseif sEvent == "paste" then
+      -- Pasted text
+      clear()
+      sLine = string.sub(sLine, 1, nPos) .. param .. string.sub(sLine, nPos + 1)
+      nPos = nPos + #param
+      recomplete()
+      redraw()
+    elseif sEvent == "key" then
+      -- All keybindigns within the read loop.
+      -- IMPORTANT: Please update the meta_keys variable up top. Ideally we'd
+      -- make each function operate on a state, and run outside the loop, but
+      -- this will do for now.
+      if param == keys.leftCtrl or param == keys.rightCtrl or param == keys.leftAlt or param == keys.rightAlt then
+        tDown[param] = true
+        updateModifier()
+      elseif param == keys.enter then
+        -- Enter
+        if nCompletion then
+          clear()
+          uncomplete()
+          redraw()
+        end
+        break
+
+      -- Moving through text/completions
+      elseif nMod == 1 and param == keys.d then
+        -- End of stream, abort
+        if nCompletion then
+          clear()
+          uncomplete()
+          redraw()
+        end
+        sLine = nil
+        nPos = 0
+        break
+      elseif (nMod == 0 and param == keys.left) or (nMod == 1 and param == keys.b) then
+        -- Left
+        if nPos > 0 then
+          clear()
+          nPos = nPos - 1
+          recomplete()
+          redraw()
+        end
+      elseif (nMod == 0 and param == keys.right) or (nMod == 1 and param == keys.f) then
+        -- Right
+        if nPos < #sLine then
+          -- Move right
+          clear()
+          nPos = nPos + 1
+          recomplete()
+          redraw()
+        else
+          -- Accept autocomplete
+          acceptCompletion()
+        end
+      elseif nMod == 2 and param == keys.b then
+        -- Word left
+        local nNewPos = prevWord()
+        if nNewPos ~= nPos then
+          clear()
+          nPos = nNewPos
+          recomplete()
+          redraw()
+        end
+      elseif nMod == 2 and param == keys.f then
+        -- Word right
+        local nNewPos = nextWord()
+        if nNewPos ~= nPos then
+          clear()
+          nPos = nNewPos
+          recomplete()
+          redraw()
+        end
+      elseif (nMod == 0 and (param == keys.up or param == keys.down))
+          or (nMod == 1 and (param == keys.p or param == keys.n)) then
+        -- Up or down
+        if nCompletion then
+          -- Cycle completions
+          clear()
+          if param == keys.up or param == keys.p then
+            nCompletion = nCompletion - 1
+            if nCompletion < 1 then
+              nCompletion = #tCompletions
+            end
+          elseif param == keys.down or param == keys.n then
+            nCompletion = nCompletion + 1
+            if nCompletion > #tCompletions then
+              nCompletion = 1
+            end
+          end
+          redraw()
+        elseif opts.history then
+          -- Cycle history
+          clear()
+          if param == keys.up or param == keys.p then
+            -- Up
+            if nHistoryPos == nil then
+              if #opts.history > 0 then
+                nHistoryPos = #opts.history
+              end
+            elseif nHistoryPos > 1 then
+              nHistoryPos = nHistoryPos - 1
+            end
+          elseif param == keys.down or param == keys.n then
+            -- Down
+            if nHistoryPos == #opts.history then
+              nHistoryPos = nil
+            elseif nHistoryPos ~= nil then
+              nHistoryPos = nHistoryPos + 1
+            end
+          end
+          if nHistoryPos then
+            sLine = opts.history[nHistoryPos]
+            nPos, nScroll = #sLine, 0
+          else
+            sLine = ""
+            nPos, nScroll = 0, 0
+          end
+          uncomplete()
+          redraw()
+        end
+      elseif (nMod == 0 and param == keys.home)
+          or (nMod == 1 and param == keys.a) then
+        -- Home
+        if nPos > 0 then
+          clear()
+          nPos = 0
+          recomplete()
+          redraw()
+        end
+      elseif (nMod == 0 and param == keys["end"])
+          or (nMod == 1 and param == keys.e) then
+        -- End
+        if nPos < #sLine then
+          clear()
+          nPos = #sLine
+          recomplete()
+          redraw()
+        end
+      -- Changing text
+      elseif nMod == 1 and param == keys.t then
+        -- Transpose char
+        local prev, cur
+        if nPos == #sLine then prev, cur = nPos - 1, nPos
+        elseif nPos == 0 then prev, cur = 1, 2
+        else prev, cur = nPos, nPos + 1
+        end
+
+        sLine = nsub(1, prev - 1) .. nsub(cur, cur) .. nsub(prev, prev) .. nsub(cur + 1, #sLine)
+        nPos = math.min(#sLine, cur)
+
+        -- We need the clear to remove the completion
+        clear(); recomplete(); redraw()
+      elseif nMod == 2 and param == keys.u then
+        -- Upcase word
+        if nPos < #sLine then
+          local nNext = nextWord()
+          sLine = nsub(1, nPos) .. nsub(nPos + 1, nNext):upper() .. nsub(nNext + 1, #sLine)
+          nPos = nNext
+          clear(); recomplete(); redraw()
+        end
+      elseif nMod == 2 and param == keys.l then
+        -- Lowercase word
+        if nPos < #sLine then
+          local nNext = nextWord()
+          sLine = nsub(1, nPos) .. nsub(nPos + 1, nNext):lower() .. nsub(nNext + 1, #sLine)
+          nPos = nNext
+          clear(); recomplete(); redraw()
+        end
+      elseif nMod == 2 and param == keys.c then
+        -- Capitalize word
+        if nPos < #sLine then
+          local nNext = nextWord()
+          sLine = nsub(1, nPos) .. nsub(nPos + 1, nPos + 1):upper()
+               .. nsub(nPos + 2, nNext):lower() .. nsub(nNext + 1, #sLine)
+          nPos = nNext
+          clear(); recomplete(); redraw()
+        end
+
+      -- Killing text
+      elseif nMod == 0 and param == keys.backspace then
+        -- Backspace
+        if nPos > 0 then
+          clear()
+          sLine = string.sub(sLine, 1, nPos - 1) .. string.sub(sLine, nPos + 1)
+          nPos = nPos - 1
+          if nScroll > 0 then nScroll = nScroll - 1 end
+          recomplete()
+          redraw()
+        end
+      elseif nMod == 0 and param == keys.delete then
+        -- Delete
+        if nPos < #sLine then
+          clear()
+          sLine = string.sub(sLine, 1, nPos) .. string.sub(sLine, nPos + 2)
+          recomplete()
+          redraw()
+        end
+      elseif nMod == 1 and param == keys.u then
+        -- Delete from cursor to beginning of line
+        if nPos > 0 then
+          clear()
+          kill(sLine:sub(1, nPos))
+          sLine = sLine:sub(nPos + 1)
+          nPos = 0
+          recomplete(); redraw()
+        end
+      elseif nMod == 1 and param == keys.k then
+        -- Delete from cursor to end of line
+        if nPos < #sLine then
+          clear()
+          kill(sLine:sub(nPos + 1))
+          sLine = sLine:sub(1, nPos)
+          nPos = #sLine
+          recomplete(); redraw()
+        end
+      elseif nMod == 2 and param == keys.d then
+        -- Delete from cursor to end of next word
+        if nPos < #sLine then
+            local nNext = nextWord()
+            if nNext ~= nPos then
+              clear()
+              kill(sLine:sub(nPos + 1, nNext))
+              sLine = sLine:sub(1, nPos) .. sLine:sub(nNext + 1)
+              recomplete(); redraw()
+            end
+        end
+      elseif nMod == 1 and param == keys.w then
+        -- Delete from cursor to beginning of previous word
+        if nPos > 0 then
+          local nPrev = prevWord(nPos)
+          if nPrev ~= nPos then
+            clear()
+            kill(sLine:sub(nPrev + 1, nPos))
+            sLine = sLine:sub(1, nPrev) .. sLine:sub(nPos + 1)
+            nPos = nPrev
+            recomplete(); redraw()
+          end
+        end
+      elseif nMod == 1 and param == keys.y then
+        local insert = tKillRing[nKillRing]
+        if insert then
+          clear()
+          sLine = sLine:sub(1, nPos) .. insert .. sLine:sub(nPos + 1)
+          nPos = nPos + #insert
+          recomplete(); redraw()
+        end
+      -- Misc
+      elseif nMod == 0 and param == keys.tab then
+        -- Tab (accept autocomplete)
+        acceptCompletion()
+      end
+    elseif sEvent == "key_up" then
+      -- Update the status of the modifier flag
+      if param == keys.leftCtrl or param == keys.rightCtrl
+      or param == keys.leftAlt or param == keys.rightAlt then
+        tDown[param] = false
+        updateModifier()
+      end
+    elseif sEvent == "mouse_click" or sEvent == "mouse_drag" and param == 1 then
+      local _, cy = term.getCursorPos()
+      if param2 == cy then
+        -- We first clamp the x position with in the start and end points
+        -- to ensure we don't scroll beyond the visible region.
+        local x = clamp(param1, sx, w)
+
+        -- Then ensure we don't scroll beyond the current line
+        nPos = clamp(nScroll + x - sx, 0, #sLine)
+
+        redraw()
+      end
+    elseif sEvent == "term_resize" then
+      -- Terminal resized
+      w = term.getSize()
+      redraw()
+    end
+  end
+
+  local _, cy = term.getCursorPos()
+  term.setCursorBlink(false)
+  term.setCursorPos(w + 1, cy)
+  print()
+
+  return sLine
+end
\ No newline at end of file
diff --git a/.mbs/lib/scroll_window.lua b/.mbs/lib/scroll_window.lua
new file mode 100644
index 0000000..75a6fb1
--- /dev/null
+++ b/.mbs/lib/scroll_window.lua
@@ -0,0 +1,459 @@
+local type = type
+
+local colour_lookup = {}
+for i = 0, 16 do
+  colour_lookup[2 ^ i] = string.format("%x", i)
+end
+
+function create(original)
+  if not original then original = term.current() end
+
+  local text = {}
+  local text_colour = {}
+  local back_colour = {}
+  local palette = {}
+
+  local cursor_x, cursor_y = 1, 1
+
+  local scroll_offset = 0
+  local scroll_cursor_y = cursor_y
+
+  local cursor_blink = false
+  local cur_text_colour = "0"
+  local cur_back_colour = "f"
+
+  local sizeX, sizeY = original.getSize()
+  local color = original.isColor()
+
+  local max_scrollback = 100
+  local bubble, delegate = true, nil
+
+  local cursor_threshold = 0
+
+  local redirect = {}
+
+  if original.getPaletteColour then
+    for i = 0, 15 do
+      local c = 2 ^ i
+      palette[c] = { original.getPaletteColour(c) }
+    end
+  end
+
+  local function trim()
+    if max_scrollback > -1 then
+      while scroll_offset > max_scrollback do
+        table.remove(text, 1)
+        table.remove(text_colour, 1)
+        table.remove(back_colour, 1)
+        scroll_offset = scroll_offset - 1
+      end
+    end
+    scroll_cursor_y = scroll_offset + cursor_y
+  end
+
+  function redirect.write(writeText)
+    if delegate then return delegate.write(writeText) end
+
+    writeText = tostring(writeText)
+    if bubble then original.write(writeText) end
+
+    local pos = cursor_x
+
+    -- If we're off the screen then just emulate a write
+    if cursor_y > sizeY or cursor_y < 1 then
+      cursor_x = pos + #writeText
+      return
+    end
+
+    if pos + #writeText <= 1 or pos > sizeX then
+      -- If we're too far off the left then skip.
+      cursor_x = pos + #writeText
+      return
+    elseif pos < 1 then
+      -- Adjust text to fit on screen starting at one.
+      writeText = string.sub(writeText, -pos + 2)
+      pos = 1
+    end
+
+    local lineText = text[scroll_cursor_y]
+    local lineColor = text_colour[scroll_cursor_y]
+    local lineBack = back_colour[scroll_cursor_y]
+    local preStop = pos - 1
+    local preStart = math.min(1, preStop)
+    local postStart = pos + string.len(writeText)
+    local postStop = sizeX
+    local sub, rep = string.sub, string.rep
+
+    text[scroll_cursor_y] = sub(lineText, preStart, preStop)..writeText..sub(lineText, postStart, postStop)
+    text_colour[scroll_cursor_y] = sub(lineColor, preStart, preStop)..rep(cur_text_colour, #writeText)..sub(lineColor, postStart, postStop)
+    back_colour[scroll_cursor_y] = sub(lineBack, preStart, preStop)..rep(cur_back_colour, #writeText)..sub(lineBack, postStart, postStop)
+    cursor_x = pos + string.len(writeText)
+  end
+
+  function redirect.blit(writeText, writeFore, writeBack)
+    if delegate then return delegate.blit(writeText, writeFore, writeBack) end
+
+    if type(writeText) ~= "string" then error("bad argument #1 (expected string, got " .. type(writeText) .. ")", 2) end
+    if type(writeFore) ~= "string" then error("bad argument #2 (expected string, got " .. type(writeFore) .. ")", 2) end
+    if type(writeBack) ~= "string" then error("bad argument #3 (expected string, got " .. type(writeBack) .. ")", 2) end
+    if #writeFore ~= #writeText or #writeBack ~= #writeText then error("Arguments must be the same length", 2) end
+
+    if bubble then original.blit(writeText, writeFore, writeBack) end
+
+    local pos = cursor_x
+
+    -- If we're off the screen then just emulate a write
+    if cursor_y > sizeY or cursor_y < 1 then
+      cursor_x = pos + #writeText
+      return
+    end
+
+    if pos + #writeText <= 1 then
+      --skip entirely.
+      cursor_x = pos + #writeText
+      return
+    elseif pos < 1 then
+      --adjust text to fit on screen starting at one.
+      writeText = string.sub(writeText, math.abs(cursor_x) + 2)
+      writeFore = string.sub(writeFore, math.abs(cursor_x) + 2)
+      writeBack = string.sub(writeBack, math.abs(cursor_x) + 2)
+      cursor_x = 1
+    elseif pos > sizeX then
+      --if we're off the edge to the right, skip entirely.
+      cursor_x = pos + #writeText
+      return
+    else
+      writeText = writeText
+    end
+
+    local lineText = text[scroll_cursor_y]
+    local lineColor = text_colour[scroll_cursor_y]
+    local lineBack = back_colour[scroll_cursor_y]
+    local preStop = cursor_x - 1
+    local preStart = math.min(1, preStop)
+    local postStart = cursor_x + string.len(writeText)
+    local postStop = sizeX
+    local sub = string.sub
+
+    text[scroll_cursor_y] = sub(lineText, preStart, preStop)..writeText..sub(lineText, postStart, postStop)
+    text_colour[scroll_cursor_y] = sub(lineColor, preStart, preStop)..writeFore..sub(lineColor, postStart, postStop)
+    back_colour[scroll_cursor_y] = sub(lineBack, preStart, preStop)..writeBack..sub(lineBack, postStart, postStop)
+    cursor_x = pos + #writeText
+  end
+
+  function redirect.clear()
+    if delegate then return delegate.clear() end
+
+    if cursor_threshold > 0 then
+      return redirect.beginPrivateMode().clear()
+    end
+
+    local text_line = (" "):rep(sizeX)
+    local fore_line = (cur_text_colour):rep(sizeX)
+    local back_line = (cur_back_colour):rep(sizeX)
+
+    for i = scroll_offset + 1, sizeY + scroll_offset do
+      text[i] = text_line
+      text_colour[i] = fore_line
+      back_colour[i] = back_line
+    end
+
+    if bubble then return original.clear() end
+  end
+  function redirect.clearLine()
+    if delegate then return delegate.clearLine() end
+
+    -- If we're off the screen then just emulate a clearLine
+    if cursor_y > sizeY or cursor_y < 1 then
+      return
+    end
+
+    text[scroll_cursor_y] = string.rep(" ", sizeX)
+    text_colour[scroll_cursor_y] = string.rep(cur_text_colour, sizeX)
+    back_colour[scroll_cursor_y] = string.rep(cur_back_colour, sizeX)
+
+    if bubble then return original.clearLine() end
+  end
+
+  function redirect.getCursorPos()
+    if delegate then return delegate.getCursorPos() end
+    return cursor_x, cursor_y
+  end
+
+  function redirect.setCursorPos(x, y)
+    if delegate then return delegate.setCursorPos(x, y) end
+
+    if type(x) ~= "number" then error("bad argument #1 (expected number, got " .. type(x) .. ")", 2) end
+    if type(y) ~= "number" then error("bad argument #2 (expected number, got " .. type(y) .. ")", 2) end
+
+    local new_y = math.floor(y)
+    if new_y >= 1 and new_y < cursor_threshold then
+      -- If we're writing within a protected region then start a private buffer
+      return redirect.beginPrivateMode().setCursorPos(x, y)
+    end
+
+    cursor_x = math.floor(x)
+    cursor_y = new_y
+    scroll_cursor_y = new_y + scroll_offset
+
+    if bubble then return original.setCursorPos(x, y) end
+  end
+
+  function redirect.setCursorBlink(b)
+    if delegate then return delegate.setCursorBlink(b) end
+
+    if type(b) ~= "boolean" then error("bad argument #1 (expected boolean, got " .. type(b) .. ")", 2) end
+
+    cursor_blink = b
+    if bubble then return original.setCursorBlink(b) end
+  end
+
+  function redirect.getSize()
+    if delegate then return delegate.getSize() end
+
+    return sizeX, sizeY
+  end
+
+  function redirect.scroll(n)
+    if delegate then return delegate.scroll(n) end
+
+    if type(n) ~= "number" then error("bad argument #1 (expected number, got " .. type(n) .. ")", 2) end
+
+    if n > 0 then
+      scroll_offset = scroll_offset + n
+      for i = sizeY + scroll_offset - n + 1, sizeY + scroll_offset do
+        text[i] = string.rep(" ", sizeX)
+        text_colour[i] = string.rep(cur_text_colour, sizeX)
+        back_colour[i] = string.rep(cur_back_colour, sizeX)
+      end
+
+      trim()
+    elseif n < 0 then
+      for i = sizeY + scroll_cursor_y, math.abs(n) + 1 + scroll_cursor_y, -1 do
+        if text[i + n] then
+          text[i] = text[i + n]
+          text_colour[i] = text_colour[i + n]
+          back_colour[i] = back_colour[i + n]
+        end
+      end
+
+      for i = scroll_cursor_y, math.abs(n) + scroll_cursor_y do
+        text[i] = string.rep(" ", sizeX)
+        text_colour[i] = string.rep(cur_text_colour, sizeX)
+        back_colour[i] = string.rep(cur_back_colour, sizeX)
+      end
+    end
+
+    cursor_threshold = cursor_threshold - n
+
+    if bubble then return original.scroll(n) end
+  end
+
+  function redirect.setTextColour(clr)
+    if delegate then return delegate.setTextColour(clr) end
+
+    if type(clr) ~= "number" then error("bad argument #1 (expected number, got " .. type(clr) .. ")", 2) end
+    cur_text_colour = colour_lookup[clr] or error("Invalid colour (got " .. clr .. ")" , 2)
+    if bubble then return original.setTextColour(clr) end
+  end
+  redirect.setTextColor = redirect.setTextColour
+
+  function redirect.setBackgroundColour(clr)
+    if delegate then return delegate.setBackgroundColour(clr) end
+
+    if type(clr) ~= "number" then error("bad argument #1 (expected number, got " .. type(clr) .. ")", 2) end
+    cur_back_colour = colour_lookup[clr] or error("Invalid colour (got " .. clr .. ")" , 2)
+    if bubble then return original.setBackgroundColour(clr) end
+  end
+  redirect.setBackgroundColor = redirect.setBackgroundColour
+
+  function redirect.isColour()
+    if delegate then return delegate.isColour() end
+    return color == true
+  end
+  redirect.isColor = redirect.isColour
+
+  function redirect.getTextColour()
+    if delegate then return delegate.getTextColour() end
+    return 2 ^ tonumber(cur_text_colour, 16)
+  end
+  redirect.getTextColor = redirect.getTextColour
+
+  function redirect.getBackgroundColour()
+    if delegate then return delegate.getBackgroundColour() end
+    return 2 ^ tonumber(cur_back_colour, 16)
+  end
+  redirect.getBackgroundColor = redirect.getBackgroundColour
+
+  if original.getPaletteColour then
+    function redirect.setPaletteColour(colour, r, g, b)
+      if delegate then return delegate.setPaletteColour(colour, r, g, b) end
+
+      local palcol = palette[colour]
+      if not palcol then error("Invalid colour (got " .. tostring(colour) .. ")", 2) end
+      if type(r) == "number" and g == nil and b == nil then
+          palcol[1], palcol[2], palcol[3] = colours.rgb8(r)
+      else
+          if type(r) ~= "number" then error("bad argument #2 (expected number, got " .. type(r) .. ")", 2) end
+          if type(g) ~= "number" then error("bad argument #3 (expected number, got " .. type(g) .. ")", 2) end
+          if type(b) ~= "number" then error("bad argument #4 (expected number, got " .. type(b) .. ")", 2) end
+
+          palcol[1], palcol[2], palcol[3] = r, g, b
+      end
+
+      if bubble then return original.setPaletteColour(colour, r, g, b) end
+    end
+    redirect.setPaletteColor = redirect.setPaletteColour
+
+    function redirect.getPaletteColour(colour)
+      if delegate then return delegate.getPaletteColour(colour) end
+
+      local palcol = palette[colour]
+      if not palcol then error("Invalid colour (got " .. tostring(colour) .. ")", 2) end
+      return palcol[1], palcol[2], palcol[3]
+    end
+    redirect.getPaletteColor = redirect.getPaletteColour
+  end
+
+  function redirect.draw(offset, clear)
+    if delegate then return end
+
+    if original.getPaletteColour then
+      for colour, pal in pairs(palette) do
+        original.setPaletteColour(colour, pal[1], pal[2], pal[3])
+      end
+    end
+
+    original.setTextColour(2 ^ tonumber(cur_text_colour, 16))
+    original.setBackgroundColor(2 ^ tonumber(cur_back_colour, 16))
+    if clear then original.clear() end
+
+    local original = original
+    local scroll_offset = scroll_offset + (offset or 0)
+    for i = 1, sizeY do
+      original.setCursorPos(1,i)
+      local yOffset = scroll_offset + i
+      original.blit(text[yOffset], text_colour[yOffset], back_colour[yOffset])
+    end
+
+    original.setCursorPos(cursor_x, cursor_y - offset)
+    original.setCursorBlink(cursor_blink)
+  end
+
+  function redirect.bubble(b)
+    bubble = b
+  end
+
+  function redirect.setCursorThreshold(y)
+    cursor_threshold = y
+  end
+
+  function redirect.endPrivateMode(redraw)
+    if delegate then
+      local old_delegate = delegate
+      delegate = nil
+      redirect.draw(0)
+
+      -- If we should redraw the old buffer then blit it to the canvas
+      if redraw then
+        if cursor_threshold > 0 then
+          redirect.scroll(cursor_threshold)
+        end
+
+        old_delegate.draw(redirect)
+      end
+    end
+  end
+
+  function redirect.beginPrivateMode()
+    if not delegate then
+      delegate = blit_window.create(original)
+
+      for y = 1, sizeY do
+        delegate.setCursorPos(1, y)
+        delegate.blit(text[y + scroll_offset], text_colour[y + scroll_offset], back_colour[y + scroll_offset])
+      end
+
+      delegate.setCursorPos(cursor_x, cursor_y)
+      delegate.setCursorBlink(cursor_blink)
+      delegate.setTextColour(2 ^ tonumber(cur_text_colour, 16))
+      delegate.setBackgroundColor(2 ^ tonumber(cur_back_colour, 16))
+
+      if original.getPaletteColour then
+        for i = 0, 15 do
+          local palcol = palette[2 ^ i]
+          delegate.setPaletteColour(2 ^ i, palcol[1], palcol[2], palcol[3])
+        end
+      end
+    end
+
+    return delegate
+  end
+
+  function redirect.isPrivateMode()
+    return delegate ~= nil
+  end
+
+  function redirect.getTotalHeight() return scroll_offset end
+
+  function redirect.setMaxScrollback(n)
+    local old_scrollback = max_scrollback
+    max_scrollback = n
+
+    if old_scrollback > max_scrollback then trim() end
+  end
+
+  function redirect.updateSize()
+    -- Update the delegate window.
+    if delegate then delegate.updateSize() end
+
+    -- If nothing has changed then just skip.
+    local new_x, new_y = original.getSize()
+    if new_x == sizeX and new_y == sizeY then return end
+
+    -- If we have an insufficient number of lines then add some in.
+    local total_height = #text
+
+    -- For any existing lines, trim them
+    for y = 1, total_height do
+      if new_x < sizeX then
+        text[y] = text[y]:sub(1, new_x)
+        text_colour[y] = text_colour[y]:sub(1, new_x)
+        back_colour[y] = back_colour[y]:sub(1, new_x)
+      elseif new_x > sizeX then
+        text[y] = text[y] .. (" "):rep(new_x - sizeX)
+        text_colour[y] = text_colour[y] .. (cur_text_colour):rep(new_x - sizeX)
+        back_colour[y] = back_colour[y] .. (cur_back_colour):rep(new_x - sizeX)
+      end
+    end
+
+    if new_y > sizeY then
+      -- Append any new lines we might need.
+      local text_line = (" "):rep(new_x)
+      local fore_line = (cur_text_colour):rep(new_x)
+      local back_line = (cur_back_colour):rep(new_x)
+      for y = total_height + 1, new_y do
+        text[y] = text_line
+        text_colour[y] = fore_line
+        back_colour[y] = back_line
+      end
+    elseif new_y < sizeY then
+      -- Move the cursor "up" the screen, as we're going to scroll the rest of
+      -- the terminal up.
+      -- Note, this is a little ugly (we lose the top of the screen even if we)
+      -- don't need to, but it's the best we can do for now.
+      cursor_y = cursor_y - sizeY + new_y
+    end
+
+    sizeX = new_x
+    sizeY = new_y
+
+    -- Update the scroll offset. For now we just go back to the bottom
+    scroll_offset = #text - sizeY
+    scroll_cursor_y = scroll_offset + cursor_y
+    trim()
+  end
+
+  redirect.clear()
+  return redirect
+end
\ No newline at end of file
diff --git a/.mbs/lib/stack_trace.lua b/.mbs/lib/stack_trace.lua
new file mode 100644
index 0000000..7674813
--- /dev/null
+++ b/.mbs/lib/stack_trace.lua
@@ -0,0 +1,88 @@
+local type = type
+local debug_traceback = type(debug) == "table" and type(debug.traceback) == "function" and debug.traceback
+
+local function traceback(x)
+  -- Attempt to detect error() and error("xyz", 0).
+  -- This probably means they're erroring the program intentionally and so we
+  -- shouldn't display anything.
+  if x == nil or (type(x) == "string" and not x:find(":%d+:")) then
+    return x
+  end
+
+  if debug_traceback then
+    -- The parens are important, as they prevent a tail call occuring, meaning
+    -- the stack level is preserved. This ensures the code behaves identically
+    -- on LuaJ and PUC Lua.
+    return (debug_traceback(tostring(x), 2))
+  else
+    local level = 3
+    local out = { tostring(x), "stack traceback:" }
+    while true do
+      local _, msg = pcall(error, "", level)
+      if msg == "" then break end
+
+      out[#out + 1] = "  " .. msg
+      level = level + 1
+    end
+
+    return table.concat(out, "\n")
+  end
+end
+
+local function trim_traceback(target, marker)
+  local ttarget, tmarker = {}, {}
+  for line in target:gmatch("([^\n]*)\n?") do ttarget[#ttarget + 1] = line end
+  for line in marker:gmatch("([^\n]*)\n?") do tmarker[#tmarker + 1] = line end
+
+  -- Trim identical suffixes
+  local t_len, m_len = #ttarget, #tmarker
+  while t_len >= 3 and ttarget[t_len] == tmarker[m_len] do
+    table.remove(ttarget, t_len)
+    t_len, m_len = t_len - 1, m_len - 1
+  end
+
+  -- Trim elements from this file and xpcall invocations
+  while t_len >= 1 and ttarget[t_len]:find("^\tstack_trace%.lua:%d+:") or
+        ttarget[t_len] == "\t[C]: in function 'xpcall'" or ttarget[t_len] == "  xpcall: " do
+    table.remove(ttarget, t_len)
+    t_len = t_len - 1
+  end
+
+  return ttarget
+end
+
+--- Run a function with
+local function xpcall_with(fn)
+  -- So this is rather grim: we need to get the full traceback and current one and remove
+  -- the common prefix
+  local trace
+  local res = table.pack(xpcall(fn, traceback)) if not res[1] then trace = traceback("trace.lua:1:") end
+  local ok, err = res[1], res[2]
+
+  if not ok and err ~= nil then
+    trace = trim_traceback(err, trace)
+
+    -- Find the position where the stack traceback actually starts
+    local trace_starts
+    for i = #trace, 1, -1 do
+      if trace[i] == "stack traceback:" then trace_starts = i; break end
+    end
+
+    -- If this traceback is more than 15 elements long, keep the first 9, last 5
+    -- and put an ellipsis between the rest
+    local max = 15
+    if trace_starts and #trace - trace_starts > max then
+      local keep_starts = trace_starts + 10
+      for i = #trace - trace_starts - max, 0, -1 do table.remove(trace, keep_starts + i) end
+      table.insert(trace, keep_starts, "  ...")
+    end
+
+    return false, table.concat(trace, "\n")
+  end
+
+  return table.unpack(res, 1, res.n)
+end
+
+_ENV.traceback = traceback
+_ENV.trim_traceback = trim_traceback
+_ENV.xpcall_with = xpcall_with
\ No newline at end of file