local colors = _G.colors
local term   = _G.term
local _gsub  = string.gsub
local _rep = string.rep
local _sub = string.sub

local Terminal = { }

-- add scrolling functions to a window
function Terminal.scrollable(win, maxScroll)
  local lines = { }
  local scrollPos = 0
  local oblit, oreposition = win.blit, win.reposition

  local palette = { }
  for n = 1, 16 do
    palette[2 ^ (n - 1)] = _sub("0123456789abcdef", n, n)
  end

  maxScroll = maxScroll or 100

  -- should only do if window is visible...
  local function redraw()
    local _, h = win.getSize()
    local x, y = win.getCursorPos()
    for i = 1, h do
      local line = lines[i + scrollPos]
      if line and line.dirty then
        win.setCursorPos(1, i)
        oblit(line.text, line.fg, line.bg)
        line.dirty = false
      end
    end
    win.setCursorPos(x, y)
  end

  local function scrollTo(p, forceRedraw)
    local _, h = win.getSize()
    local ms = #lines - h            -- max scroll
    p = math.min(math.max(p, 0), ms) -- normalize

    if p ~= scrollPos or forceRedraw then
      scrollPos = p
      for _, line in pairs(lines) do
        line.dirty = true
      end
    end
  end

  function win.write(text)
    local _, h = win.getSize()

    scrollTo(#lines - h)
    win.blit(tostring(text),
      _rep(palette[win.getTextColor()], #text),
      _rep(palette[win.getBackgroundColor()], #text))
    local x, y = win.getCursorPos()
    win.setCursorPos(x + #text, y)
  end

  function win.clearLine()
    local w, h = win.getSize()
    local _, y = win.getCursorPos()

    scrollTo(#lines - h)
    lines[y + scrollPos] = {
      text = _rep(' ', w),
      fg = _rep(palette[win.getTextColor()], w),
      bg = _rep(palette[win.getBackgroundColor()], w),
      dirty = true,
    }
    redraw()
  end

  function win.blit(text, fg, bg)
    local x, y = win.getCursorPos()
    local w, h = win.getSize()

    if y > 0 and y <= h and x <= w then
      local width = #text

      -- fix ffs
      if x < 1 then
        text = _sub(text, 2 - x)
        if bg then
          bg = _sub(bg, 2 - x)
        end
        if bg then
          fg = _sub(fg, 2 - x)
        end
        width = width + x - 1
        x = 1
      end

      if x + width - 1 > w then
        text = _sub(text, 1, w - x + 1)
        if bg then
          bg = _sub(bg, 1, w - x + 1)
        end
        if bg then
          fg = _sub(fg, 1, w - x + 1)
        end
        width = #text
      end

      if width > 0 then
        local function replace(sstr, pos, rstr)
          if pos == 1 and width == w then
            return rstr
          elseif pos == 1 then
            return rstr .. _sub(sstr, pos+width)
          elseif pos + width > w then
            return _sub(sstr, 1, pos-1) .. rstr
          end
          return _sub(sstr, 1, pos-1) .. rstr .. _sub(sstr, pos+width)
        end

        local line = lines[y + scrollPos]
        line.dirty = true
        line.text = replace(line.text, x, text, width)
        if fg then
          line.fg = replace(line.fg, x, fg, width)
        end
        if bg then
          line.bg = replace(line.bg, x, bg, width)
        end
      end
    end
    redraw()
  end

  function win.clear()
    local w, h = win.getSize()

    local text = _rep(' ', w)
    local fg = _rep(palette[win.getTextColor()], w)
    local bg = _rep(palette[win.getBackgroundColor()], w)
    lines = { }
    for y = 1, h do
      lines[y] = {
        dirty = true,
        text = text,
        fg = fg,
        bg = bg,
      }
    end
    scrollPos = 0
    redraw()
  end

  -- doesn't support negative scrolling...
  function win.scroll(n)
    local w = win.getSize()

    for _ = 1, n do
      lines[#lines + 1] = {
        text = _rep(' ', w),
        fg = _rep(palette[win.getTextColor()], w),
        bg = _rep(palette[win.getBackgroundColor()], w),
      }
    end

    while #lines > maxScroll do
      table.remove(lines, 1)
    end

    scrollTo(maxScroll, true)
    redraw()
  end

  function win.scrollUp()
    scrollTo(scrollPos - 1)
    redraw()
  end

  function win.scrollDown()
    scrollTo(scrollPos + 1)
    redraw()
  end

  function win.reposition(x, y, nw, nh)
    local w, h = win.getSize()
    local D = (nh or h) - h

    if D > 0 then
      for _ = 1, D do
        lines[#lines + 1] = {
          text = _rep(' ', w),
          fg = _rep(palette[win.getTextColor()], w),
          bg = _rep(palette[win.getBackgroundColor()], w),
        }
      end
    elseif D < 0 then
      for _ = D, -1 do
        lines[#lines] = nil
      end
    end
    return oreposition(x, y, nw, nh)
  end

  win.clear()
end

-- get windows contents
function Terminal.getContents(win, parent)
  local oblit, oscp = parent.blit, parent.setCursorPos
  local lines = { }

  parent.blit = function(text, fg, bg)
    lines[#lines + 1] = {
      text = text,
      fg = fg,
      bg = bg,
    }
  end
  parent.setCursorPos = function() end

  win.setVisible(true)
  win.redraw()

  parent.blit = oblit
  parent.setCursorPos = oscp

  return lines
end

function Terminal.toGrayscale(ct)
  local scolors = {
    [ colors.white ] = colors.white,
    [ colors.orange ] = colors.lightGray,
    [ colors.magenta ] = colors.lightGray,
    [ colors.lightBlue ] = colors.lightGray,
    [ colors.yellow ] = colors.lightGray,
    [ colors.lime ] = colors.lightGray,
    [ colors.pink ] = colors.lightGray,
    [ colors.gray ] = colors.gray,
    [ colors.lightGray ] = colors.lightGray,
    [ colors.cyan ] = colors.lightGray,
    [ colors.purple ] = colors.gray,
    [ colors.blue ] = colors.gray,
    [ colors.brown ] = colors.gray,
    [ colors.green ] = colors.lightGray,
    [ colors.red ] = colors.gray,
    [ colors.black ] = colors.black,
  }

  local methods = { 'setBackgroundColor', 'setBackgroundColour',
                    'setTextColor', 'setTextColour' }
  for _,v in pairs(methods) do
    local fn = ct[v]
    ct[v] = function(c)
      fn(scolors[c])
    end
  end

  local bcolors = {
    [ '1' ] = '8',
    [ '2' ] = '8',
    [ '3' ] = '8',
    [ '4' ] = '8',
    [ '5' ] = '8',
    [ '6' ] = '8',
    [ '9' ] = '8',
    [ 'a' ] = '7',
    [ 'b' ] = '7',
    [ 'c' ] = '7',
    [ 'd' ] = '8',
    [ 'e' ] = '7',
  }

  local function translate(s)
    if s then
      s = _gsub(s, "%w", bcolors)
    end
    return s
  end

  local fn = ct.blit
  ct.blit = function(text, fg, bg)
    fn(text, translate(fg), translate(bg))
  end
end

function Terminal.getNullTerm(ct)
  local nt = Terminal.copy(ct)

  local methods = { 'blit', 'clear', 'clearLine', 'scroll',
                    'setCursorBlink', 'setCursorPos', 'write' }
  for _,v in pairs(methods) do
    nt[v] = function() end
  end

  return nt
end

function Terminal.copy(it, ot)
  ot = ot or { }
  for k,v in pairs(it) do
    if type(v) == 'function' then
      ot[k] = v
    end
  end
  return ot
end

function Terminal.mirror(ct, dt)
  for k,f in pairs(ct) do
    ct[k] = function(...)
      local ret = { f(...) }
      if dt[k] then
        dt[k](...)
      end
      return table.unpack(ret)
    end
  end
end

function Terminal.readPassword(prompt)
  if prompt then
    term.write(prompt)
  end
  local fn = term.current().write
  term.current().write = function() end
  local s
  pcall(function() s = _G.read(prompt) end)
  term.current().write = fn

  if s == '' then
    return
  end
  return s
end

return Terminal