local class  = require('class')
local Region = require('ui.region')
local Util   = require('util')

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

local Canvas = class()

Canvas.colorPalette = { }
Canvas.darkPalette = { }
Canvas.grayscalePalette = { }

for n = 1, 16 do
  Canvas.colorPalette[2 ^ (n - 1)]     = _sub("0123456789abcdef", n, n)
  Canvas.grayscalePalette[2 ^ (n - 1)] = _sub("088888878877787f", n, n)
  Canvas.darkPalette[2 ^ (n - 1)]      = _sub("8777777f77fff77f", n, n)
end

function Canvas:init(args)
  self.x = 1
  self.y = 1
  self.layers = { }

  Util.merge(self, args)

  self.ex = self.x + self.width - 1
  self.ey = self.y + self.height - 1

  if not self.palette then
    if self.isColor then
      self.palette = Canvas.colorPalette
    else
      self.palette = Canvas.grayscalePalette
    end
  end

  self.lines = { }
  for i = 1, self.height do
    self.lines[i] = { }
  end
end

function Canvas:move(x, y)
  self.x, self.y = x, y
  self.ex = self.x + self.width - 1
  self.ey = self.y + self.height - 1
end

function Canvas:resize(w, h)
  for i = self.height, h do
    self.lines[i] = { }
  end

  while #self.lines > h do
    table.remove(self.lines, #self.lines)
  end

  if w ~= self.width then
    for i = 1, self.height do
      self.lines[i] = { dirty = true }
    end
  end

  self.ex = self.x + w - 1
  self.ey = self.y + h - 1
  self.width = w
  self.height = h
end

function Canvas:copy()
  local b = Canvas({
    x       = self.x,
    y       = self.y,
    width   = self.width,
    height  = self.height,
    isColor = self.isColor,
  })
  for i = 1, self.height do
    b.lines[i].text = self.lines[i].text
    b.lines[i].fg = self.lines[i].fg
    b.lines[i].bg = self.lines[i].bg
  end
  return b
end

function Canvas:addLayer(layer)
  local canvas = Canvas({
    x       = layer.x,
    y       = layer.y,
    width   = layer.width,
    height  = layer.height,
    isColor = self.isColor,
  })
  canvas.parent = self
  table.insert(self.layers, canvas)
  return canvas
end

function Canvas:removeLayer()
  for k, layer in pairs(self.parent.layers) do
    if layer == self then
      self:setVisible(false)
      table.remove(self.parent.layers, k)
      break
    end
  end
end

function Canvas:setVisible(visible)
  self.visible = visible
  if not visible then
    self.parent:dirty()
    -- set parent's lines to dirty for each line in self
  end
end

function Canvas:write(x, y, text, bg, fg)
  if bg then
    bg = _rep(self.palette[bg], #text)
  end
  if fg then
    fg = _rep(self.palette[fg], #text)
  end
  self:writeBlit(x, y, text, bg, fg)
end

function Canvas:writeBlit(x, y, text, bg, fg)
  if y > 0 and y <= self.height and x <= self.width 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 > self.width then
      text = _sub(text, 1, self.width - x + 1)
      if bg then
        bg = _sub(bg, 1, self.width - x + 1)
      end
      if bg then
        fg = _sub(fg, 1, self.width - x + 1)
      end
      width = #text
    end

    if width > 0 then

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

      local line = self.lines[y]
      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
end

function Canvas:writeLine(y, text, fg, bg)
  self.lines[y].dirty = true
  self.lines[y].text = text
  self.lines[y].fg = fg
  self.lines[y].bg = bg
end

function Canvas:reset()
  self.regions = nil
end

function Canvas:clear(bg, fg)
  local text = _rep(' ', self.width)
  fg = _rep(self.palette[fg or colors.white], self.width)
  bg = _rep(self.palette[bg or colors.black], self.width)
  for i = 1, self.height do
    self:writeLine(i, text, fg, bg)
  end
end

function Canvas:punch(rect)
  if not self.regions then
    self.regions = Region.new(self.x, self.y, self.ex, self.ey)
  end
  self.regions:subRect(rect.x, rect.y, rect.ex, rect.ey)
end

function Canvas:blitClipped(device)
  for _,region in ipairs(self.regions.region) do
    self:blit(device,
      { x = region[1] - self.x + 1,
        y = region[2] - self.y + 1,
        ex = region[3]- self.x + 1,
        ey = region[4] - self.y + 1 },
      { x = region[1], y = region[2] })
  end
end

function Canvas:redraw(device)
  self:reset()
  if #self.layers > 0 then
    for _,layer in pairs(self.layers) do
      self:punch(layer)
    end
    self:blitClipped(device)
  else
    self:blit(device)
  end
  self:clean()
end

function Canvas:isDirty()
  for _, line in pairs(self.lines) do
    if line.dirty then
      return true
    end
  end
end

function Canvas:dirty()
  for _, line in pairs(self.lines) do
    line.dirty = true
  end
end

function Canvas:clean()
  for _, line in pairs(self.lines) do
    line.dirty = false
  end
end

function Canvas:render(device, layers) --- redrawAll ?
  layers = layers or self.layers
  if #layers > 0 then
    self.regions = Region.new(self.x, self.y, self.ex, self.ey)
    local l = Util.shallowCopy(layers)
    for _, canvas in ipairs(layers) do
      table.remove(l, 1)
      if canvas.visible then
        self:punch(canvas)
        canvas:render(device, l)
      end
    end
    self:blitClipped(device)
    self:reset()
  else
    self:blit(device)
  end
  self:clean()
end

function Canvas:blit(device, src, tgt)
  src = src or { x = 1, y = 1, ex = self.ex - self.x + 1, ey = self.ey - self.y + 1 }
  tgt = tgt or self

  for i = 0, src.ey - src.y do
    local line = self.lines[src.y + i]
    if line and line.dirty then
      local t, fg, bg = line.text, line.fg, line.bg
      if src.x > 1 or src.ex < self.ex then
        t  = _sub(t, src.x, src.ex)
        fg = _sub(fg, src.x, src.ex)
        bg = _sub(bg, src.x, src.ex)
      end
      --if tgt.y + i > self.ey then -- wrong place to do clipping ??
      --  break
      --end
      device.setCursorPos(tgt.x, tgt.y + i)
      device.blit(t, fg, bg)
    end
  end
end

function Canvas:applyPalette(palette)

  local lookup = { }
  for n = 1, 16 do
    lookup[self.palette[2 ^ (n - 1)]] = palette[2 ^ (n - 1)]
  end

  for _, l in pairs(self.lines) do
    l.fg = _gsub(l.fg, '%w', lookup)
    l.bg = _gsub(l.bg, '%w', lookup)
    l.dirty = true
  end

  self.palette = palette
end

function Canvas.convertWindow(win, parent, wx, wy)
  local w, h = win.getSize()

  win.canvas = Canvas({
    x       = wx,
    y       = wy,
    width   = w,
    height  = h,
    isColor = win.isColor(),
  })

  function win.clear()
    win.canvas:clear(win.getBackgroundColor(), win.getTextColor())
  end

  function win.clearLine()
    local _, y = win.getCursorPos()
    win.canvas:write(1,
      y,
      _rep(' ', win.canvas.width),
      win.getBackgroundColor(),
      win.getTextColor())
  end

  function win.write(str)
    local x, y = win.getCursorPos()
    win.canvas:write(x,
      y,
      str,
      win.getBackgroundColor(),
      win.getTextColor())
    win.setCursorPos(x + #str, y)
  end

  function win.blit(text, fg, bg)
    local x, y = win.getCursorPos()
    win.canvas:writeBlit(x, y, text, bg, fg)
  end

  function win.redraw()
    win.canvas:redraw(parent)
  end

  function win.scroll(n)
    table.insert(win.canvas.lines, table.remove(win.canvas.lines, 1))
    win.canvas.lines[#win.canvas.lines].text = _rep(' ', win.canvas.width)
    win.canvas:dirty()
  end

  function win.reposition(x, y, width, height)
    win.canvas.x, win.canvas.y = x, y
    win.canvas:resize(width or win.canvas.width, height or win.canvas.height)
  end

  win.clear()
end

return Canvas