local setmetatable = setmetatable
local math,pairs   = math,pairs
local color        = require( "gears.color" )
local cairo        = require( "lgi"         ).cairo
local wibox        = require( "wibox"       )
local beautiful    = require( "beautiful"   )

local module,colors = {},nil

local function draw_label(cr,angle,radius,center_x,center_y,text)
  cr:set_source_rgba(1,1,1,1)
  cr:move_to(center_x+(radius/2)*math.cos(angle),center_y+(radius/2)*math.sin(angle))
  cr:line_to(center_x+(1.5*radius)*math.cos(angle),center_y+(1.5*radius)*math.sin(angle))
  local x,y = cr:get_current_point()
  cr:line_to(x+(x>center_x and radius/2 or -radius/2),y)
  cr:move_to(x+(x>center_x and radius/2 + 5 or (-radius/2 - cr:text_extents(text).width - 5)),y+(cr.font_extents.height/4))
  cr:show_text(text)
  cr:stroke()
  cr:arc(center_x+(radius/2)*math.cos(angle),center_y+(radius/2)*math.sin(angle),2,0,2*math.pi)
  cr:arc(x+(x>center_x and radius/2 or -radius/2),y,2,0,2*math.pi)
  cr:fill()
end

local function draw_pie(cr,start_rad,end_rad,radius,col,center_x,center_y)
  cr:arc(center_x,center_y,radius,start_rad,end_rad)
  cr:line_to(center_x,center_y)
  cr:line_to(center_x+radius*math.cos(start_rad),center_y+radius*math.sin(start_rad))
  cr:close_path()
  cr:set_source_rgba(1,1,1,1)
  cr:stroke_preserve()
  cr:set_source(col)
  cr:fill()
end

local function compute_sum(data)
  local ret = 0
  for k,v in pairs(data) do ret = ret + v end
  return ret
end

local function draw(self, w, cr, width, height)
  if not self._data then return end

  -- Load from cache
  local cached = self._cache[width*123+height*89]
  if cached then
    cr:set_source_surface(cached)
    cr:paint()
    return
  end

  local img = cairo.ImageSurface.create(cairo.Format.ARGB32, width, height)
  local cr2 = cairo.Context(img)

  local radius = (height > width and width or height) / 4
  local sum,start,count = compute_sum(self._data),0,0
  for k,v in pairs(self._data) do
    local end_angle = start + 2*math.pi*(v/sum)
    draw_pie(cr2,start,end_angle,radius,colors[math.mod(count,4)+1],width/2,height/2)
    draw_label(cr2,start+(end_angle-start)/2,radius,width/2,height/2,k)
    start,count = end_angle,count+1
  end
  self._cache[width*123+height*89] = img

  --Paint on the drawable
  cr:set_source_surface(img)
  cr:paint()
end

local function set_data(self,data)
  self._cached = {}
  self._data = data
  self:emit_signal("widget::updated")
end

local function new(data)
  if not colors then colors = {color(beautiful.fg_normal),color(beautiful.bg_alternate),color(beautiful.fg_focus),color(beautiful.bg_highlight)} end
  local im = wibox.widget.imagebox()
  im._data,im.draw,im.set_data = dummy_dataset,draw,set_data
  im._cache = {}
  return im
end

return setmetatable(module, { __call = function(_, ...) return new(...) end })
-- kate: space-indent on; indent-width 2; replace-tabs on;