local anim8 = {
    _VERSION     = 'anim8 v2.3.1',
    _DESCRIPTION = 'An animation library for LÖVE',
    _URL         = 'https://github.com/kikito/anim8',
    _LICENSE     = [[
      MIT LICENSE
      Copyright (c) 2011 Enrique García Cota
      Permission is hereby granted, free of charge, to any person obtaining a
      copy of this software and associated documentation files (the
      "Software"), to deal in the Software without restriction, including
      without limitation the rights to use, copy, modify, merge, publish,
      distribute, sublicense, and/or sell copies of the Software, and to
      permit persons to whom the Software is furnished to do so, subject to
      the following conditions:
      The above copyright notice and this permission notice shall be included
      in all copies or substantial portions of the Software.
      THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
      OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
      MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
      IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
      CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
      TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
      SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
    ]]
  }
  
  local Grid = {}
  
  local _frames = {}
  
  local function assertPositiveInteger(value, name)
    if type(value) ~= 'number' then error(("%s should be a number, was %q"):format(name, tostring(value))) end
    if value < 1 then error(("%s should be a positive number, was %d"):format(name, value)) end
    if value ~= math.floor(value) then error(("%s should be an integer, was %f"):format(name, value)) end
  end
  
  local function createFrame(self, x, y)
    local fw, fh = self.frameWidth, self.frameHeight
    return love.graphics.newQuad(
      self.left + (x-1) * fw + x * self.border,
      self.top  + (y-1) * fh + y * self.border,
      fw,
      fh,
      self.imageWidth,
      self.imageHeight
    )
  end
  
  local function getGridKey(...)
    return table.concat( {...} ,'-' )
  end
  
  local function getOrCreateFrame(self, x, y)
    if x < 1 or x > self.width or y < 1 or y > self.height then
      error(("There is no frame for x=%d, y=%d"):format(x, y))
    end
    local key = self._key
    _frames[key]       = _frames[key]       or {}
    _frames[key][x]    = _frames[key][x]    or {}
    _frames[key][x][y] = _frames[key][x][y] or createFrame(self, x, y)
    return _frames[key][x][y]
  end
  
  local function parseInterval(str)
    if type(str) == "number" then return str,str,1 end
    str = str:gsub('%s', '') -- remove spaces
    local min, max = str:match("^(%d+)-(%d+)$")
    assert(min and max, ("Could not parse interval from %q"):format(str))
    min, max = tonumber(min), tonumber(max)
    local step = min <= max and 1 or -1
    return min, max, step
  end
  
  function Grid:getFrames(...)
    local result, args = {}, {...}
    local minx, maxx, stepx, miny, maxy, stepy
  
    for i=1, #args, 2 do
      minx, maxx, stepx = parseInterval(args[i])
      miny, maxy, stepy = parseInterval(args[i+1])
      for y = miny, maxy, stepy do
        for x = minx, maxx, stepx do
          result[#result+1] = getOrCreateFrame(self,x,y)
        end
      end
    end
  
    return result
  end
  
  local Gridmt = {
    __index = Grid,
    __call  = Grid.getFrames
  }
  
  local function newGrid(frameWidth, frameHeight, imageWidth, imageHeight, left, top, border)
    assertPositiveInteger(frameWidth,  "frameWidth")
    assertPositiveInteger(frameHeight, "frameHeight")
    assertPositiveInteger(imageWidth,  "imageWidth")
    assertPositiveInteger(imageHeight, "imageHeight")
  
    left   = left   or 0
    top    = top    or 0
    border = border or 0
  
    local key  = getGridKey(frameWidth, frameHeight, imageWidth, imageHeight, left, top, border)
  
    local grid = setmetatable(
      { frameWidth  = frameWidth,
        frameHeight = frameHeight,
        imageWidth  = imageWidth,
        imageHeight = imageHeight,
        left        = left,
        top         = top,
        border      = border,
        width       = math.floor(imageWidth/frameWidth),
        height      = math.floor(imageHeight/frameHeight),
        _key        = key
      },
      Gridmt
    )
    return grid
  end
  
  -----------------------------------------------------------
  
  local Animation = {}
  
  local function cloneArray(arr)
    local result = {}
    for i=1,#arr do result[i] = arr[i] end
    return result
  end
  
  local function parseDurations(durations, frameCount)
    local result = {}
    if type(durations) == 'number' then
      for i=1,frameCount do result[i] = durations end
    else
      local min, max, step
      for key,duration in pairs(durations) do
        assert(type(duration) == 'number', "The value [" .. tostring(duration) .. "] should be a number")
        min, max, step = parseInterval(key)
        for i = min,max,step do result[i] = duration end
      end
    end
  
    if #result < frameCount then
      error("The durations table has length of " .. tostring(#result) .. ", but it should be >= " .. tostring(frameCount))
    end
  
    return result
  end
  
  local function parseIntervals(durations)
    local result, time = {0},0
    for i=1,#durations do
      time = time + durations[i]
      result[i+1] = time
    end
    return result, time
  end
  
  local Animationmt = { __index = Animation }
  local nop = function() end
  
  local function newAnimation(frames, durations, onLoop)
    local td = type(durations);
    if (td ~= 'number' or durations <= 0) and td ~= 'table' then
      error("durations must be a positive number. Was " .. tostring(durations) )
    end
    onLoop = onLoop or nop
    durations = parseDurations(durations, #frames)
    local intervals, totalDuration = parseIntervals(durations)
    return setmetatable({
        frames         = cloneArray(frames),
        durations      = durations,
        intervals      = intervals,
        totalDuration  = totalDuration,
        onLoop         = onLoop,
        timer          = 0,
        position       = 1,
        status         = "playing",
        flippedH       = false,
        flippedV       = false
      },
      Animationmt
    )
  end
  
  function Animation:clone()
    local newAnim = newAnimation(self.frames, self.durations, self.onLoop)
    newAnim.flippedH, newAnim.flippedV = self.flippedH, self.flippedV
    return newAnim
  end
  
  function Animation:flipH()
    self.flippedH = not self.flippedH
    return self
  end
  
  function Animation:flipV()
    self.flippedV = not self.flippedV
    return self
  end
  
  local function seekFrameIndex(intervals, timer)
    local high, low, i = #intervals-1, 1, 1
  
    while(low <= high) do
      i = math.floor((low + high) / 2)
      if     timer >= intervals[i+1] then low  = i + 1
      elseif timer <  intervals[i]   then high = i - 1
      else
        return i
      end
    end
  
    return i
  end
  
  function Animation:update(dt)
    if self.status ~= "playing" then return end
  
    self.timer = self.timer + dt
    local loops = math.floor(self.timer / self.totalDuration)
    if loops ~= 0 then
      self.timer = self.timer - self.totalDuration * loops
      local f = type(self.onLoop) == 'function' and self.onLoop or self[self.onLoop]
      f(self, loops)
    end
  
    self.position = seekFrameIndex(self.intervals, self.timer)
  end
  
  function Animation:pause()
    self.status = "paused"
  end
  
  function Animation:gotoFrame(position)
    self.position = position
    self.timer = self.intervals[self.position]
  end
  
  function Animation:pauseAtEnd()
    self.position = #self.frames
    self.timer = self.totalDuration
    self:pause()
  end
  
  function Animation:pauseAtStart()
    self.position = 1
    self.timer = 0
    self:pause()
  end
  
  function Animation:resume()
    self.status = "playing"
  end
  
  function Animation:draw(image, x, y, r, sx, sy, ox, oy, kx, ky)
    love.graphics.draw(image, self:getFrameInfo(x, y, r, sx, sy, ox, oy, kx, ky))
  end
  
  function Animation:getFrameInfo(x, y, r, sx, sy, ox, oy, kx, ky)
    local frame = self.frames[self.position]
    if self.flippedH or self.flippedV then
      r,sx,sy,ox,oy,kx,ky = r or 0, sx or 1, sy or 1, ox or 0, oy or 0, kx or 0, ky or 0
      local _,_,w,h = frame:getViewport()
  
      if self.flippedH then
        sx = sx * -1
        ox = w - ox
        kx = kx * -1
        ky = ky * -1
      end
  
      if self.flippedV then
        sy = sy * -1
        oy = h - oy
        kx = kx * -1
        ky = ky * -1
      end
    end
    return frame, x, y, r, sx, sy, ox, oy, kx, ky
  end
  
  function Animation:getDimensions()
    local _,_,w,h = self.frames[self.position]:getViewport()
    return w,h
  end
  
  -----------------------------------------------------------
  
  anim8.newGrid       = newGrid
  anim8.newAnimation  = newAnimation
  
  return anim8