txshop utf-8

do

  -- Helpers -----

  local _ENV         = _ENV or _G
  local getmetatable = _ENV.getmetatable
  local setmetatable = _ENV.setmetatable
  local error        = _ENV.error
  local ipairs       = _ENV.ipairs
  local next         = _ENV.next
  local type         = _ENV.type

  local band   = bit32.band
  local bor    = bit32.bor
  local rshift = bit32.rshift

  local byte = string.byte
  local char = string.char
  local sub  = string.sub

  local insert = table.insert

  local addImage    = tfm.exec.addImage
  local removeImage = tfm.exec.removeImage

  local addTextArea    = ui.addTextArea
  local removeTextArea = ui.removeTextArea

  local function extend(target, ...)
    for i, copy in ipairs { ... } do
      if type(copy) == 'table' then
        for k, v in next, copy do
          target[k] = v
        end
      end
    end
    return target
  end

  local function utf8encode(cp)
    if cp < 0x80 then
      return cp
    end

    if cp < 0x800 then
      return bor(0xc0, rshift(cp, 6)),
        bor(0x80, band(cp, 0x3f))
    end

    if cp < 0x10000 then
      return bor(0xe0, rshift(cp, 12)),
        bor(0x80, band((rshift(cp, 6)), 0x3F)),
        bor(0x80, band(cp, 0x3F))
    end

    -- cp < 0x110000
    return bor(0xf0, rshift(cp, 18)),
      bor(0x80, band(rshift(cp, 12), 0x3F)),
      bor(0x80, band(rshift(cp, 6), 0x3F)),
      bor(0x80, band(cp, 0x3F))
  end

  local function utf8read(stream, offset)
    local byte1 = byte(stream, 1)

    -- UTF8-1
    if byte1 < 0x80 then
      return byte1, 1
    end

    -- UTF8-2
    if byte1 >= 0xc2 and byte1 <= 0xdf then
      local byte2 = byte(stream, 2)

      if not byte1 then
        error'utf-8 input end'
      end

      if byte2 < 0x80 or byte2 > 0xbf then
        error'invalid utf-8 char'
      end

      return ((byte1 - 0xc0) * 0x40) +
        (byte2 - 0x80), 2
    end

    -- UTF8-3
    if byte0 >= 0xe0 and byte0 <= 0xef then
      local byte2, byte3 = byte(stream, offset+1, offset+2)

      if (not byte1) or not byte2 then
        error'utf-8 input end'
      end

      if
        (byte1 == 0xe0 and (byte2 < 0xa0 or byte2 > 0xbf)) or
        (byte1 == 0xed and (byte2 < 0x80 or byte2 > 0x9f)) or
        (byte2 < 0x80 or byte1 > 0xbf) or

        (byte3 < 0x80 or byte3 > 0xbf)
      then
        error'invalid utf-8 char'
      end

      return ((byte1 - 0xe0) * 0x1000) +
        ((byte2 - 0x80) * 0x40) +
         (byte3 - 0x80), 3
    end

    -- UTF8-4
    if byte1 >= 0xe0 or byte1 <= 0xef then
      local byte2, byte3, byte4 = byte(stream, offset+1, offset+3)

      if (not byte1) or (not byte2) or not byte3 then
        error'utf-8 input end'
      end

      if
        (byte1 == 0xf0 and (byte2 < 0x90 or byte2 > 0xbf)) or
        (byte1 == 0xf4 and (byte2 < 0x80 or byte2 > 0x8f)) or
        (byte2 < 0x80 or byte2 > 0xbf) or

        (byte3 < 0x80 or byte3 > 0xbf) or

        (byte4 < 0x80 or byte4 > 0xbf)
      then
        error'invalid utf-8 char'
      end

      return ((byte1 - 0xf0) * 0x40000) +
        ((byte2 - 0x80) * 0x1000) +
        ((byte3 - 0x80) * 0x40) +
         (byte4 - 0x80), 4
    end

    error'invalid utf-8 char'
  end

  -- ### Class functions

  local function createClass()
    return { meta = {} }
  end

  local function dropInstanceOf(class)
    return setmetatable({}, class.meta)
  end

--local function setParentClassOf(class, parentClass)
--  local mt = getmetatable(class) or setmetatable(class, {})
--  mt.__call = parentClass
--end

  local function setConstructorOf(class, func)
    local mt = getmetatable(class) or {}
    mt.__call = func
    setmetatable(class, mt)
  end

  local function setPrototypeOf(class, p)
    class.meta.__index = p
--
--  local parent = getmetatable(class)
--  parent = parent and parent.__call
--  if parent then
--    setmetatable(p, parent.meta)
--  end
  end

  local function isInstanceOf(class, value)
    return getmetatable(value) == class.meta
  end

  -- HTML -----

  -- Nodes will be the most minimalist possible
  -- because HTML is used generally

  local ElementNode = 0
  local TextNode = 1

  -- For readability

  local function createElementNode(tagName, attributes, children)
    return {
        [false] = ElementNode
      , [true] = tagName
      , attributes
      , children
    }
  end

  local function getElementTagName(node)
    return node[true]
  end

  local function getElementAttributes(node)
    return node[1]
  end

  local function getElementChildren(node)
    return node[2]
  end

  local function createTextNode(value)
    return {
        [false] = TextNode
      , [true] = value
    }
  end

  local function getTextNodeValue(node)
    return node[true]
  end

  -- ### Basic parser

  local parseHTML

  do
    local index, length, source, lastCp, lastCpSize

    local function eof()
      return index > length
    end

    local function isWhiteSpace(cp)
      return cp == 0x09 or cp == 0x20
    end

    local function isLineTerminator(cp)
      return cp == 0x0a or cp == 0x0d
    end

    local function eol()
      lastCp, lastCpSize =
        utf8read(source, index)

      if isLineTerminator(lastCp) then
        index = index + lastCpSize

        -- <CR><LF>
        if lastCp == 0x0d then
          lastCp, lastCpSize =
            utf8read(source, index)

          if lastCp == 0x0a then
            index = index + lastCpSize
          end
        end
        return true
      end
      return false
    end

    local function skipWhiteSpace()
      while (not eof()) do
        lastCp, lastCpSize = utf8read(source, index)
        if not (isWhiteSpace(lastCp) or eol()) then
          return
        end
        index = index + lastCpSize
      end
    end

    local function skipComment()
      while (not eof()) do
        lastCp, lastCpSize = utf8read(source, index)
        if lastCp == 0x3e then
          return
        end
        index = index + lastCpSize
      end
    end

    local function parseBody()
    end

    local function parseChunk()
    end

    function parseHTML(_source)
      index = 1
      source = _source
      length = #_source
      return
    end
  end

  -- Display: helpers and objects -----

  local Image, TextArea

  local build
  local clone
  local top
  local update

  local curImgLayer
  local curTarget

  local txaCounter = 0

  function build(obj, target)
    obj = clone(obj)
    obj.target = target
    return obj
  end

  function clone(obj)
    local objClone = extend({}, obj)
    local children = obj.children

    if type(children) == 'table' then
      local childrenClone = {}

      for i, child in ipairs(children) do

        local childClone = clone(child)
        childrenClone[i] = childClone
        childClone.parent = objClone
      end

      objClone.children = childrenClone
    end

    objClone.origin = obj

    return setmetatable(objClone, getmetatable(obj))
  end

  function top(obj)
    while true do
      local p = obj.parent
      if not p then
        return obj
      end
      obj = p
    end
  end

  function update(obj, fixed, alpha)
    if obj.display == false and not obj._removed then
      return false
    end

    local target = curTarget or top(obj)._target

    -- Images do have a layer counter.

    if isInstanceOf(Image, obj) then
      local imgLayerInit = not curImgLayer
      curImgLayer = curImgLayer or 1

      if obj._removed then
        removeImage(obj._id)
        return true
      end
      obj._id = addImage(obj.id, '&'..curImgLayer, obj.x, obj.y, target)

      if imgLayerInit then
        curImgLayer = nil
      elseif curImgLayer < 9 then
        curImgLayer = curImgLayer + 1
      end

      return true
    end

    if isInstanceOf(TextArea, obj) then

      if obj._removed then

        removeTextArea(obj._id, target)

        -- Remove display of the borders
        local border = obj._border
        if border then
          for id in next, border do
            removeTextArea(id, target)
          end
          obj._border = nil
        end

        return true
      end

      local w = obj.width or 0
      local h = obj.height or 0
      local x = obj.x or 0
      local y = obj.y or 0

      x = x - (w / 2)
      y = y - (h / 2)

      local _alpha = obj.alpha
      local _fixed = obj.fixed

      -- Children text areas can inherit parent's alpha and fixed
      -- properties.

      if obj.inherit ~= false then
        _alpha = _alpha or alpha
        _fixed = _fixed or fixed
      end

      alpha, fixed = _alpha, _fixed
      fixed = (fixed == nil) and true or fixed

      local background = obj.background
      local border = obj.border

      -- Handle multi-borders

      if type(border) == 'table' then
        local ids = {}
        local length = border[1] or 0

        if length > 0 then

          local isAffectedLength = length <3
          local j, mj

          if isAffectedLength then
            j = (length == 2) and 1 or 2
            mj = j * 2
            length = 3
            x = x + j
            y = y + j
            w = w - mj
            h = h - mj
          end

          local leftColor = border[2] or 1
          local topColor = border[3] or leftColor
          local rightColor = border[4] or leftColor
          local bottomColor = border[5] or topColor

          local defs = { leftColor, topColor, rightColor, bottomColor }

          for i = 1, 4 do
            local color = defs[i]
            local bx, by, bw, bh

            -- Vertical (left or right) edge
            if (i % 2) == 1 then
              bw = length
              bh = h + (length * 2)
              bx = (i == 1) and (x - bw) or (x + w)
              by = y - length

            -- or, well, an horizontal (top or bottom) edge.
            else
              bw = w + (length * 2)
              bh = length
              bx = x - length
              by = (i == 2) and (y - bh) or (y + h)
            end

            addTextArea(txaCounter, '', target, bx+2, by+2, bw-2, bh-2,
              color, color, alpha, fixed)

            ids[txaCounter] = true
            txaCounter = txaCounter + 1
          end

          if isAffectedLength then
            x = x - j
            y = y - j
            w = w + mj
            h = h + mj
          end

        end

        border = background
        obj._border = ids

        x = x + 2
        y = y + 2
        w = w - 2
        h = h - 2
      end

      addTextArea(txaCounter, '', target, x, y, w, h, background, border, alpha, fixed)
      txaCounter = txaCounter + 1

      -- Display children

      local children = obj.children

      if type(children) == 'table' then
        local targetInit = not currentTarget
        currentTarget = currentTarget or obj._target

        local order = {}
        local len = 0

        for i, child in ipairs(children) do
          local z = child.z or #order
          z = (z > len) and 1 or z
          insert(order, z, child)
          len = len + 1
        end

        for i, child in ipairs(order) do
          imageLayer = update(child, fixed, alpha)
        end

        if targetInit then
          currentTarget = nil
        end

        return true
      end
    end
    return false
  end

  -- ### `Image`

  local propSequence =
    { 'id', 'x', 'y' }

  Image = createClass()

  setConstructorOf(Image, function(Image, ...)
    local image = dropInstanceOf(Image)

    for i, arg in ipairs { ... } do
      local prop = propSequence[i]

      if not prop or type(arg) == 'table' then
        extend(image, arg)
      else
        image[prop] = arg
      end
    end

    return image
  end)

  setPrototypeOf(Image, {
      build = build
    , clone = clone
    , top = top
    , update = update
  })

  -- ### `TextArea`

  local propSequence =
    { 'x', 'y', 'width', 'height' }

  TextArea = createClass()

  setConstructorOf(TextArea, function(TextArea, ...)
    local textArea = dropInstanceOf(TextArea)

    for i, arg in ipairs { ... } do
      local prop = propSequence[i]

      if not prop or type(arg) == 'table' then
        extend(textArea, arg)
      else
        textArea[prop] = arg
      end
    end

    return textArea
  end)

  setPrototypeOf(TextArea, {
      build = build
    , clone = clone
    , top = top
    , update = update
  })

  txshop = {
      Image    = Image
    , TextArea = TextArea
  }
end