-- mod-version:3 --lite-xl 2.1
local style = require "core.style"
local config = require "core.config"
local DocView = require "core.docview"


-- TODO: replace with `doc:get_indent_info()` when 2.1 releases
local function get_indent_info(doc)
  if doc.get_indent_info then
    return doc:get_indent_info()
  end
  return config.tab_type, config.indent_size
end


local function get_line_spaces(doc, idx, dir)
  local _, indent_size = get_indent_info(doc)
  local text = doc.lines[idx]
  if not text or #text == 1 then
    return -1
  end
  local s, e = text:find("^%s*")
  if e == #text then
    return get_line_spaces(doc, idx + dir, dir)
  end
  local n = 0
  for _,b in pairs({text:byte(s, e)}) do
    n = n + (b == 9 and indent_size or 1)
  end
  return n
end


local function get_line_indent_guide_spaces(doc, idx)
  if doc.lines[idx]:find("^%s*\n") then
    return math.max(
      get_line_spaces(doc, idx - 1, -1),
      get_line_spaces(doc, idx + 1,  1))
  end
  return get_line_spaces(doc, idx)
end

local docview_update = DocView.update
function DocView:update()
  docview_update(self)

  local function get_indent(idx)
    if idx < 1 or idx > #self.doc.lines then return -1 end
    if not self.indentguide_indents[idx] then
      self.indentguide_indents[idx] = get_line_indent_guide_spaces(self.doc, idx)
    end
    return self.indentguide_indents[idx]
  end

  self.indentguide_indents = {}
  self.indentguide_indent_active = {}

  local minline, maxline = self:get_visible_line_range()
  for i = minline, maxline do
    self.indentguide_indents[i] = get_line_indent_guide_spaces(self.doc, i)
  end

  local _, indent_size = get_indent_info(self.doc)
  for _,line in self.doc:get_selections() do
    local lvl = get_indent(line)
    local top, bottom

    if not self.indentguide_indent_active[line]
     or self.indentguide_indent_active[line] > lvl then

      -- check if we're the header or the footer of a block
      if get_indent(line + 1) > lvl and get_indent(line + 1) <= lvl + indent_size then
        top = true
        lvl = get_indent(line + 1)
      elseif get_indent(line - 1) > lvl and get_indent(line - 1) <= lvl + indent_size then
        bottom = true
        lvl = get_indent(line - 1)
      end

      self.indentguide_indent_active[line] = lvl

      -- check if the lines before the current are part of the block
      local i = line - 1
      if i > 0 and not top then
        repeat
          if get_indent(i) <= lvl - indent_size then break end
          self.indentguide_indent_active[i] = lvl
          i = i - 1
        until i < minline
      end
      -- check if the lines after the current are part of the block
      i = line + 1
      if i <= #self.doc.lines and not bottom then
        repeat
          if get_indent(i) <= lvl - indent_size then break end
          self.indentguide_indent_active[i] = lvl
          i = i + 1
        until i > maxline
      end
    end
  end
end


local draw_line_text = DocView.draw_line_text
function DocView:draw_line_text(idx, x, y)
  local spaces = self.indentguide_indents[idx] or -1
  local _, indent_size = get_indent_info(self.doc)
  local w = math.max(1, SCALE)
  local h = self:get_line_height()
  local font = self:get_font()
  local space_sz = font:get_width(" ")
  for i = 0, spaces - 1, indent_size do
    local color = style.guide or style.selection
    local active_lvl = self.indentguide_indent_active[idx] or -1
    if i < active_lvl and i + indent_size >= active_lvl then
      color = style.guide_highlight or style.accent
    end
    local sw = space_sz * i
    renderer.draw_rect(math.ceil(x + sw), y, w, h, color)
  end
  return draw_line_text(self, idx, x, y)
end