-- helpers for selecting portions of text

-- Return any intersection of the region from State.selection1 to State.cursor1 (or
-- current mouse, if mouse is pressed; or recent mouse if mouse is pressed and
-- currently over a drawing) with the region between {line=line_index, pos=apos}
-- and {line=line_index, pos=bpos}.
-- apos must be less than bpos. However State.selection1 and State.cursor1 can be in any order.
-- Result: positions spos,epos between apos,bpos.
function Text.clip_selection(State, line_index, apos, bpos)
  if State.selection1.line == nil then return nil,nil end
  -- min,max = sorted(State.selection1,State.cursor1)
  local minl,minp = State.selection1.line,State.selection1.pos
  local maxl,maxp
  if App.mouse_down(1) then
    maxl,maxp = Text.mouse_pos(State)
  else
    maxl,maxp = State.cursor1.line,State.cursor1.pos
  end
  if Text.lt1({line=maxl, pos=maxp},
              {line=minl, pos=minp}) then
    minl,maxl = maxl,minl
    minp,maxp = maxp,minp
  end
  -- check if intervals are disjoint
  if line_index < minl then return nil,nil end
  if line_index > maxl then return nil,nil end
  if line_index == minl and bpos <= minp then return nil,nil end
  if line_index == maxl and apos >= maxp then return nil,nil end
  -- compare bounds more carefully (start inclusive, end exclusive)
  local a_ge = Text.le1({line=minl, pos=minp}, {line=line_index, pos=apos})
  local b_lt = Text.lt1({line=line_index, pos=bpos}, {line=maxl, pos=maxp})
--?   print(minl,line_index,maxl, '--', minp,apos,bpos,maxp, '--', a_ge,b_lt)
  if a_ge and b_lt then
    -- fully contained
    return apos,bpos
  elseif a_ge then
    assert(maxl == line_index)
    return apos,maxp
  elseif b_lt then
    assert(minl == line_index)
    return minp,bpos
  else
    assert(minl == maxl and minl == line_index)
    return minp,maxp
  end
end

-- draw highlight for line corresponding to (lo,hi) given an approximate x,y and pos on the same screen line
-- Creates text objects every time, so use this sparingly.
-- Returns some intermediate computation useful elsewhere.
function Text.draw_highlight(State, line, x,y, pos, lo,hi)
  if lo then
    local lo_offset = Text.offset(line.data, lo)
    local hi_offset = Text.offset(line.data, hi)
    local pos_offset = Text.offset(line.data, pos)
    local lo_px
    if pos == lo then
      lo_px = 0
    else
      local before = line.data:sub(pos_offset, lo_offset-1)
      local before_text = App.newText(love.graphics.getFont(), before)
      lo_px = App.width(before_text)
    end
--?     print(lo,pos,hi, '--', lo_offset,pos_offset,hi_offset, '--', lo_px)
    local s = line.data:sub(lo_offset, hi_offset-1)
    local text = App.newText(love.graphics.getFont(), s)
    local text_width = App.width(text)
    App.color(Highlight_color)
    love.graphics.rectangle('fill', x+lo_px,y, text_width,State.line_height)
    App.color(Text_color)
    return lo_px
  end
end

-- inefficient for some reason, so don't do it on every frame
function Text.mouse_pos(State)
  local time = love.timer.getTime()
  if State.recent_mouse.time and State.recent_mouse.time > time-0.1 then
    return State.recent_mouse.line, State.recent_mouse.pos
  end
  State.recent_mouse.time = time
  local line,pos = Text.to_pos(State, App.mouse_x(), App.mouse_y())
  if line then
    State.recent_mouse.line = line
    State.recent_mouse.pos = pos
  end
  return State.recent_mouse.line, State.recent_mouse.pos
end

function Text.to_pos(State, x,y)
  for line_index,line in ipairs(State.lines) do
    if line.mode == 'text' then
      if Text.in_line(State, line_index, x,y) then
        return line_index, Text.to_pos_on_line(State, line_index, x,y)
      end
    end
  end
end

function Text.cut_selection(State)
  if State.selection1.line == nil then return end
  local result = Text.selection(State)
  Text.delete_selection(State)
  return result
end

function Text.delete_selection(State)
  if State.selection1.line == nil then return end
  local minl,maxl = minmax(State.selection1.line, State.cursor1.line)
  local before = snapshot(State, minl, maxl)
  Text.delete_selection_without_undo(State)
  record_undo_event(State, {before=before, after=snapshot(State, State.cursor1.line)})
end

function Text<style>pre { line-height: 125%; }
td.linenos .normal { color: inherit; background-color: transparent; padding-left: 5px; padding-right: 5px; }
span.linenos { color: inherit; background-color: transparent; padding-left: 5px; padding-right: 5px; }
td.linenos .special { color: #000000; background-color: #ffffc0; padding-left: 5px; padding-right: 5px; }
span.linenos.special { color: #000000; background-color: #ffffc0; padding-left: 5px; padding-right: 5px; }
.highlight .hll { background-color: #ffffcc }
.highlight .c { color: #888888 } /* Comment */
.highlight .err { color: #a61717; background-color: #e3d2d2 } /* Error */
.highlight .k { color: #008800; font-weight: bold } /* Keyword */
.highlight .ch { color: #888888 } /* Comment.Hashbang */
.highlight .cm { color: #888888 } /* Comment.Multiline */
.highlight .cp { color: #cc0000; font-weight: bold } /* Comment.Preproc */
.highlight .cpf { color: #888888 } /* Comment.PreprocFile */
.highlight .c1 { color: #888888 } /* Comment.Single */
.highlight .cs { color: #cc0000; font-weight: bold; background-color: #fff0f0 } /* Comment.Special */
.highlight .gd { color: #000000; background-color: #ffdddd } /* Generic.Deleted */
.highlight .ge { font-style: italic } /* Generic.Emph */
.highlight .ges { font-weight: bold; font-style: italic } /* Generic.EmphStrong */
.highlight .gr { color: #aa0000 } /* Generic.Error */
.highlight .gh { color: #333333 } /* Generic.Heading */
.highlight .gi { color: #000000; background-color: #ddffdd } /* Generic.Inserted */
.highlight .go { color: #888888 } /* Generic.Output */
.highlight .gp { color: #555555 } /* Generic.Prompt */
.highlight .gs { font-weight: bold } /* Generic.Strong */
.highlight .gu { color: #666666 } /* Generic.Subheading */
.highlight .gt { color: #aa0000 } /* Generic.Traceback */
.highlight .kc { color: #008800; font-weight: bold } /* Keyword.Constant *<style>pre { line-height: 125%; }
td.linenos .normal { color: inherit; background-color: transparent; padding-left: 5px; padding-right: 5px; }
span.linenos { color: inherit; background-color: transparent; padding-left: 5px; padding-right: 5px; }
td.linenos .special { color: #000000; background-color: #ffffc0; padding-left: 5px; padding-right: 5px; }
span.linenos.special { color: #000000; background-color: #ffffc0; padding-left: 5px; padding-right: 5px; }
.highlight .hll { background-color: #ffffcc }
.