-- text editor, particularly text drawing, horizontal wrap, vertical scrolling
Text = {}

function Text.draw_cursor(editor, x, y)
  -- blink every 0.5s
  if math.floor(Cursor_time*2)%2 == 0 then
    App.color(Cursor_color)
    love.graphics.rectangle('fill', x,y, 3,editor.line_height)
  end
end

function Text.text_input(editor, t)
  if love.mouse.isDown(1) then return end
  if any_modifier_down() then
    if Keys_down[t] then
      -- The modifiers didn't change the key. Handle it in keychord_press.
      return
    else
      -- Key mutated by the keyboard layout. Continue below.
    end
  end
  local before = snapshot(editor, editor.cursor.line)
  Text.insert_at_cursor(editor, t)
  maybe_snap_cursor_to_bottom_of_screen(editor)
  record_undo_event(editor, {before=before, after=snapshot(editor, editor.cursor.line)})
end

function Text.insert_at_cursor(editor, t)
  assert(editor.lines[editor.cursor.line].mode == 'text', 'line is not text')
  local byte_offset = Text.offset(editor.lines[editor.cursor.line].data, editor.cursor.pos)
  editor.lines[editor.cursor.line].data = string.sub(editor.lines[editor.cursor.line].data, 1, byte_offset-1)..t..string.sub(editor.lines[editor.cursor.line].data, byte_offset)
  editor.cursor.pos = editor.cursor.pos+1
end

-- Don't handle any keys here that would trigger text_input above.
function Text.keychord_press(editor, chord)
  assert(editor.lines[editor.cursor.line].mode == editor.cursor.mode)
  --== shortcuts that mutate text (must schedule_save)
  if chord == 'return' then
    local before_line = editor.cursor.line
    local before = snapshot(editor, before_line)
    Text.insert_return(editor)
    maybe_snap_cursor_to_bottom_of_screen(editor)
    record_undo_event(editor, {before=before, after=snapshot(editor, before_line, editor.cursor.line)})
    schedule_save(editor)
  elseif chord == 'tab' then
    if editor.cursor.mode == 'text' then
      local before = snapshot(editor, editor.cursor.line)
      Text.insert_at_cursor(editor, '\t')
      maybe_snap_cursor_to_bottom_of_screen(editor)
      record_undo_event(editor, {before=before, after=snapshot(editor, editor.cursor.line)})
      schedule_save(editor)
    end
  elseif chord == 'backspace' then
    if editor.cursor.mode == 'text' then
      if editor.selection1.line then
        Text.delete_selection_and_record_undo_event(editor)
        schedule_save(editor)
        return
      end
      local before
      if editor.cursor.pos > 1 then
        before = snapshot(editor, editor.cursor.line)
        local byte_start = utf8.offset(editor.lines[editor.cursor.line].data, editor.cursor.pos-1)
        local byte_end = utf8.offset(editor.lines[editor.cursor.line].data, editor.cursor.pos)
        if byte_start then
          if byte_end then
            editor.lines[editor.cursor.line].data = string.sub(editor.lines[editor.cursor.line].data, 1, byte_start-1)..string.sub(editor.lines[editor.cursor.line].data, byte_end)
          else
            editor.lines[editor.cursor.line].data = string.sub(editor.lines[editor.cursor.line].data, 1, byte_start-1)
          end
          editor.cursor.pos = editor.cursor.pos-1
        end
      elseif editor.cursor.line > 1 then
        before = snapshot(editor, editor.cursor.line-1, editor.cursor.line)
        if editor.lines[editor.cursor.line-1].mode == 'drawing' then
          table.remove(editor.lines, editor.cursor.line-1)
          if editor.screen_top.line == editor.cursor.line-1 then
            editor.screen_top = {mode='text', line=editor.screen_top.line, pos=1}
          end
        else
          -- join lines
          editor.cursor.pos = utf8.len(editor.lines[editor.cursor.line-1].data)+1
          editor.lines[editor.cursor.line-1].data = editor.lines[editor.cursor.line-1].data..editor.lines[editor.cursor.line].data
          table.remove(editor.lines, editor.cursor.line)
        end
        editor.cursor.line = editor.cursor.line-1
      end
      if editor.screen_top.line > #editor.lines then
        editor.screen_top = vert(editor, editor.cursor, 0)
      elseif edit.lt(editor.cursor, editor.screen_top) then
        maybe_snap_cursor_to_top_of_screen(editor)
      end
      assert(edit.le(editor.screen_top, editor.cursor), ('screen_top (line=%d,pos=%d) is below cursor (line=%d,pos=%d)'):format(editor.screen_top.line, editor.screen_top.pos or -1, editor.cursor.line, editor.cursor.pos or -1))
      record_undo_event(editor, {before=before, after=snapshot(editor, editor.cursor.line)})
      schedule_save(editor)
    end
  elseif chord == 'delete' then
    if editor.cursor.mode == 'drawing' then
      assert(editor.cursor.line < #editor.lines)
      local before = snapshot(editor, editor.cursor.line, editor.cursor.line+1)
      table.remove(editor.lines, editor.cursor.line)
      assert(editor.cursor.line <= #editor.lines)
      if editor.lines[editor.cursor.line].mode == 'text' then
        editor.cursor = {mode='text', line=editor.cursor.line, pos=1}
      else
        editor.cursor = {mode='drawing', line=editor.cursor.line}
      end
      -- no need to scroll, but screen_top may have switched mode
      if editor.screen_top.line == editor.cursor.line then
        editor.screen_top = deepcopy(editor.cursor)
      end
      record_undo_event(editor, {before=before, after=snapshot(editor, editor.cursor.line)})
    else
      -- cursor in text line
      if editor.selection1.line then
        Text.delete_selection_and_record_undo_event(editor)
        schedule_save(editor)
        return
      end
      local before
      if editor.cursor.pos <= utf8.len(editor.lines[editor.cursor.line].data) then
        before = snapshot(editor, editor.cursor.line)
      else
        before = snapshot(editor, editor.cursor.line, editor.cursor.line+1)
      end
      if editor.cursor.pos <= utf8.len(editor.lines[editor.cursor.line].data) then
        local byte_start = utf8.offset(editor.lines[editor.cursor.line].data, editor.cursor.pos)
        local byte_end = utf8.offset(editor.lines[editor.cursor.line].data, editor.cursor.pos+1)
        if byte_start then
          if byte_end then
            editor.lines[editor.cursor.line].data = string.sub(editor.lines[editor.cursor.line].data, 1, byte_start-1)..string.sub(editor.lines[editor.cursor.line].data, byte_end)
          else
            editor.lines[editor.cursor.line].data = string.sub(editor.lines[editor.cursor.line].data, 1, byte_start-1)
          end
          -- no change to editor.cursor.pos
        end
      elseif editor.cursor.line < #editor.lines then
        if editor.lines[editor.cursor.line+1].mode == 'text' then
          -- join lines
          editor.lines[editor.cursor.line].data = editor.lines[editor.cursor.line].data..editor.lines[editor.cursor.line+1].data
        end
        table.remove(editor.lines, editor.cursor.line+1)
      end
      record_undo_event(editor, {before=before, after=snapshot(editor, editor.cursor.line)})
      schedule_save(editor)
    end
  --== shortcuts that move the cursor
  elseif chord == 'left' then
    Text.left(editor)
    editor.selection1 = {}
  elseif chord == 'right' then
    Text.right(editor)
    editor.selection1 = {}
  elseif chord == 'S-left' then
    if editor.selection1.line == nil then
      editor.selection1 = deepcopy(editor.cursor)
    end
    Text.left(editor)
  elseif chord == 'S-right' then
    if editor.selection1.line == nil then
      editor.selection1 = deepcopy(editor.cursor)
    end
    Text.right(editor)
  -- C- hotkeys reserved for drawings, so we'll use M-
  elseif chord == 'M-left' then
    Text.word_left(editor)
    editor.selection1 = {}
  elseif chord == 'M-right' then
    Text.word_right(editor)
    editor.selection1 = {}
  elseif chord == 'M-S-left' then
    if editor.selection1.line == nil then
      editor.selection1 = deepcopy(editor.cursor)
    end
    Text.word_left(editor)
  elseif chord == 'M-S-right' then
    if editor.selection1.line == nil then
      editor.selection1 = deepcopy(editor.cursor)
    end
    Text.word_right(editor)
  elseif chord == 'home' then
    Text.start_of_line(editor)
    editor.selection1 = {}
  elseif chord == 'end' then
    Text.end_of_line(editor)
    editor.selection1 = {}
  elseif chord == 'S-home' then
    if editor.selection1.line == nil then
      editor.selection1 = deepcopy(editor.cursor)
    end
    Text.start_of_line(editor)
  elseif chord == 'S-end' then
    if editor.selection1.line == nil then
      editor.selection1 = deepcopy(editor.cursor)
    end
    Text.end_of_line(editor)
  elseif chord == 'up' then
    Text.up(editor)
    editor.selection1 = {}
  elseif chord == 'down' then
    Text.down(editor)
    editor.selection1 = {}
  elseif chord == 'S-up' then
    if editor.selection1.line == nil then
      editor.selection1 = deepcopy(editor.cursor)
    end
    Text.up(editor)
  elseif chord == 'S-down' then
    if editor.selection1.line == nil then
      editor.selection1 = deepcopy(editor.cursor)
    end
    Text.down(editor)
  elseif chord == 'pageup' then
    Text.pageup(editor)
    editor.selection1 = {}
  elseif chord == 'pagedown' then
    Text.pagedown(editor)
    editor.selection1 = {}
  elseif chord == 'S-pageup' then
    if editor.selection1.line == nil then
      editor.selection1 = deepcopy(editor.cursor)
    end
    Text.pageup(editor)
  elseif chord == 'S-pagedown' then
    if editor.selection1.line == nil then
      editor.selection1 = deepcopy(editor.cursor)
    end
    Text.pagedown(editor)
  end
end

function Text.insert_return(editor)
  if editor.cursor.mode == 'drawing' then
    table.insert(editor.lines, editor.cursor.line+1, {mode='text', data=''})
    editor.cursor = {mode='text', line=editor.cursor.line+1, pos=1}
    return
  end
  local byte_offset = Text.offset(editor.lines[editor.cursor.line].data, editor.cursor.pos)
  table.insert(editor.lines, editor.cursor.line+1, {mode='text', data=string.sub(editor.lines[editor.cursor.line].data, byte_offset)})
  editor.lines[editor.cursor.line].data = string.sub(editor.lines[editor.cursor.line].data, 1, byte_offset-1)
  editor.cursor = {mode='text', line=editor.cursor.line+1, pos=1}
  maybe_snap_cursor_to_bottom_of_screen(editor)
end

function Text.offset(s, pos1)
  if pos1 == 1 then return 1 end
  local result = utf8.offset(s, pos1)
  if result == nil then
    assert(false, ('Text.offset(%d) called on a string of length %d (byte size %d); this is likely a failure to handle utf8\n\n^%s$\n'):format(pos1, utf8.len(s), #s, s))
  end
  return result
end